Sample records for ultra-high field mri

  1. Ultra-low field MRI: bringing MRI to new arenas

    DOE PAGES

    Magnelind, Per Erik; Matlashov, Andrei Nikolaevich; Newman, Shaun Garrett; ...

    2016-11-01

    Conventional magnetic resonance imaging (MRI) is moving toward the use of stronger and stronger magnetic fields with 3T, and even 7 T systems being increasingly used in routine clinical applications. However there is another branch of MRI, namely Ultra Low Field MRI (ULF-MRI) where the magnetic fields during readout are several orders of magnitude smaller, namely 1–100 μT. While conventional high-field MRI remains the gold standard there are several situations such as in military emergencies or in developing countries where for cost and logistical reasons, conventional MRI is not practical. In such scenarios, ULF-MRI could provide a solution. Lastly, thismore » article describes the basic principles and the potential of ULF-MRI.« less

  2. Ultra-low field MRI: bringing MRI to new arenas

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Magnelind, Per Erik; Matlashov, Andrei Nikolaevich; Newman, Shaun Garrett

    Conventional magnetic resonance imaging (MRI) is moving toward the use of stronger and stronger magnetic fields with 3T, and even 7 T systems being increasingly used in routine clinical applications. However there is another branch of MRI, namely Ultra Low Field MRI (ULF-MRI) where the magnetic fields during readout are several orders of magnitude smaller, namely 1–100 μT. While conventional high-field MRI remains the gold standard there are several situations such as in military emergencies or in developing countries where for cost and logistical reasons, conventional MRI is not practical. In such scenarios, ULF-MRI could provide a solution. Lastly, thismore » article describes the basic principles and the potential of ULF-MRI.« less

  3. Diagnosis of multiple sclerosis through the lens of ultra-high-field MRI

    NASA Astrophysics Data System (ADS)

    Sati, Pascal

    2018-06-01

    The long-standing relationship between ultra-high-field (7 T) MRI and multiple sclerosis (MS) has brought new insights to our understanding of lesion evolution and its associated pathology. With the recent FDA approval of a commercially available scanner, 7 T MRI is finally entering the clinic with great expectations about its potential added value. By looking through the prism of MS diagnosis, this perspective article discusses current limitations and prospects of 7 T MRI techniques relevant to helping clinicians diagnose patients encountered in daily practice.

  4. Gradient and shim technologies for ultra high field MRI

    PubMed Central

    Winkler, Simone A.; Schmitt, Franz; Landes, Hermann; DeBever, Josh; Wade, Trevor; Alejski, Andrew

    2017-01-01

    Ultra High Field (UHF) MRI requires improved gradient and shim performance to fully realize the promised gains (SNR as well as spatial, spectral, diffusion resolution) that higher main magnetic fields offer. Both the more challenging UHF environment by itself, as well as the higher currents used in high performance coils, require a deeper understanding combined with sophisticated engineering modeling and construction, to optimize gradient and shim hardware for safe operation and for highest image quality. This review summarizes the basics of gradient and shim technologies, and outlines a number of UHF-related challenges and solutions. In particular, Lorentz forces, vibroacoustics, eddy currents, and peripheral nerve stimulation are discussed. Several promising UHF-relevant gradient concepts are described, including insertable gradient coils aimed at higher performance neuroimaging. PMID:27915120

  5. Temporal reliability of ultra-high field resting-state MRI for single-subject sensorimotor and language mapping.

    PubMed

    Branco, Paulo; Seixas, Daniela; Castro, São Luís

    2018-03-01

    Resting-state fMRI is a well-suited technique to map functional networks in the brain because unlike task-based approaches it requires little collaboration from subjects. This is especially relevant in clinical settings where a number of subjects cannot comply with task demands. Previous studies using conventional scanner fields have shown that resting-state fMRI is able to map functional networks in single subjects, albeit with moderate temporal reliability. Ultra-high resolution (7T) imaging provides higher signal-to-noise ratio and better spatial resolution and is thus well suited to assess the temporal reliability of mapping results, and to determine if resting-state fMRI can be applied in clinical decision making including preoperative planning. We used resting-state fMRI at ultra-high resolution to examine whether the sensorimotor and language networks are reliable over time - same session and one week after. Resting-state networks were identified for all subjects and sessions with good accuracy. Both networks were well delimited within classical regions of interest. Mapping was temporally reliable at short and medium time-scales as demonstrated by high values of overlap in the same session and one week after for both networks. Results were stable independently of data quality metrics and physiological variables. Taken together, these findings provide strong support for the suitability of ultra-high field resting-state fMRI mapping at the single-subject level. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

  6. Ultra-high field MRI for primate imaging using the travelling-wave concept.

    PubMed

    Mallow, Johannes; Herrmann, Tim; Kim, Kyoung-Nam; Stadler, Joerg; Mylius, Judith; Brosch, Michael; Bernarding, Johannes

    2013-08-01

    Ultra-high field (UHF) neuroimaging is usually conducted with volume transmit (Tx) and phased array receive (Rx) coils, both tightly enclosing the object. The travelling-wave (TW) concept allows a remote excitation offering more flexible experimental setups. To investigate the feasibility of primate MRI in horizontal UHF MRI, we first compared the distribution of the electromagnetic fields in an oil phantom and then verified the concept with an in vivo experiment. In the phantom experiments an in-house circularly polarized hybrid birdcage coil and a self-developed patch antenna were used for Tx and an eight-element phased array antenna for Rx. B1+ fields were calculated and measured for both approaches. For in vivo experiments the Rx part was replaced with an optimized three-element phased array head coil. The SAR was calculated using field simulation. In the phantom the field distribution was homogenous in a central volume of interest of about 10 cm diameter. The TW concept showed a slightly better homogeneity. Examination of a female crab-eating macaque led to homogeneous high-contrast images with a good delineation of anatomical details. The TW concept opens up a new approach for MRI of medium-sized animals in horizontal UHF scanners.

  7. Rapid brain MRI acquisition techniques at ultra-high fields

    PubMed Central

    Setsompop, Kawin; Feinberg, David A.; Polimeni, Jonathan R.

    2017-01-01

    Ultra-high-field MRI provides large increases in signal-to-noise ratio as well as enhancement of several contrast mechanisms in both structural and functional imaging. Combined, these gains result in a substantial boost in contrast-to-noise ratio that can be exploited for higher spatial resolution imaging to extract finer-scale information about the brain. With increased spatial resolution, however, is a concurrent increased image encoding burden that can cause unacceptably long scan times for structural imaging and slow temporal sampling of the hemodynamic response in functional MRI—particularly when whole-brain imaging is desired. To address this issue, new directions of imaging technology development—such as the move from conventional 2D slice-by-slice imaging to more efficient Simultaneous MultiSlice (SMS) or MultiBand imaging (which can be viewed as “pseudo-3D” encoding) as well as full 3D imaging—have provided dramatic improvements in acquisition speed. Such imaging paradigms provide higher SNR efficiency as well as improved encoding efficiency. Moreover, SMS and 3D imaging can make better use of coil sensitivity information in multi-channel receiver arrays used for parallel imaging acquisitions through controlled aliasing in multiple spatial directions. This has enabled unprecedented acceleration factors of an order of magnitude or higher in these imaging acquisition schemes, with low image artifact levels and high SNR. Here we review the latest developments of SMS and 3D imaging methods and related technologies at ultra-high field for rapid high-resolution functional and structural imaging of the brain. PMID:26835884

  8. Post-mortem inference of the human hippocampal connectivity and microstructure using ultra-high field diffusion MRI at 11.7 T.

    PubMed

    Beaujoin, Justine; Palomero-Gallagher, Nicola; Boumezbeur, Fawzi; Axer, Markus; Bernard, Jeremy; Poupon, Fabrice; Schmitz, Daniel; Mangin, Jean-François; Poupon, Cyril

    2018-06-01

    The human hippocampus plays a key role in memory management and is one of the first structures affected by Alzheimer's disease. Ultra-high magnetic resonance imaging provides access to its inner structure in vivo. However, gradient limitations on clinical systems hinder access to its inner connectivity and microstructure. A major target of this paper is the demonstration of diffusion MRI potential, using ultra-high field (11.7 T) and strong gradients (750 mT/m), to reveal the extra- and intra-hippocampal connectivity in addition to its microstructure. To this purpose, a multiple-shell diffusion-weighted acquisition protocol was developed to reach an ultra-high spatio-angular resolution with a good signal-to-noise ratio. The MRI data set was analyzed using analytical Q-Ball Imaging, Diffusion Tensor Imaging (DTI), and Neurite Orientation Dispersion and Density Imaging models. High Angular Resolution Diffusion Imaging estimates allowed us to obtain an accurate tractography resolving more complex fiber architecture than DTI models, and subsequently provided a map of the cross-regional connectivity. The neurite density was akin to that found in the histological literature, revealing the three hippocampal layers. Moreover, a gradient of connectivity and neurite density was observed between the anterior and the posterior part of the hippocampus. These results demonstrate that ex vivo ultra-high field/ultra-high gradients diffusion-weighted MRI allows the mapping of the inner connectivity of the human hippocampus, its microstructure, and to accurately reconstruct elements of the polysynaptic intra-hippocampal pathway using fiber tractography techniques at very high spatial/angular resolutions.

  9. Ultra-high field magnets for whole-body MRI

    NASA Astrophysics Data System (ADS)

    Warner, Rory

    2016-09-01

    For whole-body MRI, an ultra-high field (UHF) magnet is currently defined as a system operating at 7 T or above. Over 70 UHF magnets have been built, all with the same technical approach originally developed by Magnex Scientific Ltd. The preferred coil configuration is a compensated solenoid. In this case, the majority of the field is generated by a simple long solenoid that stretches the entire length of the magnet. Additional coils are wound on a separate former outside the main windings with the purpose of balancing the homogeneity. Most of the magnets currently in operation are passively shielded systems where the magnet is surrounded by a steel box of 200-870 tonnes of carbon steel. More recently actively shielded magnets have been built for operation at 7 T; in this case the stray field is controlled by with reverse turns wound on a separate former outside the primary coils. Protection against quench damage is much more complex with an actively shielded magnet design due to the requirement to prevent the stray field from increasing during a quench. In the case of the 7 T 900 magnet this controlled by combining some of the screening coils into each section of the protection circuit. Correction of the field variations caused by manufacturing tolerances and environmental effects are made with a combination of superconducting shims and passive shims. Modern UHF magnets operate in zero boil-off mode with the use of cryocoolers with cooling capacity at 4.2 K. Although there are no cryogen costs associated with normal operation UHF magnets require a significant volume (10 000-20 000 l) of liquid helium for the cool-down. Liquid helium is expensive therefore new methods of cool-down using high-power cryocoolers are being implemented to reduce the requirement.

  10. Integration of ultra-high field MRI and histology for connectome based research of brain disorders

    PubMed Central

    Yang, Shan; Yang, Zhengyi; Fischer, Karin; Zhong, Kai; Stadler, Jörg; Godenschweger, Frank; Steiner, Johann; Heinze, Hans-Jochen; Bernstein, Hans-Gert; Bogerts, Bernhard; Mawrin, Christian; Reutens, David C.; Speck, Oliver; Walter, Martin

    2013-01-01

    Ultra-high field magnetic resonance imaging (MRI) became increasingly relevant for in vivo neuroscientific research because of improved spatial resolutions. However, this is still the unchallenged domain of histological studies, which long played an important role in the investigation of neuropsychiatric disorders. While the field of biological psychiatry strongly advanced on macroscopic levels, current developments are rediscovering the richness of immunohistological information when attempting a multi-level systematic approach to brain function and dysfunction. For most studies, histology sections lost information on three-dimensional reconstructions. Translating histological sections to 3D-volumes would thus not only allow for multi-stain and multi-subject alignment in post mortem data, but also provide a crucial step in big data initiatives involving the network analyses currently performed with in vivo MRI. We therefore investigated potential pitfalls during integration of MR and histological information where no additional blockface information is available. We demonstrated that strengths and requirements from both methods can be effectively combined at a spatial resolution of 200 μm. However, the success of this approach is heavily dependent on choices of hardware, sequence and reconstruction. We provide a fully automated pipeline that optimizes histological 3D reconstructions, providing a potentially powerful solution not only for primary human post mortem research institutions in neuropsychiatric research, but also to help alleviate the massive workloads in neuroanatomical atlas initiatives. We further demonstrate (for the first time) the feasibility and quality of ultra-high spatial resolution (150 μm isotopic) imaging of the entire human brain MRI at 7T, offering new opportunities for analyses on MR-derived information. PMID:24098272

  11. Tracking the unconscious generation of free decisions using ultra-high field fMRI.

    PubMed

    Bode, Stefan; He, Anna Hanxi; Soon, Chun Siong; Trampel, Robert; Turner, Robert; Haynes, John-Dylan

    2011-01-01

    Recently, we demonstrated using functional magnetic resonance imaging (fMRI) that the outcome of free decisions can be decoded from brain activity several seconds before reaching conscious awareness. Activity patterns in anterior frontopolar cortex (BA 10) were temporally the first to carry intention-related information and thus a candidate region for the unconscious generation of free decisions. In the present study, the original paradigm was replicated and multivariate pattern classification was applied to functional images of frontopolar cortex, acquired using ultra-high field fMRI at 7 Tesla. Here, we show that predictive activity patterns recorded before a decision was made became increasingly stable with increasing temporal proximity to the time point of the conscious decision. Furthermore, detailed questionnaires exploring subjects' thoughts before and during the decision confirmed that decisions were made spontaneously and subjects were unaware of the evolution of their decision outcomes. These results give further evidence that FPC stands at the top of the prefrontal executive hierarchy in the unconscious generation of free decisions.

  12. Ultra-low field MRI food inspection system prototype

    NASA Astrophysics Data System (ADS)

    Kawagoe, Satoshi; Toyota, Hirotomo; Hatta, Junichi; Ariyoshi, Seiichiro; Tanaka, Saburo

    2016-11-01

    We develop an ultra-low field (ULF) magnetic resonance imaging (MRI) system using a high-temperature superconducting quantum interference device (HTS-SQUID) for food inspection. A two-dimensional (2D)-MR image is reconstructed from the grid processing raw data using the 2D fast Fourier transform method. In a previous study, we combined an LC resonator with the ULF-MRI system to improve the detection area of the HTS-SQUID. The sensitivity was improved, but since the experiments were performed in a semi-open magnetically shielded room (MSR), external noise was a problem. In this study, we develop a compact magnetically shielded box (CMSB), which has a small open window for transfer of a pre-polarized sample. Experiments were performed in the CMSB and 2D-MR images were compared with images taken in the semi-open MSR. A clear image of a disk-shaped water sample is obtained, with an outer dimension closer to that of the real sample than in the image taken in the semi-open MSR. Furthermore, the 2D-MR image of a multiple cell water sample is clearly reconstructed. These results show the applicability of the ULF-MRI system in food inspection.

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

    PubMed

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

    2005-05-01

    Hyperpolarized noble gases (HNGs) provide exciting possibilities for MR imaging at ultra-low magnetic field strengths (<0.15 T) due to the extremely high polarizations available from optical pumping. The fringe field of many superconductive magnets used in clinical MR imaging can provide a stable magnetic field for this purpose. In addition to offering the benefit of HNG MR imaging alongside conventional high field proton MRI, this approach offers the other useful advantage of providing different field strengths at different distances from the magnet. However, the extremely strong field gradients associated with the fringe field present a major challenge for imaging since impractically high active shim currents would be required to achieve the necessary homogeneity. In this work, a simple passive shimming method based on the placement of a small number of ferromagnetic pieces is proposed to reduce the fringe field inhomogeneities to a level that can be corrected using standard active shims. The method explicitly takes into account the strong variations of the field over the volume of the ferromagnetic pieces used to shim. The method is used to obtain spectra in the fringe field of a high-field (1.89 T) superconducting magnet from hyperpolarized 129Xe gas samples at two different ultra-low field strengths (8.5 and 17 mT). The linewidths of spectra measured from imaging phantoms (30 Hz) indicate a homogeneity sufficient for MRI of the rat lung.

  14. Distortion correction in EPI at ultra-high-field MRI using PSF mapping with optimal combination of shift detection dimension.

    PubMed

    Oh, Se-Hong; Chung, Jun-Young; In, Myung-Ho; Zaitsev, Maxim; Kim, Young-Bo; Speck, Oliver; Cho, Zang-Hee

    2012-10-01

    Despite its wide use, echo-planar imaging (EPI) suffers from geometric distortions due to off-resonance effects, i.e., strong magnetic field inhomogeneity and susceptibility. This article reports a novel method for correcting the distortions observed in EPI acquired at ultra-high-field such as 7 T. Point spread function (PSF) mapping methods have been proposed for correcting the distortions in EPI. The PSF shift map can be derived either along the nondistorted or the distorted coordinates. Along the nondistorted coordinates more information about compressed areas is present but it is prone to PSF-ghosting artifacts induced by large k-space shift in PSF encoding direction. In contrast, shift maps along the distorted coordinates contain more information in stretched areas and are more robust against PSF-ghosting. In ultra-high-field MRI, an EPI contains both compressed and stretched regions depending on the B0 field inhomogeneity and local susceptibility. In this study, we present a new geometric distortion correction scheme, which selectively applies the shift map with more information content. We propose a PSF-ghost elimination method to generate an artifact-free pixel shift map along nondistorted coordinates. The proposed method can correct the effects of the local magnetic field inhomogeneity induced by the susceptibility effects along with the PSF-ghost artifact cancellation. We have experimentally demonstrated the advantages of the proposed method in EPI data acquisitions in phantom and human brain using 7-T MRI. Copyright © 2011 Wiley Periodicals, Inc.

  15. Threats to ultra-high-field MRI

    NASA Astrophysics Data System (ADS)

    Le Bihan, Denis

    2009-08-01

    In 2004 the European Commission (EC) adopted a directive restricting occupational exposure to electromagnetic fields. This directive (2004/40/CE), which examines the possible health risks of the electromagnetic fields from mobile phones, Wi-Fi, Bluetooth and other devices, concluded that upper limits on radiation and applied electromagnetic fields are necessary to prevent workers from suffering any undue acute health effects. But although not initially intended, the biggest impact of the directive could be on magnetic resonance imaging (MRI), which is used in hospitals worldwide to produce images of unrivalled quality of the brain and other soft tissues.

  16. A scalable method to improve gray matter segmentation at ultra high field MRI.

    PubMed

    Gulban, Omer Faruk; Schneider, Marian; Marquardt, Ingo; Haast, Roy A M; De Martino, Federico

    2018-01-01

    High-resolution (functional) magnetic resonance imaging (MRI) at ultra high magnetic fields (7 Tesla and above) enables researchers to study how anatomical and functional properties change within the cortical ribbon, along surfaces and across cortical depths. These studies require an accurate delineation of the gray matter ribbon, which often suffers from inclusion of blood vessels, dura mater and other non-brain tissue. Residual segmentation errors are commonly corrected by browsing the data slice-by-slice and manually changing labels. This task becomes increasingly laborious and prone to error at higher resolutions since both work and error scale with the number of voxels. Here we show that many mislabeled, non-brain voxels can be corrected more efficiently and semi-automatically by representing three-dimensional anatomical images using two-dimensional histograms. We propose both a uni-modal (based on first spatial derivative) and multi-modal (based on compositional data analysis) approach to this representation and quantify the benefits in 7 Tesla MRI data of nine volunteers. We present an openly accessible Python implementation of these approaches and demonstrate that editing cortical segmentations using two-dimensional histogram representations as an additional post-processing step aids existing algorithms and yields improved gray matter borders. By making our data and corresponding expert (ground truth) segmentations openly available, we facilitate future efforts to develop and test segmentation algorithms on this challenging type of data.

  17. A scalable method to improve gray matter segmentation at ultra high field MRI

    PubMed Central

    De Martino, Federico

    2018-01-01

    High-resolution (functional) magnetic resonance imaging (MRI) at ultra high magnetic fields (7 Tesla and above) enables researchers to study how anatomical and functional properties change within the cortical ribbon, along surfaces and across cortical depths. These studies require an accurate delineation of the gray matter ribbon, which often suffers from inclusion of blood vessels, dura mater and other non-brain tissue. Residual segmentation errors are commonly corrected by browsing the data slice-by-slice and manually changing labels. This task becomes increasingly laborious and prone to error at higher resolutions since both work and error scale with the number of voxels. Here we show that many mislabeled, non-brain voxels can be corrected more efficiently and semi-automatically by representing three-dimensional anatomical images using two-dimensional histograms. We propose both a uni-modal (based on first spatial derivative) and multi-modal (based on compositional data analysis) approach to this representation and quantify the benefits in 7 Tesla MRI data of nine volunteers. We present an openly accessible Python implementation of these approaches and demonstrate that editing cortical segmentations using two-dimensional histogram representations as an additional post-processing step aids existing algorithms and yields improved gray matter borders. By making our data and corresponding expert (ground truth) segmentations openly available, we facilitate future efforts to develop and test segmentation algorithms on this challenging type of data. PMID:29874295

  18. Free induction decay MR signal measurements toward ultra-low field MRI with an optically pumped atomic magnetometer.

    PubMed

    Oida, Takenori; Kobayashi, Tetsuo

    2013-01-01

    Ultra-low field magnetic resonance imaging (ULF-MRI) has attracted attention because of its low running costs and minimum patient exposure. An optically pumped atomic magnetometer (OPAM) is a magnetic sensor with high sensitivity in the low frequency range, which does not require a cryogenic cooling system. In an effort to develop a ULF-MRI, we attempted to measure the free induction decay MR signals with an OPAM. We successfully detected the MR signals by combining an OPAM and a flux transformer, demonstrating the feasibility of the proposed system.

  19. High-resolution T2-weighted cervical cancer imaging: a feasibility study on ultra-high-field 7.0-T MRI with an endorectal monopole antenna.

    PubMed

    Hoogendam, Jacob P; Kalleveen, Irene M L; de Castro, Catalina S Arteaga; Raaijmakers, Alexander J E; Verheijen, René H M; van den Bosch, Maurice A A J; Klomp, Dennis W J; Zweemer, Ronald P; Veldhuis, Wouter B

    2017-03-01

    We studied the feasibility of high-resolution T 2 -weighted cervical cancer imaging on an ultra-high-field 7.0-T magnetic resonance imaging (MRI) system using an endorectal antenna of 4.7-mm thickness. A feasibility study on 20 stage IB1-IIB cervical cancer patients was conducted. All underwent pre-treatment 1.5-T MRI. At 7.0-T MRI, an external transmit/receive array with seven dipole antennae and a single endorectal monopole receive antenna were used. Discomfort levels were assessed. Following individualised phase-based B 1 + shimming, T 2 -weighted turbo spin echo sequences were completed. Patients had stage IB1 (n = 9), IB2 (n = 4), IIA1 (n = 1) or IIB (n = 6) cervical cancer. Discomfort (ten-point scale) was minimal at placement and removal of the endorectal antenna with a median score of 1 (range, 0-5) and 0 (range, 0-2) respectively. Its use did not result in adverse events or pre-term session discontinuation. To demonstrate feasibility, T 2 -weighted acquisitions from 7.0-T MRI are presented in comparison to 1.5-T MRI. Artefacts on 7.0-T MRI were due to motion, locally destructive B 1 interference, excessive B 1 under the external antennae and SENSE reconstruction. High-resolution T 2 -weighted 7.0-T MRI of stage IB1-IIB cervical cancer is feasible. The addition of an endorectal antenna is well tolerated by patients. • High resolution T 2 -weighted 7.0-T MRI of the inner female pelvis is challenging • We demonstrate a feasible approach for T 2 -weighted 7.0-T MRI of cervical cancer • An endorectal monopole receive antenna is well tolerated by participants • The endorectal antenna did not lead to adverse events or session discontinuation.

  20. Low-Cost High-Performance MRI

    NASA Astrophysics Data System (ADS)

    Sarracanie, Mathieu; Lapierre, Cristen D.; Salameh, Najat; Waddington, David E. J.; Witzel, Thomas; Rosen, Matthew S.

    2015-10-01

    Magnetic Resonance Imaging (MRI) is unparalleled in its ability to visualize anatomical structure and function non-invasively with high spatial and temporal resolution. Yet to overcome the low sensitivity inherent in inductive detection of weakly polarized nuclear spins, the vast majority of clinical MRI scanners employ superconducting magnets producing very high magnetic fields. Commonly found at 1.5-3 tesla (T), these powerful magnets are massive and have very strict infrastructure demands that preclude operation in many environments. MRI scanners are costly to purchase, site, and maintain, with the purchase price approaching $1 M per tesla (T) of magnetic field. We present here a remarkably simple, non-cryogenic approach to high-performance human MRI at ultra-low magnetic field, whereby modern under-sampling strategies are combined with fully-refocused dynamic spin control using steady-state free precession techniques. At 6.5 mT (more than 450 times lower than clinical MRI scanners) we demonstrate (2.5 × 3.5 × 8.5) mm3 imaging resolution in the living human brain using a simple, open-geometry electromagnet, with 3D image acquisition over the entire brain in 6 minutes. We contend that these practical ultra-low magnetic field implementations of MRI (<10 mT) will complement traditional MRI, providing clinically relevant images and setting new standards for affordable (<$50,000) and robust portable devices.

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

    NASA Astrophysics Data System (ADS)

    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.

  2. Sensitivity and specificity considerations for fMRI encoding, decoding, and mapping of auditory cortex at ultra-high field.

    PubMed

    Moerel, Michelle; De Martino, Federico; Kemper, Valentin G; Schmitter, Sebastian; Vu, An T; Uğurbil, Kâmil; Formisano, Elia; Yacoub, Essa

    2018-01-01

    Following rapid technological advances, ultra-high field functional MRI (fMRI) enables exploring correlates of neuronal population activity at an increasing spatial resolution. However, as the fMRI blood-oxygenation-level-dependent (BOLD) contrast is a vascular signal, the spatial specificity of fMRI data is ultimately determined by the characteristics of the underlying vasculature. At 7T, fMRI measurement parameters determine the relative contribution of the macro- and microvasculature to the acquired signal. Here we investigate how these parameters affect relevant high-end fMRI analyses such as encoding, decoding, and submillimeter mapping of voxel preferences in the human auditory cortex. Specifically, we compare a T 2 * weighted fMRI dataset, obtained with 2D gradient echo (GE) EPI, to a predominantly T 2 weighted dataset obtained with 3D GRASE. We first investigated the decoding accuracy based on two encoding models that represented different hypotheses about auditory cortical processing. This encoding/decoding analysis profited from the large spatial coverage and sensitivity of the T 2 * weighted acquisitions, as evidenced by a significantly higher prediction accuracy in the GE-EPI dataset compared to the 3D GRASE dataset for both encoding models. The main disadvantage of the T 2 * weighted GE-EPI dataset for encoding/decoding analyses was that the prediction accuracy exhibited cortical depth dependent vascular biases. However, we propose that the comparison of prediction accuracy across the different encoding models may be used as a post processing technique to salvage the spatial interpretability of the GE-EPI cortical depth-dependent prediction accuracy. Second, we explored the mapping of voxel preferences. Large-scale maps of frequency preference (i.e., tonotopy) were similar across datasets, yet the GE-EPI dataset was preferable due to its larger spatial coverage and sensitivity. However, submillimeter tonotopy maps revealed biases in assigned frequency

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

    PubMed Central

    Raven, Erika P.; Duyn, Jeff H.

    2016-01-01

    Magnetic resonance imaging (MRI) at ultra-high field (UHF) strengths (7 T and above) offers unique opportunities for studying the human brain with increased spatial resolution, contrast and sensitivity. However, its reliability can be compromised by factors such as head motion, image distortion and non-neural fluctuations of the functional MRI signal. The objective of this review is to provide a critical discussion of the advantages and trade-offs associated with UHF imaging, focusing on the application to studying brain–heart interactions. We describe how UHF MRI may provide contrast and resolution benefits for measuring neural activity of regions involved in the control and mediation of autonomic processes, and in delineating such regions based on anatomical MRI contrast. Limitations arising from confounding signals are discussed, including challenges with distinguishing non-neural physiological effects from the neural signals of interest that reflect cardiorespiratory function. We also consider how recently developed data analysis techniques may be applied to high-field imaging data to uncover novel information about brain–heart interactions. PMID:27044994

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

    PubMed

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

    2016-05-13

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

  5. MGH-USC Human Connectome Project Datasets with Ultra-High b-Value Diffusion MRI

    PubMed Central

    Fan, Qiuyun; Witzel, Thomas; Nummenmaa, Aapo; Van Dijk, Koene R.A.; Van Horn, John D.; Drews, Michelle K.; Somerville, Leah H.; Sheridan, Margaret A.; Santillana, Rosario M.; Snyder, Jenna; Hedden, Trey; Shaw, Emily E.; Hollinshead, Marisa O.; Renvall, Ville; Zanzonico, Roberta; Keil, Boris; Cauley, Stephen; Polimeni, Jonathan R.; Tisdall, Dylan; Buckner, Randy L.; Wedeen, Van J.; Wald, Lawrence L.; Toga, Arthur W.; Rosen, Bruce R.

    2015-01-01

    The MGH-USC CONNECTOM MRI scanner housed at the Massachusetts General Hospital (MGH) is a major hardware innovation of the Human Connectome Project (HCP). The 3T CONNECTOM scanner is capable of producing magnetic field gradient of up to 300 mT/m strength for in vivo human brain imaging, which greatly shortens the time spent on diffusion encoding, and decreases the signal loss due to T2 decay. To demonstrate the capability of the novel gradient system, data of healthy adult participants were acquired for this MGH-USC Adult Diffusion Dataset (N=35), minimally preprocessed, and shared through the Laboratory of Neuro Imaging Image Data Archive (LONI IDA) and the WU-Minn Connectome Database (ConnecomeDB). Another purpose of sharing the data is to facilitate methodological studies of diffusion MRI (dMRI) analyses utilizing high diffusion contrast, which perhaps is not easily feasible with standard MR gradient system. In addition, acquisition of the MGH-Harvard-USC Lifespan Dataset is currently underway to include 120 healthy participants ranging from 8 to 90 years old, which will also be shared through LONI IDA and ConnectomeDB. Here we describe the efforts of the MGH-USC HCP consortium in acquiring and sharing the ultra-high b-value diffusion MRI data and provide a report on data preprocessing and access. We conclude with a demonstration of the example data, along with results of standard diffusion analyses, including q-ball Orientation Distribution Function (ODF) reconstruction and tractography. PMID:26364861

  6. In vivo imaging of cortical pathology in multiple sclerosis using ultra-high field MRI

    PubMed Central

    Mainero, C; Benner, T; Radding, A; van der Kouwe, A; Jensen, R; Rosen, B R.; Kinkel, R P.

    2009-01-01

    Objective: We used ultra-high field MRI to visualize cortical lesion types described by neuropathology in 16 patients with multiple sclerosis (MS) compared with 8 age-matched controls; to characterize the contrast properties of cortical lesions including T2*, T2, T1, and phase images; and to investigate the relationship between cortical lesion types and clinical data. Methods: We collected, on a 7-T scanner, 2-dimensional fast low-angle shot (FLASH)-T2*-weighted spoiled gradient-echo, T2-weighted turbo spin-echo (TSE) images (0.33 × 033 × 1 mm3), and a 3-dimensional magnetization-prepared rapid gradient echo. Results: Overall, 199 cortical lesions were detected in patients on both FLASH-T2* and T2-TSE scans. Seven-tesla MRI allowed for characterization of cortical plaques into type I (leukocortical), type II (intracortical), and type III/IV (subpial extending partly or completely through the cortical width) lesions as described histopathologically. Types III and IV were the most frequent type of cortical plaques (50.2%), followed by type I (36.2%) and type II (13.6%) lesions. Each lesion type was more frequent in secondary progressive than in relapsing–remitting MS. This difference, however, was significant only for type III/IV lesions. T2*-weighted images showed the highest, while phase images showed the lowest, contrast-to-noise ratio for all cortical lesion types. In patients, the number of type III/IV lesions was associated with greater disability (p < 0.02 by Spearman test) and older age (p < 0.04 by Spearman test). Conclusions: Seven-tesla MRI detected different histologic cortical lesion types in our small multiple sclerosis (MS) sample, suggesting, if validated in a larger population, that it may prove a valuable tool to assess the contribution of cortical MS pathology to clinical disability. GLOSSARY ANOVA = analysis of variance; BN = background noise; CNR = contrast-to-noise ratio; DIR = double-inversion recovery; EDSS = Expanded Disability Status

  7. Ultra-high-field fMRI insights on insight: Neural correlates of the Aha!-moment.

    PubMed

    Tik, Martin; Sladky, Ronald; Luft, Caroline Di Bernardi; Willinger, David; Hoffmann, André; Banissy, Michael J; Bhattacharya, Joydeep; Windischberger, Christian

    2018-04-17

    Finding creative solutions to difficult problems is a fundamental aspect of human culture and a skill highly needed. However, the exact neural processes underlying creative problem solving remain unclear. Insightful problem solving tasks were shown to be a valid method for investigating one subcomponent of creativity: the Aha!-moment. Finding insightful solutions during a remote associates task (RAT) was found to elicit specific cortical activity changes. Considering the strong affective components of Aha!-moments, as manifested in the subjectively experienced feeling of relief following the sudden emergence of the solution of the problem without any conscious forewarning, we hypothesized the subcortical dopaminergic reward network to be critically engaged during Aha. To investigate those subcortical contributions to insight, we employed ultra-high-field 7 T fMRI during a German Version of the RAT. During this task, subjects were exposed to word triplets and instructed to find a solution word being associated with all the three given words. They were supposed to press a button as soon as they felt confident about their solution without further revision, allowing us to capture the exact event of Aha!-moment. Besides the finding on cortical involvement of the left anterior middle temporal gyrus (aMTG), here we showed for the first time robust subcortical activity changes related to insightful problem solving in the bilateral thalamus, hippocampus, and the dopaminergic midbrain comprising ventral tegmental area (VTA), nucleus accumbens (NAcc), and caudate nucleus. These results shed new light on the affective neural mechanisms underlying insightful problem solving. © 2018 The Authors Human Brain Mapping Published by Wiley Periodicals, Inc.

  8. Bridging the gap between system and cell: The role of ultra-high field MRI in human neuroscience.

    PubMed

    Turner, Robert; De Haan, Daniel

    2017-01-01

    The volume of published research at the levels of systems and cellular neuroscience continues to increase at an accelerating rate. At the same time, progress in psychiatric medicine has stagnated and scientific confidence in cognitive psychology research is under threat due to careless analysis methods and underpowered experiments. With the advent of ultra-high field MRI, with submillimeter image voxels, imaging neuroscience holds the potential to bridge the cellular and systems levels. Use of these accurate and precisely localized quantitative measures of brain activity may go far in providing more secure foundations for psychology, and hence for more appropriate treatment and management of psychiatric illness. However, fundamental issues regarding the construction of testable mechanistic models using imaging data require careful consideration. This chapter summarizes the characteristics of acceptable models of brain function and provides concise descriptions of the relevant types of neuroimaging data that have recently become available. Approaches to data-driven experiments and analyses are described that may lead to more realistic conceptions of the competences of neural assemblages, as they vary across the brain's complex neuroanatomy. © 2017 Elsevier B.V. All rights reserved.

  9. MGH-USC Human Connectome Project datasets with ultra-high b-value diffusion MRI.

    PubMed

    Fan, Qiuyun; Witzel, Thomas; Nummenmaa, Aapo; Van Dijk, Koene R A; Van Horn, John D; Drews, Michelle K; Somerville, Leah H; Sheridan, Margaret A; Santillana, Rosario M; Snyder, Jenna; Hedden, Trey; Shaw, Emily E; Hollinshead, Marisa O; Renvall, Ville; Zanzonico, Roberta; Keil, Boris; Cauley, Stephen; Polimeni, Jonathan R; Tisdall, Dylan; Buckner, Randy L; Wedeen, Van J; Wald, Lawrence L; Toga, Arthur W; Rosen, Bruce R

    2016-01-01

    The MGH-USC CONNECTOM MRI scanner housed at the Massachusetts General Hospital (MGH) is a major hardware innovation of the Human Connectome Project (HCP). The 3T CONNECTOM scanner is capable of producing a magnetic field gradient of up to 300 mT/m strength for in vivo human brain imaging, which greatly shortens the time spent on diffusion encoding, and decreases the signal loss due to T2 decay. To demonstrate the capability of the novel gradient system, data of healthy adult participants were acquired for this MGH-USC Adult Diffusion Dataset (N=35), minimally preprocessed, and shared through the Laboratory of Neuro Imaging Image Data Archive (LONI IDA) and the WU-Minn Connectome Database (ConnectomeDB). Another purpose of sharing the data is to facilitate methodological studies of diffusion MRI (dMRI) analyses utilizing high diffusion contrast, which perhaps is not easily feasible with standard MR gradient system. In addition, acquisition of the MGH-Harvard-USC Lifespan Dataset is currently underway to include 120 healthy participants ranging from 8 to 90 years old, which will also be shared through LONI IDA and ConnectomeDB. Here we describe the efforts of the MGH-USC HCP consortium in acquiring and sharing the ultra-high b-value diffusion MRI data and provide a report on data preprocessing and access. We conclude with a demonstration of the example data, along with results of standard diffusion analyses, including q-ball Orientation Distribution Function (ODF) reconstruction and tractography. Copyright © 2015 Elsevier Inc. All rights reserved.

  10. Understanding and manipulating the RF fields at high field MRI

    PubMed Central

    Ibrahim, Tamer S.; Hue, YiK-Kiong; Tang, Lin

    2015-01-01

    This paper presents a complete overview of the electromagnetics (radiofrequency aspect) of MRI at low and high fields. Using analytical formulations, numerical modeling (computational electromagnetics), and ultrahigh field imaging experiments, the physics that impacts the electromagnetic quantities associated with MRI, namely (1) the transmit field, (2) receive field, and (3) total electromagnetic power absorption, is analyzed. The physical interpretation of the above-mentioned quantities is investigated by electromagnetic theory, to understand ‘What happens, in terms of electromagnetics, when operating at different static field strengths?’ Using experimental studies and numerical simulations, this paper also examines the physical and technological feasibilities by which all or any of these specified electromagnetic quantities can be manipulated through techniques such as B1 shimming (phased array excitation) and signal combination using a receive array in order to advance MRI at high field strengths. Pertinent to this subject and with highly coupled coils operating at 7 T, this paper also presents the first phantom work on B1 shimming without B1 measurements. PMID:19621335

  11. Organic field effect transistor with ultra high amplification

    NASA Astrophysics Data System (ADS)

    Torricelli, Fabrizio

    2016-09-01

    High-gain transistors are essential for the large-scale circuit integration, high-sensitivity sensors and signal amplification in sensing systems. Unfortunately, organic field-effect transistors show limited gain, usually of the order of tens, because of the large contact resistance and channel-length modulation. Here we show organic transistors fabricated on plastic foils enabling unipolar amplifiers with ultra-gain. The proposed approach is general and opens up new opportunities for ultra-large signal amplification in organic circuits and sensors.

  12. [Methodological aspects of functional neuroimaging at high field strength: a critical review].

    PubMed

    Scheef, L; Landsberg, M W; Boecker, H

    2007-09-01

    The last few years have proven that high field magnetic resonance imaging (MRI) is superior in nearly every way to conventional equipment up to 1.5 tesla (T). Following the global success of 3T-scanners in research institutes and medical practices, a new generation of MRI devices with field strengths of 7T and higher is now on the horizon. The introduction of ultra high fields has brought MRI technology closer to the physical limitations and increasingly greater costs are required to achieve this goal. This article provides a critical overview of the advantages and problems of functional neuroimaging using ultra high field strengths. This review is principally limited to T2*-based functional imaging techniques not dependent on contrast agents. The main issues include the significance of high field technology with respect to SNR, CNR, resolution, and sequences, as well as artifacts, noise exposure, and SAR. Of great relevance is the discussion of parallel imaging, which will presumably determine the further development of high and ultra high field strengths. Finally, the importance of high field strengths for functional neuroimaging is explained by selected publications.

  13. Correlative Analysis of Vertebral Trabecular Bone Microarchitecture and Mechanical Properties: A Combined Ultra-high Field (7 Tesla) MRI and Biomechanical Investigation.

    PubMed

    Guenoun, Daphne; Fouré, Alexandre; Pithioux, Martine; Guis, Sandrine; Le Corroller, Thomas; Mattei, Jean-Pierre; Pauly, Vanessa; Guye, Maxime; Bernard, Monique; Chabrand, Patrick; Champsaur, Pierre; Bendahan, David

    2017-10-15

    High-resolution imaging and biomechanical investigation of ex-vivo vertebrae. The aim of this study was to assess bone microarchitecture of cadaveric vertebrae using ultra-high field (UHF) 7 Tesla magnetic resonance imaging (MRI) and to determine whether the corresponding microarchitecture parameters were related to bone mineral density (BMD) and bone strength assessed by dual-energy x-ray absorptiometry (DXA) and mechanical compression tests. Limitations of DXA for the assessment of bone fragility and osteoporosis have been recognized and criteria of microarchitecture alteration have been included in the definition of osteoporosis. Although vertebral fracture is the most common osteoporotic fracture, no study has assessed directly vertebral trabecular bone microarchitecture. BMD of 24 vertebrae (L2, L3, L4) from eight cadavers was investigated using DXA. The bone volume fraction (BVF), trabecular thickness (Tb.Th), and trabecular spacing (Tb.Sp) of each vertebra were quantified using UHF MRI. Measurements were performed by two operators to characterize the inter-rater reliability. The whole set of specimens underwent mechanical compression tests to failure and the corresponding failure stress was calculated. The inter-rater reliability for bone microarchitecture parameters was good with intraclass correlation coefficients ranging from 0.82 to 0.94. Failure load and stress were significantly correlated with BVF, Tb.Sp, and BMD (P < 0.05). Tb.Th was only correlated with the failure stress (P < 0.05). Multiple regression analysis demonstrated that the combination of BVF and BMD improved the prediction of the failure stress from an adjusted R = 0.384 for BMD alone to an adjusted R = 0.414. We demonstrated for the first time that the vertebral bone microarchitecture assessed with UHF MRI was significantly correlated with biomechanical parameters. Our data suggest that the multimodal assessment of BMD and trabecular bone microarchitecture with UHF MRI

  14. Magnetic Resonance Relaxometry at Low and Ultra low Fields.

    PubMed

    Volegov, P; Flynn, M; Kraus, R; Magnelind, P; Matlashov, A; Nath, P; Owens, T; Sandin, H; Savukov, I; Schultz, L; Urbaitis, A; Zotev, V; Espy, M

    2010-01-01

    Nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) are ubiquitous tools in science and medicine. NMR provides powerful probes of local and macromolecular chemical structure and dynamics. Recently it has become possible and practical to perform MR at very low fields (from 1 μT to 1 mT), the so-called ultra-low field (ULF) regime. Pulsed pre-polarizing fields greatly enhance the signal strength and allow flexibility in signal acquisition sequences. Improvements in SQUID sensor technology allow ultra-sensitive detection in a pulsed field environment.In this regime the proton Larmor frequencies (1 Hz - 100 kHz) of ULF MR overlap (on a time scale of 10 μs to 100 ms) with "slow" molecular dynamic processes such as diffusion, intra-molecular motion, chemical reactions, and biological processes such as protein folding, catalysis and ligand binding. The frequency dependence of relaxation at ultra-low fields may provide a probe for biomolecular dynamics on the millisecond timescale (protein folding and aggregation, conformational motions of enzymes, binding and structural fluctuations of coupled domains in allosteric mechanisms) relevant to host-pathogen interactions, biofuels, and biomediation. Also this resonance-enhanced coupling at ULF can greatly enhance contrast in medical applications of ULF-MRI resulting in better diagnostic techniques.We have developed a number of instruments and techniques to study relaxation vs. frequency at the ULF regime. Details of the techniques and results are presented.Ultra-low field methods are already being applied at LANL in brain imaging, and detection of liquid explosives at airports. However, the potential power of ultra-low field MR remains to be fully exploited.

  15. Ultra-Low Field SQUID-NMR using LN2 Cooled Cu Polarizing Field coil

    NASA Astrophysics Data System (ADS)

    Demachi, K.; Kawagoe, S.; Ariyoshi, S.; Tanaka, S.

    2017-07-01

    We are developing an Ultra-Low Field (ULF) Magnetic Resonance Imaging (MRI) system using a High-Temperature Superconductor superconducting quantum interference device (HTS rf-SQUID) for food inspection. The advantages of the ULF-NMR (Nuclear Magnetic Resonance) / MRI as compared with a conventional high field MRI are that they are compact and of low cost. In this study, we developed a ULF SQUID-NMR system using a polarizing coil to measure fat of which relaxation time T1 is shorter. The handmade polarizing coil was cooled by liquid nitrogen to reduce the resistance and accordingly increase the allowable current. The measured decay time of the polarizing field was 40 ms. The measurement system consisted of the liquid nitrogen cooled polarizing coil, a SQUID, a Cu wound flux transformer, a measurement field coil for the field of 47 μT, and an AC pulse coil for a 90°pulse field. The NMR measurements were performed in a magnetically shielded room to reduce the environmental magnetic field. The size of the sample was ϕ35 mm × L80 mm. After applying a polarizing field and a 90°pulse, an NMR signal was detected by the SQUID through the flux transformer. As a result, the NMR spectra of fat samples were obtained at 2.0 kHz corresponding to the measurement field Bm of 47 μT. The T1 relaxation time of the mineral oil measured in Bm was 45 ms. These results suggested that the ULF-NMR/MRI system has potential for food inspection.

  16. R1 dispersion contrast at high field with fast field-cycling MRI

    NASA Astrophysics Data System (ADS)

    Bödenler, Markus; Basini, Martina; Casula, Maria Francesca; Umut, Evrim; Gösweiner, Christian; Petrovic, Andreas; Kruk, Danuta; Scharfetter, Hermann

    2018-05-01

    Contrast agents with a strong R1 dispersion have been shown to be effective in generating target-specific contrast in MRI. The utilization of this R1 field dependence requires the adaptation of an MRI scanner for fast field-cycling (FFC). Here, we present the first implementation and validation of FFC-MRI at a clinical field strength of 3 T. A field-cycling range of ±100 mT around the nominal B0 field was realized by inserting an additional insert coil into an otherwise conventional MRI system. System validation was successfully performed with selected iron oxide magnetic nanoparticles and comparison to FFC-NMR relaxometry measurements. Furthermore, we show proof-of-principle R1 dispersion imaging and demonstrate the capability of generating R1 dispersion contrast at high field with suppressed background signal. With the presented ready-to-use hardware setup it is possible to investigate MRI contrast agents with a strong R1 dispersion at a field strength of 3 T.

  17. Dysprosium-Modified Tobacco Mosaic Virus Nanoparticles for Ultra-High-Field Magnetic Resonance and Near-Infrared Fluorescence Imaging of Prostate Cancer.

    PubMed

    Hu, He; Zhang, Yifan; Shukla, Sourabh; Gu, Yuning; Yu, Xin; Steinmetz, Nicole F

    2017-09-26

    The increasing prevalence of ultra-high-field magnetic resonance imaging (UHFMRI) in biomedical research and clinical settings will improve the resolution and diagnostic accuracy of MRI scans. However, better contrast agents are needed to achieve a satisfactory signal-to-noise ratio. Here, we report the synthesis of a bimodal contrast agent prepared by loading the internal cavity of tobacco mosaic virus (TMV) nanoparticles with a dysprosium (Dy 3+ ) complex and the near-infrared fluorescence (NIRF) dye Cy7.5. The external surface of TMV was conjugated with an Asp-Gly-Glu-Ala (DGEA) peptide via a polyethylene glycol linker to target integrin α 2 β 1 . The resulting nanoparticle (Dy-Cy7.5-TMV-DGEA) was stable and achieved a high transverse relaxivity in ultra-high-strength magnetic fields (326 and 399 mM -1 s -1 at 7 and 9.4 T, respectively). The contrast agent was also biocompatible (low cytotoxicity) and targeted PC-3 prostate cancer cells and tumors in vitro and in vivo as confirmed by bimodal NIRF imaging and T 2 -mapping UHFMRI. Our results show that Dy-Cy7.5-TMV-DGEA is suitable for multiscale MRI scanning from the cellular level to the whole body, particularly in the context of UHFMRI applications.

  18. R1 dispersion contrast at high field with fast field-cycling MRI.

    PubMed

    Bödenler, Markus; Basini, Martina; Casula, Maria Francesca; Umut, Evrim; Gösweiner, Christian; Petrovic, Andreas; Kruk, Danuta; Scharfetter, Hermann

    2018-05-01

    Contrast agents with a strong R 1 dispersion have been shown to be effective in generating target-specific contrast in MRI. The utilization of this R 1 field dependence requires the adaptation of an MRI scanner for fast field-cycling (FFC). Here, we present the first implementation and validation of FFC-MRI at a clinical field strength of 3 T. A field-cycling range of ±100 mT around the nominal B 0 field was realized by inserting an additional insert coil into an otherwise conventional MRI system. System validation was successfully performed with selected iron oxide magnetic nanoparticles and comparison to FFC-NMR relaxometry measurements. Furthermore, we show proof-of-principle R 1 dispersion imaging and demonstrate the capability of generating R 1 dispersion contrast at high field with suppressed background signal. With the presented ready-to-use hardware setup it is possible to investigate MRI contrast agents with a strong R 1 dispersion at a field strength of 3 T. Copyright © 2018 Elsevier Inc. All rights reserved.

  19. Analysis strategies for high-resolution UHF-fMRI data.

    PubMed

    Polimeni, Jonathan R; Renvall, Ville; Zaretskaya, Natalia; Fischl, Bruce

    2018-03-01

    Functional MRI (fMRI) benefits from both increased sensitivity and specificity with increasing magnetic field strength, making it a key application for Ultra-High Field (UHF) MRI scanners. Most UHF-fMRI studies utilize the dramatic increases in sensitivity and specificity to acquire high-resolution data reaching sub-millimeter scales, which enable new classes of experiments to probe the functional organization of the human brain. This review article surveys advanced data analysis strategies developed for high-resolution fMRI at UHF. These include strategies designed to mitigate distortion and artifacts associated with higher fields in ways that attempt to preserve spatial resolution of the fMRI data, as well as recently introduced analysis techniques that are enabled by these extremely high-resolution data. Particular focus is placed on anatomically-informed analyses, including cortical surface-based analysis, which are powerful techniques that can guide each step of the analysis from preprocessing to statistical analysis to interpretation and visualization. New intracortical analysis techniques for laminar and columnar fMRI are also reviewed and discussed. Prospects for single-subject individualized analyses are also presented and discussed. Altogether, there are both specific challenges and opportunities presented by UHF-fMRI, and the use of proper analysis strategies can help these valuable data reach their full potential. Copyright © 2017 Elsevier Inc. All rights reserved.

  20. MRI of the Musculoskeletal System: Advanced Applications using High and Ultrahigh Field MRI.

    PubMed

    Alizai, Hamza; Chang, Gregory; Regatte, Ravinder R

    2015-09-01

    In vivo MRI has revolutionized the diagnosis and treatment of musculoskeletal disorders over the past 3 decades. Traditionally performed at 1.5 T, MRI at higher field strengths offers several advantages over lower field strengths including increased signal-to-noise ratio, higher spatial resolution, improved spectral resolution for spectroscopy, improved sensitivity for X-nucleus imaging, and decreased image acquisition times. However, the physics of imaging at higher field strengths also presents technical challenges. These include B0 and B1+ field inhomogeneity, design and construction of dedicated radiofrequency (RF) coils for use at high field, increased chemical shift and susceptibility artifacts, increased RF energy deposition (specific absorption rate), increased metal artifacts, and changes in relaxation times compared with the lower field scanners. These challenges were overcome in optimizing high-field (HF) (3 T) MRI over a decade ago. HF MRI systems have since gained universal acceptance for clinical musculoskeletal imaging and have also been widely utilized for the study of musculoskeletal anatomy and physiology. Recently there has been an increasing interest in exploring musculoskeletal applications of ultrahigh field (UHF) (7 T) systems. However, technical challenges similar to those encountered when moving from 1.5 T to 3 T have to be overcome to optimize 7 T musculoskeletal imaging. In this narrative review, we discuss the many potential opportunities and technical challenges presented by the HF and UHF MRI systems. We highlight recent developments in in vivo imaging of musculoskeletal tissues that benefit most from HF imaging including cartilage, skeletal muscle, and bone. Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

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

    PubMed

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

    2017-10-01

    Intra-neural microstimulation (INMS) is a technique that allows the precise delivery of low-current electrical pulses into human peripheral nerves. Single unit INMS can be used to stimulate individual afferent nerve fibres during microneurography. Combining this with neuroimaging allows the unique monitoring of central nervous system activation in response to unitary, controlled tactile input, with functional magnetic resonance imaging (fMRI) providing exquisite spatial localisation of brain activity and magnetoencephalography (MEG) high temporal resolution. INMS systems suitable for use within electrophysiology laboratories have been available for many years. We describe an INMS system specifically designed to provide compatibility with both ultra-high field (7T) fMRI and MEG. Numerous technical and safety issues are addressed. The system is fully analogue, allowing for arbitrary frequency and amplitude INMS stimulation. Unitary recordings obtained within both the MRI and MEG screened-room environments are comparable with those obtained in 'clean' electrophysiology recording environments. Single unit INMS (current <7μA, 200μs pulses) of individual mechanoreceptive afferents produces appropriate and robust responses during fMRI and MEG. This custom-built MRI- and MEG-compatible stimulator overcomes issues with existing INMS approaches; it allows well-controlled switching between recording and stimulus mode, prevents electrical shocks because of long cable lengths, permits unlimited patterns of stimulation, and provides a system with improved work-flow and participant comfort. We demonstrate that the requirements for an INMS-integrated system, which can be used with both fMRI and MEG imaging systems, have been fully met. Copyright © 2017 The Author(s). Published by Elsevier B.V. All rights reserved.

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

    PubMed

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

    2008-10-01

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

  3. Fast Spectroscopic Imaging and Field Compensation Using Frequency Modulation at Ultra-High-Field

    NASA Astrophysics Data System (ADS)

    Jang, Albert Woo Ju

    The high energy phosphates (HEP) in the myocardium, which are critical to understanding the cardiac function in both normal and pathophysiologic states, can be assessed non-invasively in vivo using phosphorus-31 (31P) spectroscopy. Compared to proton, for the same volume and magnetic field strength, the available signal-to-noise (SNR) ratio of the HEP metabolites is orders of magnitude lower mainly due to its intrinsically low concentration. Hence, cardiac spectroscopy greatly benefits when performed at ultra-high-fields (UHF, ≥ 7 T), both in terms of increased SNR and increased spectroscopic resolution. However, at ultra-high-field strengths, complications arise from the RF transmit wavelength becoming comparable or smaller than the field-of-view (FOV), thus exhibiting wave-like behavior. Furthermore, even with the spectroscopic resolution afforded at UHF, measuring myocardial inorganic phosphate (Pi) is still a challenge and has been a major barrier in extracting the ATP turnover rate. Recently, an indirect way of extracting the ATP hydrolysis rate forgoing direct measurement of Pi was established. In this work, we combine this method with the T1 nom method to monitor the transmural distribution of forward creatine kinase reaction (kf,CK) and ATP hydrolysis rate (kr,ATPase) of the myocardium, effectively reducing data acquisition time by up to an order of magnitude. In addition, a new class of 2D FM pulses and multidimensional adiabatic pulses are presented, which can compensate for B1 inhomogeneity through its spatiotemporal properties. These pulses should be valuable for spectroscopic applications at ultra-high-fields.

  4. Whole-globe biomechanics using high-field MRI.

    PubMed

    Voorhees, Andrew P; Ho, Leon C; Jan, Ning-Jiun; Tran, Huong; van der Merwe, Yolandi; Chan, Kevin; Sigal, Ian A

    2017-07-01

    The eye is a complex structure composed of several interconnected tissues acting together, across the whole globe, to resist deformation due to intraocular pressure (IOP). However, most work in the ocular biomechanics field only examines the response to IOP over smaller regions of the eye. We used high-field MRI to measure IOP induced ocular displacements and deformations over the whole globe. Seven sheep eyes were obtained from a local abattoir and imaged within 48 h using MRI at multiple levels of IOP. IOP was controlled with a gravity perfusion system and a cannula inserted into the anterior chamber. T2-weighted imaging was performed to the eyes serially at 0 mmHg, 10 mmHg, 20 mmHg and 40 mmHg of IOP using a 9.4 T MRI scanner. Manual morphometry was conducted using 3D visualization software to quantify IOP-induced effects at the globe scale (e.g. axial length and equatorial diameters) or optic nerve head scale (e.g. canal diameter, peripapillary sclera bowing). Measurement sensitivity analysis was conducted to determine measurement precision. High-field MRI revealed an outward bowing of the posterior sclera and anterior bulging of the cornea due to IOP elevation. Increments in IOP from 10 to 40 mmHg caused measurable increases in axial length in 6 of 7 eyes of 7.9 ± 5.7% (mean ± SD). Changes in equatorial diameter were minimal, 0.4 ± 1.2% between 10 and 40 mmHg, and in all cases less than the measurement sensitivity. The effects were nonlinear, with larger deformations at normal IOPs (10-20 mmHg) than at elevated IOPs (20-40 mmHg). IOP also caused measurable increases in the nasal-temporal scleral canal diameter of 13.4 ± 9.7% between 0 and 20 mmHg, but not in the superior-inferior diameter. This study demonstrates that high-field MRI can be used to visualize and measure simultaneously the effects of IOP over the whole globe, including the effects on axial length and equatorial diameter, posterior sclera displacement and bowing, and even

  5. Ultra-high field upper extremity peripheral nerve and non-contrast enhanced vascular imaging

    PubMed Central

    Raval, Shailesh B.; Britton, Cynthia A.; Zhao, Tiejun; Krishnamurthy, Narayanan; Santini, Tales; Gorantla, Vijay S.; Ibrahim, Tamer S.

    2017-01-01

    Objective The purpose of this study was to explore the efficacy of Ultra-high field [UHF] 7 Tesla [T] MRI as compared to 3T MRI in non-contrast enhanced [nCE] imaging of structural anatomy in the elbow, forearm, and hand [upper extremity]. Materials and method A wide range of sequences including T1 weighted [T1] volumetric interpolate breath-hold exam [VIBE], T2 weighted [T2] double-echo steady state [DESS], susceptibility weighted imaging [SWI], time-of-flight [TOF], diffusion tensor imaging [DTI], and diffusion spectrum imaging [DSI] were optimized and incorporated with a radiofrequency [RF] coil system composed of a transverse electromagnetic [TEM] transmit coil combined with an 8-channel receive-only array for 7T upper extremity [UE] imaging. In addition, Siemens optimized protocol/sequences were used on a 3T scanner and the resulting images from T1 VIBE and T2 DESS were compared to that obtained at 7T qualitatively and quantitatively [SWI was only qualitatively compared]. DSI studio was utilized to identify nerves based on analysis of diffusion weighted derived fractional anisotropy images. Images of forearm vasculature were extracted using a paint grow manual segmentation method based on MIPAV [Medical Image Processing, Analysis, and Visualization]. Results High resolution and high quality signal-to-noise ratio [SNR] and contrast-to-noise ratio [CNR]—images of the hand, forearm, and elbow were acquired with nearly homogeneous 7T excitation. Measured [performed on the T1 VIBE and T2 DESS sequences] SNR and CNR values were almost doubled at 7T vs. 3T. Cartilage, synovial fluid and tendon structures could be seen with higher clarity in the 7T T1 and T2 weighted images. SWI allowed high resolution and better quality imaging of large and medium sized arteries and veins, capillary networks and arteriovenous anastomoses at 7T when compared to 3T. 7T diffusion weighted sequence [not performed at 3T] demonstrates that the forearm nerves are clearly delineated by

  6. Field Evaluation of Ultra-High Pressure Water Systems for Runway Rubber Removal

    DTIC Science & Technology

    2014-04-01

    ER D C/ G SL T R- 14 -1 1 Field Evaluation of Ultra-High Pressure Water Systems for Runway Rubber Removal G eo te ch ni ca l a nd S tr...Field Evaluation of Ultra-High Pressure Water Systems for Runway Rubber Removal Aaron B. Pullen Applied Research Associates, Inc. 421 Oak Avenue...collaboration with Applied Research Associates, Inc. (ARA). Several types of commercial UHPW water blasting systems were tested on an ungrooved portland cement

  7. High-field fMRI unveils orientation columns in humans.

    PubMed

    Yacoub, Essa; Harel, Noam; Ugurbil, Kâmil

    2008-07-29

    Functional (f)MRI has revolutionized the field of human brain research. fMRI can noninvasively map the spatial architecture of brain function via localized increases in blood flow after sensory or cognitive stimulation. Recent advances in fMRI have led to enhanced sensitivity and spatial accuracy of the measured signals, indicating the possibility of detecting small neuronal ensembles that constitute fundamental computational units in the brain, such as cortical columns. Orientation columns in visual cortex are perhaps the best known example of such a functional organization in the brain. They cannot be discerned via anatomical characteristics, as with ocular dominance columns. Instead, the elucidation of their organization requires functional imaging methods. However, because of insufficient sensitivity, spatial accuracy, and image resolution of the available mapping techniques, thus far, they have not been detected in humans. Here, we demonstrate, by using high-field (7-T) fMRI, the existence and spatial features of orientation- selective columns in humans. Striking similarities were found with the known spatial features of these columns in monkeys. In addition, we found that a larger number of orientation columns are devoted to processing orientations around 90 degrees (vertical stimuli with horizontal motion), whereas relatively similar fMRI signal changes were observed across any given active column. With the current proliferation of high-field MRI systems and constant evolution of fMRI techniques, this study heralds the exciting prospect of exploring unmapped and/or unknown columnar level functional organizations in the human brain.

  8. Concurrent recording of RF pulses and gradient fields - comprehensive field monitoring for MRI.

    PubMed

    Brunner, David O; Dietrich, Benjamin E; Çavuşoğlu, Mustafa; Wilm, Bertram J; Schmid, Thomas; Gross, Simon; Barmet, Christoph; Pruessmann, Klaas P

    2016-09-01

    Reconstruction of MRI data is based on exact knowledge of all magnetic field dynamics, since the interplay of RF and gradient pulses generates the signal, defines the contrast and forms the basis of resolution in spatial and spectral dimensions. Deviations caused by various sources, such as system imperfections, delays, eddy currents, drifts or externally induced fields, can therefore critically limit the accuracy of MRI examinations. This is true especially at ultra-high fields, because many error terms scale with the main field strength, and higher available SNR renders even smaller errors relevant. Higher baseline field also often requires higher acquisition bandwidths and faster signal encoding, increasing hardware demands and the severity of many types of hardware imperfection. To address field imperfections comprehensively, in this work we propose to expand the concept of magnetic field monitoring to also encompass the recording of RF fields. In this way, all dynamic magnetic fields relevant for spin evolution are covered, including low- to audio-frequency magnetic fields as produced by main magnets, gradients and shim systems, as well as RF pulses generated with single- and multiple-channel transmission systems. The proposed approach permits field measurements concurrently with actual MRI procedures on a strict common time base. The combined measurement is achieved with an array of miniaturized field probes that measure low- to audio-frequency fields via (19) F NMR and simultaneously pick up RF pulses in the MRI system's (1) H transmit band. Field recordings can form the basis of system calibration, retrospective correction of imaging data or closed-loop feedback correction, all of which hold potential to render MRI more robust and relax hardware requirements. The proposed approach is demonstrated for a range of imaging methods performed on a 7 T human MRI system, including accelerated multiple-channel RF pulses. Copyright © 2015 John Wiley & Sons, Ltd

  9. Ultra-high-field (9.4 T) MRI Analysis of Contrast Agent Transport Across the Blood-Perilymph Barrier and Intrastrial Fluid-Blood Barrier in the Mouse Inner Ear.

    PubMed

    Counter, S Allen; Nikkhou-Aski, Sahar; Damberg, Peter; Berglin, Cecilia Engmér; Laurell, Göran

    2017-08-01

    Effective paramagnetic contrast agent for the penetration of the perilymphatic spaces of the scala tympani, scala vestibuli, and scala media of the mouse inner ear can be determined using intravenous injection of various gadolinium (Gd) complexes and ultra-high-field magnetic resonance imaging (MRI) at 9.4 Tesla. A number of contrast agents have been explored in experimental high-field MRI to determine the most effective Gd complex for ideal signal-to-noise ratio and maximal visualization of the in vivo mammalian inner ear in analyzing the temporal and spatial parameters involved in drug penetration of the blood-perilymph barrier and intrastrial fluid-blood barrier in the mouse model using MRI. Gadoteric acid (Dotarem), Gadobutrol (Gadovist), Gadodiamide (Omniscan), Gadopent acid (Magnevist), and Mangafodipir (Teslascan) were administered intravenously using the tail vein of 60 Balb/C mice. High-resolution T1 images of drug penetration were acquired with a horizontal 9.4 T Agilent magnet after intravenously injection. Signal intensity was used as a metric of temporal and spatial parameters of drug delivery and penetration of the perilymphatic and endolymphatic spaces. ANOVA analysis of the area under the curve of intensity enhancement in perilymph revealed a significant difference (p < 0.05) in the scalae uptake using different contrast agents (F (3,25) = 3.54, p = 0.029). The Gadoteric acid complex Dotarem was found to be the most effective Gd compound in terms of rapid, morphological enhancement for analysis of the temporal, and spatial distribution in the perilymphatic space of the inner ear. Gadoteric acid (Dotarem) demonstrated efficacy as a contrast agent for enhanced visualization of the perilymphatic spaces of the inner ear labyrinthine in the mouse, including the scala tympani and scala vestibuli of the cochlea, and the semicircular canals of the vestibular apparatus. These findings may inform the clinical application of Gd compounds in

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

    PubMed

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

    2015-01-01

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

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

    PubMed Central

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

    2015-01-01

    Introduction Neuroimaging of macaques at ultra-high field (UHF) is usually conducted by combining a volume coil for transmit (Tx) and a phased array coil for receive (Rx) tightly enclosing the monkey’s head. Good results have been achieved using vertical or horizontal magnets with implanted or near-surface coils. An alternative and less costly approach, the travelling-wave (TW) excitation concept, may offer more flexible experimental setups on human whole-body UHF magnetic resonance imaging (MRI) systems, which are now more widely available. Goal of the study was developing and validating the TW concept for in vivo primate MRI. Methods The TW Primate System (TWPS) uses the radio frequency shield of the gradient system of a human whole-body 7 T MRI system as a waveguide to propagate a circularly polarized B1 field represented by the TE11 mode. This mode is excited by a specifically designed 2-port patch antenna. For receive, a customized neuroimaging monkey head receive-only coil was designed. Field simulation was used for development and evaluation. Signal-to-noise ratio (SNR) was compared with data acquired with a conventional monkey volume head coil consisting of a homogeneous transmit coil and a 12-element receive coil. Results The TWPS offered good image homogeneity in the volume-of-interest Turbo spin echo images exhibited a high contrast, allowing a clear depiction of the cerebral anatomy. As a prerequisite for functional MRI, whole brain ultrafast echo planar images were successfully acquired. Conclusion The TWPS presents a promising new approach to fMRI of macaques for research groups with access to a horizontal UHF MRI system. PMID:26066653

  12. Improvements in RF Shimming in High Field MRI Using High Permittivity Materials With Low Order Pre-Fractal Geometries.

    PubMed

    Schmidt, Rita; Webb, Andrew

    2016-08-01

    Ultra-high field MRI is an area of great interest for clinical research and basic science due to the increased signal-to-noise, spatial resolution and magnetic-susceptibility-based contrast. However, the fact that the electromagnetic wavelength in tissue is comparable to the relevant body dimensions means that the uniformity of the excitation field is much poorer than at lower field strengths. In addition to techniques such as transmit arrays, one simple but effective method to counteract this effect is to use high permittivity "pads". Very high permittivities enable thinner, flexible pads to be used, but the limiting factor is wavelength effects within the pads themselves, which can lead to image artifacts. So far, all studies have used simple continuous rectangular/circular pad geometries. In this work we investigate how the wavelength effects can be partially mitigated utilizing shaped pad with holes. Several arrangements have been simulated, including low order pre-fractal geometries, which maintain the overall coverage of the pad, but can provide better image homogeneity in the region of interest or higher sensitivity depending on the setup. Experimental data in the form of in vivo human images at 7T were acquired to validate the simulation results.

  13. Awake craniotomy, electrophysiologic mapping, and tumor resection with high-field intraoperative MRI.

    PubMed

    Parney, Ian F; Goerss, Stephan J; McGee, Kiaran; Huston, John; Perkins, William J; Meyer, Frederic B

    2010-05-01

    Awake craniotomy and electrophysiologic mapping (EPM) is an established technique to facilitate the resection of near eloquent cortex. Intraoperative magnetic resonance imaging (iMRI) is increasingly used to aid in the resection of intracranial lesions. Standard draping protocols in high-field iMRI units make awake craniotomies challenging, and only two groups have previously reported combined EPM and high-field iMRI. We present an illustrative case describing a simple technique for combining awake craniotomy and EPM with high-field iMRI. A movable platter is used to transfer the patient from the operating table to a transport trolley and into the adjacent MRI and still maintaining the patient's surgical position. This system allows excess drapes to be removed, facilitating awake craniotomy. A 57-year-old right-handed man presented with new onset seizures. Magnetic resonance imaging demonstrated a large left temporal mass. The patient underwent an awake, left frontotemporal craniotomy. The EPM demonstrated a single critical area for speech in his inferior frontal gyrus. After an initial tumor debulking, the scalp flap was loosely approximated, the wound was covered with additional drapes, and the excess surrounding drapes were trimmed. An iMRI was obtained. The image-guidance system was re-registered and the patient was redraped. Additional resection was performed, allowing extensive removal of what proved to be an anaplastic astrocytoma. The patient tolerated this well without any new neurological deficits. Standard protocols for positioning and draping in high-field iMRI units make awake craniotomies problematic. This straightforward technique for combined awake EPM and iMRI may facilitate safe removal of large lesions in eloquent cortex. Copyright © 2010 Elsevier Inc. All rights reserved.

  14. Technical Note: Experimental results from a prototype high-field inline MRI-linac

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Liney, G. P., E-mail: gary.liney@sswahs.nsw.gov.au

    Purpose: The pursuit of real-time image guided radiotherapy using optimal tissue contrast has seen the development of several hybrid magnetic resonance imaging (MRI)-treatment systems, high field and low field, and inline and perpendicular configurations. As part of a new MRI-linac program, an MRI scanner was integrated with a linear accelerator to enable investigations of a coupled inline MRI-linac system. This work describes results from a prototype experimental system to demonstrate the feasibility of a high field inline MR-linac. Methods: The magnet is a 1.5 T MRI system (Sonata, Siemens Healthcare) was located in a purpose built radiofrequency (RF) cage enablingmore » shielding from and close proximity to a linear accelerator with inline (and future perpendicular) orientation. A portable linear accelerator (Linatron, Varian) was installed together with a multileaf collimator (Millennium, Varian) to provide dynamic field collimation and the whole assembly built onto a stainless-steel rail system. A series of MRI-linac experiments was performed to investigate (1) image quality with beam on measured using a macropodine (kangaroo) ex vivo phantom; (2) the noise as a function of beam state measured using a 6-channel surface coil array; and (3) electron contamination effects measured using Gafchromic film and an electronic portal imaging device (EPID). Results: (1) Image quality was unaffected by the radiation beam with the macropodine phantom image with the beam on being almost identical to the image with the beam off. (2) Noise measured with a surface RF coil produced a 25% elevation of background intensity when the radiation beam was on. (3) Film and EPID measurements demonstrated electron focusing occurring along the centerline of the magnet axis. Conclusions: A proof-of-concept high-field MRI-linac has been built and experimentally characterized. This system has allowed us to establish the efficacy of a high field inline MRI-linac and study a number of the

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

    NASA Astrophysics Data System (ADS)

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

    2017-08-01

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

  16. Restoration of MRI Data for Field Nonuniformities using High Order Neighborhood Statistics

    PubMed Central

    Hadjidemetriou, Stathis; Studholme, Colin; Mueller, Susanne; Weiner, Michael; Schuff, Norbert

    2007-01-01

    MRI at high magnetic fields (> 3.0 T ) is complicated by strong inhomogeneous radio-frequency fields, sometimes termed the “bias field”. These lead to nonuniformity of image intensity, greatly complicating further analysis such as registration and segmentation. Existing methods for bias field correction are effective for 1.5 T or 3.0 T MRI, but are not completely satisfactory for higher field data. This paper develops an effective bias field correction for high field MRI based on the assumption that the nonuniformity is smoothly varying in space. Also, nonuniformity is quantified and unmixed using high order neighborhood statistics of intensity cooccurrences. They are computed within spherical windows of limited size over the entire image. The restoration is iterative and makes use of a novel stable stopping criterion that depends on the scaled entropy of the cooccurrence statistics, which is a non monotonic function of the iterations; the Shannon entropy of the cooccurrence statistics normalized to the effective dynamic range of the image. The algorithm restores whole head data, is robust to intense nonuniformities present in high field acquisitions, and is robust to variations in anatomy. This algorithm significantly improves bias field correction in comparison to N3 on phantom 1.5 T head data and high field 4 T human head data. PMID:18193095

  17. High longitudinal relaxivity of ultra-small gadolinium oxide prepared by microsecond laser ablation in diethylene glycol

    NASA Astrophysics Data System (ADS)

    Luo, Ningqi; Tian, Xiumei; Xiao, Jun; Hu, Wenyong; Yang, Chuan; Li, Li; Chen, Dihu

    2013-04-01

    Ultra-small gadolinium oxide (Gd2O3) can be used as T1-weighted Magnetic Resonance Imaging (MRI) contrast agent own to its high longitudinal relaxivity (r1) and has attracted intensive attention in these years. In this paper, ultra-small Gd2O3 nanoparticles of 3.8 nm in diameter have been successfully synthesized by a microsecond laser ablating a gadolinium (Gd) target in diethylene glycol (DEG). The growth inhibition effect induced by the large viscosity of DEG makes it possible to synthesize ultra-small Gd2O3 by laser ablation in DEG. The r1 value and T1-weighted MR images are measured by a 3.0 T MRI spectroscope. The results show these nanoparticles with a high r1 value of 9.76 s-1 mM-1 to be good MRI contrast agents. We propose an explanation for the high r1 value of ultra-small Gd2O3 by considering the decreasing factor (surface to volume ratio of the nanoparticles, S/V) and the increasing factor (water hydration number of the Gd3+ on Gd2O3 surface, q), which offer a new look into the relaxivity studies of MRI contrast agents. Our research provides a new approach to preparing ultra-small Gd2O3 of high r1 value by laser ablation in DEG and develops the understanding of high relaxivity of ultra-small Gd2O3 MRI contrast agents.

  18. TH-AB-BRA-12: Experimental Results From the First High-Field Inline MRI-Linac

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Keall, P; Dong, B; Zhang, K

    Purpose: The pursuit of real-time image guided radiotherapy using optimal tissue contrast has seen the development of several hybrid MRI-treatment systems, high field and low field, and inline and perpendicular configurations. As part of a new MRI-Linac program, an MRI scanner was integrated with a linear accelerator to enable investigations of a coupled inline MRI-Linac system. This work describes our experimental results from the first high-field inline MRI-Linac. Methods: A 1.5 Tesla magnet (Sonata, Siemens) was located in a purpose built RF cage enabling shielding from and close proximity to a linear accelerator with inline orientation. A portable linear acceleratormore » (Linatron, Varian) was installed together with a multi-leaf collimator (Millennium, Varian) to provide dynamic field collimation and the whole assembly built onto a stainless-steel rail system. A series of MRI-Linac experiments was performed to investigate: (1) image quality with beam on measured using a macropodine (kangaroo) ex vivo phantom; (2) the noise as a function of beam state measured using a 6-channel surface coil array and; (3) electron focusing measured using GafChromic film. Results: (1) The macropodine phantom image quality with the beam on was almost identical to that with the beam off. (2) Noise measured with a surface RF coil produced a 25% elevation of background noise when the radiation beam was on. (3) Film measurements demonstrated electron focusing occurring at the center of the radiation field. Conclusion: The first high-field MRI-Linac has been built and experimentally characterized. This system has allowed us to establish the efficacy of a high field in-line MRI-Linac and study a number of the technical challenges and solutions. Supported by the Australian National Health and Medical Research Council, the Australian Research Council, the Australian Cancer Research Foundation and the Health and Hospitals Fund.« less

  19. Fuzzy cluster analysis of high-field functional MRI data.

    PubMed

    Windischberger, Christian; Barth, Markus; Lamm, Claus; Schroeder, Lee; Bauer, Herbert; Gur, Ruben C; Moser, Ewald

    2003-11-01

    Functional magnetic resonance imaging (fMRI) based on blood-oxygen level dependent (BOLD) contrast today is an established brain research method and quickly gains acceptance for complementary clinical diagnosis. However, neither the basic mechanisms like coupling between neuronal activation and haemodynamic response are known exactly, nor can the various artifacts be predicted or controlled. Thus, modeling functional signal changes is non-trivial and exploratory data analysis (EDA) may be rather useful. In particular, identification and separation of artifacts as well as quantification of expected, i.e. stimulus correlated, and novel information on brain activity is important for both, new insights in neuroscience and future developments in functional MRI of the human brain. After an introduction on fuzzy clustering and very high-field fMRI we present several examples where fuzzy cluster analysis (FCA) of fMRI time series helps to identify and locally separate various artifacts. We also present and discuss applications and limitations of fuzzy cluster analysis in very high-field functional MRI: differentiate temporal patterns in MRI using (a) a test object with static and dynamic parts, (b) artifacts due to gross head motion artifacts. Using a synthetic fMRI data set we quantitatively examine the influences of relevant FCA parameters on clustering results in terms of receiver-operator characteristics (ROC) and compare them with a commonly used model-based correlation analysis (CA) approach. The application of FCA in analyzing in vivo fMRI data is shown for (a) a motor paradigm, (b) data from multi-echo imaging, and (c) a fMRI study using mental rotation of three-dimensional cubes. We found that differentiation of true "neural" from false "vascular" activation is possible based on echo time dependence and specific activation levels, as well as based on their signal time-course. Exploratory data analysis methods in general and fuzzy cluster analysis in particular may

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

    PubMed

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

    2016-01-01

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

  1. The Galactic Magnetic Field and Ultra-High Energy Cosmic Rays

    NASA Astrophysics Data System (ADS)

    Urban, Federico R.

    The Galactic Magnetic Field is a peeving and importune screen between Ultra-High Energy Cosmic Rays and us cosmologists, engaged in the combat to unveil their properties and origin, as it deviates their paths towards the Earth in unpredictable ways. I will, in this order: briefly review the available field models on the market; explain a little trick which allows one to obtain cosmic rays deflection variances without even knowing what the (random) GMF model is; and argue that there is a lack of anisotropy in the large scales cosmic rays signal, which the Galactic field can do nothing about.

  2. Ultra high spatial and temporal resolution breast imaging at 7T.

    PubMed

    van de Bank, B L; Voogt, I J; Italiaander, M; Stehouwer, B L; Boer, V O; Luijten, P R; Klomp, D W J

    2013-04-01

    There is a need to obtain higher specificity in the detection of breast lesions using MRI. To address this need, Dynamic Contrast-Enhanced (DCE) MRI has been combined with other structural and functional MRI techniques. Unfortunately, owing to time constraints structural images at ultra-high spatial resolution can generally not be obtained during contrast uptake, whereas the relatively low spatial resolution of functional imaging (e.g. diffusion and perfusion) limits the detection of small lesions. To be able to increase spatial as well as temporal resolution simultaneously, the sensitivity of MR detection needs to increase as well as the ability to effectively accelerate the acquisition. The required gain in signal-to-noise ratio (SNR) can be obtained at 7T, whereas acceleration can be obtained with high-density receiver coil arrays. In this case, morphological imaging can be merged with DCE-MRI, and other functional techniques can be obtained at higher spatial resolution, and with less distortion [e.g. Diffusion Weighted Imaging (DWI)]. To test the feasibility of this concept, we developed a unilateral breast coil for 7T. It comprises a volume optimized dual-channel transmit coil combined with a 30-channel receive array coil. The high density of small coil elements enabled efficient acceleration in any direction to acquire ultra high spatial resolution MRI of close to 0.6 mm isotropic detail within a temporal resolution of 69 s, high spatial resolution MRI of 1.5 mm isotropic within an ultra high temporal resolution of 6.7 s and low distortion DWI at 7T, all validated in phantoms, healthy volunteers and a patient with a lesion in the right breast classified as Breast Imaging Reporting and Data System (BI-RADS) IV. Copyright © 2012 John Wiley & Sons, Ltd.

  3. Multishot PROPELLER for high-field preclinical MRI.

    PubMed

    Pandit, Prachi; Qi, Yi; Story, Jennifer; King, Kevin F; Johnson, G Allan

    2010-07-01

    With the development of numerous mouse models of cancer, there is a tremendous need for an appropriate imaging technique to study the disease evolution. High-field T(2)-weighted imaging using PROPELLER (Periodically Rotated Overlapping ParallEL Lines with Enhanced Reconstruction) MRI meets this need. The two-shot PROPELLER technique presented here provides (a) high spatial resolution, (b) high contrast resolution, and (c) rapid and noninvasive imaging, which enables high-throughput, longitudinal studies in free-breathing mice. Unique data collection and reconstruction makes this method robust against motion artifacts. The two-shot modification introduced here retains more high-frequency information and provides higher signal-to-noise ratio than conventional single-shot PROPELLER, making this sequence feasible at high fields, where signal loss is rapid. Results are shown in a liver metastases model to demonstrate the utility of this technique in one of the more challenging regions of the mouse, which is the abdomen. (c) 2010 Wiley-Liss, Inc.

  4. Ultra high field TOF-MRA: A method to visualize small cerebral vessels. 7T TOF-MRA sequence parameters on different MRI scanners - Literature review.

    PubMed

    Grochowski, Cezary; Staśkiewicz, Grzegorz

    Time-of-flight (TOF) angiography is a technique allowing to visualize the blood flow in vessels. 7T ToF-MRA is able to visualize the whole Circle of Willis including small perforating branches without any known side effects as opposed to usually used DSA and CTA with high exposition to the radiation and high doses of contrast as far as CTA is concerned. The aim of this review is to describe ultra-high field ToF-MRA and present different protocol data depending on the scanner used in the study. PubMed, Embase, Ovid, Google Scholar databases were searched. Selection of studies for this systematic review included 7T magnetic resonance angiography studies. We searched for type of head coil used in various studies, flip angle, echo time, repetition time, field-of-view (FOV), number of slices per slab, matrix, voxel size and acquisition time. Visualization for the small perforating vessels of the Circle of Willis, that are not fully visualized using low-field-strength MRA is improving with increasing magnetic field strength, which has been proved by several studies. Ultra-high filed ToF-MRA has found to be a superior method in depicting cerebral microvasculature. 7T ToF-MRA seems to be a reliable method for visualization of arteries up to the second order cerebral arteries and has a potential to replace DSA. Copyright © 2017. Published by Elsevier Urban & Partner Sp. z o.o.

  5. Diagnostic relevance of high field MRI in clinical neuroradiology: the advantages and challenges of driving a sports car.

    PubMed

    Wattjes, Mike P; Barkhof, Frederik

    2012-11-01

    High field MRI operating at 3 T is increasingly being used in the field of neuroradiology on the grounds that higher magnetic field strength should theoretically lead to a higher diagnostic accuracy in the diagnosis of several disease entities. This Editorial discusses the exhaustive review by Wardlaw and colleagues of research comparing 3 T MRI with 1.5 T MRI in the field of neuroradiology. Interestingly, the authors found no convincing evidence of improved image quality, diagnostic accuracy, or reduced total examination times using 3 T MRI instead of 1.5 T MRI. These findings are highly relevant since a new generation of high field MRI systems operating at 7 T has recently been introduced. • Higher magnetic field strengths do not necessarily lead to a better diagnostic accuracy. • Disadvantages of high field MR systems have to be considered in clinical practice. • Higher field strengths are needed for functional imaging, spectroscopy, etc. • Disappointingly there are few direct comparisons of 1.5 and 3 T MRI. • Whether the next high field MR generation (7 T) will improve diagnostic accuracy has to be investigated.

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

    PubMed Central

    Vegh, Viktor; Reutens, David C.

    2016-01-01

    Object We studied the feasibility of generating the variable magnetic fields required for ultra-low field nuclear magnetic resonance relaxometry with dynamically adjustable permanent magnets. Our motivation was to substitute traditional electromagnets by distributed permanent magnets, increasing system portability. Materials and Methods The finite element method (COMSOL®) was employed for the numerical study of a small permanent magnet array to calculate achievable magnetic field strength, homogeneity, switching time and magnetic forces. A manually operated prototype was simulated and constructed to validate the numerical approach and to verify the generated magnetic field. Results A concentric small permanent magnet array can be used to generate strong sample pre-polarisation and variable measurement fields for ultra-low field relaxometry via simple prescribed magnet rotations. Using the array, it is possible to achieve a pre-polarisation field strength above 100 mT and variable measurement fields ranging from 20–50 μT with 200 ppm absolute field homogeneity within a field-of-view of 5 x 5 x 5 cubic centimetres. Conclusions A dynamic small permanent magnet array can generate multiple highly homogeneous magnetic fields required in ultra-low field nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) instruments. This design can significantly reduce the volume and energy requirements of traditional systems based on electromagnets, improving portability considerably. PMID:27271886

  7. Decoding the direction of imagined visual motion using 7 T ultra-high field fMRI

    PubMed Central

    Emmerling, Thomas C.; Zimmermann, Jan; Sorger, Bettina; Frost, Martin A.; Goebel, Rainer

    2016-01-01

    There is a long-standing debate about the neurocognitive implementation of mental imagery. One form of mental imagery is the imagery of visual motion, which is of interest due to its naturalistic and dynamic character. However, so far only the mere occurrence rather than the specific content of motion imagery was shown to be detectable. In the current study, the application of multi-voxel pattern analysis to high-resolution functional data of 12 subjects acquired with ultra-high field 7 T functional magnetic resonance imaging allowed us to show that imagery of visual motion can indeed activate the earliest levels of the visual hierarchy, but the extent thereof varies highly between subjects. Our approach enabled classification not only of complex imagery, but also of its actual contents, in that the direction of imagined motion out of four options was successfully identified in two thirds of the subjects and with accuracies of up to 91.3% in individual subjects. A searchlight analysis confirmed the local origin of decodable information in striate and extra-striate cortex. These high-accuracy findings not only shed new light on a central question in vision science on the constituents of mental imagery, but also show for the first time that the specific sub-categorical content of visual motion imagery is reliably decodable from brain imaging data on a single-subject level. PMID:26481673

  8. A computational atlas of the hippocampal formation using ex vivo, ultra-high resolution MRI: Application to adaptive segmentation of in vivo MRI.

    PubMed

    Iglesias, Juan Eugenio; Augustinack, Jean C; Nguyen, Khoa; Player, Christopher M; Player, Allison; Wright, Michelle; Roy, Nicole; Frosch, Matthew P; McKee, Ann C; Wald, Lawrence L; Fischl, Bruce; Van Leemput, Koen

    2015-07-15

    Automated analysis of MRI data of the subregions of the hippocampus requires computational atlases built at a higher resolution than those that are typically used in current neuroimaging studies. Here we describe the construction of a statistical atlas of the hippocampal formation at the subregion level using ultra-high resolution, ex vivo MRI. Fifteen autopsy samples were scanned at 0.13 mm isotropic resolution (on average) using customized hardware. The images were manually segmented into 13 different hippocampal substructures using a protocol specifically designed for this study; precise delineations were made possible by the extraordinary resolution of the scans. In addition to the subregions, manual annotations for neighboring structures (e.g., amygdala, cortex) were obtained from a separate dataset of in vivo, T1-weighted MRI scans of the whole brain (1mm resolution). The manual labels from the in vivo and ex vivo data were combined into a single computational atlas of the hippocampal formation with a novel atlas building algorithm based on Bayesian inference. The resulting atlas can be used to automatically segment the hippocampal subregions in structural MRI images, using an algorithm that can analyze multimodal data and adapt to variations in MRI contrast due to differences in acquisition hardware or pulse sequences. The applicability of the atlas, which we are releasing as part of FreeSurfer (version 6.0), is demonstrated with experiments on three different publicly available datasets with different types of MRI contrast. The results show that the atlas and companion segmentation method: 1) can segment T1 and T2 images, as well as their combination, 2) replicate findings on mild cognitive impairment based on high-resolution T2 data, and 3) can discriminate between Alzheimer's disease subjects and elderly controls with 88% accuracy in standard resolution (1mm) T1 data, significantly outperforming the atlas in FreeSurfer version 5.3 (86% accuracy) and

  9. Comparative study of microelectrode recording-based STN location and MRI-based STN location in low to ultra-high field (7.0 T) T2-weighted MRI images

    NASA Astrophysics Data System (ADS)

    Verhagen, Rens; Schuurman, P. Richard; van den Munckhof, Pepijn; Fiorella Contarino, M.; de Bie, Rob M. A.; Bour, Lo J.

    2016-12-01

    Objective. The correspondence between the anatomical STN and the STN observed in T2-weighted MRI images used for deep brain stimulation (DBS) targeting remains unclear. Using a new method, we compared the STN borders seen on MRI images with those estimated by intraoperative microelectrode recordings (MER). Approach. We developed a method to automatically generate a detailed estimation of STN shape and the location of its borders, based on multiple-channel MER measurements. In 33 STNs of 19 Parkinson patients, we quantitatively compared the dorsal and lateral borders of this MER-based STN model with the STN borders visualized by 1.5 T (n = 14), 3.0 T (n = 10) and 7.0 T (n = 9) T2-weighted MRI. Main results. The dorsal border was identified more dorsally on coronal T2 MRI than by the MER-based STN model, with a significant difference in the 3.0 T (range 0.97-1.19 mm) and 7.0 T (range 1.23-1.25 mm) groups. The lateral border was significantly more medial on 1.5 T (mean: 1.97 mm) and 3.0 T (mean: 2.49 mm) MRI than in the MER-based STN; a difference that was not found in the 7.0 T group. Significance. The STN extends further in the dorsal direction on coronal T2 MRI images than is measured by MER. Increasing MRI field strength to 3.0 T or 7.0 T yields similar discrepancies between MER and MRI at the dorsal STN border. In contrast, increasing MRI field strength to 7.0 T may be useful for identification of the lateral STN border and thereby improve DBS targeting.

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

    NASA Astrophysics Data System (ADS)

    Takeda, Shun; Kumagai, Hiroshi

    2018-02-01

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

  11. Multi-shot PROPELLER for high-field preclinical MRI

    PubMed Central

    Pandit, Prachi; Qi, Yi; Story, Jennifer; King, Kevin F.; Johnson, G. Allan

    2012-01-01

    With the development of numerous mouse models of cancer, there is a tremendous need for an appropriate imaging technique to study the disease evolution. High-field T2-weighted imaging using PROPELLER MRI meets this need. The 2-shot PROPELLER technique presented here, provides (a) high spatial resolution, (b) high contrast resolution, and (c) rapid and non-invasive imaging, which enables high-throughput, longitudinal studies in free-breathing mice. Unique data collection and reconstruction makes this method robust against motion artifacts. The 2-shot modification introduced here, retains more high-frequency information and provides higher SNR than conventional single-shot PROPELLER, making this sequence feasible at high-fields, where signal loss is rapid. Results are shown in a liver metastases model to demonstrate the utility of this technique in one of the more challenging regions of the mouse, which is the abdomen. PMID:20572138

  12. Generation and evaluation of an ultra-high-field atlas with applications in DBS planning

    NASA Astrophysics Data System (ADS)

    Wang, Brian T.; Poirier, Stefan; Guo, Ting; Parrent, Andrew G.; Peters, Terry M.; Khan, Ali R.

    2016-03-01

    Purpose Deep brain stimulation (DBS) is a common treatment for Parkinson's disease (PD) and involves the use of brain atlases or intrinsic landmarks to estimate the location of target deep brain structures, such as the subthalamic nucleus (STN) and the globus pallidus pars interna (GPi). However, these structures can be difficult to localize with conventional clinical magnetic resonance imaging (MRI), and thus targeting can be prone to error. Ultra-high-field imaging at 7T has the ability to clearly resolve these structures and thus atlases built with these data have the potential to improve targeting accuracy. Methods T1 and T2-weighted images of 12 healthy control subjects were acquired using a 7T MR scanner. These images were then used with groupwise registration to generate an unbiased average template with T1w and T2w contrast. Deep brain structures were manually labelled in each subject by two raters and rater reliability was assessed. We compared the use of this unbiased atlas with two other methods of atlas-based segmentation (single-template and multi-template) for subthalamic nucleus (STN) segmentation on 7T MRI data. We also applied this atlas to clinical DBS data acquired at 1.5T to evaluate its efficacy for DBS target localization as compared to using a standard atlas. Results The unbiased templates provide superb detail of subcortical structures. Through one-way ANOVA tests, the unbiased template is significantly (p <0.05) more accurate than a single-template in atlas-based segmentation and DBS target localization tasks. Conclusion The generated unbiased averaged templates provide better visualization of deep brain nuclei and an increase in accuracy over single-template and lower field strength atlases.

  13. First patients treated with a 1.5 T MRI-Linac: clinical proof of concept of a high-precision, high-field MRI guided radiotherapy treatment

    NASA Astrophysics Data System (ADS)

    Raaymakers, B. W.; Jürgenliemk-Schulz, I. M.; Bol, G. H.; Glitzner, M.; Kotte, A. N. T. J.; van Asselen, B.; de Boer, J. C. J.; Bluemink, J. J.; Hackett, S. L.; Moerland, M. A.; Woodings, S. J.; Wolthaus, J. W. H.; van Zijp, H. M.; Philippens, M. E. P.; Tijssen, R.; Kok, J. G. M.; de Groot-van Breugel, E. N.; Kiekebosch, I.; Meijers, L. T. C.; Nomden, C. N.; Sikkes, G. G.; Doornaert, P. A. H.; Eppinga, W. S. C.; Kasperts, N.; Kerkmeijer, L. G. W.; Tersteeg, J. H. A.; Brown, K. J.; Pais, B.; Woodhead, P.; Lagendijk, J. J. W.

    2017-12-01

    The integration of 1.5 T MRI functionality with a radiotherapy linear accelerator (linac) has been pursued since 1999 by the UMC Utrecht in close collaboration with Elekta and Philips. The idea behind this integrated device is to offer unrivalled, online and real-time, soft-tissue visualization of the tumour and the surroundings for more precise radiation delivery. The proof of concept of this device was given in 2009 by demonstrating simultaneous irradiation and MR imaging on phantoms, since then the device has been further developed and commercialized by Elekta. The aim of this work is to demonstrate the clinical feasibility of online, high-precision, high-field MRI guidance of radiotherapy using the first clinical prototype MRI-Linac. Four patients with lumbar spine bone metastases were treated with a 3 or 5 beam step-and-shoot IMRT plan. The IMRT plan was created while the patient was on the treatment table and based on the online 1.5 T MR images; pre-treatment CT was deformably registered to the online MRI to obtain Hounsfield values. Bone metastases were chosen as the first site as these tumors can be clearly visualized on MRI and the surrounding spine bone can be detected on the integrated portal imager. This way the portal images served as an independent verification of the MRI based guidance to quantify the geometric precision of radiation delivery. Dosimetric accuracy was assessed post-treatment from phantom measurements with an ionization chamber and film. Absolute doses were found to be highly accurate, with deviations ranging from 0.0% to 1.7% in the isocenter. The geometrical, MRI based targeting as confirmed using portal images was better than 0.5 mm, ranging from 0.2 mm to 0.4 mm. In conclusion, high precision, high-field, 1.5 T MRI guided radiotherapy is clinically feasible.

  14. Steering Electromagnetic Fields in MRI: Investigating Radiofrequency Field Interactions with Endogenous and External Dielectric Materials for Improved Coil Performance at High Field

    NASA Astrophysics Data System (ADS)

    Vaidya, Manushka

    Although 1.5 and 3 Tesla (T) magnetic resonance (MR) systems remain the clinical standard, the number of 7 T MR systems has increased over the past decade because of the promise of higher signal-to-noise ratio (SNR), which can translate to images with higher resolution, improved image quality and faster acquisition times. However, there are a number of technical challenges that have prevented exploiting the full potential of ultra-high field (≥ 7 T) MR imaging (MRI), such as the inhomogeneous distribution of the radiofrequency (RF) electromagnetic field and specific energy absorption rate (SAR), which can compromise image quality and patient safety. To better understand the origin of these issues, we first investigated the dependence of the spatial distribution of the magnetic field associated with a surface RF coil on the operating frequency and electrical properties of the sample. Our results demonstrated that the asymmetries between the transmit (B1+) and receive (B 1-) circularly polarized components of the magnetic field, which are in part responsible for RF inhomogeneity, depend on the electric conductivity of the sample. On the other hand, when sample conductivity is low, a high relative permittivity can result in an inhomogeneous RF field distribution, due to significant constructive and destructive interference patterns between forward and reflected propagating magnetic field within the sample. We then investigated the use of high permittivity materials (HPMs) as a method to alter the field distribution and improve transmit and receive coil performance in MRI. We showed that HPM placed at a distance from an RF loop coil can passively shape the field within the sample. Our results showed improvement in transmit and receive sensitivity overlap, extension of coil field-of-view, and enhancement in transmit/receive efficiency. We demonstrated the utility of this concept by employing HPM to improve performance of an existing commercial head coil for the

  15. SQUIDs vs. Induction Coils for Ultra-Low Field Nuclear Magnetic Resonance: Experimental and Simulation Comparison

    PubMed Central

    Matlashov, Andrei N.; Schultz, Larry J.; Espy, Michelle A.; Kraus, Robert H.; Savukov, Igor M.; Volegov, Petr L.; Wurden, Caroline J.

    2011-01-01

    Nuclear magnetic resonance (NMR) is widely used in medicine, chemistry and industry. One application area is magnetic resonance imaging (MRI). Recently it has become possible to perform NMR and MRI in the ultra-low field (ULF) regime requiring measurement field strengths of the order of only 1 Gauss. This technique exploits the advantages offered by superconducting quantum interference devices or SQUIDs. Our group has built SQUID based MRI systems for brain imaging and for liquid explosives detection at airport security checkpoints. The requirement for liquid helium cooling limits potential applications of ULF MRI for liquid identification and security purposes. Our experimental comparative investigation shows that room temperature inductive magnetometers may provide enough sensitivity in the 3–10 kHz range and can be used for fast liquid explosives detection based on ULF NMR technique. We describe experimental and computer-simulation results comparing multichannel SQUID based and induction coils based instruments that are capable of performing ULF MRI for liquid identification. PMID:21747638

  16. Portable MRI

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Espy, Michelle A.

    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,more » 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.« less

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

    PubMed

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

    2018-01-01

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

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

    PubMed Central

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

    2018-01-01

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

  19. A cytoarchitecture-driven myelin model reveals area-specific signatures in human primary and secondary areas using ultra-high resolution in-vivo brain MRI.

    PubMed

    Dinse, J; Härtwich, N; Waehnert, M D; Tardif, C L; Schäfer, A; Geyer, S; Preim, B; Turner, R; Bazin, P-L

    2015-07-01

    This work presents a novel approach for modelling laminar myelin patterns in the human cortex in brain MR images on the basis of known cytoarchitecture. For the first time, it is possible to estimate intracortical contrast visible in quantitative ultra-high resolution MR images in specific primary and secondary cytoarchitectonic areas. The presented technique reveals different area-specific signatures which may help to study the spatial distribution of cortical T1 values and the distribution of cortical myelin in general. It may lead to a new discussion on the concordance of cyto- and myeloarchitectonic boundaries, given the absence of such concordance atlases. The modelled myelin patterns are quantitatively compared with data from human ultra-high resolution in-vivo 7T brain MR images (9 subjects). In the validation, the results are compared to one post-mortem brain sample and its ex-vivo MRI and histological data. Details of the analysis pipeline are provided. In the context of the increasing interest in advanced methods in brain segmentation and cortical architectural studies, the presented model helps to bridge the gap between the microanatomy revealed by classical histology and the macroanatomy visible in MRI. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

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

    DOEpatents

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

    2009-08-11

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

  1. Au Nanocage Functionalized with Ultra-small Fe3O4 Nanoparticles for Targeting T1-T2Dual MRI and CT Imaging of Tumor

    NASA Astrophysics Data System (ADS)

    Wang, Guannan; Gao, Wei; Zhang, Xuanjun; Mei, Xifan

    2016-06-01

    Diagnostic approaches based on multimodal imaging of clinical noninvasive imaging (eg. MRI/CT scanner) are highly developed in recent years for accurate selection of the therapeutic regimens in critical diseases. Therefore, it is highly demanded in the development of appropriate all-in-one multimodal contrast agents (MCAs) for the MRI/CT multimodal imaging. Here a novel ideal MCAs (F-AuNC@Fe3O4) were engineered by assemble Au nanocages (Au NC) and ultra-small iron oxide nanoparticles (Fe3O4) for simultaneous T1-T2dual MRI and CT contrast imaging. In this system, the Au nanocages offer facile thiol modification and strong X-ray attenuation property for CT imaging. The ultra-small Fe3O4 nanoparticles, as excellent contrast agent, is able to provide great enhanced signal of T1- and T2-weighted MRI (r1 = 6.263 mM-1 s-1, r2 = 28.117 mM-1 s-1) due to their ultra-refined size. After functionalization, the present MCAs nanoparticles exhibited small average size, low aggregation and excellent biocompatible. In vitro and In vivo studies revealed that the MCAs show long-term circulation time, renal clearance properties and outstanding capability of selective accumulation in tumor tissues for simultaneous CT imaging and T1- and T2-weighted MRI. Taken together, these results show that as-prepared MCAs are excellent candidates as MRI/CT multimodal imaging contrast agents.

  2. k-space and q-space: combining ultra-high spatial and angular resolution in diffusion imaging using ZOOPPA at 7 T.

    PubMed

    Heidemann, Robin M; Anwander, Alfred; Feiweier, Thorsten; Knösche, Thomas R; Turner, Robert

    2012-04-02

    There is ongoing debate whether using a higher spatial resolution (sampling k-space) or a higher angular resolution (sampling q-space angles) is the better way to improve diffusion MRI (dMRI) based tractography results in living humans. In both cases, the limiting factor is the signal-to-noise ratio (SNR), due to the restricted acquisition time. One possible way to increase the spatial resolution without sacrificing either SNR or angular resolution is to move to a higher magnetic field strength. Nevertheless, dMRI has not been the preferred application for ultra-high field strength (7 T). This is because single-shot echo-planar imaging (EPI) has been the method of choice for human in vivo dMRI. EPI faces several challenges related to the use of a high resolution at high field strength, for example, distortions and image blurring. These problems can easily compromise the expected SNR gain with field strength. In the current study, we introduce an adapted EPI sequence in conjunction with a combination of ZOOmed imaging and Partially Parallel Acquisition (ZOOPPA). We demonstrate that the method can produce high quality diffusion-weighted images with high spatial and angular resolution at 7 T. We provide examples of in vivo human dMRI with isotropic resolutions of 1 mm and 800 μm. These data sets are particularly suitable for resolving complex and subtle fiber architectures, including fiber crossings in the white matter, anisotropy in the cortex and fibers entering the cortex. Copyright © 2011 Elsevier Inc. All rights reserved.

  3. Ultra-High-Field Magnetic Resonance Spectroscopy in Psychiatry.

    PubMed

    Godlewska, Beata R; Clare, Stuart; Cowen, Philip J; Emir, Uzay E

    2017-01-01

    The advantages of ultra-high-field (UHF ≥ 7T) MR have been demonstrated in a variety of MR acquisition modalities. Magnetic resonance spectroscopy (MRS) can particularly benefit from substantial gains in signal-to-noise ratio (SNR) and spectral resolution at UHF, enabling the quantification of numerous metabolites, including glutamate, glutamine, glutathione, and γ-aminobutyric acid that are relevant to psychiatric disorders. The aim of this review is to give an overview about the advantages and advances of UHF MRS and its application to psychiatric disorders. In order to provide a practical guide for potential applications of MRS at UHF, a literature review is given, surveying advantages and disadvantages of MRS at UHF. Key concepts, emerging technologies, practical considerations, and applications of UHF MRS are provided. Second, the strength of UHF MRS is demonstrated using some examples of its application in psychiatric disorders.

  4. Ultra-High-Field Magnetic Resonance Spectroscopy in Psychiatry

    PubMed Central

    Godlewska, Beata R.; Clare, Stuart; Cowen, Philip J.; Emir, Uzay E.

    2017-01-01

    The advantages of ultra-high-field (UHF ≥ 7T) MR have been demonstrated in a variety of MR acquisition modalities. Magnetic resonance spectroscopy (MRS) can particularly benefit from substantial gains in signal-to-noise ratio (SNR) and spectral resolution at UHF, enabling the quantification of numerous metabolites, including glutamate, glutamine, glutathione, and γ-aminobutyric acid that are relevant to psychiatric disorders. The aim of this review is to give an overview about the advantages and advances of UHF MRS and its application to psychiatric disorders. In order to provide a practical guide for potential applications of MRS at UHF, a literature review is given, surveying advantages and disadvantages of MRS at UHF. Key concepts, emerging technologies, practical considerations, and applications of UHF MRS are provided. Second, the strength of UHF MRS is demonstrated using some examples of its application in psychiatric disorders. PMID:28744229

  5. MRI-negative refractory partial epilepsy: role for diffusion tensor imaging in high field MRI.

    PubMed

    Chen, Qin; Lui, Su; Li, Chun-Xiao; Jiang, Li-Jun; Ou-Yang, Luo; Tang, He-Han; Shang, Hui-Fang; Huang, Xiao-Qi; Gong, Qi-Yong; Zhou, Dong

    2008-07-01

    Our aim is to use the high field MR scanner (3T) to verify whether diffusion tensor imaging (DTI) could help in locating the epileptogenic zone in patients with MRI-negative refractory partial epilepsy. Fifteen patients with refractory partial epilepsy who had normal conventional MRI, and 40 healthy volunteers were recruited for the study. DTI was performed on a 3T MR scanner, individual maps of mean diffusivity (MD) and fractional anisotropy (FA) were calculated, and Voxel-Based Analysis (VBA) was performed for individual comparison between patients and controls. Voxel-based analysis revealed significant MD increase in variant regions in 13 patients. The electroclinical seizure localization was concurred to seven patients. No patient exhibited regions of significant decreased MD. Regions of significant reduced FA were observed in five patients, with two of these concurring with electroclinical seizure localization. Two patients had regions of significant increase in FA, which were distinct from electroclinical seizure localization. Our study's results revealed that DTI is a responsive neuroradiologic technique that provides information about the epileptogenic areas in patients with MRI-negative refractory partial epilepsy. This technique may also helpful in pre-surgical evaluation.

  6. Ultra-wide-field imaging in diabetic retinopathy; an overview.

    PubMed

    Ghasemi Falavarjani, Khalil; Wang, Kang; Khadamy, Joobin; Sadda, Srinivas R

    2016-06-01

    To present an overview on ultra-wide-field imaging in diabetic retinopathy. A comprehensive search of the pubmed database was performed using the search terms of "ultra-wide-field imaging", "ultra-wide-field fluorescein angiography" and "diabetic retinopathy". The relevant original articles were reviewed. New advances in ultra-wide-field imaging allow for precise measurements of the peripheral retinal lesions. A consistent finding amongst these articles was that ultra-wide-field imaging improved detection of peripheral lesion. There was discordance among the studies, however, on the correlation between peripheral diabetic lesions and diabetic macular edema. Visualization of the peripheral retina using ultra-wide-field imaging improves diagnosis and classification of diabetic retinopathy. Additional studies are needed to better define the association of peripheral diabetic lesions with diabetic macular edema.

  7. Investigation of Molecular Exchange Using DEXSY with Ultra-High Pulsed Field Gradients

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Gratz, Marcel; Galvosas, Petrik

    2008-12-05

    Diffusion exchange spectroscopy has been employed for the investigation of water exchange between different regions of a cosmetic lotion as well as for the exchange of n-pentane between the inter- and intra-crystalline space in zeolite NaX. We successfully combined this two-dimensional (2D) NMR experiment with methods for the application of ultra-high pulsed field gradients of up to 35 T/m, resulting in observation times and mixing times as short as 2 ms and 2.8 ms, respectively.

  8. Transverse slot antennas for high field MRI

    PubMed Central

    Lattanzi, Riccardo; Lakshmanan, Karthik; Brown, Ryan; Deniz, Cem M.; Sodickson, Daniel K.; Collins, Christopher M.

    2018-01-01

    Purpose Introduce a novel coil design using an electrically long transversely oriented slot in a conductive sheet. Theory and Methods Theoretical considerations, numerical simulations, and experimental measurements are presented for transverse slot antennas as compared with electric dipole antennas. Results Simulations show improved central and average transmit and receive efficiency, as well as larger coverage in the transverse plane, for a single slot as compared to a single dipole element. Experiments on a body phantom confirm the simulation results for a slot antenna relative to a dipole, demonstrating a large region of relatively high sensitivity and homogeneity. Images in a human subject also show a large imaging volume for a single slot and six slot antenna array. High central transmit efficiency was observed for slot arrays relative to dipole arrays. Conclusion Transverse slots can exhibit improved sensitivity and larger field of view compared with traditional conductive dipoles. Simulations and experiments indicate high potential for slot antennas in high field MRI. Magn Reson Med 80:1233–1242, 2018. © 2018 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes. PMID:29388250

  9. Transport studies in polymer electrolyte fuel cell with porous metallic flow field at ultra high current density

    NASA Astrophysics Data System (ADS)

    Srouji, Abdul-Kader

    Achieving cost reduction for polymer electrolyte fuel cells (PEFC) requires a simultaneous effort in increasing power density while reducing precious metal loading. In PEFCs, the cathode performance is often limiting due to both the slow oxygen reduction reaction (ORR), and mass transport limitation caused by limited oxygen diffusion and liquid water flooding at high current density. This study is motivated by the achievement of ultra-high current density through the elimination of the channel/land (C/L) paradigm in PEFC flow field design. An open metallic element (OME) flow field capable of operating at unprecedented ultra-high current density (3 A/cm2) introduces new advantages and limitations for PEFC operation. The first part of this study compares the OME with a conventional C/L flow field, through performance and electrochemical diagnostic tools such as electrochemical impedance spectroscopy (EIS). The results indicate the uniqueness of the OME's mass transport improvement. No sign of operation limitation due to flooding is noted. The second part specifically examines water management at high current density using the OME flow field. A unique experimental setup is developed to measure steady-state and transient net water drag across the membrane, in order to characterize the fundamental aspects of water transport at high current density with the OME. Instead of flooding, the new limitation is identified to be anode side dry-out of the membrane, caused by electroosmotic drag. The OME improves water removal from the cathode, which immediately improves oxygen transport and performance. However, the low water content in the cathode reduces back diffusion of water to the membrane, and electroosmotic drag dominates at high current density, leading to dry-out. The third part employs the OME flow field as a tool that avoids C/L effects endemic to a typical flow field, in order to study oxygen transport resistance at the catalyst layer of a PEFC. In open literature, a

  10. Encoding methods for B1+ mapping in parallel transmit systems at ultra high field

    NASA Astrophysics Data System (ADS)

    Tse, Desmond H. Y.; Poole, Michael S.; Magill, Arthur W.; Felder, Jörg; Brenner, Daniel; Jon Shah, N.

    2014-08-01

    Parallel radiofrequency (RF) transmission, either in the form of RF shimming or pulse design, has been proposed as a solution to the B1+ inhomogeneity problem in ultra high field magnetic resonance imaging. As a prerequisite, accurate B1+ maps from each of the available transmit channels are required. In this work, four different encoding methods for B1+ mapping, namely 1-channel-on, all-channels-on-except-1, all-channels-on-1-inverted and Fourier phase encoding, were evaluated using dual refocusing acquisition mode (DREAM) at 9.4 T. Fourier phase encoding was demonstrated in both phantom and in vivo to be the least susceptible to artefacts caused by destructive RF interference at 9.4 T. Unlike the other two interferometric encoding schemes, Fourier phase encoding showed negligible dependency on the initial RF phase setting and therefore no prior B1+ knowledge is required. Fourier phase encoding also provides a flexible way to increase the number of measurements to increase SNR, and to allow further reduction of artefacts by weighted decoding. These advantages of Fourier phase encoding suggest that it is a good choice for B1+ mapping in parallel transmit systems at ultra high field.

  11. Thermal noise calculation method for precise estimation of the signal-to-noise ratio of ultra-low-field MRI with an atomic magnetometer.

    PubMed

    Yamashita, Tatsuya; Oida, Takenori; Hamada, Shoji; Kobayashi, Tetsuo

    2012-02-01

    In recent years, there has been considerable interest in developing an ultra-low-field magnetic resonance imaging (ULF-MRI) system using an optically pumped atomic magnetometer (OPAM). However, a precise estimation of the signal-to-noise ratio (SNR) of ULF-MRI has not been carried out. Conventionally, to calculate the SNR of an MR image, thermal noise, also called Nyquist noise, has been estimated by considering a resistor that is electrically equivalent to a biological-conductive sample and is connected in series to a pickup coil. However, this method has major limitations in that the receiver has to be a coil and that it cannot be applied directly to a system using OPAM. In this paper, we propose a method to estimate the thermal noise of an MRI system using OPAM. We calculate the thermal noise from the variance of the magnetic sensor output produced by current-dipole moments that simulate thermally fluctuating current sources in a biological sample. We assume that the random magnitude of the current dipole in each volume element of the biological sample is described by the Maxwell-Boltzmann distribution. The sensor output produced by each current-dipole moment is calculated either by an analytical formula or a numerical method based on the boundary element method. We validate the proposed method by comparing our results with those obtained by conventional methods that consider resistors connected in series to a pickup coil using single-layered sphere, multi-layered sphere, and realistic head models. Finally, we apply the proposed method to the ULF-MRI model using OPAM as the receiver with multi-layered sphere and realistic head models and estimate their SNR. Copyright © 2011 Elsevier Inc. All rights reserved.

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

    PubMed Central

    Thiel, Florian; Kosch, Olaf; Seifert, Frank

    2010-01-01

    The specific advantages of ultra-wideband electromagnetic remote sensing (UWB radar) make it a particularly attractive technique for biomedical applications. We partially review our activities in utilizing this novel approach for the benefit of high and ultra-high field magnetic resonance imaging (MRI) and other applications, e.g., for intensive care medicine and biomedical research. We could show that our approach is beneficial for applications like motion tracking for high resolution brain imaging due to the non-contact acquisition of involuntary head motions with high spatial resolution, navigation for cardiac MRI due to our interpretation of the detected physiological mechanical contraction of the heart muscle and for MR safety, since we have investigated the influence of high static magnetic fields on myocardial mechanics. From our findings we could conclude, that UWB radar can serve as a navigator technique for high and ultra-high field magnetic resonance imaging and can be beneficial preserving the high resolution capability of this imaging modality. Furthermore it can potentially be used to support standard ECG analysis by complementary information where sole ECG analysis fails. Further analytical investigations have proven the feasibility of this method for intracranial displacements detection and the rendition of a tumour’s contrast agent based perfusion dynamic. Beside these analytical approaches we have carried out FDTD simulations of a complex arrangement mimicking the illumination of a human torso model incorporating the geometry of the antennas applied. PMID:22163498

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

    PubMed

    Thiel, Florian; Kosch, Olaf; Seifert, Frank

    2010-01-01

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

  14. The role of high-field magnetic resonance imaging in parkinsonian disorders: Pushing the boundaries forward.

    PubMed

    Lehericy, Stéphane; Vaillancourt, David E; Seppi, Klaus; Monchi, Oury; Rektorova, Irena; Antonini, Angelo; McKeown, Martin J; Masellis, Mario; Berg, Daniela; Rowe, James B; Lewis, Simon J G; Williams-Gray, Caroline H; Tessitore, Alessandro; Siebner, Hartwig R

    2017-04-01

    Historically, magnetic resonance imaging (MRI) has contributed little to the study of Parkinson's disease (PD), but modern MRI approaches have unveiled several complementary markers that are useful for research and clinical applications. Iron- and neuromelanin-sensitive MRI detect qualitative changes in the substantia nigra. Quantitative MRI markers can be derived from diffusion weighted and iron-sensitive imaging or volumetry. Functional brain alterations at rest or during task performance have been captured with functional and arterial spin labeling perfusion MRI. These markers are useful for the diagnosis of PD and atypical parkinsonism, to track disease progression from the premotor stages of these diseases and to better understand the neurobiological basis of clinical deficits. A current research goal using MRI is to generate time-dependent models of the evolution of PD biomarkers that can help understand neurodegeneration and provide reliable markers for therapeutic trials. This article reviews recent advances in MRI biomarker research at high-field (3T) and ultra high field-imaging (7T) in PD and atypical parkinsonism. © 2017 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society. © 2017 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.

  15. INTERCOMPARISON OF PERFORMANCE OF RF COIL GEOMETRIES FOR HIGH FIELD MOUSE CARDIAC MRI

    PubMed Central

    Constantinides, Christakis; Angeli, S.; Gkagkarellis, S.; Cofer, G.

    2012-01-01

    Multi-turn spiral surface coils are constructed in flat and cylindrical arrangements and used for high field (7.1 T) mouse cardiac MRI. Their electrical and imaging performances, based on experimental measurements, simulations, and MRI experiments in free space, and under phantom, and animal loading conditions, are compared with a commercially available birdcage coil. Results show that the four-turn cylindrical spiral coil exhibits improved relative SNR (rSNR) performance to the flat coil counterpart, and compares fairly well with a commercially available birdcage coil. Phantom experiments indicate a 50% improvement in the SNR for penetration depths ≤ 6.1 mm from the coil surface compared to the birdcage coil, and an increased penetration depth at the half-maximum field response of 8 mm in the 4-spiral cylindrical coil case, in contrast to 2.9 mm in the flat 4-turn spiral case. Quantitative comparison of the performance of the two spiral coil geometries in anterior, lateral, inferior, and septal regions of the murine heart yield maximum mean percentage rSNR increases of the order of 27–167% in vivo post-mortem (cylindrical compared to flat coil). The commercially available birdcage outperforms the cylindrical spiral coil in rSNR by a factor of 3–5 times. The comprehensive approach and methodology adopted to accurately design, simulate, implement, and test radiofrequency coils of any geometry and type, under any loading conditions, can be generalized for any application of high field mouse cardiac MRI. PMID:23204945

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

    NASA Astrophysics Data System (ADS)

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

    2018-04-01

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

  17. Numerical field evaluation of healthcare workers when bending towards high-field MRI magnets.

    PubMed

    Wang, H; Trakic, A; Liu, F; Crozier, S

    2008-02-01

    In MRI, healthcare workers may be exposed to strong static and dynamic magnetic fields outside of the imager. Body motion through the strong, non-uniform static magnetic field generated by the main superconducting magnet and exposure to gradient-pulsed magnetic fields can result in the induction of electric fields and current densities in the tissue. The interaction of these fields and occupational workers has attracted an increasing awareness. To protect occupational workers from overexposure, the member states of the European Union are required to incorporate the Physical Agents Directive (PAD) 2004/40/EC into their legislation. This study presents numerical evaluations of electric fields and current densities in anatomically equivalent male and female human models (healthcare workers) as they lean towards the bores of three superconducting magnet models (1.5, 4, and 7 T) and x-, y-, and z- gradient coils. The combined effect of the 1.5 T superconducting magnet and the three gradient coils on the body models is compared with the contributions of the magnet and gradient coils in separation. The simulation results indicate that it is possible to induce field quantities of physiological significance, especially when the MRI operator is bending close towards the main magnet and all three gradient coils are switched simultaneously. (c) 2008 Wiley-Liss, Inc.

  18. Three-dimensional brain MRI for DBS patients within ultra-low radiofrequency power limits.

    PubMed

    Sarkar, Subhendra N; Papavassiliou, Efstathios; Hackney, David B; Alsop, David C; Shih, Ludy C; Madhuranthakam, Ananth J; Busse, Reed F; La Ruche, Susan; Bhadelia, Rafeeque A

    2014-04-01

    For patients with deep brain stimulators (DBS), local absorbed radiofrequency (RF) power is unknown and is much higher than what the system estimates. We developed a comprehensive, high-quality brain magnetic resonance imaging (MRI) protocol for DBS patients utilizing three-dimensional (3D) magnetic resonance sequences at very low RF power. Six patients with DBS were imaged (10 sessions) using a transmit/receive head coil at 1.5 Tesla with modified 3D sequences within ultra-low specific absorption rate (SAR) limits (0.1 W/kg) using T2 , fast fluid-attenuated inversion recovery (FLAIR) and T1 -weighted image contrast. Tissue signal and tissue contrast from the low-SAR images were subjectively and objectively compared with routine clinical images of six age-matched controls. Low-SAR images of DBS patients demonstrated tissue contrast comparable to high-SAR images and were of diagnostic quality except for slightly reduced signal. Although preliminary, we demonstrated diagnostic quality brain MRI with optimized, volumetric sequences in DBS patients within very conservative RF safety guidelines offering a greater safety margin. © 2014 International Parkinson and Movement Disorder Society.

  19. The High Field Ultra Low Aspect Ratio Tokamak (HF-ULART)

    NASA Astrophysics Data System (ADS)

    Ribeiro, Celso

    2017-10-01

    Recently, a medium-size HF-ULART has been proposed. The major objective is to explore the high beta and pressure under the high toroidal field, using present day technology. This might be one of pathway scenarios for a potential ultra-compact pulsed neutron source (UCP-NS) based on the spherical tokamak (ST) concept, which may lead to more steady-state NS or even to a fusion reactor, via realistic design scaling. The HF-ULART pulsed mode operation is created by quasi-simultaneous adiabatic compression (AC) in both minor and major radius of a very high beta plasma, possibly with further help of passive-wall stabilization, as envisaged in the RULART concept. This may help the revival of the studies of the AC technique in tokamaks, alongside the less compact and more complex ST-40 device, currently under construction. In addition, by similarities, studies in HF-ULART as a UCP-NS may also help to test the feasibility of the compact NS via the spheromak concept, which also uses the AC technique. Simulations of AC in HF-ULART plasmas will be presented.

  20. Ultra-wide-field imaging in diabetic retinopathy.

    PubMed

    Ghasemi Falavarjani, Khalil; Tsui, Irena; Sadda, Srinivas R

    2017-10-01

    Since 1991, 7-field images captured with 30-50 degree cameras in the Early Treatment Diabetic Retinopathy Study were the gold standard for fundus imaging to study diabetic retinopathy. Ultra-wide-field images cover significantly more area (up to 82%) of the fundus and with ocular steering can in many cases image 100% of the fundus ("panretinal"). Recent advances in image analysis of ultra-wide-field imaging allow for precise measurements of the peripheral retinal lesions. There is a growing consensus in the literature that ultra-wide-field imaging improves detection of peripheral lesions in diabetic retinopathy and leads to more accurate classification of the disease. There is discordance among studies, however, on the correlation between peripheral diabetic lesions and diabetic macular edema and optimal management strategies to treat diabetic retinopathy. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. 27 T ultra-high static magnetic field changes orientation and morphology of mitotic spindles in human cells

    PubMed Central

    Zhang, Lei; Hou, Yubin; Li, Zhiyuan; Ji, Xinmiao; Wang, Ze; Wang, Huizhen; Tian, Xiaofei; Yu, Fazhi; Yang, Zhenye; Pi, Li; Mitchison, Timothy J; Lu, Qingyou; Zhang, Xin

    2017-01-01

    Purified microtubules have been shown to align along the static magnetic field (SMF) in vitro because of their diamagnetic anisotropy. However, whether mitotic spindle in mammalian cells can be aligned by magnetic field has not been experimentally proved. In particular, the biological effects of SMF of above 20 T (Tesla) on mammalian cells have never been reported. Here we found that in both CNE-2Z and RPE1 human cells spindle orients in 27 T SMF. The direction of spindle alignment depended on the extent to which chromosomes were aligned to form a planar metaphase plate. Our results show that the magnetic torque acts on both microtubules and chromosomes, and the preferred direction of spindle alignment relative to the field depends more on chromosome alignment than microtubules. In addition, spindle morphology was also perturbed by 27 T SMF. This is the first reported study that investigated the mammalian cellular responses to ultra-high magnetic field of above 20 T. Our study not only found that ultra-high magnetic field can change the orientation and morphology of mitotic spindles, but also provided a tool to probe the role of spindle orientation and perturbation in developmental and cancer biology. DOI: http://dx.doi.org/10.7554/eLife.22911.001 PMID:28244368

  2. Open Science CBS Neuroimaging Repository: Sharing ultra-high-field MR images of the brain.

    PubMed

    Tardif, Christine Lucas; Schäfer, Andreas; Trampel, Robert; Villringer, Arno; Turner, Robert; Bazin, Pierre-Louis

    2016-01-01

    Magnetic resonance imaging at ultra high field opens the door to quantitative brain imaging at sub-millimeter isotropic resolutions. However, novel image processing tools to analyze these new rich datasets are lacking. In this article, we introduce the Open Science CBS Neuroimaging Repository: a unique repository of high-resolution and quantitative images acquired at 7 T. The motivation for this project is to increase interest for high-resolution and quantitative imaging and stimulate the development of image processing tools developed specifically for high-field data. Our growing repository currently includes datasets from MP2RAGE and multi-echo FLASH sequences from 28 and 20 healthy subjects respectively. These datasets represent the current state-of-the-art in in-vivo relaxometry at 7 T, and are now fully available to the entire neuroimaging community. Copyright © 2015 Elsevier Inc. All rights reserved.

  3. Ultra-broadband near-field antenna for terahertz plasmonic applications

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Polischuk, O. V., E-mail: polischuk.sfire@mail.ru; Popov, V. V., E-mail: popov-slava@yahoo.co.uk; Knap, W.

    A new type of ultra-broadband near-field antenna for terahertz frequencies is proposed. This antenna is a short-period planar metal array. It is theoretically shown that irradiation of the short-period array antenna by a plane homogeneous terahertz waves excite a highly inhomogeneous near electric field near the metal array. In this case, the amplitude of the excited inhomogeneous near electric field is almost independent of frequency in the entire terahertz frequency range. The excitation of plasma oscillations in a two-dimensional electron system using the antenna under study is numerically simulated in the resonant and non-resonant plasmonic response modes. This type ofmore » antenna can be used for developing ultra-broadband plasmonic detectors of terahertz radiation.« less

  4. Ultra-high magnetic resonance imaging (MRI): a potential examination for deep brain stimulation devices and the limitation study concerning MRI-related heating injury.

    PubMed

    Chen, Ying-Chuan; Li, Jun-Ju; Zhu, Guan-Yu; Shi, Lin; Yang, An-Chao; Jiang, Yin; Zhang, Xin; Zhang, Jian-Guo

    2017-03-01

    Nowadays, the patients with deep brain stimulation (DBS) devices are restricted to undertake 1.5T magnetic resonance imaging (MRI) according to the guideline. Nevertheless, we conducted an experiment to test pathological change near the leads in different field-strength MRI. Twenty-four male New Zealand rabbits were assigned to Group 1 (G1, n = 6, 7.0T, DBS), Group 2 (G2, n = 6, 3.0T, DBS), Group 3 (G3, n = 6, 1.5T, DBS), and Group 4 (G4, n = 6, 1.5T, paracentesis). DBS leads were implanted in G1, G2 and G3, targeting left nucleus ventralis posterior thalami. Paracentesis was performed in G4. 24 h after MRI scan, all animals were killed for examining pathological alternation (at different distance from lead) via transmission electron microscopy. Our results suggest that the severity of tissue injury correlates with the distance to electrode instead of field strength of MRI. Up to now, the reason for the restriction of MRI indicated no significantly different pathological change.

  5. Vacuum Bloch-Siegert shift in Landau polaritons with ultra-high cooperativity

    NASA Astrophysics Data System (ADS)

    Li, Xinwei; Bamba, Motoaki; Zhang, Qi; Fallahi, Saeed; Gardner, Geoff C.; Gao, Weilu; Lou, Minhan; Yoshioka, Katsumasa; Manfra, Michael J.; Kono, Junichiro

    2018-06-01

    A two-level system resonantly interacting with an a.c. magnetic or electric field constitutes the physical basis of diverse phenomena and technologies. However, Schrödinger's equation for this seemingly simple system can be solved exactly only under the rotating-wave approximation, which neglects the counter-rotating field component. When the a.c. field is sufficiently strong, this approximation fails, leading to a resonance-frequency shift known as the Bloch-Siegert shift. Here, we report the vacuum Bloch-Siegert shift, which is induced by the ultra-strong coupling of matter with the counter-rotating component of the vacuum fluctuation field in a cavity. Specifically, an ultra-high-mobility two-dimensional electron gas inside a high-Q terahertz cavity in a quantizing magnetic field revealed ultra-narrow Landau polaritons, which exhibited a vacuum Bloch-Siegert shift up to 40 GHz. This shift, clearly distinguishable from the photon-field self-interaction effect, represents a unique manifestation of a strong-field phenomenon without a strong field.

  6. GPU-accelerated FDTD modeling of radio-frequency field-tissue interactions in high-field MRI.

    PubMed

    Chi, Jieru; Liu, Feng; Weber, Ewald; Li, Yu; Crozier, Stuart

    2011-06-01

    The analysis of high-field RF field-tissue interactions requires high-performance finite-difference time-domain (FDTD) computing. Conventional CPU-based FDTD calculations offer limited computing performance in a PC environment. This study presents a graphics processing unit (GPU)-based parallel-computing framework, producing substantially boosted computing efficiency (with a two-order speedup factor) at a PC-level cost. Specific details of implementing the FDTD method on a GPU architecture have been presented and the new computational strategy has been successfully applied to the design of a novel 8-element transceive RF coil system at 9.4 T. Facilitated by the powerful GPU-FDTD computing, the new RF coil array offers optimized fields (averaging 25% improvement in sensitivity, and 20% reduction in loop coupling compared with conventional array structures of the same size) for small animal imaging with a robust RF configuration. The GPU-enabled acceleration paves the way for FDTD to be applied for both detailed forward modeling and inverse design of MRI coils, which were previously impractical.

  7. In vivo wide-field calcium imaging of mouse thalamocortical synapses with an 8 K ultra-high-definition camera.

    PubMed

    Yoshida, Eriko; Terada, Shin-Ichiro; Tanaka, Yasuyo H; Kobayashi, Kenta; Ohkura, Masamichi; Nakai, Junichi; Matsuzaki, Masanori

    2018-05-29

    In vivo wide-field imaging of neural activity with a high spatio-temporal resolution is a challenge in modern neuroscience. Although two-photon imaging is very powerful, high-speed imaging of the activity of individual synapses is mostly limited to a field of approximately 200 µm on a side. Wide-field one-photon epifluorescence imaging can reveal neuronal activity over a field of ≥1 mm 2 at a high speed, but is not able to resolve a single synapse. Here, to achieve a high spatio-temporal resolution, we combine an 8 K ultra-high-definition camera with spinning-disk one-photon confocal microscopy. This combination allowed us to image a 1 mm 2 field with a pixel resolution of 0.21 µm at 60 fps. When we imaged motor cortical layer 1 in a behaving head-restrained mouse, calcium transients were detected in presynaptic boutons of thalamocortical axons sparsely labeled with GCaMP6s, although their density was lower than when two-photon imaging was used. The effects of out-of-focus fluorescence changes on calcium transients in individual boutons appeared minimal. Axonal boutons with highly correlated activity were detected over the 1 mm 2 field, and were probably distributed on multiple axonal arbors originating from the same thalamic neuron. This new microscopy with an 8 K ultra-high-definition camera should serve to clarify the activity and plasticity of widely distributed cortical synapses.

  8. Ultra high resolution imaging of the human head at 8 tesla: 2K x 2K for Y2K.

    PubMed

    Robitaille, P M; Abduljalil, A M; Kangarlu, A

    2000-01-01

    To acquire ultra high resolution MRI images of the human brain at 8 Tesla within a clinically acceptable time frame. Gradient echo images were acquired from the human head of normal subjects using a transverse electromagnetic resonator operating in quadrature and tuned to 340 MHz. In each study, a group of six images was obtained containing a total of 208 MB of unprocessed information. Typical acquisition parameters were as follows: matrix = 2,000 x 2,000, field of view = 20 cm, slice thickness = 2 mm, number of excitations (NEX) = 1, flip angle = 45 degrees, TR = 750 ms, TE = 17 ms, receiver bandwidth = 69.4 kHz. This resulted in a total scan time of 23 minutes, an in-plane resolution of 100 microm, and a pixel volume of 0.02 mm3. The ultra high resolution images acquired in this study represent more than a 50-fold increase in in-plane resolution relative to conventional 256 x 256 images obtained with a 20 cm field of view and a 5 mm slice thickness. Nonetheless, the ultra high resolution images could be acquired both with adequate image quality and signal to noise. They revealed numerous small venous structures throughout the image plane and provided reasonable delineation between gray and white matter. The elevated signal-to-noise ratio observed in ultra high field magnetic resonance imaging can be utilized to acquire images with a level of resolution approaching the histological level under in vivo conditions. However, brain motion is likely to degrade the useful resolution. This situation may be remedied in part with cardiac gating. Nonetheless, these images represent a significant advance in our ability to examine small anatomical features with noninvasive imaging methods.

  9. Adaptive suppression of power line interference in ultra-low field magnetic resonance imaging in an unshielded environment

    NASA Astrophysics Data System (ADS)

    Huang, Xiaolei; Dong, Hui; Qiu, Yang; Li, Bo; Tao, Quan; Zhang, Yi; Krause, Hans-Joachim; Offenhäusser, Andreas; Xie, Xiaoming

    2018-01-01

    Power-line harmonic interference and fixed-frequency noise peaks may cause stripe-artifacts in ultra-low field (ULF) magnetic resonance imaging (MRI) in an unshielded environment and in a conductively shielded room. In this paper we describe an adaptive suppression method to eliminate these artifacts in MRI images. This technique utilizes spatial correlation of the interference from different positions, and is realized by subtracting the outputs of the reference channel(s) from those of the signal channel(s) using wavelet analysis and the least squares method. The adaptive suppression method is first implemented to remove the image artifacts in simulation. We then experimentally demonstrate the feasibility of this technique by adding three orthogonal superconducting quantum interference device (SQUID) magnetometers as reference channels to compensate the output of one 2nd-order gradiometer. The experimental results show great improvement in the imaging quality in both 1D and 2D MRI images at two common imaging frequencies, 1.3 kHz and 4.8 kHz. At both frequencies, the effective compensation bandwidth is as high as 2 kHz. Furthermore, we examine the longitudinal relaxation times of the same sample before and after compensation, and show that the MRI properties of the sample did not change after applying adaptive suppression. This technique can effectively increase the imaging bandwidth and be applied to ULF MRI detected by either SQUIDs or Faraday coil in both an unshielded environment and a conductively shielded room.

  10. Recording Visual Evoked Potentials and Auditory Evoked P300 at 9.4T Static Magnetic Field

    PubMed Central

    Hahn, David; Boers, Frank; Shah, N. Jon

    2013-01-01

    Simultaneous recording of electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) has shown a number of advantages that make this multimodal technique superior to fMRI alone. The feasibility of recording EEG at ultra-high static magnetic field up to 9.4T was recently demonstrated and promises to be implemented soon in fMRI studies at ultra high magnetic fields. Recording visual evoked potentials are expected to be amongst the most simple for simultaneous EEG/fMRI at ultra-high magnetic field due to the easy assessment of the visual cortex. Auditory evoked P300 measurements are of interest since it is believed that they represent the earliest stage of cognitive processing. In this study, we investigate the feasibility of recording visual evoked potentials and auditory evoked P300 in a 9.4T static magnetic field. For this purpose, EEG data were recorded from 26 healthy volunteers inside a 9.4T MR scanner using a 32-channel MR compatible EEG system. Visual stimulation and auditory oddball paradigm were presented in order to elicit evoked related potentials (ERP). Recordings made outside the scanner were performed using the same stimuli and EEG system for comparison purposes. We were able to retrieve visual P100 and auditory P300 evoked potentials at 9.4T static magnetic field after correction of the ballistocardiogram artefact using independent component analysis. The latencies of the ERPs recorded at 9.4T were not different from those recorded at 0T. The amplitudes of ERPs were higher at 9.4T when compared to recordings at 0T. Nevertheless, it seems that the increased amplitudes of the ERPs are due to the effect of the ultra-high field on the EEG recording system rather than alteration in the intrinsic processes that generate the electrophysiological responses. PMID:23650538

  11. Recording visual evoked potentials and auditory evoked P300 at 9.4T static magnetic field.

    PubMed

    Arrubla, Jorge; Neuner, Irene; Hahn, David; Boers, Frank; Shah, N Jon

    2013-01-01

    Simultaneous recording of electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) has shown a number of advantages that make this multimodal technique superior to fMRI alone. The feasibility of recording EEG at ultra-high static magnetic field up to 9.4 T was recently demonstrated and promises to be implemented soon in fMRI studies at ultra high magnetic fields. Recording visual evoked potentials are expected to be amongst the most simple for simultaneous EEG/fMRI at ultra-high magnetic field due to the easy assessment of the visual cortex. Auditory evoked P300 measurements are of interest since it is believed that they represent the earliest stage of cognitive processing. In this study, we investigate the feasibility of recording visual evoked potentials and auditory evoked P300 in a 9.4 T static magnetic field. For this purpose, EEG data were recorded from 26 healthy volunteers inside a 9.4 T MR scanner using a 32-channel MR compatible EEG system. Visual stimulation and auditory oddball paradigm were presented in order to elicit evoked related potentials (ERP). Recordings made outside the scanner were performed using the same stimuli and EEG system for comparison purposes. We were able to retrieve visual P100 and auditory P300 evoked potentials at 9.4 T static magnetic field after correction of the ballistocardiogram artefact using independent component analysis. The latencies of the ERPs recorded at 9.4 T were not different from those recorded at 0 T. The amplitudes of ERPs were higher at 9.4 T when compared to recordings at 0 T. Nevertheless, it seems that the increased amplitudes of the ERPs are due to the effect of the ultra-high field on the EEG recording system rather than alteration in the intrinsic processes that generate the electrophysiological responses.

  12. NMR, MRI, and spectroscopic MRI in inhomogeneous fields

    DOEpatents

    Demas, Vasiliki; Pines, Alexander; Martin, Rachel W; Franck, John; Reimer, Jeffrey A

    2013-12-24

    A method for locally creating effectively homogeneous or "clean" magnetic field gradients (of high uniformity) for imaging (with NMR, MRI, or spectroscopic MRI) both in in-situ and ex-situ systems with high degrees of inhomogeneous field strength. THe method of imaging comprises: a) providing a functional approximation of an inhomogeneous static magnetic field strength B.sub.0({right arrow over (r)}) at a spatial position {right arrow over (r)}; b) providing a temporal functional approximation of {right arrow over (G)}.sub.shim(t) with i basis functions and j variables for each basis function, resulting in v.sub.ij variables; c) providing a measured value .OMEGA., which is an temporally accumulated dephasing due to the inhomogeneities of B.sub.0({right arrow over(r)}); and d) minimizing a difference in the local dephasing angle .phi.({right arrow over (r)},t)=.gamma..intg..sub.0.sup.t{square root over (|{right arrow over (B)}.sub.1({right arrow over (r)},t')|.sup.2+({right arrow over (r)}{right arrow over (G)}.sub.shimG.sub.shim(t')+.parallel.{right arrow over (B)}.sub.0({right arrow over (r)}).parallel..DELTA..omega.({right arrow over (r)},t'/.gamma/).sup.2)}dt'-.OMEGA. by varying the v.sub.ij variables to form a set of minimized v.sub.ij variables. The method requires calibration of the static fields prior to minimization, but may thereafter be implemented without such calibration, may be used in open or closed systems, and potentially portable systems.

  13. Portable MRI developed at Los Alamos

    ScienceCinema

    Espy, Michelle

    2018-02-14

    Scientists at Los Alamos National Laboratory are developing an ultra-low-field Magnetic Resonance Imaging (MRI) system that could be low-power and lightweight enough for forward deployment on the battlefield and to field hospitals in the World's poorest regions. "MRI technology is a powerful medical diagnostic tool," said Michelle Espy, the Battlefield MRI (bMRI) project leader, "ideally suited for imaging soft-tissue injury, particularly to the brain." But hospital-based MRI devices are big and expensive, and require considerable infrastructure, such as large quantities of cryogens like liquid nitrogen and helium, and they typically use a large amount of energy. "Standard MRI machines just can't go everywhere," said Espy. "Soldiers wounded in battle usually have to be flown to a large hospital and people in emerging nations just don't have access to MRI at all. We've been in contact with doctors who routinely work in the Third World and report that MRI would be extremely valuable in treating pediatric encephalopathy, and other serious diseases in children." So the Los Alamos team started thinking about a way to make an MRI device that could be relatively easy to transport, set up, and use in an unconventional setting. Conventional MRI machines use very large magnetic fields that align the protons in water molecules to then create magnetic resonance signals, which are detected by the machine and turned into images. The large magnetic fields create exceptionally detailed images, but they are difficult and expensive to make. Espy and her team wanted to see if images of sufficient quality could be made with ultra-low-magnetic fields, similar in strength to the Earth's magnetic field. To achieve images at such low fields they use exquisitely sensitive detectors called Superconducting Quantum Interference Devices, or SQUIDs. SQUIDs are among the most sensitive magnetic field detectors available, so interference with the signal is the primary stumbling block. "SQUIDs are

  14. Portable MRI developed at Los Alamos

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Espy, Michelle

    Scientists at Los Alamos National Laboratory are developing an ultra-low-field Magnetic Resonance Imaging (MRI) system that could be low-power and lightweight enough for forward deployment on the battlefield and to field hospitals in the World's poorest regions. "MRI technology is a powerful medical diagnostic tool," said Michelle Espy, the Battlefield MRI (bMRI) project leader, "ideally suited for imaging soft-tissue injury, particularly to the brain." But hospital-based MRI devices are big and expensive, and require considerable infrastructure, such as large quantities of cryogens like liquid nitrogen and helium, and they typically use a large amount of energy. "Standard MRI machines justmore » can't go everywhere," said Espy. "Soldiers wounded in battle usually have to be flown to a large hospital and people in emerging nations just don't have access to MRI at all. We've been in contact with doctors who routinely work in the Third World and report that MRI would be extremely valuable in treating pediatric encephalopathy, and other serious diseases in children." So the Los Alamos team started thinking about a way to make an MRI device that could be relatively easy to transport, set up, and use in an unconventional setting. Conventional MRI machines use very large magnetic fields that align the protons in water molecules to then create magnetic resonance signals, which are detected by the machine and turned into images. The large magnetic fields create exceptionally detailed images, but they are difficult and expensive to make. Espy and her team wanted to see if images of sufficient quality could be made with ultra-low-magnetic fields, similar in strength to the Earth's magnetic field. To achieve images at such low fields they use exquisitely sensitive detectors called Superconducting Quantum Interference Devices, or SQUIDs. SQUIDs are among the most sensitive magnetic field detectors available, so interference with the signal is the primary stumbling block

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

    NASA Astrophysics Data System (ADS)

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

    2018-06-01

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

  16. [Microinjection Monitoring System Design Applied to MRI Scanning].

    PubMed

    Xu, Yongfeng

    2017-09-30

    A microinjection monitoring system applied to the MRI scanning was introduced. The micro camera probe was used to stretch into the main magnet for real-time video injection monitoring of injection tube terminal. The programming based on LabVIEW was created to analysis and process the real-time video information. The feedback signal was used for intelligent controlling of the modified injection pump. The real-time monitoring system can make the best use of injection under the condition that the injection device was away from the sample which inside the magnetic room and unvisible. 9.4 T MRI scanning experiment showed that the system in ultra-high field can work stability and doesn't affect the MRI scans.

  17. Low Field Squid MRI Devices, Components and Methods

    NASA Technical Reports Server (NTRS)

    Hahn, Inseob (Inventor); Penanen, Konstantin I. (Inventor); Eom, Byeong H. (Inventor)

    2013-01-01

    Low field SQUID MRI devices, components and methods are disclosed. They include a portable low field (SQUID)-based MRI instrument and a portable low field SQUID-based MRI system to be operated under a bed where a subject is adapted to be located. Also disclosed is a method of distributing wires on an image encoding coil system adapted to be used with an NMR or MRI device for analyzing a sample or subject and a second order superconducting gradiometer adapted to be used with a low field SQUID-based MRI device as a sensing component for an MRI signal related to a subject or sample.

  18. Low Field Squid MRI Devices, Components and Methods

    NASA Technical Reports Server (NTRS)

    Penanen, Konstantin I. (Inventor); Eom, Byeong H. (Inventor); Hahn, Inseob (Inventor)

    2014-01-01

    Low field SQUID MRI devices, components and methods are disclosed. They include a portable low field (SQUID)-based MRI instrument and a portable low field SQUID-based MRI system to be operated under a bed where a subject is adapted to be located. Also disclosed is a method of distributing wires on an image encoding coil system adapted to be used with an NMR or MRI device for analyzing a sample or subject and a second order superconducting gradiometer adapted to be used with a low field SQUID-based MRI device as a sensing component for an MRI signal related to a subject or sample.

  19. Low field SQUID MRI devices, components and methods

    NASA Technical Reports Server (NTRS)

    Penanen, Konstantin I. (Inventor); Eom, Byeong H. (Inventor); Hahn, Inseob (Inventor)

    2011-01-01

    Low field SQUID MRI devices, components and methods are disclosed. They include a portable low field (SQUID)-based MRI instrument and a portable low field SQUID-based MRI system to be operated under a bed where a subject is adapted to be located. Also disclosed is a method of distributing wires on an image encoding coil system adapted to be used with an NMR or MRI device for analyzing a sample or subject and a second order superconducting gradiometer adapted to be used with a low field SQUID-based MRI device as a sensing component for an MRI signal related to a subject or sample.

  20. Low field SQUID MRI devices, components and methods

    NASA Technical Reports Server (NTRS)

    Penanen, Konstantin I. (Inventor); Eom, Byeong H (Inventor); Hahn, Inseob (Inventor)

    2010-01-01

    Low field SQUID MRI devices, components and methods are disclosed. They include a portable low field (SQUID)-based MRI instrument and a portable low field SQUID-based MRI system to be operated under a bed where a subject is adapted to be located. Also disclosed is a method of distributing wires on an image encoding coil system adapted to be used with an NMR or MRI device for analyzing a sample or subject and a second order superconducting gradiometer adapted to be used with a low field SQUID-based MRI device as a sensing component for an MRI signal related to a subject or sample.

  1. Ultra-compact Marx-type high-voltage generator

    DOEpatents

    Goerz, David A.; Wilson, Michael J.

    2000-01-01

    An ultra-compact Marx-type high-voltage generator includes individual high-performance components that are closely coupled and integrated into an extremely compact assembly. In one embodiment, a repetitively-switched, ultra-compact Marx generator includes low-profile, annular-shaped, high-voltage, ceramic capacitors with contoured edges and coplanar extended electrodes used for primary energy storage; low-profile, low-inductance, high-voltage, pressurized gas switches with compact gas envelopes suitably designed to be integrated with the annular capacitors; feed-forward, high-voltage, ceramic capacitors attached across successive switch-capacitor-switch stages to couple the necessary energy forward to sufficiently overvoltage the spark gap of the next in-line switch; optimally shaped electrodes and insulator surfaces to reduce electric field stresses in the weakest regions where dissimilar materials meet, and to spread the fields more evenly throughout the dielectric materials, allowing them to operate closer to their intrinsic breakdown levels; and uses manufacturing and assembly methods to integrate the capacitors and switches into stages that can be arranged into a low-profile Marx generator.

  2. A practical and flexible implementation of 3D MRI in the Earth’s magnetic field

    NASA Astrophysics Data System (ADS)

    Halse, Meghan E.; Coy, Andrew; Dykstra, Robin; Eccles, Craig; Hunter, Mark; Ward, Rob; Callaghan, Paul T.

    2006-09-01

    The Earth's magnetic field, though weak, is appealing for NMR applications because it is highly homogeneous, globally available and free. However, the practicality of Earth's field NMR (EFNMR) has long been limited by the need to perform experiments in outdoor locations where the local field homogeneity is not disrupted by ferrous or magnetic objects and where ultra-low frequency (ULF) noise sources are at a minimum. Herein we present a flexible and practical implementation of MRI in the Earth's magnetic field that demonstrates that EFNMR is not as difficult as it was previously thought to be. In this implementation, pre-polarization and ULF noise shielding, achieved using a crude electromagnet, are used to significantly improve signal-to-noise ratio (SNR) even in relatively noisy environments. A three axis gradient coil set, in addition to providing imaging gradients, is used to provide first-order shims such that sub-hertz linewidths can routinely be achieved, even in locations of significant local field inhomogeneity such as indoor scientific laboratories. Temporal fluctuations in the magnitude of the Earth's magnetic field are measured and a regime found within which these variations in Larmor frequency produce no observable artefacts in reconstructed images.

  3. High resolution separations of charge variants and disulfide isomers of monoclonal antibodies and antibody drug conjugates using ultra-high voltage capillary electrophoresis with high electric field strength.

    PubMed

    Henley, W Hampton; He, Yan; Mellors, J Scott; Batz, Nicholas G; Ramsey, J Michael; Jorgenson, James W

    2017-11-10

    Ultra-high voltage capillary electrophoresis with high electric field strength has been applied to the separation of the charge variants, drug conjugates, and disulfide isomers of monoclonal antibodies. Samples composed of many closely related species are difficult to resolve and quantify using traditional analytical instrumentation. High performance instrumentation can often save considerable time and effort otherwise spent on extensive method development. Ideally, the resolution obtained for a given CE buffer system scales with the square root of the applied voltage. Currently available commercial CE instrumentation is limited to an applied voltage of approximately 30kV and a maximum electric field strength of 1kV/cm due to design limitations. The instrumentation described here is capable of safely applying potentials of at least 120kV with electric field strengths over 2000V/cm, potentially doubling the resolution of the best conventional CE buffer/capillary systems while decreasing analysis time in some applications. Separations of these complex mixtures using this new instrumentation demonstrate the potential of ultra-high voltage CE to identify the presence of previously unresolved components and to reduce analysis time for complex mixtures of antibody variants and drug conjugates. Copyright © 2017 Elsevier B.V. All rights reserved.

  4. Electric Field Strength Of Coherent Radio Emission In Rock Salt Concerning Ultra High-Energy Neutrino Detection

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Watanabe, Y.; Chiba, M.; Yasuda, O.

    2006-07-12

    Detection possibility of ultra high-energy (UHE) neutrino (E >1015 eV) in natural huge rock salt formation has been studied. Collision between the UHE neutrino and the rock salt produces electromagnetic (EM) shower. Charge difference (excess electrons) between electrons and positrons in EM shower radiates radio wave coherently (Askar'yan effect). Angular distribution and frequency spectrum of electric field strength of radio wave radiated from 3-dimensional EM shower in rock salt are presented.

  5. Multishot versus Single-Shot Pulse Sequences in Very High Field fMRI: A Comparison Using Retinotopic Mapping

    PubMed Central

    Gatenby, J. Christopher; Gore, John C.; Tong, Frank

    2012-01-01

    High-resolution functional MRI is a leading application for very high field (7 Tesla) human MR imaging. Though higher field strengths promise improvements in signal-to-noise ratios (SNR) and BOLD contrast relative to fMRI at 3 Tesla, these benefits may be partially offset by accompanying increases in geometric distortion and other off-resonance effects. Such effects may be especially pronounced with the single-shot EPI pulse sequences typically used for fMRI at standard field strengths. As an alternative, one might consider multishot pulse sequences, which may lead to somewhat lower temporal SNR than standard EPI, but which are also often substantially less susceptible to off-resonance effects. Here we consider retinotopic mapping of human visual cortex as a practical test case by which to compare examples of these sequence types for high-resolution fMRI at 7 Tesla. We performed polar angle retinotopic mapping at each of 3 isotropic resolutions (2.0, 1.7, and 1.1 mm) using both accelerated single-shot 2D EPI and accelerated multishot 3D gradient-echo pulse sequences. We found that single-shot EPI indeed led to greater temporal SNR and contrast-to-noise ratios (CNR) than the multishot sequences. However, additional distortion correction in postprocessing was required in order to fully realize these advantages, particularly at higher resolutions. The retinotopic maps produced by both sequence types were qualitatively comparable, and showed equivalent test/retest reliability. Thus, when surface-based analyses are planned, or in other circumstances where geometric distortion is of particular concern, multishot pulse sequences could provide a viable alternative to single-shot EPI. PMID:22514646

  6. Multishot versus single-shot pulse sequences in very high field fMRI: a comparison using retinotopic mapping.

    PubMed

    Swisher, Jascha D; Sexton, John A; Gatenby, J Christopher; Gore, John C; Tong, Frank

    2012-01-01

    High-resolution functional MRI is a leading application for very high field (7 Tesla) human MR imaging. Though higher field strengths promise improvements in signal-to-noise ratios (SNR) and BOLD contrast relative to fMRI at 3 Tesla, these benefits may be partially offset by accompanying increases in geometric distortion and other off-resonance effects. Such effects may be especially pronounced with the single-shot EPI pulse sequences typically used for fMRI at standard field strengths. As an alternative, one might consider multishot pulse sequences, which may lead to somewhat lower temporal SNR than standard EPI, but which are also often substantially less susceptible to off-resonance effects. Here we consider retinotopic mapping of human visual cortex as a practical test case by which to compare examples of these sequence types for high-resolution fMRI at 7 Tesla. We performed polar angle retinotopic mapping at each of 3 isotropic resolutions (2.0, 1.7, and 1.1 mm) using both accelerated single-shot 2D EPI and accelerated multishot 3D gradient-echo pulse sequences. We found that single-shot EPI indeed led to greater temporal SNR and contrast-to-noise ratios (CNR) than the multishot sequences. However, additional distortion correction in postprocessing was required in order to fully realize these advantages, particularly at higher resolutions. The retinotopic maps produced by both sequence types were qualitatively comparable, and showed equivalent test/retest reliability. Thus, when surface-based analyses are planned, or in other circumstances where geometric distortion is of particular concern, multishot pulse sequences could provide a viable alternative to single-shot EPI.

  7. Magnetic field simulation and shimming analysis of 3.0T superconducting MRI system

    NASA Astrophysics Data System (ADS)

    Yue, Z. K.; Liu, Z. Z.; Tang, G. S.; Zhang, X. C.; Duan, L. J.; Liu, W. C.

    2018-04-01

    3.0T superconducting magnetic resonance imaging (MRI) system has become the mainstream of modern clinical MRI system because of its high field intensity and high degree of uniformity and stability. It has broad prospects in scientific research and other fields. We analyze the principle of magnet designing in this paper. We also perform the magnetic field simulation and shimming analysis of the first 3.0T/850 superconducting MRI system in the world using the Ansoft Maxwell simulation software. We guide the production and optimization of the prototype based on the results of simulation analysis. Thus the magnetic field strength, magnetic field uniformity and magnetic field stability of the prototype is guided to achieve the expected target.

  8. Adaptive suppression of power line interference in ultra-low field magnetic resonance imaging in an unshielded environment.

    PubMed

    Huang, Xiaolei; Dong, Hui; Qiu, Yang; Li, Bo; Tao, Quan; Zhang, Yi; Krause, Hans-Joachim; Offenhäusser, Andreas; Xie, Xiaoming

    2018-01-01

    Power-line harmonic interference and fixed-frequency noise peaks may cause stripe-artifacts in ultra-low field (ULF) magnetic resonance imaging (MRI) in an unshielded environment and in a conductively shielded room. In this paper we describe an adaptive suppression method to eliminate these artifacts in MRI images. This technique utilizes spatial correlation of the interference from different positions, and is realized by subtracting the outputs of the reference channel(s) from those of the signal channel(s) using wavelet analysis and the least squares method. The adaptive suppression method is first implemented to remove the image artifacts in simulation. We then experimentally demonstrate the feasibility of this technique by adding three orthogonal superconducting quantum interference device (SQUID) magnetometers as reference channels to compensate the output of one 2nd-order gradiometer. The experimental results show great improvement in the imaging quality in both 1D and 2D MRI images at two common imaging frequencies, 1.3 kHz and 4.8 kHz. At both frequencies, the effective compensation bandwidth is as high as 2 kHz. Furthermore, we examine the longitudinal relaxation times of the same sample before and after compensation, and show that the MRI properties of the sample did not change after applying adaptive suppression. This technique can effectively increase the imaging bandwidth and be applied to ULF MRI detected by either SQUIDs or Faraday coil in both an unshielded environment and a conductively shielded room. Copyright © 2017 Elsevier Inc. All rights reserved.

  9. High-Speed Real-Time Resting-State fMRI Using Multi-Slab Echo-Volumar Imaging

    PubMed Central

    Posse, Stefan; Ackley, Elena; Mutihac, Radu; Zhang, Tongsheng; Hummatov, Ruslan; Akhtari, Massoud; Chohan, Muhammad; Fisch, Bruce; Yonas, Howard

    2013-01-01

    We recently demonstrated that ultra-high-speed real-time fMRI using multi-slab echo-volumar imaging (MEVI) significantly increases sensitivity for mapping task-related activation and resting-state networks (RSNs) compared to echo-planar imaging (Posse et al., 2012). In the present study we characterize the sensitivity of MEVI for mapping RSN connectivity dynamics, comparing independent component analysis (ICA) and a novel seed-based connectivity analysis (SBCA) that combines sliding-window correlation analysis with meta-statistics. This SBCA approach is shown to minimize the effects of confounds, such as movement, and CSF and white matter signal changes, and enables real-time monitoring of RSN dynamics at time scales of tens of seconds. We demonstrate highly sensitive mapping of eloquent cortex in the vicinity of brain tumors and arterio-venous malformations, and detection of abnormal resting-state connectivity in epilepsy. In patients with motor impairment, resting-state fMRI provided focal localization of sensorimotor cortex compared with more diffuse activation in task-based fMRI. The fast acquisition speed of MEVI enabled segregation of cardiac-related signal pulsation using ICA, which revealed distinct regional differences in pulsation amplitude and waveform, elevated signal pulsation in patients with arterio-venous malformations and a trend toward reduced pulsatility in gray matter of patients compared with healthy controls. Mapping cardiac pulsation in cortical gray matter may carry important functional information that distinguishes healthy from diseased tissue vasculature. This novel fMRI methodology is particularly promising for mapping eloquent cortex in patients with neurological disease, having variable degree of cooperation in task-based fMRI. In conclusion, ultra-high-real-time speed fMRI enhances the sensitivity of mapping the dynamics of resting-state connectivity and cerebro-vascular pulsatility for clinical and neuroscience research applications

  10. MRI in multiple sclerosis: current status and future prospects

    PubMed Central

    Bakshi, Rohit; Thompson, Alan J; Rocca, Maria A; Pelletier, Daniel; Dousset, Vincent; Barkhof, Frederik; Inglese, Matilde; Guttmann, Charles R G; Horsfield, Mark A; Filippi, Massimo

    2008-01-01

    Many promising MRI approaches for research or clinical management of multiple sclerosis (MS) have recently emerged, or are under development or refinement. Advanced MRI methods need to be assessed to determine whether they allow earlier diagnosis or better identification of phenotypes. Improved post-processing should allow more efficient and complete extraction of information from images. Magnetic resonance spectroscopy should improve in sensitivity and specificity with higher field strengths and should enable the detection of a wider array of metabolites. Diffusion imaging is moving closer to the goal of defining structural connectivity and, thereby, determining the functional significance of lesions at specific locations. Cell-specific imaging now seems feasible with new magnetic resonance contrast agents. The imaging of myelin water fraction brings the hope of providing a specific measure of myelin content. Ultra-high-field MRI increases sensitivity, but also presents new technical challenges. Here, we review these recent developments in MRI for MS, and also look forward to refinements in spinal-cord imaging, optic-nerve imaging, perfusion MRI, and functional MRI. Advances in MRI should improve our ability to diagnose, monitor, and understand the pathophysiology of MS. PMID:18565455

  11. Arterial Spin Labeling - Fast Imaging with Steady-State Free Precession (ASL-FISP): A Rapid and Quantitative Perfusion Technique for High Field MRI

    PubMed Central

    Gao, Ying; Goodnough, Candida L.; Erokwu, Bernadette O.; Farr, George W.; Darrah, Rebecca; Lu, Lan; Dell, Katherine M.; Yu, Xin; Flask, Chris A.

    2014-01-01

    Arterial Spin Labeling (ASL) is a valuable non-contrast perfusion MRI technique with numerous clinical applications. Many previous ASL MRI studies have utilized either Echo-Planar Imaging (EPI) or True Fast Imaging with Steady-State Free Precession (True FISP) readouts that are prone to off-resonance artifacts on high field MRI scanners. We have developed a rapid ASL-FISP MRI acquisition for high field preclinical MRI scanners providing perfusion-weighted images with little or no artifacts in less than 2 seconds. In this initial implementation, a FAIR (Flow-Sensitive Alternating Inversion Recovery) ASL preparation was combined with a rapid, centrically-encoded FISP readout. Validation studies on healthy C57/BL6 mice provided consistent estimation of in vivo mouse brain perfusion at 7 T and 9.4 T (249±38 ml/min/100g and 241±17 ml/min/100g, respectively). The utility of this method was further demonstrated in detecting significant perfusion deficits in a C57/BL6 mouse model of ischemic stroke. Reasonable kidney perfusion estimates were also obtained for a healthy C57/BL6 mouse exhibiting differential perfusion in the renal cortex and medulla. Overall, the ASL-FISP technique provides a rapid and quantitative in vivo assessment of tissue perfusion for high field MRI scanners with minimal image artifacts. PMID:24891124

  12. An Ultra-High Field Study of Cerebellar Pathology in Early Relapsing-Remitting Multiple Sclerosis Using MP2RAGE.

    PubMed

    Fartaria, Mário João; OʼBrien, Kieran; Şorega, Alexandra; Bonnier, Guillaume; Roche, Alexis; Falkovskiy, Pavel; Krueger, Gunnar; Kober, Tobias; Bach Cuadra, Meritxell; Granziera, Cristina

    2017-05-01

    The aim of this study was to study focal cerebellar pathology in early stages of multiple sclerosis (MS) using ultra-high-field magnetization-prepared 2 inversion-contrast rapid gradient-echo (7T MP2RAGE). Twenty early-stage relapsing-remitting MS patients underwent an MP2RAGE acquisition at 7 T magnetic resonance imaging (MRI) (images acquired at 2 different resolutions: 0.58 × 0.58 × 0.58 mm, 7T_0.58, and 0.75 × 0.75 × 0.90 mm, 7T_0.75) and 3 T MRI (1.0 × 1.0 × 1.2 mm, 3T_1.0). Total cerebellar lesion load and volume and mean cerebellar lesion volume were compared across images using a Wilcoxon signed-rank test. Mean T1 relaxation times in lesions and normal-appearing tissue as well as contrast-to-noise ratio (CNR) measurements were also compared using a Wilcoxon signed-rank test. A multivariate analysis was applied to assess the contribution of MRI metrics to clinical performance in MS patients. Both 7T_0.58 and 7T_0.75 MP2RAGE showed significantly higher lesion load compared with 3T_1.0 MP2RAGE (P < 0.001). Plaques that were judged as leukocortical in 7T_0.75 and 3T_1.0 MP2RAGEs were instead identified as WM lesions in 7T_0.58 MP2RAGE. Cortical lesion CNR was significantly higher in MP2RAGEs at 7 T than at 3 T. Total lesion load as well as total and mean lesion volume obtained at both 7 T and 3 T MP2RAGE significantly predicted attention (P < 0.05, adjusted R = 0.5), verbal fluency (P < 0.01, adjusted R = 0.6), and motor performance (P = 0.01, adjusted R = 0.7). This study demonstrates the value of 7 T MP2RAGE to study the cerebellum in early MS patients. 7T_0.58 MP2RAGE provides a more accurate anatomical description of white and gray matter pathology compared with 7T_0.75 and 3T_1.0 MP2RAGE, likely due to the improved spatial resolution, lower partial volume effects, and higher CNR.

  13. The MUSE Hubble Ultra Deep Field Survey. II. Spectroscopic redshifts and comparisons to color selections of high-redshift galaxies

    NASA Astrophysics Data System (ADS)

    Inami, H.; Bacon, R.; Brinchmann, J.; Richard, J.; Contini, T.; Conseil, S.; Hamer, S.; Akhlaghi, M.; Bouché, N.; Clément, B.; Desprez, G.; Drake, A. B.; Hashimoto, T.; Leclercq, F.; Maseda, M.; Michel-Dansac, L.; Paalvast, M.; Tresse, L.; Ventou, E.; Kollatschny, W.; Boogaard, L. A.; Finley, H.; Marino, R. A.; Schaye, J.; Wisotzki, L.

    2017-11-01

    We have conducted a two-layered spectroscopic survey (1' × 1' ultra deep and 3' × 3' deep regions) in the Hubble Ultra Deep Field (HUDF) with the Multi Unit Spectroscopic Explorer (MUSE). The combination of a large field of view, high sensitivity, and wide wavelength coverage provides an order of magnitude improvement in spectroscopically confirmed redshifts in the HUDF; i.e., 1206 secure spectroscopic redshifts for Hubble Space Telescope (HST) continuum selected objects, which corresponds to 15% of the total (7904). The redshift distribution extends well beyond z> 3 and to HST/F775W magnitudes as faint as ≈ 30 mag (AB, 1σ). In addition, 132 secure redshifts were obtained for sources with no HST counterparts that were discovered in the MUSE data cubes by a blind search for emission-line features. In total, we present 1338 high quality redshifts, which is a factor of eight increase compared with the previously known spectroscopic redshifts in the same field. We assessed redshifts mainly with the spectral features [O II] at z< 1.5 (473 objects) and Lyα at 2.9 ultra deep and 25.5 mag for deep fields, and the completeness remains ≳ 20% up to 28-29 mag and ≈ 27 mag, respectively. We used the determined redshifts to test continuum color selection (dropout) diagrams of high-z galaxies. The selection condition for F336W dropouts successfully captures ≈ 80% of the targeted z 2.7 galaxies. However, for higher redshift selections (F435W, F606W, and F775W dropouts), the success rates decrease to ≈ 20-40%. We empirically redefine the selection boundaries to make an attempt to improve them to ≈ 60%. The revised boundaries allow bluer colors that capture Lyα emitters with high Lyα equivalent widths falling in the broadbands used for the color-color selection. Along with this paper, we release the redshift and line flux catalog. Based on observations made with

  14. Inventory of MRI applications and workers exposed to MRI-related electromagnetic fields in the Netherlands.

    PubMed

    Schaap, Kristel; Christopher-De Vries, Yvette; Slottje, Pauline; Kromhout, Hans

    2013-12-01

    This study aims to characterise and quantify the population that is occupationally exposed to electromagnetic fields (EMF) from magnetic resonance imaging (MRI) devices and to identify factors that determine the probability and type of exposure. A questionnaire survey was used to collect information about scanners, procedures, historical developments and employees working with or near MRI scanners in clinical and research MRI departments in the Netherlands. Data were obtained from 145 MRI departments. A rapid increase in the use of MRI and field strength of the scanners was observed and quantified. The strongest magnets were employed by academic hospitals and research departments. Approximately 7000 individuals were reported to be working inside an MRI scanner room and were thus considered to have high probability of occupational exposure to static magnetic fields (SMF). Fifty-four per cent was exposed to SMF at least one day per month. The largest occupationally exposed group were radiographers (n ~ 1700). Nine per cent of the 7000 involved workers were regularly present inside a scanner room during image acquisition, when exposure to additional types of EMF is considered a possibility. This practice was most prevalent among workers involved in scanning animals. The data illustrate recent trends and historical developments in magnetic resonance imaging and provide an extensive characterisation of the occupationally exposed population. A considerable number of workers are potentially exposed to MRI-related EMF. Type and frequency of potential exposure depend on the job performed, as well as the type of workplace. Copyright © 2013 The Authors. Published by Elsevier Ireland Ltd.. All rights reserved.

  15. Intracellular bimodal nanoparticles based on quantum dots for high-field MRI at 21.1 T.

    PubMed

    Rosenberg, Jens T; Kogot, Joshua M; Lovingood, Derek D; Strouse, Geoffrey F; Grant, Samuel C

    2010-09-01

    Multimodal, biocompatible contrast agents for high magnetic field applications represent a new class of nanomaterials with significant potential for tracking of fluorescence and MR in vitro and vivo. Optimized for high-field MR applications-including biomedical imaging at 21.1 T, the highest magnetic field available for MRI-these nanoparticles capitalize on the improved performance of chelated Dy(3+) with increasing magnetic field coupled to a noncytotoxic Indium Phosphide/Zinc Sulfide (InP/ZnS) quantum dot that provides fluorescence detection, MR responsiveness, and payload delivery. By surface modifying the quantum dot with a cell-penetrating peptide sequence coupled to an MR contrast agent, the bimodal nanomaterial functions as a self-transfecting high-field MR/optical contrast agent for nonspecific intracellular labeling. Fluorescent images confirm sequestration in perinuclear vesicles of labeled cells, with no apparent cytotoxicity. These techniques can be extended to impart cell selectivity or act as a delivery vehicle for genetic or pharmaceutical interventions. 2010 Wiley-Liss, Inc.

  16. Spatial Distortion in MRI-Guided Stereotactic Procedures: Evaluation in 1.5-, 3- and 7-Tesla MRI Scanners.

    PubMed

    Neumann, Jan-Oliver; Giese, Henrik; Biller, Armin; Nagel, Armin M; Kiening, Karl

    2015-01-01

    Magnetic resonance imaging (MRI) is replacing computed tomography (CT) as the main imaging modality for stereotactic transformations. MRI is prone to spatial distortion artifacts, which can lead to inaccuracy in stereotactic procedures. Modern MRI systems provide distortion correction algorithms that may ameliorate this problem. This study investigates the different options of distortion correction using standard 1.5-, 3- and 7-tesla MRI scanners. A phantom was mounted on a stereotactic frame. One CT scan and three MRI scans were performed. At all three field strengths, two 3-dimensional sequences, volumetric interpolated breath-hold examination (VIBE) and magnetization-prepared rapid acquisition with gradient echo, were acquired, and automatic distortion correction was performed. Global stereotactic transformation of all 13 datasets was performed and two stereotactic planning workflows (MRI only vs. CT/MR image fusion) were subsequently analysed. Distortion correction on the 1.5- and 3-tesla scanners caused a considerable reduction in positional error. The effect was more pronounced when using the VIBE sequences. By using co-registration (CT/MR image fusion), even a lower positional error could be obtained. In ultra-high-field (7 T) MR imaging, distortion correction introduced even higher errors. However, the accuracy of non-corrected 7-tesla sequences was comparable to CT/MR image fusion 3-tesla imaging. MRI distortion correction algorithms can reduce positional errors by up to 60%. For stereotactic applications of utmost precision, we recommend a co-registration to an additional CT dataset. © 2015 S. Karger AG, Basel.

  17. Dissecting the pathobiology of altered MRI signal in amyotrophic lateral sclerosis: A post mortem whole brain sampling strategy for the integration of ultra-high-field MRI and quantitative neuropathology.

    PubMed

    Pallebage-Gamarallage, Menuka; Foxley, Sean; Menke, Ricarda A L; Huszar, Istvan N; Jenkinson, Mark; Tendler, Benjamin C; Wang, Chaoyue; Jbabdi, Saad; Turner, Martin R; Miller, Karla L; Ansorge, Olaf

    2018-03-13

    Amyotrophic lateral sclerosis (ALS) is a clinically and histopathologically heterogeneous neurodegenerative disorder, in which therapy is hindered by the rapid progression of disease and lack of biomarkers. Magnetic resonance imaging (MRI) has demonstrated its potential for detecting the pathological signature and tracking disease progression in ALS. However, the microstructural and molecular pathological substrate is poorly understood and generally defined histologically. One route to understanding and validating the pathophysiological correlates of MRI signal changes in ALS is to directly compare MRI to histology in post mortem human brains. The article delineates a universal whole brain sampling strategy of pathologically relevant grey matter (cortical and subcortical) and white matter tracts of interest suitable for histological evaluation and direct correlation with MRI. A standardised systematic sampling strategy that was compatible with co-registration of images across modalities was established for regions representing phosphorylated 43-kDa TAR DNA-binding protein (pTDP-43) patterns that were topographically recognisable with defined neuroanatomical landmarks. Moreover, tractography-guided sampling facilitated accurate delineation of white matter tracts of interest. A digital photography pipeline at various stages of sampling and histological processing was established to account for structural deformations that might impact alignment and registration of histological images to MRI volumes. Combined with quantitative digital histology image analysis, the proposed sampling strategy is suitable for routine implementation in a high-throughput manner for acquisition of large-scale histology datasets. Proof of concept was determined in the spinal cord of an ALS patient where multiple MRI modalities (T1, T2, FA and MD) demonstrated sensitivity to axonal degeneration and associated heightened inflammatory changes in the lateral corticospinal tract. Furthermore

  18. Exploring structure and function of sensory cortex with 7T MRI.

    PubMed

    Schluppeck, Denis; Sanchez-Panchuelo, Rosa-Maria; Francis, Susan T

    2018-01-01

    In this paper, we present an overview of 7T magnetic resonance imaging (MRI) studies of the detailed function and anatomy of sensory areas of the human brain. We discuss the motivation for the studies, with particular emphasis on increasing the spatial resolution of functional MRI (fMRI) using reduced field-of-view (FOV) data acquisitions. MRI at ultra-high-field (UHF) - defined here as 7T and above - has several advantages over lower field strengths. The intrinsic signal-to-noise ratio (SNR) of images is higher at UHF, and coupled with the increased blood-oxygen-level-dependent (BOLD) signal change, this results in increased BOLD contrast-to-noise ratio (CNR), which can be exploited to improve spatial resolution or detect weaker signals. Additionally, the BOLD signal from the intra-vascular (IV) compartment is relatively diminished compared to lower field strengths. Together, these properties make 7T functional MRI an attractive proposition for high spatial specificity measures. But with the advantages come some challenges. For example, increased vulnerability to susceptibility-induced geometric distortions and signal loss in EPI acquisitions tend to be much larger. Some of these technical issues can be addressed with currently available tools and will be discussed. We highlight the key methodological considerations for high resolution functional and structural imaging at 7 T. We then present recent data using the high spatial resolution available at UHF in studies of the visual and somatosensory cortex to highlight promising developments in this area. Copyright © 2017 Elsevier Inc. All rights reserved.

  19. Ultra-wide-field angiography improves the detection and classification of diabetic retinopathy.

    PubMed

    Wessel, Matthew M; Aaker, Grant D; Parlitsis, George; Cho, Minhee; D'Amico, Donald J; Kiss, Szilárd

    2012-04-01

    To evaluate patients with diabetic retinopathy using ultra-wide-field fluorescein angiography and to compare the visualized retinal pathology with that seen on an overly of conventional 7 standard field (7SF) imaging. Two hundred and eighteen eyes of 118 diabetic patients who underwent diagnostic fluorescein angiography using the Optos Optomap Panoramic 200A imaging system were included. The visualized area of the retina, retinal nonperfusion, retinal neovascularization, and panretinal photocoagulation were quantified by two independent masked graders. The respective areas identified on the ultra-wide-field fluorescein angiography image were compared with an overly of a modified 7SF image as outlined in the Early Treatment Diabetic Retinopathy Study. Ultra-wide-field fluorescein angiograms imaging, on average, demonstrated 3.2 times more total retinal surface area than 7SF. When compared with 7SF, ultra-wide-field fluorescein angiography showed 3.9 times more nonperfusion (P < 0.001), 1.9 times more neovascularization (P = 0.036), and 3.8 times more panretinal photocoagulation (P < 0.001). In 22 eyes (10%), ultra-wide-field fluorescein angiography demonstrated retinal pathology (including nonperfusion and neovascularization) not evident in an 7SF overly. Compared with conventional 7SF imaging, ultra-wide-field fluorescein angiography reveals significantly more retinal vascular pathology in patients with diabetic retinopathy. Improved retinal visualization may alter the classification of diabetic retinopathy and may therefore influence follow-up and treatment of these patients.

  20. Ultra-high vacuum photoelectron linear accelerator

    DOEpatents

    Yu, David U.L.; Luo, Yan

    2013-07-16

    An rf linear accelerator for producing an electron beam. The outer wall of the rf cavity of said linear accelerator being perforated to allow gas inside said rf cavity to flow to a pressure chamber surrounding said rf cavity and having means of ultra high vacuum pumping of the cathode of said rf linear accelerator. Said rf linear accelerator is used to accelerate polarized or unpolarized electrons produced by a photocathode, or to accelerate thermally heated electrons produced by a thermionic cathode, or to accelerate rf heated field emission electrons produced by a field emission cathode.

  1. Fusion: ultra-high-speed and IR image sensors

    NASA Astrophysics Data System (ADS)

    Etoh, T. Goji; Dao, V. T. S.; Nguyen, Quang A.; Kimata, M.

    2015-08-01

    Most targets of ultra-high-speed video cameras operating at more than 1 Mfps, such as combustion, crack propagation, collision, plasma, spark discharge, an air bag at a car accident and a tire under a sudden brake, generate sudden heat. Researchers in these fields require tools to measure the high-speed motion and heat simultaneously. Ultra-high frame rate imaging is achieved by an in-situ storage image sensor. Each pixel of the sensor is equipped with multiple memory elements to record a series of image signals simultaneously at all pixels. Image signals stored in each pixel are read out after an image capturing operation. In 2002, we developed an in-situ storage image sensor operating at 1 Mfps 1). However, the fill factor of the sensor was only 15% due to a light shield covering the wide in-situ storage area. Therefore, in 2011, we developed a backside illuminated (BSI) in-situ storage image sensor to increase the sensitivity with 100% fill factor and a very high quantum efficiency 2). The sensor also achieved a much higher frame rate,16.7 Mfps, thanks to the wiring on the front side with more freedom 3). The BSI structure has another advantage that it has less difficulties in attaching an additional layer on the backside, such as scintillators. This paper proposes development of an ultra-high-speed IR image sensor in combination of advanced nano-technologies for IR imaging and the in-situ storage technology for ultra-highspeed imaging with discussion on issues in the integration.

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

    PubMed

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

    2013-10-01

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

  3. Synthetic Spin-Orbit and Light Field Coupling in Ultra-cold Quantum Gases

    NASA Astrophysics Data System (ADS)

    Dong, Lin

    Ultra-cold quantum gases subjected to light-induced synthetic gauge potentials have become an emergent field of theoretical and experimental studies. Because of the novel application of two-photon Raman transitions, ultra-cold neutral atoms behave like charged particles in magnetic field. The Raman coupling naturally gives rise to an effective spin-orbit interaction which couples the atoms center-of-mass motion to its selected pseudo-spin degrees of freedom. Combined with unprecedented controllability of interactions, geometry, disorder strength, spectroscopy, and high resolution measurement of momentum distribution, etc., we are truly in an exciting era of fulfilling and going beyond Richard Feynman's vision. of realizing quantum simulators to better understand the quantum mechanical nature of the universe, manifested immensely in the ultra-cold regimes. In this dissertation, we present a collection of theoretical progresses made by the doctoral candidate and his colleagues and collaborators. From the past few years of work, we mainly address three aspects of the synthetic spin-orbit and light field induced coupling in ultracold quantum gases: a) The ground-state physics of singleparticle system, two-body bound states, and many-body systems, all of which are subjected to spin-orbit coupling originated from synthetic gauge potentials; b) The symmetry breaking, topological phase transition and quench dynamics, which are conveniently offered by the realized experimental setup; c) The proposal and implications of light field induced dynamical spin-orbit coupling for atoms inside optical cavity. Our work represents an important advancement of theoretical understanding to the active research frontier of ultra-cold atom physics with spin-orbit coupling.

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

    PubMed

    Henning, Anke

    2018-03-01

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

  5. High resolution anatomical and quantitative MRI of the entire human occipital lobe ex vivo at 9.4T.

    PubMed

    Sengupta, S; Fritz, F J; Harms, R L; Hildebrand, S; Tse, D H Y; Poser, B A; Goebel, R; Roebroeck, A

    2018-03-01

    Several magnetic resonance imaging (MRI) contrasts are sensitive to myelin content in gray matter in vivo which has ignited ambitions of MRI-based in vivo cortical histology. Ultra-high field (UHF) MRI, at fields of 7T and beyond, is crucial to provide the resolution and contrast needed to sample contrasts over the depth of the cortex and get closer to layer resolved imaging. Ex vivo MRI of human post mortem samples is an important stepping stone to investigate MRI contrast in the cortex, validate it against histology techniques applied in situ to the same tissue, and investigate the resolutions needed to translate ex vivo findings to in vivo UHF MRI. Here, we investigate key technology to extend such UHF studies to large human brain samples while maintaining high resolution, which allows investigation of the layered architecture of several cortical areas over their entire 3D extent and their complete borders where architecture changes. A 16 channel cylindrical phased array radiofrequency (RF) receive coil was constructed to image a large post mortem occipital lobe sample (~80×80×80mm 3 ) in a wide-bore 9.4T human scanner with the aim of achieving high-resolution anatomical and quantitative MR images. Compared with a human head coil at 9.4T, the maximum Signal-to-Noise ratio (SNR) was increased by a factor of about five in the peripheral cortex. Although the transmit profile with a circularly polarized transmit mode at 9.4T is relatively inhomogeneous over the large sample, this challenge was successfully resolved with parallel transmit using the kT-points method. Using this setup, we achieved 60μm anatomical images for the entire occipital lobe showing increased spatial definition of cortical details compared to lower resolutions. In addition, we were able to achieve sufficient control over SNR, B 0 and B 1 homogeneity and multi-contrast sampling to perform quantitative T 2 * mapping over the same volume at 200μm. Markov Chain Monte Carlo sampling provided

  6. Acoustic pressure waves induced in human heads by RF pulses from high-field MRI scanners.

    PubMed

    Lin, James C; Wang, Zhangwei

    2010-04-01

    The current evolution toward greater image resolution from magnetic resonance image (MRI) scanners has prompted the exploration of higher strength magnetic fields and use of higher levels of radio frequencies (RFs). Auditory perception of RF pulses by humans has been reported during MRI with head coils. It has shown that the mechanism of interaction for the auditory effect is caused by an RF pulse-induced thermoelastic pressure wave inside the head. We report a computational study of the intensity and frequency of thermoelastic pressure waves generated by RF pulses in the human head inside high-field MRI and clinical scanners. The U.S. Food and Drug Administration (U.S. FDA) guides limit the local specific absorption rate (SAR) in the body-including the head-to 8 W kg(-1). We present results as functions of SAR and show that for a given SAR the peak acoustic pressures generated in the anatomic head model were essentially the same at 64, 300, and 400 MHz (1.5, 7.0, and 9.4 T). Pressures generated in the anatomic head are comparable to the threshold pressure of 20 mPa for sound perception by humans at the cochlea for 4 W kg(-1). Moreover, results indicate that the peak acoustic pressure in the brain is only 2 to 3 times the auditory threshold at the U.S. FDA guideline of 8 W kg(-1). Even at a high SAR of 20 W kg(-1), where the acoustic pressure in the brain could be more than 7 times the auditory threshold, the sound pressure levels would not be more than 17 db above threshold of perception at the cochlea.

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

    PubMed

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

    2013-03-01

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

  8. Microstructural imaging of the human brain with a 'super-scanner': 10 key advantages of ultra-strong gradients for diffusion MRI.

    PubMed

    Jones, D K; Alexander, D C; Bowtell, R; Cercignani, M; Dell'Acqua, F; McHugh, D J; Miller, K L; Palombo, M; Parker, G J M; Rudrapatna, U S; Tax, C M W

    2018-05-22

    The key component of a microstructural diffusion MRI 'super-scanner' is a dedicated high-strength gradient system that enables stronger diffusion weightings per unit time compared to conventional gradient designs. This can, in turn, drastically shorten the time needed for diffusion encoding, increase the signal-to-noise ratio, and facilitate measurements at shorter diffusion times. This review, written from the perspective of the UK National Facility for In Vivo MR Imaging of Human Tissue Microstructure, an initiative to establish a shared 300 mT/m-gradient facility amongst the microstructural imaging community, describes ten advantages of ultra-strong gradients for microstructural imaging. Specifically, we will discuss how the increase of the accessible measurement space compared to a lower-gradient systems (in terms of Δ, b-value, and TE) can accelerate developments in the areas of 1) axon diameter distribution mapping; 2) microstructural parameter estimation; 3) mapping micro-vs macroscopic anisotropy features with gradient waveforms beyond a single pair of pulsed-gradients; 4) multi-contrast experiments, e.g. diffusion-relaxometry; 5) tractography and high-resolution imaging in vivo and 6) post mortem; 7) diffusion-weighted spectroscopy of metabolites other than water; 8) tumour characterisation; 9) functional diffusion MRI; and 10) quality enhancement of images acquired on lower-gradient systems. We finally discuss practical barriers in the use of ultra-strong gradients, and provide an outlook on the next generation of 'super-scanners'. Copyright © 2018. Published by Elsevier Inc.

  9. Multi-flux-transformer MRI detection with an atomic magnetometer

    PubMed Central

    Savukov, Igor; Karaulanov, Todor

    2014-01-01

    Recently, anatomical ultra-low field (ULF) MRI has been demonstrated with an atomic magnetometer (AM). A flux-transformer (FT) has been used for decoupling MRI fields and gradients to avoid their negative effects on AM performance. The field of view (FOV) was limited because of the need to compromise between the size of the FT input coil and MRI sensitivity per voxel. Multi-channel acquisition is a well-known solution to increase FOV without significantly reducing sensitivity. In this paper, we demonstrate two-fold FOV increase with the use of three FT input coils. We also show that it is possible to use a single atomic magnetometer and single acquisition channel to acquire three independent MRI signals by applying a frequency-encoding gradient along the direction of the detection array span. The approach can be generalized to more channels and can be critical for imaging applications of non-cryogenic ULF MRI where FOV needs to be large, including head, hand, spine, and whole-body imaging. PMID:25462946

  10. High and ultra-high resolution metabolite mapping of the human brain using 1H FID MRSI at 9.4T.

    PubMed

    Nassirpour, Sahar; Chang, Paul; Henning, Anke

    2018-03-01

    Magnetic resonance spectroscopic imaging (MRSI) is a promising technique for mapping the spatial distribution of multiple metabolites in the human brain. These metabolite maps can be used as a diagnostic tool to gain insight into several biochemical processes and diseases in the brain. In comparison to lower field strengths, MRSI at ultra-high field strengths benefits from a higher signal to noise ratio (SNR) as well as higher chemical shift dispersion, and hence spectral resolution. This study combines the benefits of an ultra-high field magnet with the advantages of an ultra-short TE and TR single-slice FID-MRSI sequence (such as negligible J-evolution and loss of SNR due to T 2 relaxation effects) and presents the first metabolite maps acquired at 9.4T in the healthy human brain at both high (voxel size of 97.6µL) and ultra-high (voxel size of 24.4µL) spatial resolutions in a scan time of 11 and 46min respectively. In comparison to lower field strengths, more anatomically-detailed maps with higher SNR from a larger number of metabolites are shown. A total of 12 metabolites including glutamate (Glu), glutamine (Gln), N-acetyl-aspartyl-glutamate (NAAG), Gamma-aminobutyric acid (GABA) and glutathione (GSH) are reliably mapped. Comprehensive description of the methodology behind these maps is provided. Copyright © 2016 Elsevier Inc. All rights reserved.

  11. Flexible, phase-matched, linear receive arrays for high-field MRI in monkeys.

    PubMed

    Goense, Jozien; Logothetis, Nikos K; Merkle, Hellmut

    2010-10-01

    High signal-to-noise ratios (SNR) are essential for high-resolution anatomical and functional MRI. Phased arrays are advantageous for this but have the drawback that they often have inflexible and bulky configurations. Particularly in experiments where functional MRI is combined with simultaneous electrophysiology, space constraints can be prohibitive. To this end we developed a highly flexible multiple receive element phased array for use on anesthetized monkeys. The elements are interchangeable and different sizes and combinations of coil elements can be used, for instance, combinations of single and overlapped elements. The preamplifiers including control electronics are detachable and can serve a variety of prefabricated and phase matched arrays of different configurations, allowing the elements to always be placed in close proximity to the area of interest. Optimizing performance of the individual elements ensured high SNR at the cortical surface as well as in deeper laying structures. Performance of a variety of arrangements of gapped linear arrays was evaluated at 4.7 and 7T in high-resolution anatomical and functional MRI. Copyright © 2010 Elsevier Inc. All rights reserved.

  12. Exposure to MRI-related magnetic fields and vertigo in MRI workers.

    PubMed

    Schaap, Kristel; Portengen, Lützen; Kromhout, Hans

    2016-03-01

    Vertigo has been reported by people working around magnetic resonance imaging (MRI) scanners and was found to increase with increasing strength of scanner magnets. This suggests an association with exposure to static magnetic fields (SMF) and/or motion-induced time-varying magnetic fields (TVMF). This study assessed the association between various metrics of shift-long exposure to SMF and TVMF and self-reported vertigo among MRI workers. We analysed 358 shifts from 234 employees at 14 MRI facilities in the Netherlands. Participants used logbooks to report vertigo experienced during the work day at the MRI facility. In addition, personal exposure to SMF and TVMF was measured during the same shifts, using portable magnetic field dosimeters. Vertigo was reported during 22 shifts by 20 participants and was significantly associated with peak and time-weighted average (TWA) metrics of SMF as well as TVMF exposure. Associations were most evident with full-shift TWA TVMF exposure. The probability of vertigo occurrence during a work shift exceeded 5% at peak exposure levels of 409 mT and 477 mT/s and at full-shift TWA levels of 3 mT and 0.6 mT/s. These results confirm the hypothesis that vertigo is associated with exposure to MRI-related SMF and TVMF. Strong correlations between various metrics of shift-long exposure make it difficult to disentangle the effects of SMF and TVMF exposure, or identify the most relevant exposure metric. On the other hand, this also implies that several metrics of shift-long exposure to SMF and TVMF should perform similarly in epidemiological studies on MRI-related vertigo. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

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

    DOEpatents

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

    2016-02-09

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

  14. Safety Implications of High-Field MRI: Actuation of Endogenous Magnetic Iron Oxides in the Human Body

    PubMed Central

    Dobson, Jon; Bowtell, Richard; Garcia-Prieto, Ana; Pankhurst, Quentin

    2009-01-01

    Background Magnetic Resonance Imaging scanners have become ubiquitous in hospitals and high-field systems (greater than 3 Tesla) are becoming increasingly common. In light of recent European Union moves to limit high-field exposure for those working with MRI scanners, we have evaluated the potential for detrimental cellular effects via nanomagnetic actuation of endogenous iron oxides in the body. Methodology Theoretical models and experimental data on the composition and magnetic properties of endogenous iron oxides in human tissue were used to analyze the forces on iron oxide particles. Principal Finding and Conclusions Results show that, even at 9.4 Tesla, forces on these particles are unlikely to disrupt normal cellular function via nanomagnetic actuation. PMID:19412550

  15. SMUVS: Spitzer Matching survey of the UltraVISTA ultra-deep Stripes

    NASA Astrophysics Data System (ADS)

    Caputi, Karina; Ashby, Matthew; Fazio, Giovanni; Huang, Jiasheng; Dunlop, James; Franx, Marijn; Le Fevre, Olivier; Fynbo, Johan; McCracken, Henry; Milvang-Jensen, Bo; Muzzin, Adam; Ilbert, Olivier; Somerville, Rachel; Wechsler, Risa; Behroozi, Peter; Lu, Yu

    2014-12-01

    We request 2026.5 hours to homogenize the matching ultra-deep IRAC data of the UltraVISTA ultra-deep stripes, producing a final area of ~0.6 square degrees with the deepest near- and mid-IR coverage existing in any such large area of the sky (H, Ks, [3.6], [4.5] ~ 25.3-26.1 AB mag; 5 sigma). The UltraVISTA ultra-deep stripes are contained within the larger COSMOS field, which has a rich collection of multi-wavelength, ancillary data, making it ideal to study different aspects of galaxy evolution with high statistical significance and excellent redshift accuracy. The UltraVISTA ultra-deep stripes are the region of the COSMOS field where these studies can be pushed to the highest redshifts, but securely identifying high-z galaxies, and determining their stellar masses, will only be possible if ultra-deep mid-IR data are available. Our IRAC observations will allow us to: 1) extend the galaxy stellar mass function at redshifts z=3 to z=5 to the intermediate mass regime (M~5x10^9-10^10 Msun), which is critical to constrain galaxy formation models; 2) gain a factor of six in the area where it is possible to effectively search for z>=6 galaxies and study their properties; 3) measure, for the first time, the large-scale structure traced by an unbiased galaxy sample at z=5 to z=7, and make the link to their host dark matter haloes. This cannot be done in any other field of the sky, as the UltraVISTA ultra-deep stripes form a quasi-contiguous, regular-shape field, which has a unique combination of large area and photometric depth. 4) provide a unique resource for the selection of secure z>5 targets for JWST and ALMA follow up. Our observations will have an enormous legacy value which amply justifies this new observing-time investment in the COSMOS field. Spitzer cannot miss this unique opportunity to open up a large 0.6 square-degree window to the early Universe.

  16. MRI of the lung gas-space at very low-field using hyperpolarized noble gases

    NASA Technical Reports Server (NTRS)

    Venkatesh, Arvind K.; Zhang, Adelaide X.; Mansour, Joey; Kubatina, Lyubov; Oh, Chang Hyun; Blasche, Gregory; Selim Unlu, M.; Balamore, Dilip; Jolesz, Ferenc A.; Goldberg, Bennett B.; hide

    2003-01-01

    In hyperpolarized (HP) noble-gas magnetic resonance imaging, large nuclear spin polarizations, about 100,000 times that ordinarily obtainable at thermal equilibrium, are created in 3He and 129Xe. The enhanced signal that results can be employed in high-resolution MRI studies of void spaces such as in the lungs. In HP gas MRI the signal-to-noise ratio (SNR) depends only weakly on the static magnetic field (B(0)), making very low-field (VLF) MRI possible; indeed, it is possible to contemplate portable MRI using light-weight solenoids or permanent magnets. This article reports the first in vivo VLF MR images of the lungs in humans and in rats, obtained at a field of only 15 millitesla (150 Gauss).

  17. Zero- to low-field MRI with averaging of concomitant gradient fields.

    PubMed

    Meriles, Carlos A; Sakellariou, Dimitris; Trabesinger, Andreas H; Demas, Vasiliki; Pines, Alexander

    2005-02-08

    Magnetic resonance imaging (MRI) encounters fundamental limits in circumstances in which the static magnetic field is not sufficiently strong to truncate unwanted, so-called concomitant components of the gradient field. This limitation affects the attainable optimal image fidelity and resolution most prominently in low-field imaging. In this article, we introduce the use of pulsed magnetic-field averaging toward relaxing these constraints. It is found that the image of an object can be retrieved by pulsed low fields in the presence of the full spatial variation of the imaging encoding gradient field even in the absence of the typical uniform high-field time-independent contribution. In addition, error-compensation schemes can be introduced through the application of symmetrized pulse sequences. Such schemes substantially mitigate artifacts related to evolution in strong magnetic-field gradients, magnetic fields that vary in direction and orientation, and imperfections of the applied field pulses.

  18. Formation of Multi-Layer Structures in Bi3Pb7 Intermetallic Compounds under an Ultra-High Gravitational Field

    NASA Astrophysics Data System (ADS)

    Mashimo, T.; Iguchi, Y.; Bagum, R.; Sano, T.; Sakata, O.; Ono, M.; Okayasu, S.

    2008-02-01

    Ultra-high gravitational field (Mega-gravity field) can promote sedimentation of atoms (diffusion) even in solids, and is expected to form a compositionally-graded structure and/or nonequilibrium phase in multi-component condensed matter. We had achieved sedimentation of substitutional solute atoms in miscible systems (Bi-Sb, In-Pb, etc.). In this study, a mega-gravity experiment at high temperature was performed on a thin-plate sample (0.7 mm in thickness) of the intermetallic compound Bi3Pb7. A visible four-layer structure was produced, which exhibited different microscopic structures. In the lowest-gravity region layer, Bi phase appeared. In the mid layers, a compositionally-graded structure was formed, with differences observed in the powder X-ray diffraction patterns. Such a multi-layer structure is expected to exhibit unique physical properties such as superconductivity.

  19. Ultra-low field T1 vs. T1rho at 3T and 7T: study of rotationally immobilized protein gels and animal brain tissues

    NASA Astrophysics Data System (ADS)

    Dong, Hui; Inglis, Ben; Barr, Ian; Clarke, John

    2015-03-01

    Clinical magnetic resonance imaging (MRI) machines operating in static fields of typically 1.5 T or 3 T can capture information on slow molecular dynamics utilizing the so-called T1rho technique. This technique, in which a radiofrequency (RF) spin-lock field is applied with microtesla amplitude, has been used, for example, to determine the onset time of stroke in studies on rats. The long RF pulse, however, may exceed the specific absorption rate (SAR) limit, putting subjects at risk. Ultra-low-field (ULF) MRI, based on Superconducting Quantum Interference Devices (SQUIDs), directly detects proton signals at a static magnetic field of typically 50-250 μT. Using our ULF MRI system with adjustable static field of typically 55 to 240 μT, we systematically measured the T1 and T2 dispersion profiles of rotationally immobilized protein gels (bovine serum albumin), ex vivo pig brains, and ex vivo rat brains with induced stroke. Comparing the ULF results with T1rho dispersion obtained at 3 T and 7 T, we find that the degree of protein immobilization determines the frequency-dependence of both T1 and T1rho. Furthermore, T1rho and ULF T1 show similar results for stroke, suggesting that ULF MRI may be used to image traumatic brain injury with negligible SAR. This research was supported by the Henry H. Wheeler, Jr. Brain Imaging Center and the Donaldson Trust.

  20. Ultra-wide-field fundus autofluorescence in multiple evanescent white dot syndrome.

    PubMed

    Hashimoto, Hideaki; Kishi, Shoji

    2015-04-01

    To observe the progression of affected lesions using ultra-wide-field fundus autofluorescence (FAF) in multiple evanescent white dot syndrome. Retrospective, observational case series. setting: Institutional. 14 eyes of 13 patients (mean age, 35.8 years) with acute disease unilaterally. Patients underwent ultra-wide-field FAF, spectral-domain optical coherence tomography (SD OCT), multifocal electroretinography (mfERG), and Goldmann or automated perimetry; the best-corrected visual acuity (BCVA) and refractive error were measured. Ability of ultra-wide-field FAF to detect lesions with greater sensitivity compared with color fundus photography. Ultra-wide-field FAF imaging enabled improved visualization of the affected lesions and showed that the core lesion was in the posterior fundus involving the peripapillary retina and posterior pole and surrounded by hyper-autofluorescent spots outside the vascular arcade. The posterior lesions expanded rapidly and peripheral spots spread farther peripherally and reached a maximal extent during the acute stage. During follow-up, the peripheral hyper-autofluorescent spots resolved and then hyper-autofluorescence of the posterior fundus gradually faded. SD OCT showed diffuse disruption of the photoreceptor inner segment/outer segment junction (IS/OS) in the posterior fundus during the acute stage. The correlation between the IS/OS abnormality and hyper-autofluorescent areas was unclear. The disrupted IS/OS was restored with normalization of the FAF. Ultra-wide-field FAF showed that the lesions arise from the peripapillary retina and the posterior pole and spread peripherally in a centrifugal manner during the acute stage. The hyper-autofluorescent spots faded from the periphery in a centripetal manner. Copyright © 2015 Elsevier Inc. All rights reserved.

  1. In Situ and Ex Situ Low-Field NMR Spectroscopy and MRI Endowed by SABRE Hyperpolarization**

    PubMed Central

    Barskiy, Danila A.; Kovtunov, Kirill V.; Koptyug, Igor V.; He, Ping; Groome, Kirsten A.; Best, Quinn A.; Shi, Fan; Goodson, Boyd M.; Shchepin, Roman V.; Truong, Milton L.; Coffey, Aaron M.; Waddell, Kevin W.; Chekmenev, Eduard Y.

    2015-01-01

    By using 5.75 and 47.5 mT nuclear magnetic resonance (NMR) spectroscopy, up to 105-fold sensitivity enhancement through signal amplification by reversible exchange (SABRE) was enabled, and subsecond temporal resolution was used to monitor an exchange reaction that resulted in the buildup and decay of hyperpolarized species after parahydrogen bubbling. We demonstrated the high-resolution low-field proton magnetic resonance imaging (MRI) of pyridine in a 47.5 mT magnetic field endowed by SABRE. Molecular imaging (i.e. imaging of dilute hyperpolarized substances rather than the bulk medium) was conducted in two regimes: in situ real-time MRI of the reaction mixture (in which pyridine was hyperpolarized), and ex situ MRI (in which hyperpolarization decays) of the liquid hyperpolarized product. Low-field (milli-Tesla range, e.g. 5.75 and 47.5 mT used in this study) parahydrogen-enhanced NMR and MRI, which are free from the limitations of high-field magnetic resonance (including susceptibility-induced gradients of the static magnetic field at phase interfaces), potentially enables new imaging applications as well as differentiation of hyperpolarized chemical species on demand by exploiting spin manipulations with static and alternating magnetic fields. PMID:25367202

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

    NASA Astrophysics Data System (ADS)

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

    2013-06-01

    High sensitivity magnetoelectric sensors with their electromechanical resonance frequencies < 200 kHz have been recently demonstrated using magnetostrictive/piezoelectric magnetoelectric heterostructures. In this work, we demonstrate a novel magnetoelectric nano-electromechanical systems (NEMS) resonator with an electromechanical resonance frequency of 215 MHz based on an AlN/(FeGaB/Al2O3) × 10 magnetoelectric heterostructure for detecting DC magnetic fields. This magnetoelectric NEMS resonator showed a high quality factor of 735, and strong magnetoelectric coupling with a large voltage tunable sensitivity. The admittance of the magnetoelectric NEMS resonator was very sensitive to DC magnetic fields at its electromechanical resonance, which led to a new detection mechanism for ultra-sensitive self-biased RF NEMS magnetoelectric sensor with a low limit of detection of DC magnetic fields of ~300 picoTelsa. The magnetic/piezoelectric heterostructure based RF NEMS magnetoelectric sensor is compact, power efficient and readily integrated with CMOS technology, which represents a new class of ultra-sensitive magnetometers for DC and low frequency AC magnetic fields.

  3. Windows on the human body--in vivo high-field magnetic resonance research and applications in medicine and psychology.

    PubMed

    Moser, Ewald; Meyerspeer, Martin; Fischmeister, Florian Ph S; Grabner, Günther; Bauer, Herbert; Trattnig, Siegfried

    2010-01-01

    Analogous to the evolution of biological sensor-systems, the progress in "medical sensor-systems", i.e., diagnostic procedures, is paradigmatically described. Outstanding highlights of this progress are magnetic resonance imaging (MRI) and spectroscopy (MRS), which enable non-invasive, in vivo acquisition of morphological, functional, and metabolic information from the human body with unsurpassed quality. Recent achievements in high and ultra-high field MR (at 3 and 7 Tesla) are described, and representative research applications in Medicine and Psychology in Austria are discussed. Finally, an overview of current and prospective research in multi-modal imaging, potential clinical applications, as well as current limitations and challenges is given.

  4. Impact of the MLC on the MRI field distortion of a prototype MRI-linac

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kolling, Stefan; Keall, Paul; Oborn, Brad

    2013-12-15

    Purpose: To cope with intrafraction tumor motion, integrated MRI-linac systems for real-time image guidance are currently under development. The multileaf collimator (MLC) is a key component in every state-of-the-art radiotherapy treatment system, allowing for accurate field shaping and tumor tracking. This work quantifies the magnetic impact of a widely used MLC on the MRI field homogeneity for such a modality.Methods: The finite element method was employed to model a MRI-linac assembly comprised of a 1.0 T split-bore MRI magnet and the key ferromagnetic components of a Varian Millennium 120 MLC, namely, the leaves and motors. Full 3D magnetic field maps ofmore » the system were generated. From these field maps, the peak-to-peak distortion within the MRI imaging volume was evaluated over a 30 cm diameter sphere volume (DSV) around the isocenter and compared to a maximum preshim inhomogeneity of 300 μT. Five parametric studies were performed: (1) The source-to-isocenter distance (SID) was varied from 100 to 200 cm, to span the range of a compact system to that with lower magnetic coupling. (2) The MLC model was changed from leaves only to leaves with motors, to determine the contribution to the total distortion caused by MLC leaves and motors separately. (3) The system was configured in the inline or perpendicular orientation, i.e., the linac treatment beam was oriented parallel or perpendicular to the magnetic field direction. (4) The treatment field size was varied from 0 × 0 to 20×20 cm{sup 2}, to span the range of clinical treatment fields. (5) The coil currents were scaled linearly to produce magnetic field strengths B{sub 0} of 0.5, 1.0, and 1.5 T, to estimate how the MLC impact changes with B{sub 0}.Results: (1) The MLC-induced MRI field distortion fell continuously with increasing SID. (2) MLC leaves and motors were found to contribute to the distortion in approximately equal measure. (3) Due to faster falloff of the fringe field, the field

  5. Proton beam deflection in MRI fields: Implications for MRI-guided proton therapy.

    PubMed

    Oborn, B M; Dowdell, S; Metcalfe, P E; Crozier, S; Mohan, R; Keall, P J

    2015-05-01

    This paper investigates, via magnetic modeling and Monte Carlo simulation, the ability to deliver proton beams to the treatment zone inside a split-bore MRI-guided proton therapy system. Field maps from a split-bore 1 T MRI-Linac system are used as input to geant4 Monte Carlo simulations which model the trajectory of proton beams during their paths to the isocenter of the treatment area. Both inline (along the MRI bore) and perpendicular (through the split-bore gap) orientations are simulated. Monoenergetic parallel and diverging beams of energy 90, 195, and 300 MeV starting from 1.5 and 5 m above isocenter are modeled. A phase space file detailing a 2D calibration pattern is used to set the particle starting positions, and their spatial location as they cross isocenter is recorded. No beam scattering, collimation, or modulation of the proton beams is modeled. In the inline orientation, the radial symmetry of the solenoidal style fringe field acts to rotate the protons around the beam's central axis. For protons starting at 1.5 m from isocenter, this rotation is 19° (90 MeV) and 9.8° (300 MeV). A minor focusing toward the beam's central axis is also seen, but only significant, i.e., 2 mm shift at 150 mm off-axis, for 90 MeV protons. For the perpendicular orientation, the main MRI field and near fringe field act as the strongest to deflect the protons in a consistent direction. When starting from 1.5 m above isocenter shifts of 135 mm (90 MeV) and 65 mm (300 MeV) were observed. Further to this, off-axis protons are slightly deflected toward or away from the central axis in the direction perpendicular to the main deflection direction. This leads to a distortion of the phase space pattern, not just a shift. This distortion increases from zero at the central axis to 10 mm (90 MeV) and 5 mm (300 MeV) for a proton 150 mm off-axis. In both orientations, there is a small but subtle difference in the deflection and distortion pattern between protons fired parallel to the

  6. Multi-flux-transformer MRI detection with an atomic magnetometer.

    PubMed

    Savukov, Igor; Karaulanov, Todor

    2014-12-01

    Recently, anatomical ultra-low field (ULF) MRI has been demonstrated with an atomic magnetometer (AM). A flux-transformer (FT) has been used for decoupling MRI fields and gradients to avoid their negative effects on AM performance. The field of view (FOV) was limited because of the need to compromise between the size of the FT input coil and MRI sensitivity per voxel. Multi-channel acquisition is a well-known solution to increase FOV without significantly reducing sensitivity. In this paper, we demonstrate twofold FOV increase with the use of three FT input coils. We also show that it is possible to use a single atomic magnetometer and single acquisition channel to acquire three independent MRI signals by applying a frequency-encoding gradient along the direction of the detection array span. The approach can be generalized to more channels and can be critical for imaging applications of non-cryogenic ULF MRI where FOV needs to be large, including head, hand, spine, and whole-body imaging. Copyright © 2014 Elsevier Inc. All rights reserved.

  7. Laser beam welding of new ultra-high strength and supra-ductile steels

    NASA Astrophysics Data System (ADS)

    Dahmen, Martin

    2015-03-01

    Ultra-high strength and supra-ductile are entering fields of new applications. Those materials are excellent candidates for modern light-weight construction and functional integration. As ultra-high strength steels the stainless martensitic grade 1.4034 and the bainitic steel UNS 53835 are investigated. For the supra-ductile steels stand two high austenitic steels with 18 and 28 % manganese. As there are no processing windows an approach from the metallurgical base on is required. Adjusting the weld microstructure the Q+P and the QT steels require weld heat treatment. The HSD steel is weldable without. Due to their applications the ultra-high strength steels are welded in as-rolled and strengthened condition. Also the reaction of the weld on hot stamping is reflected for the martensitic grades. The supra-ductile steels are welded as solution annealed and work hardened by 50%. The results show the general suitability for laser beam welding.

  8. Development of Non-Proprietary Ultra-High Performance Concrete : Research Topic Statement

    DOT National Transportation Integrated Search

    2014-05-29

    Ultra-high performance concrete became commercially available in the U.S. in 2000. Since then, UHPC has been actively promoted by the Federal Highway Administration. UHPC has mostly been used in the U.S. for field-cast connections of prefabricated br...

  9. Ultra thin metallic coatings to control near field radiative heat transfer

    NASA Astrophysics Data System (ADS)

    Esquivel-Sirvent, R.

    2016-09-01

    We present a theoretical calculation of the changes in the near field radiative heat transfer between two surfaces due to the presence of ultra thin metallic coatings on semiconductors. Depending on the substrates, the radiative heat transfer is modulated by the thickness of the ultra thin film. In particular we consider gold thin films with thicknesses varying from 4 to 20 nm. The ultra-thin film has an insulator-conductor transition close to a critical thickness of dc = 6.4 nm and there is an increase in the near field spectral heat transfer just before the percolation transition. Depending on the substrates (Si or SiC) and the thickness of the metallic coatings we show how the near field heat transfer can be increased or decreased as a function of the metallic coating thickness. The calculations are based on available experimental data for the optical properties of ultrathin coatings.

  10. Ultra-wide-field and autofluorescence imaging of choroidal dystrophies.

    PubMed

    Yuan, Alex; Kaines, Andrew; Jain, Atul; Reddy, Shantan; Schwartz, Steven D; Sarraf, David

    2010-10-28

    The authors retrospectively identified 2 cases of gyrate atrophy, 3 cases of choroideremia, and 1 case of the carrier state of choroideremia who underwent ultra-wide-field fundus photography and fluorescein angiography. The findings were studied and compared to standard fundus photography and fluorescein angiography. Gyrate atrophy demonstrated a diffuse confluent extent of chorioretinal atrophy extending from the anterior to the posterior pole to the periphery. Choroideremia demonstrated a patchy irregular pattern of chorioretinal atrophy extending from the posterior pole to the periphery. Peripheral reticular degeneration without chorioretinal atrophy was appreciated in the carrier state. Ultra-wide-field imaging of these choroidal dystrophies demonstrated distinctive patterns that may aid in their identification and diagnosis. Copyright 2010, SLACK Incorporated.

  11. Development of ultra-high temperature material characterization capabilities using digital image correlation analysis

    NASA Astrophysics Data System (ADS)

    Cline, Julia Elaine

    2011-12-01

    Ultra-high temperature deformation measurements are required to characterize the thermo-mechanical response of material systems for thermal protection systems for aerospace applications. The use of conventional surface-contacting strain measurement techniques is not practical in elevated temperature conditions. Technological advancements in digital imaging provide impetus to measure full-field displacement and determine strain fields with sub-pixel accuracy by image processing. In this work, an Instron electromechanical axial testing machine with a custom-designed high temperature gripping mechanism is used to apply quasi-static tensile loads to graphite specimens heated to 2000°F (1093°C). Specimen heating via Joule effect is achieved and maintained with a custom-designed temperature control system. Images are captured at monotonically increasing load levels throughout the test duration using an 18 megapixel Canon EOS Rebel T2i digital camera with a modified Schneider Kreutznach telecentric lens and a combination of blue light illumination and narrow band-pass filter system. Images are processed using an open-source Matlab-based digital image correlation (DIC) code. Validation of source code is performed using Mathematica generated images with specified known displacement fields in order to gain confidence in accurate software tracking capabilities. Room temperature results are compared with extensometer readings. Ultra-high temperature strain measurements for graphite are obtained at low load levels, demonstrating the potential for non-contacting digital image correlation techniques to accurately determine full-field strain measurements at ultra-high temperature. Recommendations are given to improve the experimental set-up to achieve displacement field measurements accurate to 1/10 pixel and strain field accuracy of less than 2%.

  12. Ultra High Bypass Integrated System Test

    NASA Image and Video Library

    2015-09-14

    NASA’s Environmentally Responsible Aviation Project, in collaboration with the Federal Aviation Administration (FAA) and Pratt & Whitney, completed testing of an Ultra High Bypass Ratio Turbofan Model in the 9’ x 15’ Low Speed Wind Tunnel at NASA Glenn Research Center. The fan model is representative of the next generation of efficient and quiet Ultra High Bypass Ratio Turbofan Engine designs.

  13. Ultra Thin Poly-Si Nanosheet Junctionless Field-Effect Transistor with Nickel Silicide Contact

    PubMed Central

    Lin, Yu-Ru; Tsai, Wan-Ting; Wu, Yung-Chun; Lin, Yu-Hsien

    2017-01-01

    This study demonstrated an ultra thin poly-Si junctionless nanosheet field-effect transistor (JL NS-FET) with nickel silicide contact. For the nickel silicide film, two-step annealing and a Ti capping layer were adopted to form an ultra thin uniform nickel silicide film with low sheet resistance (Rs). The JL NS-FET with nickel silicide contact exhibited favorable electrical properties, including a high driving current (>107A), subthreshold slope (186 mV/dec.), and low parasitic resistance. In addition, this study compared the electrical characteristics of JL NS-FETs with and without nickel silicide contact. PMID:29112139

  14. Ultra Thin Poly-Si Nanosheet Junctionless Field-Effect Transistor with Nickel Silicide Contact.

    PubMed

    Lin, Yu-Ru; Tsai, Wan-Ting; Wu, Yung-Chun; Lin, Yu-Hsien

    2017-11-07

    This study demonstrated an ultra thin poly-Si junctionless nanosheet field-effect transistor (JL NS-FET) with nickel silicide contact. For the nickel silicide film, two-step annealing and a Ti capping layer were adopted to form an ultra thin uniform nickel silicide film with low sheet resistance (Rs). The JL NS-FET with nickel silicide contact exhibited favorable electrical properties, including a high driving current (>10⁷A), subthreshold slope (186 mV/dec.), and low parasitic resistance. In addition, this study compared the electrical characteristics of JL NS-FETs with and without nickel silicide contact.

  15. Low-field MRI of laser polarized noble gas

    NASA Technical Reports Server (NTRS)

    Tseng, C. H.; Wong, G. P.; Pomeroy, V. R.; Mair, R. W.; Hinton, D. P.; Hoffmann, D.; Stoner, R. E.; Hersman, F. W.; Cory, D. G.; Walsworth, R. L.

    1998-01-01

    NMR images of laser polarized 3He gas were obtained at 21 G using a simple, homebuilt instrument. At such low fields magnetic resonance imaging (MRI) of thermally polarized samples (e.g., water) is not practical. Low-field noble gas MRI has novel scientific, engineering, and medical applications. Examples include portable systems for diagnosis of lung disease, as well as imaging of voids in porous media and within metallic systems.

  16. Ultra-high quality factors in superconducting niobium cavities in ambient magnetic fields up to 190 mG

    DOE PAGES

    Romanenko, A.; Grassellino, A.; Crawford, A. C.; ...

    2014-12-10

    Ambient magnetic field, if trapped in the penetration depth, leads to the residual resistance and therefore sets the limit for the achievable quality factors in superconducting niobium resonators for particle accelerators. Here, we show that a complete expulsion of the magnetic flux can be performed and leads to: (1) record quality factors Q > 2 x 10¹¹ up to accelerating gradient of 22 MV/m; (2) Q ~ 3 x 10¹⁰ at 2 K and 16 MV/m in up to 190 mG magnetic fields. This is achieved by large thermal gradients at the normal/superconducting phase front during the cooldown. Our findingsmore » open up a way to ultra-high quality factors at low temperatures and show an alternative to the sophisticated magnetic shielding implemented in modern superconducting accelerators.« less

  17. Proposed Ultra-High Sensitivity High-Frequency Gravitational Wave Detector

    NASA Astrophysics Data System (ADS)

    Baker, Robert M. L.; Stephenson, Gary V.; Li, Fangyu

    2008-01-01

    The paper discusses the proposed improvement of a High-Frequency Relic Gravitational Wave (HFRGW) detector designed by Li, Baker, Fang, Stephenson and Chen in order to greatly improve its sensitivity. The improved detector is inspired by the Laser Interferometer Gravitational Observatory or LIGO, but is sensitive to the high-frequency end of the gravitational-wave spectrum. As described in prior papers it utilizes the Gertsenshtein effect, which introduces the conversion of gravitational waves to electromagnetic (EM) waves in the presence of a static magnetic field. Such a conversion, if it leads to photons moving in a direction perpendicular to the plane of the EM waves and the magnetic field, will allow for ultra-high sensitivity HFRGW detection. The use of sensitive microwave, single photon detectors such as a circuit QED and/or the Rydberg Atom Cavity Detector, or off-the-shelf detectors, could lead to such detection. When the EM-detection photons are focused at the microwave detectors by fractal-membrane reflectors sensitivity is also improved. Noise sources external to the HFRGW detector will be eliminated by placing a tight mosaic of superconducting tiles (e.g., YBCO) and/or fractal membranes on the interior surface of the detector's cryogenic containment vessel in order to provide a perfect Faraday cage. Internal thermal noise will be eliminated by means of a microwave absorbing (or reflecting) interior enclosure shaped to conform to a high-intensity continuous microwave Gaussian beam (GB), will reduce any background photon flux (BPF) noise radiated normal to the GB's axis. Such BPF will be further attenuated by a series of microwave absorbing baffles forming tunnels to the sensitive microwave detectors on each side of the GB and at right angles to the static magnetic field. A HFGW detector of bandwidth of 1 KHz to 10 KHz or less in the GHz band has been selected. It is concluded that the utilization of the new ultra-high-sensitivity microwave detectors

  18. Open-Access, Low-Magnetic-Field MRI System for Lung Research

    NASA Technical Reports Server (NTRS)

    Mair, Ross W.; Rosen, Matthew S.; Tsai, Leo L.; Walsworth, Ronald L.; Hrovat, Mirko I.; Patz, Samuel; Ruset, Iullian C.; Hersman, F. William

    2009-01-01

    An open-access magnetic resonance imaging (MRI) system is being developed for use in research on orientational/gravitational effects on lung physiology and function. The open-access geometry enables study of human subjects in diverse orientations. This system operates at a magnetic flux density, considerably smaller than the flux densities of typical other MRI systems, that can be generated by resistive electromagnet coils (instead of the more-expensive superconducting coils of the other systems). The human subject inhales air containing He-3 or Xe-129 atoms, the nuclear spins of which have been polarized by use of a laser beam to obtain a magnetic resonance that enables high-resolution gas space imaging at the low applied magnetic field. The system includes a bi-planar, constant-current, four-coil electromagnet assembly and associated electronic circuitry to apply a static magnetic field of 6.5 mT throughout the lung volume; planar coils and associated circuitry to apply a pulsed magnetic-field-gradient for each spatial dimension; a single, detachable radio-frequency coil and associated circuitry for inducing and detecting MRI signals; a table for supporting a horizontal subject; and electromagnetic shielding surrounding the electromagnet coils.

  19. Windows on the Human Body – in Vivo High-Field Magnetic Resonance Research and Applications in Medicine and Psychology

    PubMed Central

    Moser, Ewald; Meyerspeer, Martin; Fischmeister, Florian Ph. S.; Grabner, Günther; Bauer, Herbert; Trattnig, Siegfried

    2010-01-01

    Analogous to the evolution of biological sensor-systems, the progress in “medical sensor-systems”, i.e., diagnostic procedures, is paradigmatically described. Outstanding highlights of this progress are magnetic resonance imaging (MRI) and spectroscopy (MRS), which enable non-invasive, in vivo acquisition of morphological, functional, and metabolic information from the human body with unsurpassed quality. Recent achievements in high and ultra-high field MR (at 3 and 7 Tesla) are described, and representative research applications in Medicine and Psychology in Austria are discussed. Finally, an overview of current and prospective research in multi-modal imaging, potential clinical applications, as well as current limitations and challenges is given. PMID:22219684

  20. In situ and ex situ low-field NMR spectroscopy and MRI endowed by SABRE hyperpolarization.

    PubMed

    Barskiy, Danila A; Kovtunov, Kirill V; Koptyug, Igor V; He, Ping; Groome, Kirsten A; Best, Quinn A; Shi, Fan; Goodson, Boyd M; Shchepin, Roman V; Truong, Milton L; Coffey, Aaron M; Waddell, Kevin W; Chekmenev, Eduard Y

    2014-12-15

    By using 5.75 and 47.5 mT nuclear magnetic resonance (NMR) spectroscopy, up to 10(5)-fold sensitivity enhancement through signal amplification by reversible exchange (SABRE) was enabled, and subsecond temporal resolution was used to monitor an exchange reaction that resulted in the buildup and decay of hyperpolarized species after parahydrogen bubbling. We demonstrated the high-resolution low-field proton magnetic resonance imaging (MRI) of pyridine in a 47.5 mT magnetic field endowed by SABRE. Molecular imaging (i.e. imaging of dilute hyperpolarized substances rather than the bulk medium) was conducted in two regimes: in situ real-time MRI of the reaction mixture (in which pyridine was hyperpolarized), and ex situ MRI (in which hyperpolarization decays) of the liquid hyperpolarized product. Low-field (milli-Tesla range, e.g. 5.75 and 47.5 mT used in this study) parahydrogen-enhanced NMR and MRI, which are free from the limitations of high-field magnetic resonance (including susceptibility-induced gradients of the static magnetic field at phase interfaces), potentially enables new imaging applications as well as differentiation of hyperpolarized chemical species on demand by exploiting spin manipulations with static and alternating magnetic fields. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Design, construction, and field testing of an ultra high performance concrete pi-girder bridge.

    DOT National Transportation Integrated Search

    2011-01-01

    The Jakway Park Bridge in Buchanan County, Iowa is the first bridge constructed with a new prestesssed girder system composed of : precast Ultra-High Performance Concrete (UHPC). These girders employ an integral deck to facilitate construction and ar...

  2. Structural and functional correlates of visual field asymmetry in the human brain by diffusion kurtosis MRI and functional MRI.

    PubMed

    O'Connell, Caitlin; Ho, Leon C; Murphy, Matthew C; Conner, Ian P; Wollstein, Gadi; Cham, Rakie; Chan, Kevin C

    2016-11-09

    Human visual performance has been observed to show superiority in localized regions of the visual field across many classes of stimuli. However, the underlying neural mechanisms remain unclear. This study aims to determine whether the visual information processing in the human brain is dependent on the location of stimuli in the visual field and the corresponding neuroarchitecture using blood-oxygenation-level-dependent functional MRI (fMRI) and diffusion kurtosis MRI, respectively, in 15 healthy individuals at 3 T. In fMRI, visual stimulation to the lower hemifield showed stronger brain responses and larger brain activation volumes than the upper hemifield, indicative of the differential sensitivity of the human brain across the visual field. In diffusion kurtosis MRI, the brain regions mapping to the lower visual field showed higher mean kurtosis, but not fractional anisotropy or mean diffusivity compared with the upper visual field. These results suggested the different distributions of microstructural organization across visual field brain representations. There was also a strong positive relationship between diffusion kurtosis and fMRI responses in the lower field brain representations. In summary, this study suggested the structural and functional brain involvements in the asymmetry of visual field responses in humans, and is important to the neurophysiological and psychological understanding of human visual information processing.

  3. Network Modeling for Functional Magnetic Resonance Imaging (fMRI) Signals during Ultra-Fast Speech Comprehension in Late-Blind Listeners

    PubMed Central

    Dietrich, Susanne; Hertrich, Ingo; Ackermann, Hermann

    2015-01-01

    In many functional magnetic resonance imaging (fMRI) studies blind humans were found to show cross-modal reorganization engaging the visual system in non-visual tasks. For example, blind people can manage to understand (synthetic) spoken language at very high speaking rates up to ca. 20 syllables/s (syl/s). FMRI data showed that hemodynamic activation within right-hemispheric primary visual cortex (V1), bilateral pulvinar (Pv), and left-hemispheric supplementary motor area (pre-SMA) covaried with their capability of ultra-fast speech (16 syllables/s) comprehension. It has been suggested that right V1 plays an important role with respect to the perception of ultra-fast speech features, particularly the detection of syllable onsets. Furthermore, left pre-SMA seems to be an interface between these syllabic representations and the frontal speech processing and working memory network. So far, little is known about the networks linking V1 to Pv, auditory cortex (A1), and (mesio-) frontal areas. Dynamic causal modeling (DCM) was applied to investigate (i) the input structure from A1 and Pv toward right V1 and (ii) output from right V1 and A1 to left pre-SMA. As concerns the input Pv was significantly connected to V1, in addition to A1, in blind participants, but not in sighted controls. Regarding the output V1 was significantly connected to pre-SMA in blind individuals, and the strength of V1-SMA connectivity correlated with the performance of ultra-fast speech comprehension. By contrast, in sighted controls, not understanding ultra-fast speech, pre-SMA did neither receive input from A1 nor V1. Taken together, right V1 might facilitate the “parsing” of the ultra-fast speech stream in blind subjects by receiving subcortical auditory input via the Pv (= secondary visual pathway) and transmitting this information toward contralateral pre-SMA. PMID:26148062

  4. Network Modeling for Functional Magnetic Resonance Imaging (fMRI) Signals during Ultra-Fast Speech Comprehension in Late-Blind Listeners.

    PubMed

    Dietrich, Susanne; Hertrich, Ingo; Ackermann, Hermann

    2015-01-01

    In many functional magnetic resonance imaging (fMRI) studies blind humans were found to show cross-modal reorganization engaging the visual system in non-visual tasks. For example, blind people can manage to understand (synthetic) spoken language at very high speaking rates up to ca. 20 syllables/s (syl/s). FMRI data showed that hemodynamic activation within right-hemispheric primary visual cortex (V1), bilateral pulvinar (Pv), and left-hemispheric supplementary motor area (pre-SMA) covaried with their capability of ultra-fast speech (16 syllables/s) comprehension. It has been suggested that right V1 plays an important role with respect to the perception of ultra-fast speech features, particularly the detection of syllable onsets. Furthermore, left pre-SMA seems to be an interface between these syllabic representations and the frontal speech processing and working memory network. So far, little is known about the networks linking V1 to Pv, auditory cortex (A1), and (mesio-) frontal areas. Dynamic causal modeling (DCM) was applied to investigate (i) the input structure from A1 and Pv toward right V1 and (ii) output from right V1 and A1 to left pre-SMA. As concerns the input Pv was significantly connected to V1, in addition to A1, in blind participants, but not in sighted controls. Regarding the output V1 was significantly connected to pre-SMA in blind individuals, and the strength of V1-SMA connectivity correlated with the performance of ultra-fast speech comprehension. By contrast, in sighted controls, not understanding ultra-fast speech, pre-SMA did neither receive input from A1 nor V1. Taken together, right V1 might facilitate the "parsing" of the ultra-fast speech stream in blind subjects by receiving subcortical auditory input via the Pv (= secondary visual pathway) and transmitting this information toward contralateral pre-SMA.

  5. Interaction of MRI field gradients with the human body.

    PubMed

    Glover, P M

    2009-11-07

    In this review, the effects of low-frequency electromagnetic fields encountered specifically during magnetic resonance imaging (MRI) are examined. The primary biological effect at frequencies of between 100 and 5000 Hz (typical of MRI magnetic field gradient switching) is peripheral nerve stimulation, the result of which can be a mild tingling and muscle twitching to a sensation of pain. The models for nerve stimulation and how they are related to the rate of change of magnetic field are examined. The experimental measurements, and analytic and computational modelling work in this area are reviewed. The review concludes with a discussion of current regulation in this area and current practice as both are applied to MRI.

  6. Comparison of ultra high performance supercritical fluid chromatography, ultra high performance liquid chromatography, and gas chromatography for the separation of synthetic cathinones.

    PubMed

    Carnes, Stephanie; O'Brien, Stacey; Szewczak, Angelica; Tremeau-Cayel, Lauriane; Rowe, Walter F; McCord, Bruce; Lurie, Ira S

    2017-09-01

    A comparison of ultra high performance supercritical fluid chromatography, ultra high performance liquid chromatography, and gas chromatography for the separation of synthetic cathinones has been conducted. Nine different mixtures of bath salts were analyzed in this study. The three different chromatographic techniques were examined using a general set of controlled synthetic cathinones as well as a variety of other synthetic cathinones that exist as positional isomers. Overall 35 different synthetic cathinones were analyzed. A variety of column types and chromatographic modes were examined for developing each separation. For the ultra high performance supercritical fluid chromatography separations, analyses were performed using a series of Torus and Trefoil columns with either ammonium formate or ammonium hydroxide as additives, and methanol, ethanol or isopropanol organic solvents as modifiers. Ultra high performance liquid chromatographic separations were performed in both reversed phase and hydrophilic interaction chromatographic modes using SPP C18 and SPP HILIC columns. Gas chromatography separations were performed using an Elite-5MS capillary column. The orthogonality of ultra high performance supercritical fluid chromatography, ultra high performance liquid chromatography, and gas chromatography was examined using principal component analysis. For the best overall separation of synthetic cathinones, the use of ultra high performance supercritical fluid chromatography in combination with gas chromatography is recommended. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Ionic liquid gating on atomic layer deposition passivated GaN: Ultra-high electron density induced high drain current and low contact resistance

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhou, Hong; Du, Yuchen; Ye, Peide D., E-mail: yep@purdue.edu

    2016-05-16

    Herein, we report on achieving ultra-high electron density (exceeding 10{sup 14 }cm{sup −2}) in a GaN bulk material device by ionic liquid gating, through the application of atomic layer deposition (ALD) of Al{sub 2}O{sub 3} to passivate the GaN surface. Output characteristics demonstrate a maximum drain current of 1.47 A/mm, the highest reported among all bulk GaN field-effect transistors, with an on/off ratio of 10{sup 5} at room temperature. An ultra-high electron density exceeding 10{sup 14 }cm{sup −2} accumulated at the surface is confirmed via Hall-effect measurement and transfer length measurement. In addition to the ultra-high electron density, we also observe a reductionmore » of the contact resistance due to the narrowing of the Schottky barrier width on the contacts. Taking advantage of the ALD surface passivation and ionic liquid gating technique, this work provides a route to study the field-effect and carrier transport properties of conventional semiconductors in unprecedented ultra-high charge density regions.« less

  8. Triaxial fiber optic magnetic field sensor for MRI applications

    NASA Astrophysics Data System (ADS)

    Filograno, Massimo L.; Pisco, Marco; Catalano, Angelo; Forte, Ernesto; Aiello, Marco; Soricelli, Andrea; Davino, Daniele; Visone, Ciro; Cutolo, Antonello; Cusano, Andrea

    2016-05-01

    In this paper, we report a fiber-optic triaxial magnetic field sensor, based on Fiber Bragg Gratings (FBGs) integrated with giant magnetostrictive material, the Terfenol-D. The realized sensor has been designed and engineered for Magnetic Resonance Imaging (MRI) applications. A full magneto-optical characterization of the triaxial sensing probe has been carried out, providing the complex relationship among the FBGs wavelength shift and the applied magnetostatic field vector. Finally, the developed fiber optic sensors have been arranged in a sensor network composed of 20 triaxial sensors for mapping the magnetic field distribution in a MRI-room at a diagnostic center in Naples (SDN), equipped with Positron emission tomography/magnetic resonance (PET/MR) instrumentation. Experimental results reveal that the proposed sensor network can be efficiently used in MRI centers for performing quality assurance tests, paving the way for novel integrated tools to measure the magnetic dose accumulated day by day by MRI operators.

  9. [3 Tesla MRI: successful results with higher field strengths].

    PubMed

    Schmitt, F; Grosu, D; Mohr, C; Purdy, D; Salem, K; Scott, K T; Stoeckel, B

    2004-01-01

    The recent development of 3 Tesla MRI (3T MRI) has been fueled by promise of increased signal-to-noise ratio(SNR). Many are excited about the opportunity to not only use the increased SNR for clearer images, but also the chance to exchange it for better resolution or faster scans. These possibilities have caused a rapid increase in the market for 3T MRI, where the faster scanning tips an already advantageous economic outlook in favor of the user. As a result, the global market for 3T has grown from a research only market just a few years ago to an ever-increasing clinically oriented customer base. There are, however, significant obstacles to 3T MRI presented by the physics at higher field strengths. For example, the T1 relaxation times are prolonged with increasing magnet field strength. Further, the increased RF-energy deposition (SAR), the larger the chemical shift and the stronger susceptibility effect have to be considered as challenges. It is critical that one looks at both the advantages and disadvantages of using 3T. While there are many issues to address aand a number of different methods for doing so, to properly tackle each of these concerns will take time and effort on the part od researchers and clinicians. The optimization of 3T MRI scanning will have to be a combined effort, though much of the work to date has been in neuroimaging. Multiple applications have been explored in addition to clinical anatomical imaging, where resolution is improved showing structure in the brain never seen before in human MRI. Body and cardiac imaging provide a great challenge but are also achievable at 3T. As an example, the full range of clinical applications currently achieved on today's state-of-the-art 1.5T cardiac MR scanners has also been demonstrated at 3T. In the body, the full range of contrast is available over large fields of view allowing whole liver studies in the clinic or, as needed, one may choose a smaller field of view for high-resolution imaging of the

  10. The performance of interventional loopless MRI antennae at higher magnetic field strengths

    PubMed Central

    El-Sharkawy, AbdEl-Monem M.; Qian, Di; Bottomley, Paul A.

    2008-01-01

    Interventional, “loopless antenna” MRI detectors are currently limited to 1.5 T. This study investigates whether loopless antennae offer signal-to-noise ratio (SNR) and field-of-view (FOV) advantages at higher fields, and whether device heating can be controlled within safe limits. The absolute SNR performance of loopless antennae from 0.5 to 5 T is investigated both analytically, using electromagnetic (EM) dipole antenna theory, and numerically with the EM method of moments, and found to vary almost quadratically with field strength depending on the medium’s electrical properties, the noise being dominated by direct sample conduction losses. The prediction is confirmed by measurements of the absolute SNR of low-loss loopless antennae fabricated for 1.5, 3, and 4.7 T, immersed in physiologically comparable saline. Gains of 3.8±0.2- and 9.7±0.3-fold in SNR, and approximately 10- and 50-fold gains in the useful FOV area are observed at 3 and 4.7 T, respectively, compared to 1.5 T. Heat testing of a 3 T biocompatible nitinol-antenna fabricated with a redesigned decoupling circuit shows maximum heating of ∼1 °C for MRI operating at high MRI exposure levels. Experiments in the rabbit aorta confirm the SNR and FOV advantages of the 3 T antenna versus an equivalent commercial 1.5 T device in vivo. This work is the first to study the performance of experimental internal MRI detectors above 1.5 T. The large SNR and FOV gains realized present a major opportunity for high-resolution imaging of vascular pathology and MRI-guided intervention. PMID:18561676

  11. Self-transcendence trait and its relationship with in vivo serotonin transporter availability in brainstem raphe nuclei: An ultra-high resolution PET-MRI study.

    PubMed

    Kim, Jong-Hoon; Son, Young-Don; Kim, Jeong-Hee; Choi, Eun-Jung; Lee, Sang-Yoon; Joo, Yo-Han; Kim, Young-Bo; Cho, Zang-Hee

    2015-12-10

    Self-transcendence is an inherent human personality trait relating to the experience of spiritual aspects of the self. We examined the relationship between self-transcendence and serotonin transporter (SERT) availability in brainstem raphe nuclei, which are collections of five different serotonergic nuclei with rostro-caudal extension, using ultra-high resolution magnetic resonance imaging (MRI) and positron emission tomography (PET) with (11)C-3-amino-4-(2-dimethylaminomethylphenylthio)benzonitrile ([(11)C]DASB) to elucidate potential roles of serotonergic neuronal activities in this personality trait. Sixteen healthy subjects completed 7.0T MRI and High Resolution Research Tomograph (HRRT) PET. The regions of interest (ROIs) included the dorsal raphe nucleus (R1), median raphe nucleus (R2), raphe pontis (R3), and the caudal raphe nuclei (R4 and R5). For the estimation of SERT availability, the binding potential (BPND) was derived using the simplified reference tissue model (SRTM2). The Temperament and Character Inventory was used to measure self-transcendence. The analysis revealed that the self-transcendence total score had a significant negative correlation with the [(11)C]DASB BPND in the caudal raphe (R5). The subscale score for spiritual acceptance was significantly negatively correlated with the [(11)C]DASB BPND in the median raphe nucleus (R2). The results indicate that the self-transcendence trait is associated with SERT availability in specific raphe subnuclei, suggesting that the serotonin system may serve as an important biological basis for human self-transcendence. Based on the connections of these nuclei with cortico-limbic and visceral autonomic structures, the functional activity of these nuclei and their related neural circuitry may play a crucial role in the manifestation of self-transcendence. Copyright © 2015. Published by Elsevier B.V.

  12. Fabrication of W-Cu alloy via combustion synthesis infiltration under an ultra-gravity field

    NASA Astrophysics Data System (ADS)

    Song, Yuepeng; Li, Qian; Li, Jiangtao; He, Gang; Chen, Yixiang; Kim, Hyoung Seop

    2014-11-01

    Tungsten copper alloy with a tungsten concentrate of 70 vol% was prepared by self-propagating high-temperature synthesis in an ultra-gravity field. The phase structures and components of the W-Cu alloy fabricated via this approach were the same as those via traditional sintering methods. The temperature and stress distributions during this process were simulated using a new scheme of the finite element method. The results indicated that nonequilibrium crystallization conditions can be created for combustion synthesis infiltration in an ultra-gravity field by the rapid infiltration of the liquid copper product into the tungsten compact at high temperature and low viscosity. The cooling rate can be above 100,000 K/s and high stresses in tungsten ( 5 GPa) and copper ( 2.6 GPa) were developed, which passivates the tungsten particle surface, resulting in easy sintering and densifying the W-Cu alloy. The reliability of the simulation was verified through temperature measurement and investigation of the microstructure. The W-Cu composite-formation mechanism was also analyzed and discussed with the simulation results.

  13. Cluster-level statistical inference in fMRI datasets: The unexpected behavior of random fields in high dimensions.

    PubMed

    Bansal, Ravi; Peterson, Bradley S

    2018-06-01

    Identifying regional effects of interest in MRI datasets usually entails testing a priori hypotheses across many thousands of brain voxels, requiring control for false positive findings in these multiple hypotheses testing. Recent studies have suggested that parametric statistical methods may have incorrectly modeled functional MRI data, thereby leading to higher false positive rates than their nominal rates. Nonparametric methods for statistical inference when conducting multiple statistical tests, in contrast, are thought to produce false positives at the nominal rate, which has thus led to the suggestion that previously reported studies should reanalyze their fMRI data using nonparametric tools. To understand better why parametric methods may yield excessive false positives, we assessed their performance when applied both to simulated datasets of 1D, 2D, and 3D Gaussian Random Fields (GRFs) and to 710 real-world, resting-state fMRI datasets. We showed that both the simulated 2D and 3D GRFs and the real-world data contain a small percentage (<6%) of very large clusters (on average 60 times larger than the average cluster size), which were not present in 1D GRFs. These unexpectedly large clusters were deemed statistically significant using parametric methods, leading to empirical familywise error rates (FWERs) as high as 65%: the high empirical FWERs were not a consequence of parametric methods failing to model spatial smoothness accurately, but rather of these very large clusters that are inherently present in smooth, high-dimensional random fields. In fact, when discounting these very large clusters, the empirical FWER for parametric methods was 3.24%. Furthermore, even an empirical FWER of 65% would yield on average less than one of those very large clusters in each brain-wide analysis. Nonparametric methods, in contrast, estimated distributions from those large clusters, and therefore, by construct rejected the large clusters as false positives at the nominal

  14. Structural and Functional Correlates of Visual Field Asymmetry in the Human Brain by Diffusion Kurtosis MRI and Functional MRI

    PubMed Central

    O’Connell, Caitlin; Ho, Leon C.; Murphy, Matthew C.; Conner, Ian P.; Wollstein, Gadi; Cham, Rakie; Chan, Kevin C.

    2016-01-01

    Human visual performance has been observed to exhibit superiority in localized regions of the visual field across many classes of stimuli. However, the underlying neural mechanisms remain unclear. This study aims to determine if the visual information processing in the human brain is dependent on the location of stimuli in the visual field and the corresponding neuroarchitecture using blood-oxygenation-level-dependent functional MRI (fMRI) and diffusion kurtosis MRI (DKI), respectively in 15 healthy individuals at 3 Tesla. In fMRI, visual stimulation to the lower hemifield showed stronger brain responses and larger brain activation volumes than the upper hemifield, indicative of the differential sensitivity of the human brain across the visual field. In DKI, the brain regions mapping to the lower visual field exhibited higher mean kurtosis but not fractional anisotropy or mean diffusivity when compared to the upper visual field. These results suggested the different distributions of microstructural organization across visual field brain representations. There was also a strong positive relationship between diffusion kurtosis and fMRI responses in the lower field brain representations. In summary, this study suggested the structural and functional brain involvements in the asymmetry of visual field responses in humans, and is important to the neurophysiological and psychological understanding of human visual information processing. PMID:27631541

  15. Design of a mobile, homogeneous, and efficient electromagnet with a large field of view for neonatal low-field MRI.

    PubMed

    Lother, Steffen; Schiff, Steven J; Neuberger, Thomas; Jakob, Peter M; Fidler, Florian

    2016-08-01

    In this work, a prototype of an effective electromagnet with a field-of-view (FoV) of 140 mm for neonatal head imaging is presented. The efficient implementation succeeded by exploiting the use of steel plates as a housing system. We achieved a compromise between large sample volumes, high homogeneity, high B0 field, low power consumption, light weight, simple fabrication, and conserved mobility without the necessity of a dedicated water cooling system. The entire magnetic resonance imaging (MRI) system (electromagnet, gradient system, transmit/receive coil, control system) is introduced and its unique features discussed. Furthermore, simulations using a numerical optimization algorithm for magnet and gradient system are presented. Functionality and quality of this low-field scanner operating at 23 mT (generated with 500 W) is illustrated using spin-echo imaging (in-plane resolution 1.6 mm × 1.6 mm, slice thickness 5 mm, and signal-to-noise ratio (SNR) of 23 with a acquisition time of 29 min). B0 field-mapping measurements are presented to characterize the homogeneity of the magnet, and the B0 field limitations of 80 mT of the system are fully discussed. The cryogen-free system presented here demonstrates that this electromagnet with a ferromagnetic housing can be optimized for MRI with an enhanced and homogeneous magnetic field. It offers an alternative to prepolarized MRI designs in both readout field strength and power use. There are multiple indications for the clinical medical application of such low-field devices.

  16. Design of a mobile, homogeneous, and efficient electromagnet with a large field of view for neonatal low-field MRI

    PubMed Central

    Schiff, Steven J.; Neuberger, Thomas; Jakob, Peter M.; Fidler, Florian

    2017-01-01

    Objective In this work, a prototype of an effective electromagnet with a field-of-view (FoV) of 140 mm for neonatal head imaging is presented. The efficient implementation succeeded by exploiting the use of steel plates as a housing system. We achieved a compromise between large sample volumes, high homogeneity, high B0 field, low power consumption, light weight, simple fabrication, and conserved mobility without the necessity of a dedicated water cooling system. Materials and methods The entire magnetic resonance imaging (MRI) system (electromagnet, gradient system, transmit/receive coil, control system) is introduced and its unique features discussed. Furthermore, simulations using a numerical optimization algorithm for magnet and gradient system are presented. Results Functionality and quality of this low-field scanner operating at 23 mT (generated with 500 W) is illustrated using spin-echo imaging (in-plane resolution 1.6 mm × 1.6 mm, slice thickness 5 mm, and signal-to-noise ratio (SNR) of 23 with a acquisition time of 29 min). B0 field-mapping measurements are presented to characterize the homogeneity of the magnet, and the B0 field limitations of 80 mT of the system are fully discussed. Conclusion The cryogen-free system presented here demonstrates that this electromagnet with a ferromagnetic housing can be optimized for MRI with an enhanced and homogeneous magnetic field. It offers an alternative to pre-polarized MRI designs in both readout field strength and power use. There are multiple indications for the clinical medical application of such low-field devices. PMID:26861046

  17. In vivo functional connectome of human brainstem nuclei of the ascending arousal, autonomic, and motor systems by high spatial resolution 7-Tesla fMRI.

    PubMed

    Bianciardi, Marta; Toschi, Nicola; Eichner, Cornelius; Polimeni, Jonathan R; Setsompop, Kawin; Brown, Emery N; Hämäläinen, Matti S; Rosen, Bruce R; Wald, Lawrence L

    2016-06-01

    Our aim was to map the in vivo human functional connectivity of several brainstem nuclei with the rest of the brain by using seed-based correlation of ultra-high magnetic field functional magnetic resonance imaging (fMRI) data. We used the recently developed template of 11 brainstem nuclei derived from multi-contrast structural MRI at 7 Tesla as seed regions to determine their connectivity to the rest of the brain. To achieve this, we used the increased contrast-to-noise ratio of 7-Tesla fMRI compared with 3 Tesla and time-efficient simultaneous multi-slice imaging to cover the brain with high spatial resolution (1.1-mm isotropic nominal resolution) while maintaining a short repetition time (2.5 s). The delineated Pearson's correlation-based functional connectivity diagrams (connectomes) of 11 brainstem nuclei of the ascending arousal, motor, and autonomic systems from 12 controls are presented and discussed in the context of existing histology and animal work. Considering that the investigated brainstem nuclei play a crucial role in several vital functions, the delineated preliminary connectomes might prove useful for future in vivo research and clinical studies of human brainstem function and pathology, including disorders of consciousness, sleep disorders, autonomic disorders, Parkinson's disease, and other motor disorders.

  18. Ultrahigh Field NMR and MRI: Science at a Crossroads Workshop Report

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Polenova, Tatyana; Budinger, Thomas F.

    2016-01-04

    The workshop “Ultrahigh Field NMR and MRI: Science at Crossroads”, initiated by the scientific community and supported by the National Science Foundation, the Department of Energy, and the National Institutes of Health, took place on November 12-13, 2015, in Bethesda, MD, on the NIH campus. The meeting was held to assess the science drivers, technological challenges, prospects for achieving field strengths for NMR and MRI nearly double their current value, and strategies on how to provide ultrahigh field NMR/MRI capabilities to a national user community.

  19. High Spatiotemporal Resolution Prostate MRI

    DTIC Science & Technology

    2016-09-01

    1 AD AWARD NUMBER: W81XWH-15-1-0341 TITLE: High Spatiotemporal Resolution Prostate MRI PRINCIPAL INVESTIGATOR: Stephen J. Riederer CONTRACTING...REPORT TYPE Annual 3. DATES COVERED 15 Aug 2015 - 14 Aug 2016 4. TITLE AND SUBTITLE High Spatiotemporal Resolution Prostate MRI 5a. CONTRACT NUMBER...improved means using MRI for detecting prostate cancer with the potential for differentiating disease aggressiveness. The hypothesis is that dynamic

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

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Grezes, C.; Alzate, J. G.; Cai, X.

    2016-01-04

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

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

    DOEpatents

    Kraus, Robert H.; Matlashov, Andrei N.; Espy, Michelle A.; Volegov, Petr L.

    2010-03-30

    An ultra-low magnetic field NMR system can non-invasively examine containers. Database matching techniques can then identify hazardous materials within the containers. Ultra-low field NMR systems are ideal for this purpose because they do not require large powerful magnets and because they can examine materials enclosed in conductive shells such as lead shells. The NMR examination technique can be combined with ultra-low field NMR imaging, where an NMR image is obtained and analyzed to identify target volumes. Spatial sensitivity encoding can also be used to identify target volumes. After the target volumes are identified the NMR measurement technique can be used to identify their contents.

  2. Review of total cross sections and forward scattering parameters at ultra-high energies

    NASA Astrophysics Data System (ADS)

    Block, M. M.; White, A. R.

    1991-10-01

    We review the field of the elastic scattering of pp and (bar p)p at the ultra-high energies. The recent total cross section, sigma (sub tot), and rho-value results from the Fermilab Tevatron Collider experiments presented at the 4th 'Blois' Workshop on Elastic and Diffractive Scattering (Elba, Italy, in May, 1991), allow us a comprehensive overview of the field.

  3. R&D Progress of HTS Magnet Project for Ultrahigh-field MRI

    NASA Astrophysics Data System (ADS)

    Tosaka, Taizo; Miyazaki, Hiroshi; Iwai, Sadanori; Otani, Yasumi; Takahashi, Masahiko; Tasaki, Kenji; Nomura, Shunji; Kurusu, Tsutomu; Ueda, Hiroshi; Noguchi, So; Ishiyama, Atsushi; Urayama, Shinichi; Fukuyama, Hidenao

    An R&D project on high-temperature superconducting (HTS) magnets using rare-earth Ba2Cu3O7 (REBCO) wires was started in 2013. The project objective is to investigate the feasibility of adapting REBCO magnets to ultrahigh field (UHF) magnetic resonance imaging (MRI) systems. REBCO wires are promising components for UHF-MRI magnets because of their superior superconducting and mechanical properties, which make them smaller and lighter than conventional ones. Moreover, REBCO magnets can be cooled by the conduction-cooling method, making liquid helium unnecessary. In the past two years, some test coils and model magnets have been fabricated and tested. This year is the final year of the project. The goals of the project are: (1) to generate a 9.4 T magnetic field with a small test coil, (2) to generate a homogeneous magnetic field in a 200 mm diameter spherical volume with a 1.5 T model magnet, and (3) to perform imaging with the 1.5 T model magnet. In this paper, the progress of this R&D is described. The knowledge gained through these R&D results will be reflected in the design of 9.4 T MRI magnets for brain and whole body imaging.

  4. Quantile Regression for Analyzing Heterogeneity in Ultra-high Dimension

    PubMed Central

    Wang, Lan; Wu, Yichao

    2012-01-01

    Ultra-high dimensional data often display heterogeneity due to either heteroscedastic variance or other forms of non-location-scale covariate effects. To accommodate heterogeneity, we advocate a more general interpretation of sparsity which assumes that only a small number of covariates influence the conditional distribution of the response variable given all candidate covariates; however, the sets of relevant covariates may differ when we consider different segments of the conditional distribution. In this framework, we investigate the methodology and theory of nonconvex penalized quantile regression in ultra-high dimension. The proposed approach has two distinctive features: (1) it enables us to explore the entire conditional distribution of the response variable given the ultra-high dimensional covariates and provides a more realistic picture of the sparsity pattern; (2) it requires substantially weaker conditions compared with alternative methods in the literature; thus, it greatly alleviates the difficulty of model checking in the ultra-high dimension. In theoretic development, it is challenging to deal with both the nonsmooth loss function and the nonconvex penalty function in ultra-high dimensional parameter space. We introduce a novel sufficient optimality condition which relies on a convex differencing representation of the penalized loss function and the subdifferential calculus. Exploring this optimality condition enables us to establish the oracle property for sparse quantile regression in the ultra-high dimension under relaxed conditions. The proposed method greatly enhances existing tools for ultra-high dimensional data analysis. Monte Carlo simulations demonstrate the usefulness of the proposed procedure. The real data example we analyzed demonstrates that the new approach reveals substantially more information compared with alternative methods. PMID:23082036

  5. Quantitative ultra-fast MRI of HPMC swelling and dissolution.

    PubMed

    Chen, Ya Ying; Hughes, L P; Gladden, L F; Mantle, M D

    2010-08-01

    For the first time quantitative Rapid Acquisition with Relaxation Enhancement (RARE) based ultra-fast two-dimensional magnetic resonance imaging has been used to follow the dissolution of hydroxypropylmethyl cellulose (HPMC) in water. Quantitative maps of absolute water concentration, spin-spin relaxation times and water self-diffusion coefficient are obtained at a spatial resolution of 469 microm in less than 3 min each. These maps allow the dynamic development of the medium release rate HPMC/water system to be followed. It is demonstrated that the evolution of the gel layer and, in particular, the gradient in water concentration across it, is significantly different when comparing the quantitative RARE sequence with a standard (nonquantitative) implementation of RARE. The total gel thickness in the axial direction grows faster than that in the radial direction and that the dry core initially expands anisotropically. Additionally, while HPMC absorbs a large amount of water during the dissolution process, the concentration gradient of water within the gel layer is relatively small. For the first time MRI evidence is presented for a transition swollen glassy layer which resides between the outer edge of the dry tablet core and the inner edge of the gel layer. (c) 2010 Wiley-Liss, Inc. and the American Pharmacists Association

  6. In Vivo Evaluation of Magnetic Targeting in Mice Colon Tumors with Ultra-Magnetic Liposomes Monitored by MRI.

    PubMed

    Thébault, Caroline J; Ramniceanu, Grégory; Michel, Aude; Beauvineau, Claire; Girard, Christian; Seguin, Johanne; Mignet, Nathalie; Ménager, Christine; Doan, Bich-Thuy

    2018-06-25

    The development of theranostic nanocarriers as an innovative therapy against cancer has been improved by targeting properties in order to optimize the drug delivery to safely achieve its desired therapeutic effect. The aim of this paper is to evaluate the magnetic targeting (MT) efficiency of ultra-magnetic liposomes (UML) into CT26 murine colon tumor by magnetic resonance imaging (MRI). Dynamic susceptibility contrast MRI was applied to assess the bloodstream circulation time. A novel semi-quantitative method called %I 0.25 , based on the intensity distribution in T 2 * -weighted MRI images was developed to compare the accumulation of T 2 contrast agent in tumors with or without MT. To evaluate the efficiency of magnetic targeting, the percentage of pixels under the intensity value I 0.25 (I 0.25  = 0.25(I max  - I min )) was calculated on the intensity distribution histogram. This innovative method of processing MRI images showed the MT efficiency by a %I 0.25 that was significantly higher in tumors using MT compared to passive accumulation, from 15.3 to 28.6 %. This methodology was validated by ex vivo methods with an iron concentration that is 3-fold higher in tumors using MT. We have developed a method that allows a semi-quantitative evaluation of targeting efficiency in tumors, which could be applied to different T 2 contrast agents.

  7. Novel frontiers in ultra-structural and molecular MRI of the brain.

    PubMed

    Duyn, Jeff H; Koretsky, Alan P

    2011-08-01

    Recent developments in the MRI of the brain continue to expand its use in basic and clinical neuroscience. This review highlights some areas of recent progress. Higher magnetic field strengths and improved signal detectors have allowed improved visualization of the various properties of the brain, facilitating the anatomical definition of function-specific areas and their connections. For example, by sensitizing the MRI signal to the magnetic susceptibility of tissue, it is starting to become possible to reveal the laminar structure of the cortex and identify millimeter-scale fiber bundles. Using exogenous contrast agents, and innovative ways to manipulate contrast, it is becoming possible to highlight specific fiber tracts and cell populations. These techniques are bringing us closer to understanding the evolutionary blueprint of the brain, improving the detection and characterization of disease, and help to guide treatment. Recent MRI techniques are leading to more detailed and more specific contrast in the study of the brain.

  8. A voxel-based investigation for MRI-only radiotherapy of the brain using ultra short echo times

    NASA Astrophysics Data System (ADS)

    Edmund, Jens M.; Kjer, Hans M.; Van Leemput, Koen; Hansen, Rasmus H.; Andersen, Jon AL; Andreasen, Daniel

    2014-12-01

    Radiotherapy (RT) based on magnetic resonance imaging (MRI) as the only modality, so-called MRI-only RT, would remove the systematic registration error between MR and computed tomography (CT), and provide co-registered MRI for assessment of treatment response and adaptive RT. Electron densities, however, need to be assigned to the MRI images for dose calculation and patient setup based on digitally reconstructed radiographs (DRRs). Here, we investigate the geometric and dosimetric performance for a number of popular voxel-based methods to generate a so-called pseudo CT (pCT). Five patients receiving cranial irradiation, each containing a co-registered MRI and CT scan, were included. An ultra short echo time MRI sequence for bone visualization was used. Six methods were investigated for three popular types of voxel-based approaches; (1) threshold-based segmentation, (2) Bayesian segmentation and (3) statistical regression. Each approach contained two methods. Approach 1 used bulk density assignment of MRI voxels into air, soft tissue and bone based on logical masks and the transverse relaxation time T2 of the bone. Approach 2 used similar bulk density assignments with Bayesian statistics including or excluding additional spatial information. Approach 3 used a statistical regression correlating MRI voxels with their corresponding CT voxels. A similar photon and proton treatment plan was generated for a target positioned between the nasal cavity and the brainstem for all patients. The CT agreement with the pCT of each method was quantified and compared with the other methods geometrically and dosimetrically using both a number of reported metrics and introducing some novel metrics. The best geometrical agreement with CT was obtained with the statistical regression methods which performed significantly better than the threshold and Bayesian segmentation methods (excluding spatial information). All methods agreed significantly better with CT than a reference water MRI

  9. A validation of dynamic causal modelling for 7T fMRI.

    PubMed

    Tak, S; Noh, J; Cheong, C; Zeidman, P; Razi, A; Penny, W D; Friston, K J

    2018-07-15

    There is growing interest in ultra-high field magnetic resonance imaging (MRI) in cognitive and clinical neuroscience studies. However, the benefits offered by higher field strength have not been evaluated in terms of effective connectivity and dynamic causal modelling (DCM). In this study, we address the validity of DCM for 7T functional MRI data at two levels. First, we evaluate the predictive validity of DCM estimates based upon 3T and 7T in terms of reproducibility. Second, we assess improvements in the efficiency of DCM estimates at 7T, in terms of the entropy of the posterior distribution over model parameters (i.e., information gain). Using empirical data recorded during fist-closing movements with 3T and 7T fMRI, we found a high reproducibility of average connectivity and condition-specific changes in connectivity - as quantified by the intra-class correlation coefficient (ICC = 0.862 and 0.936, respectively). Furthermore, we found that the posterior entropy of 7T parameter estimates was substantially less than that of 3T parameter estimates; suggesting the 7T data are more informative - and furnish more efficient estimates. In the framework of DCM, we treated field-dependent parameters for the BOLD signal model as free parameters, to accommodate fMRI data at 3T and 7T. In addition, we made the resting blood volume fraction a free parameter, because different brain regions can differ in their vascularization. In this paper, we showed DCM enables one to infer changes in effective connectivity from 7T data reliably and efficiently. Copyright © 2018 Elsevier B.V. All rights reserved.

  10. Wavelet-space correlation imaging for high-speed MRI without motion monitoring or data segmentation.

    PubMed

    Li, Yu; Wang, Hui; Tkach, Jean; Roach, David; Woods, Jason; Dumoulin, Charles

    2015-12-01

    This study aims to (i) develop a new high-speed MRI approach by implementing correlation imaging in wavelet-space, and (ii) demonstrate the ability of wavelet-space correlation imaging to image human anatomy with involuntary or physiological motion. Correlation imaging is a high-speed MRI framework in which image reconstruction relies on quantification of data correlation. The presented work integrates correlation imaging with a wavelet transform technique developed originally in the field of signal and image processing. This provides a new high-speed MRI approach to motion-free data collection without motion monitoring or data segmentation. The new approach, called "wavelet-space correlation imaging", is investigated in brain imaging with involuntary motion and chest imaging with free-breathing. Wavelet-space correlation imaging can exceed the speed limit of conventional parallel imaging methods. Using this approach with high acceleration factors (6 for brain MRI, 16 for cardiac MRI, and 8 for lung MRI), motion-free images can be generated in static brain MRI with involuntary motion and nonsegmented dynamic cardiac/lung MRI with free-breathing. Wavelet-space correlation imaging enables high-speed MRI in the presence of involuntary motion or physiological dynamics without motion monitoring or data segmentation. © 2014 Wiley Periodicals, Inc.

  11. Wavelet-space Correlation Imaging for High-speed MRI without Motion Monitoring or Data Segmentation

    PubMed Central

    Li, Yu; Wang, Hui; Tkach, Jean; Roach, David; Woods, Jason; Dumoulin, Charles

    2014-01-01

    Purpose This study aims to 1) develop a new high-speed MRI approach by implementing correlation imaging in wavelet-space, and 2) demonstrate the ability of wavelet-space correlation imaging to image human anatomy with involuntary or physiological motion. Methods Correlation imaging is a high-speed MRI framework in which image reconstruction relies on quantification of data correlation. The presented work integrates correlation imaging with a wavelet transform technique developed originally in the field of signal and image processing. This provides a new high-speed MRI approach to motion-free data collection without motion monitoring or data segmentation. The new approach, called “wavelet-space correlation imaging”, is investigated in brain imaging with involuntary motion and chest imaging with free-breathing. Results Wavelet-space correlation imaging can exceed the speed limit of conventional parallel imaging methods. Using this approach with high acceleration factors (6 for brain MRI, 16 for cardiac MRI and 8 for lung MRI), motion-free images can be generated in static brain MRI with involuntary motion and nonsegmented dynamic cardiac/lung MRI with free-breathing. Conclusion Wavelet-space correlation imaging enables high-speed MRI in the presence of involuntary motion or physiological dynamics without motion monitoring or data segmentation. PMID:25470230

  12. Parallel transmission RF pulse design for eddy current correction at ultra high field.

    PubMed

    Zheng, Hai; Zhao, Tiejun; Qian, Yongxian; Ibrahim, Tamer; Boada, Fernando

    2012-08-01

    Multidimensional spatially selective RF pulses have been used in MRI applications such as B₁ and B₀ inhomogeneities mitigation. However, the long pulse duration has limited their practical applications. Recently, theoretical and experimental studies have shown that parallel transmission can effectively shorten pulse duration without sacrificing the quality of the excitation pattern. Nonetheless, parallel transmission with accelerated pulses can be severely impeded by hardware and/or system imperfections. One of such imperfections is the effect of the eddy current field. In this paper, we first show the effects of the eddy current field on the excitation pattern and then report an RF pulse the design method to correct eddy current fields caused by the RF coil and the gradient system. Experimental results on a 7 T human eight-channel parallel transmit system show substantial improvements on excitation patterns with the use of eddy current correction. Moreover, the proposed model-based correction method not only demonstrates comparable excitation patterns as the trajectory measurement method, but also significantly improves time efficiency. Copyright © 2012. Published by Elsevier Inc.

  13. Ultra-compact high-performance MCT MWIR engine

    NASA Astrophysics Data System (ADS)

    Lutz, H.; Breiter, R.; Eich, D.; Figgemeier, H.; Oelmaier, R.; Rutzinger, S.; Schenk, H.; Wendler, J.

    2017-02-01

    Size, weight and power (SWaP) reduction is highly desired by applications such as sights for the dismounted soldier or small gimbals for UAVs. But why have high performance and small size of IR systems inevitably exclude each other? Namely, recent development progress in the fields of miniature cryocoolers, short dewars and high operating temperature (HOT) FPAs combined with pitch size reduction opens the door for very compact MWIR-modules while keeping high electro-optical performance. Now, AIM has realized first prototypes of an ultra-compact high-performance MWIR engine in a total volume of only 18cl (60mm length x 60mm height x 50mm width). Impressive SWaP characteristics are completed by a total weight below 400g and a power consumption < 4W in basic imaging mode. The engine consists of a XGA-format (1024x768) MCT detector array with 10μm pitch and a low power consuming ROIC. It is cooled down to a typical operating temperature of 160K by the miniature linear cryocooler SX020. The dewar uses a short coldfinger and is designed to reduce the heat load as much as possible. The cooler drive electronics is implemented in the CCE layout in order to reduce the required space of the printed boards and to save power. Uncorrected 14bit video data is provided via Camera Link. Optionally, a small image processing board can be stacked on top of the CCE to gain access to basic functions such as BPR, 2- point NUC and dynamic reduction. This paper will present the design, functionalities and performance data of the ultra-compact MCT MWIR engine operated at HOT.

  14. Fast fMRI can detect oscillatory neural activity in humans.

    PubMed

    Lewis, Laura D; Setsompop, Kawin; Rosen, Bruce R; Polimeni, Jonathan R

    2016-10-25

    Oscillatory neural dynamics play an important role in the coordination of large-scale brain networks. High-level cognitive processes depend on dynamics evolving over hundreds of milliseconds, so measuring neural activity in this frequency range is important for cognitive neuroscience. However, current noninvasive neuroimaging methods are not able to precisely localize oscillatory neural activity above 0.2 Hz. Electroencephalography and magnetoencephalography have limited spatial resolution, whereas fMRI has limited temporal resolution because it measures vascular responses rather than directly recording neural activity. We hypothesized that the recent development of fast fMRI techniques, combined with the extra sensitivity afforded by ultra-high-field systems, could enable precise localization of neural oscillations. We tested whether fMRI can detect neural oscillations using human visual cortex as a model system. We detected small oscillatory fMRI signals in response to stimuli oscillating at up to 0.75 Hz within single scan sessions, and these responses were an order of magnitude larger than predicted by canonical linear models. Simultaneous EEG-fMRI and simulations based on a biophysical model of the hemodynamic response to neuronal activity suggested that the blood oxygen level-dependent response becomes faster for rapidly varying stimuli, enabling the detection of higher frequencies than expected. Accounting for phase delays across voxels further improved detection, demonstrating that identifying vascular delays will be of increasing importance with higher-frequency activity. These results challenge the assumption that the hemodynamic response is slow, and demonstrate that fMRI has the potential to map neural oscillations directly throughout the brain.

  15. High Field Small Animal Magnetic Resonance Oncology Studies

    PubMed Central

    Bokacheva, Louisa; Ackerstaff, Ellen; LeKaye, H. Carl; Zakian, Kristen; Koutcher, Jason A.

    2014-01-01

    This review focuses on the applications of high magnetic field magnetic resonance imaging (MRI) and spectroscopy (MRS) to cancer studies in small animals. High field MRI can provide information about tumor physiology, the microenvironment, metabolism, vascularity and cellularity. Such studies are invaluable for understanding tumor growth and proliferation, response to treatment and drug development. The MR techniques reviewed here include 1H, 31P, Chemical Exchange Saturation Transfer (CEST) imaging, and hyperpolarized 13C MR spectroscopy as well as diffusion-weighted, Blood Oxygen Level Dependent (BOLD) contrast imaging, and dynamic contrast-enhanced MR imaging. These methods have been proven effective in animal studies and are highly relevant to human clinical studies. PMID:24374985

  16. Simulated Design Strategies for SPECT Collimators to Reduce the Eddy Currents Induced by MRI Gradient Fields

    NASA Astrophysics Data System (ADS)

    Samoudi, Amine M.; Van Audenhaege, Karen; Vermeeren, Günter; Verhoyen, Gregory; Martens, Luc; Van Holen, Roel; Joseph, Wout

    2015-10-01

    Combining single photon emission computed tomography (SPECT) with magnetic resonance imaging (MRI) requires the insertion of highly conductive SPECT collimators inside the MRI scanner, resulting in an induced eddy current disturbing the combined system. We reduced the eddy currents due to the insert of a novel tungsten collimator inside transverse and longitudinal gradient coils. The collimator was produced with metal additive manufacturing, that is part of a microSPECT insert for a preclinical SPECT/MRI scanner. We characterized the induced magnetic field due to the gradient field and adapted the collimators to reduce the induced eddy currents. We modeled the x-, y-, and z-gradient coil and the different collimator designs and simulated them with FEKO, a three-dimensional method of moments / finite element methods (MoM/FEM) full-wave simulation tool. We used a time analysis approach to generate the pulsed magnetic field gradient. Simulation results show that the maximum induced field can be reduced by 50.82% in the final design bringing the maximum induced magnetic field to less than 2% of the applied gradient for all the gradient coils. The numerical model was validated with measurements and was proposed as a tool for studying the effect of a SPECT collimator within the MRI gradient coils.

  17. Cine phase contrast MRI to measure continuum Lagrangian finite strain fields in contracting skeletal muscle.

    PubMed

    Zhou, Hehe; Novotny, John E

    2007-01-01

    To measure the complex mechanics and Lagrangian finite strain of contracting human skeletal muscle in vivo with cine phase contrast MRI (CPC-MRI) applied to the human supraspinatus muscle of the shoulder. Processing techniques are applied to transform velocities from CPC-MRI images to displacements and planar Lagrangian finite strain. An interpolation method describing the continuity of the velocity field and forward-backward and Fourier transform methods were used to track the displacement of regions of interest during a cyclic abduction motion of a subject's arm. The components of the Lagrangian strain tensor were derived during the motion and principal and maximum in-plane shear strain fields calculated. Derived displacement and strain fields are shown that describe the contraction mechanics of the supraspinatus. Strains vary over time during the cyclic motion and are highly nonuniform throughout the muscle. This method presented overcomes the physical resolution of the MRI scanner, which is crucial for the detection of detailed information within muscles, such as the changes that might occur with partial tears of the supraspinatus. These can then be used as input or validation data for modeling human skeletal muscle.

  18. Fusion of PET and MRI for Hybrid Imaging

    NASA Astrophysics Data System (ADS)

    Cho, Zang-Hee; Son, Young-Don; Kim, Young-Bo; Yoo, Seung-Schik

    Recently, the development of the fusion PET-MRI system has been actively studied to meet the increasing demand for integrated molecular and anatomical imaging. MRI can provide detailed anatomical information on the brain, such as the locations of gray and white matter, blood vessels, axonal tracts with high resolution, while PET can measure molecular and genetic information, such as glucose metabolism, neurotransmitter-neuroreceptor binding and affinity, protein-protein interactions, and gene trafficking among biological tissues. State-of-the-art MRI systems, such as the 7.0 T whole-body MRI, now can visualize super-fine structures including neuronal bundles in the pons, fine blood vessels (such as lenticulostriate arteries) without invasive contrast agents, in vivo hippocampal substructures, and substantia nigra with excellent image contrast. High-resolution PET, known as High-Resolution Research Tomograph (HRRT), is a brain-dedicated system capable of imaging minute changes of chemicals, such as neurotransmitters and -receptors, with high spatial resolution and sensitivity. The synergistic power of the two, i.e., ultra high-resolution anatomical information offered by a 7.0 T MRI system combined with the high-sensitivity molecular information offered by HRRT-PET, will significantly elevate the level of our current understanding of the human brain, one of the most delicate, complex, and mysterious biological organs. This chapter introduces MRI, PET, and PET-MRI fusion system, and its algorithms are discussed in detail.

  19. Simulation of ultra-high energy photon propagation in the geomagnetic field

    NASA Astrophysics Data System (ADS)

    Homola, P.; Góra, D.; Heck, D.; Klages, H.; PeĶala, J.; Risse, M.; Wilczyńska, B.; Wilczyński, H.

    2005-12-01

    The identification of primary photons or specifying stringent limits on the photon flux is of major importance for understanding the origin of ultra-high energy (UHE) cosmic rays. UHE photons can initiate particle cascades in the geomagnetic field, which leads to significant changes in the subsequent atmospheric shower development. We present a Monte Carlo program allowing detailed studies of conversion and cascading of UHE photons in the geomagnetic field. The program named PRESHOWER can be used both as an independent tool or together with a shower simulation code. With the stand-alone version of the code it is possible to investigate various properties of the particle cascade induced by UHE photons interacting in the Earth's magnetic field before entering the Earth's atmosphere. Combining this program with an extensive air shower simulation code such as CORSIKA offers the possibility of investigating signatures of photon-initiated showers. In particular, features can be studied that help to discern such showers from the ones induced by hadrons. As an illustration, calculations for the conditions of the southern part of the Pierre Auger Observatory are presented. Catalogue identifier:ADWG Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADWG Program obtainable: CPC Program Library, Quen's University of Belfast, N. Ireland Computer on which the program has been thoroughly tested:Intel-Pentium based PC Operating system:Linux, DEC-Unix Programming language used:C, FORTRAN 77 Memory required to execute with typical data:<100 kB No. of bits in a word:32 Has the code been vectorized?:no Number of lines in distributed program, including test data, etc.:2567 Number of bytes in distributed program, including test data, etc.:25 690 Distribution format:tar.gz Other procedures used in PRESHOWER:IGRF [N.A. Tsyganenko, National Space Science Data Center, NASA GSFC, Greenbelt, MD 20771, USA, http://nssdc.gsfc.nasa.gov/space/model/magnetos/data-based/geopack.html], bessik

  20. Ultra-high Temperature Emittance Measurements for Space and Missile Applications

    NASA Technical Reports Server (NTRS)

    Rogers, Jan; Crandall, David

    2009-01-01

    Advanced modeling and design efforts for many aerospace components require high temperature emittance data. Applications requiring emittance data include propulsion systems, radiators, aeroshells, heatshields/thermal protection systems, and leading edge surfaces. The objective of this work is to provide emittance data at ultra-high temperatures. MSFC has a new instrument for the measurement of emittance at ultra-high temperatures, the Ultra-High Temperature Emissometer System (Ultra-HITEMS). AZ Technology Inc. developed the instrument, designed to provide emittance measurements over the temperature range 700-3500K. The Ultra-HITEMS instrument measures the emittance of samples, heated by lasers, in vacuum, using a blackbody source and a Fourier Transform Spectrometer. Detectors in a Nicolet 6700 FT-IR spectrometer measure emittance over the spectral range of 0.4-25 microns. Emitted energy from the specimen and output from a Mikron M390S blackbody source at the same temperature with matched collection geometry are measured. Integrating emittance over the spectral range yields the total emittance. The ratio provides a direct measure of total hemispherical emittance. Samples are heated using lasers. Optical pyrometry provides temperature data. Optical filters prevent interference from the heating lasers. Data for Inconel 718 show excellent agreement with results from literature and ASTM 835. Measurements taken from levitated spherical specimens provide total hemispherical emittance data; measurements taken from flat specimens mounted in the chamber provide near-normal emittance data. Data from selected characterization studies will be presented. The Ultra-HITEMS technique could advance space and missile technologies by advancing the knowledge base and the technology readiness level for ultra-high temperature materials.

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

    PubMed

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

    2011-05-01

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

  2. A method for establishing constraints on galactic magnetic field models using ultra high energy cosmic rays and results from the data of the Pierre Auger Observatory

    NASA Astrophysics Data System (ADS)

    Sutherland, Michael Stephen

    2010-12-01

    The Galactic magnetic field is poorly understood. Essentially the only reliable measurements of its properties are the local orientation and field strength. Its behavior at galactic scales is unknown. Historically, magnetic field measurements have been performed using radio astronomy techniques which are sensitive to certain regions of the Galaxy and rely upon models of the distribution of gas and dust within the disk. However, the deflection of trajectories of ultra high energy cosmic rays arriving from extragalactic sources depends only on the properties of the magnetic field. In this work, a method is developed for determining acceptable global models of the Galactic magnetic field by backtracking cosmic rays through the field model. This method constrains the parameter space of magnetic field models by comparing a test statistic between backtracked cosmic rays and isotropic expectations for assumed cosmic ray source and composition hypotheses. Constraints on Galactic magnetic field models are established using data from the southern site of the Pierre Auger Observatory under various source distribution and cosmic ray composition hypotheses. Field models possessing structure similar to the stellar spiral arms are found to be inconsistent with hypotheses of an iron cosmic ray composition and sources selected from catalogs tracing the local matter distribution in the universe. These field models are consistent with hypothesis combinations of proton composition and sources tracing the local matter distribution. In particular, strong constraints are found on the parameter space of bisymmetric magnetic field models scanned under hypotheses of proton composition and sources selected from the 2MRS-VS, Swift 39-month, and VCV catalogs. Assuming that the Galactic magnetic field is well-described by a bisymmetric model under these hypotheses, the magnetic field strength near the Sun is less than 3-4 muG and magnetic pitch angle is less than -8°. These results comprise

  3. Near-UV Sources in the Hubble Ultra Deep Field: The Catalog

    NASA Technical Reports Server (NTRS)

    Gardner, Jonathan P.; Voyrer, Elysse; de Mello, Duilia F.; Siana, Brian; Quirk, Cori; Teplitz, Harry I.

    2009-01-01

    The catalog from the first high resolution U-band image of the Hubble Ultra Deep Field, taken with Hubble s Wide Field Planetary Camera 2 through the F300W filter, is presented. We detect 96 U-band objects and compare and combine this catalog with a Great Observatories Origins Deep Survey (GOODS) B-selected catalog that provides B, V, i, and z photometry, spectral types, and photometric redshifts. We have also obtained Far-Ultraviolet (FUV, 1614 Angstroms) data with Hubble s Advanced Camera for Surveys Solar Blind Channel (ACS/SBC) and with Galaxy Evolution Explorer (GALEX). We detected 31 sources with ACS/SBC, 28 with GALEX/FUV, and 45 with GALEX/NUV. The methods of observations, image processing, object identification, catalog preparation, and catalog matching are presented.

  4. Stunning Aurora Borealis from Space - Ultra-High Definition 4K

    NASA Image and Video Library

    2016-04-17

    NASA Television’s newest offering, NASA TV UHD, brings ultra-high definition video to a new level with the kind of imagery only the world’s leader in space exploration could provide. Harmonic produced this show exclusively for NASA TV UHD, using time-lapses shot from the International Space Station, showing both the Aurora Borealis and Aurora Australis phenomena that occur when electrically charged electrons and protons in the Earth's magnetic field collide with neutral atoms in the upper atmosphere.

  5. High-resolution small field-of-view magnetic resonance image acquisition system using a small planar coil and a pneumatic manipulator in an open MRI scanner.

    PubMed

    Miki, Kohei; Masamune, Ken

    2015-10-01

    Low-field open magnetic resonance imaging (MRI) is frequently used for performing image-guided neurosurgical procedures. Intraoperative magnetic resonance (MR) images are useful for tracking brain shifts and verifying residual tumors. However, it is difficult to precisely determine the boundary of the brain tumors and normal brain tissues because the MR image resolution is low, especially when using a low-field open MRI scanner. To overcome this problem, a high-resolution MR image acquisition system was developed and tested. An MR-compatible manipulator with pneumatic actuators containing an MR signal receiver with a small radiofrequency (RF) coil was developed. The manipulator had five degrees of freedom for position and orientation control of the RF coil. An 8-mm planar RF coil with resistance and inductance of 2.04 [Formula: see text] and 1.00 [Formula: see text] was attached to the MR signal receiver at the distal end of the probe. MR images of phantom test devices were acquired using the MR signal receiver and normal head coil for signal-to-noise ratio (SNR) testing. The SNR of MR images acquired using the MR signal receiver was 8.0 times greater than that of MR images acquired using the normal head coil. The RF coil was moved by the manipulator, and local MR images of a phantom with a 2-mm grid were acquired using the MR signal receiver. A wide field-of-view MR image was generated from a montage of local MR images. A small field-of-view RF system with a pneumatic manipulator was integrated in a low-field MRI scanner to allow acquisition of both wide field-of-view and high-resolution MR images. This system is promising for image-guided neurosurgery as it may allow brain tumors to be observed more clearly and removed precisely.

  6. Handheld Optical Coherence Tomography Angiography and Ultra-Wide-Field Optical Coherence Tomography in Retinopathy of Prematurity.

    PubMed

    Campbell, J Peter; Nudleman, Eric; Yang, Jianlong; Tan, Ou; Chan, R V Paul; Chiang, Michael F; Huang, David; Liu, Gangjun

    2017-09-01

    Retinopathy of prematurity (ROP) is a leading cause of childhood blindness worldwide. Optical coherence tomography (OCT) has improved the care of adults with vitreoretinal disease, and OCT angiography (OCTA) is demonstrating promise as a technique to visualize the retinal vasculature with lower risk and cost than fluorescein angiography. However, to date, there are no commercially available devices able to obtain ultra-wide-field OCT or OCTA images in neonates. To obtain ultra-wide-field OCT and OCTA images in neonates with ROP using a prototype handheld OCT and OCTA device. This observational case series was conducted from March 1 to April 1, 2017, in an academic medical center among 4 neonates with ROP in the neonatal intensive care unit and in the operating room. Acquisition of wide-field OCT and OCTA images using a handheld prototype OCTA and ultra-wide-field OCT device. Images were obtained from 4 neonates (1 girl and 3 boys; mean age, 38 weeks' postmenstrual age [range, 34-43 weeks]) with various stages of ROP: 3 in the neonatal intensive care unit and 1 in the operating room. The system can obtain noncontact en face OCT images and horizontal line scans with an approximately 40° field of view and up to 100° (ultra-wide-field) using a contact lens-based approach in a single 2-second scan. In addition, 20° × 20° (approximately 4 × 4-mm) OCTA scans were obtained in patients with ROP in a single 2-second scan. Optical coherence tomography and OCTA are gaining popularity in pediatric retinal imaging. This study reports on OCTA and ultra-wide-field OCT images in 4 neonates with various stages of ROP that were obtained using a prototype handheld device. Additional studies will be needed to prove the clinical value of this technology.

  7. Megahertz ultra-wide-field swept-source retina optical coherence tomography compared to current existing imaging devices.

    PubMed

    Reznicek, Lukas; Klein, Thomas; Wieser, Wolfgang; Kernt, Marcus; Wolf, Armin; Haritoglou, Christos; Kampik, Anselm; Huber, Robert; Neubauer, Aljoscha S

    2014-06-01

    To investigate the image quality of wide-angle cross-sectional and reconstructed fundus images based on ultra-megahertz swept-source Fourier domain mode locking (FDML) OCT compared to current generation diagnostic devices. A 1,050 nm swept-source FDML OCT system was constructed running at 1.68 MHz A-scan rate covering approximately 70° field of view. Twelve normal eyes were imaged with the device applying an isotropically dense sampling protocol (1,900 × 1,900 A-scans) with a fill factor of 100 %. Obtained OCT scan image quality was compared with two commercial OCT systems (Heidelberg Spectralis and Stratus OCT) of the same 12 eyes. Reconstructed en-face fundus images from the same FDML-OCT data set were compared to color fundus, infrared and ultra-wide-field scanning laser images (SLO). Comparison of cross-sectional scans showed a high overall image quality of the 15× averaged FDML images at 1.68 MHz [overall quality grading score: 8.42 ± 0.52, range 0 (bad)-10 (excellent)] comparable to current spectral-domain OCTs (overall quality grading score: 8.83 ± 0.39, p = 0.731). On FDML OCT, a dense 3D data set was obtained covering also the central and mid-peripheral retina. The reconstructed FDML OCT en-face fundus images had high image quality comparable to scanning laser ophthalmoscope (SLO) as judged from retinal structures such as vessels and optic disc. Overall grading score was 8.36 ± 0.51 for FDML OCT vs 8.27 ± 0.65 for SLO (p = 0.717). Ultra-wide-field megahertz 3D FDML OCT at 1.68 MHz is feasible, and provides cross-sectional image quality comparable to current spectral-domain OCT devices. In addition, reconstructed en-face visualization of fundus images result in a wide-field view with high image quality as compared to currently available fundus imaging devices. The improvement of >30× in imaging speed over commercial spectral-domain OCT technology enables high-density scan protocols leading to a data set for high

  8. Fabrication of a wide-field NIR integral field unit for SWIMS using ultra-precision cutting

    NASA Astrophysics Data System (ADS)

    Kitagawa, Yutaro; Yamagata, Yutaka; Morita, Shin-ya; Motohara, Kentaro; Ozaki, Shinobu; Takahashi, Hidenori; Konishi, Masahiro; Kato, Natsuko M.; Kobayakawa, Yutaka; Terao, Yasunori; Ohashi, Hirofumi

    2016-07-01

    We describe overview of fabrication methods and measurement results of test fabrications of optical surfaces for an integral field unit (IFU) for Simultaneous color Wide-field Infrared Multi-object Spectrograph, SWIMS, which is a first-generation instrument for the University of Tokyo Atacama Observatory 6.5-m telescope. SWIMS-IFU provides entire near-infrared spectrum from 0.9 to 2.5 μm simultaneously covering wider field of view of 17" × 13" compared with current near-infrared IFUs. We investigate an ultra-precision cutting technique to monolithically fabricate optical surfaces of IFU optics such as an image slicer. Using 4- or 5-axis ultra precision machine we compare the milling process and shaper cutting process to find the best way of fabrication of image slicers. The measurement results show that the surface roughness almost satisfies our requirement in both of two methods. Moreover, we also obtain ideal surface form in the shaper cutting process. This method will be adopted to other mirror arrays (i.e. pupil mirror and slit mirror, and such monolithic fabrications will also help us to considerably reduce alignment procedure of each optical elements.

  9. Squid detected NMR and MRI at ultralow fields

    DOEpatents

    Clarke, John [Berkeley, CA; McDermott, Robert [Louisville, CO; Pines, Alexander [Berkeley, CA; Trabesinger, Andreas Heinz [CH-8006 Zurich, CH

    2007-05-15

    Nuclear magnetic resonance (NMR) signals are detected in microtesla fields. Prepolarization in millitesla fields is followed by detection with an untuned dc superconducting quantum interference device (SQUID) magnetometer. Because the sensitivity of the SQUID is frequency independent, both signal-to-noise ratio (SNR) and spectral resolution are enhanced by detecting the NMR signal in extremely low magnetic fields, where the NMR lines become very narrow even for grossly inhomogeneous measurement fields. MRI in ultralow magnetic field is based on the NMR at ultralow fields. Gradient magnetic fields are applied, and images are constructed from the detected NMR signals.

  10. Squid detected NMR and MRI at ultralow fields

    DOEpatents

    Clarke, John; McDermott, Robert; Pines, Alexander; Trabesinger, Andreas Heinz

    2006-05-30

    Nuclear magnetic resonance (NMR) signals are detected in microtesla fields. Prepolarization in millitesla fields is followed by detection with an untuned dc superconducting quantum interference device (SQUID) magnetometer. Because the sensitivity of the SQUID is frequency independent, both signal-to-noise ratio (SNR) and spectral resolution are enhanced by detecting the NMR signal in extremely low magnetic fields, where the NMR lines become very narrow even for grossly inhomogeneous measurement fields. MRI in ultralow magnetic field is based on the NMR at ultralow fields. Gradient magnetic fields are applied, and images are constructed from the detected NMR signals.

  11. Squid detected NMR and MRI at ultralow fields

    DOEpatents

    Clarke, John [Berkeley, CA; Pines, Alexander [Berkeley, CA; McDermott, Robert F [Monona, WI; Trabesinger, Andreas H [London, GB

    2008-12-16

    Nuclear magnetic resonance (NMR) signals are detected in microtesla fields. Prepolarization in millitesla fields is followed by detection with an untuned dc superconducting quantum interference device (SQUID) magnetometer. Because the sensitivity of the SQUID is frequency independent, both signal-to-noise ratio (SNR) and spectral resolution are enhanced by detecting the NMR signal in extremely low magnetic fields, where the NMR lines become very narrow even for grossly inhomogeneous measurement fields. MRI in ultralow magnetic field is based on the NMR at ultralow fields. Gradient magnetic fields are applied, and images are constructed from the detected NMR signals.

  12. SQUID detected NMR and MRI at ultralow fields

    DOEpatents

    Clarke, John; McDermott, Robert; Pines, Alexander; Trabesinger, Andreas Heinz

    2006-10-03

    Nuclear magnetic resonance (NMR) signals are detected in microtesla fields. Prepolarization in millitesla fields is followed by detection with an untuned dc superconducting quantum interference device (SQUID) magnetometer. Because the sensitivity of the SQUID is frequency independent, both signal-to-noise ratio (SNR) and spectral resolution are enhanced by detecting the NMR signal in extremely low magnetic fields, where the NMR lines become very narrow even for grossly inhomogeneous measurement fields. MRI in ultralow magnetic field is based on the NMR at ultralow fields. Gradient magnetic fields are applied, and images are constructed from the detected NMR signals.

  13. SU-G-TeP3-12: Retrospective Assessment of R2star Using Ultra-High Field MRI in a Rodent Model of Radiation Necrosis

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Belliveau, J; Menon, R

    Purpose: To establish a quantitative MRI method that would be capable of predicting radiation necrosis without using a contrast agent. Methods: Healthy male Fischer 344 rats were irradiated using an animal irradiator capable of delivering 2.3 Gy/min with a kVp of 225 V. A dose of 40 Gy was given to half the brain in a single session. Rats were scanned using a 9.4 T animal MRI before irradiation and every two weeks following radiation until either necrosis developed or they were sacrificed for health reasons. A multi-echo gradient-echo sequence was acquired at every time point and the apparent transversemore » relaxation rate R{sub 2}* was calculated based on the measured signal decay. At the last time point, an ROI mask with an R{sub 2}* value of greater than 45 s{sup −1} was applied in the area of the external and internal capsule where radiation necrosis was confirmed. A retrospective analysis was performed to determine whether R{sub 2}* values would be able to predict where radiation necrosis would occur. Results: Radiation necrosis was morphologically visible between weeks 22–24 following treatment. Gadolinium MRI and histology confirmed radiation necrosis in the area of MRI enhancement. Our data suggests that there is a trend towards significance in the lesion as early as 12 weeks prior to morphological changes on MRI with significance occurring 6 weeks prior (p≤0.05, p≤0.01 at week 24). Measurements of the R{sub 2}* in the hippocampus did not show any significant difference; however, there are areas of visible R{sub 2}* change within sub-hippocampal regions. Conclusion: R{sub 2}* is a promising method that could be able to predict an underlying disease process that occurs prior to radiation necrosis. The constant increase in R{sub 2}* values suggests a possible neuroinflammatory mechanism rather than an acute vascular event where R{sub 2}* would tend to decrease in the area.« less

  14. Formal thought disorder in people at ultra-high risk of psychosis

    PubMed Central

    Weinstein, Sara; Stahl, Daniel; Day, Fern; Valmaggia, Lucia; Rutigliano, Grazia; De Micheli, Andrea; Fusar-Poli, Paolo; McGuire, Philip

    2017-01-01

    Background Formal thought disorder is a cardinal feature of psychosis. However, the extent to which formal thought disorder is evident in ultra-high-risk individuals and whether it is linked to the progression to psychosis remains unclear. Aims Examine the severity of formal thought disorder in ultra-high-risk participants and its association with future psychosis. Method The Thought and Language Index (TLI) was used to assess 24 ultra-high-risk participants, 16 people with first-episode psychosis and 13 healthy controls. Ultra-high-risk individuals were followed up for a mean duration of 7 years (s.d.=1.5) to determine the relationship between formal thought disorder at baseline and transition to psychosis. Results TLI scores were significantly greater in the ultra-high-risk group compared with the healthy control group (effect size (ES)=1.2), but lower than in people with first-episode psychosis (ES=0.8). Total and negative TLI scores were higher in ultra-high-risk individuals who developed psychosis, but this was not significant. Combining negative TLI scores with attenuated psychotic symptoms and basic symptoms predicted transition to psychosis (P=0.04; ES=1.04). Conclusions TLI is beneficial in evaluating formal thought disorder in ultra-high-risk participants, and complements existing instruments for the evaluation of psychopathology in this group. Declaration of interests None. Copyright and usage © The Royal College of Psychiatrists 2017. This is an open access article distributed under the terms of the Creative Commons Non-Commercial, No Derivatives (CC BY-NC-ND) license. PMID:28713586

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

    PubMed Central

    2013-01-01

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

  16. Ultra High Energy Cosmic Rays: Strangelets?

    NASA Astrophysics Data System (ADS)

    Xu, Ren-Xin; Wu, Fei

    2003-06-01

    The conjecture that ultra-high-energy cosmic rays (UHECRs) are actually strangelets is discussed. Besides the reason that strangelets can do as cosmic rays beyond the Greisen-Zatsepin-Kuzmin-cutoff, another argument to support the conjecture is addressed by the study of formation of TeV-scale microscopic black holes when UHECRs bombarding bare strange stars. It is proposed that the exotic quark surface of a bare strange star could be an effective astro-laboratory in the investigations of the extra dimensions and of the detection of ultra-high-energy neutrino fluxes. The flux of neutrinos (and other point-like particles) with energy larger than 2.3×1020 eV could be expected to be smaller than 10-26 cm-2 s-1 if there are two extra spatial dimensions.

  17. Anatomic study of the canine stifle using low-field magnetic resonance imaging (MRI) and MRI arthrography.

    PubMed

    Pujol, Esteban; Van Bree, Henri; Cauzinille, Laurent; Poncet, Cyrill; Gielen, Ingrid; Bouvy, Bernard

    2011-06-01

    To investigate the use of low-field magnetic resonance imaging (MRI) and MR arthrography in normal canine stifles and to compare MRI images to gross dissection. Descriptive study. Adult canine pelvic limbs (n=17). Stifle joints from 12 dogs were examined by orthopedic and radiographic examination, synovial fluid analysis, and MRI performed using a 0.2 T system. Limbs 1 to 7 were used to develop the MR and MR arthrography imaging protocol. Limbs 8-17 were studied with the developed MR and MR arthrography protocol and by gross dissection. Three sequences were obtained: T1-weighted spin echo (SE) in sagittal, dorsal, and transverse plane; T2-weighted SE in sagittal plane and T1-gradient echo in sagittal plane. Specific bony and soft tissue structures were easily identifiable with the exception of articular cartilage. The cranial and caudal cruciate ligaments were identified. Medial and lateral menisci were seen as wedge-shaped hypointense areas. MR arthrography permitted further delineation of specific structures. MR images corresponded with gross dissection morphology. With the exception of poor delineation of articular cartilage, a low-field MRI and MR arthrography protocol provides images of adequate quality to assess the normal canine stifle joint. © Copyright 2011 by The American College of Veterinary Surgeons.

  18. Quantitative techniques for musculoskeletal MRI at 7 Tesla.

    PubMed

    Bangerter, Neal K; Taylor, Meredith D; Tarbox, Grayson J; Palmer, Antony J; Park, Daniel J

    2016-12-01

    Whole-body 7 Tesla MRI scanners have been approved solely for research since they appeared on the market over 10 years ago, but may soon be approved for selected clinical neurological and musculoskeletal applications in both the EU and the United States. There has been considerable research work on musculoskeletal applications at 7 Tesla over the past decade, including techniques for ultra-high resolution morphological imaging, 3D T2 and T2* mapping, ultra-short TE applications, diffusion tensor imaging of cartilage, and several techniques for assessing proteoglycan content in cartilage. Most of this work has been done in the knee or other extremities, due to technical difficulties associated with scanning areas such as the hip and torso at 7 Tesla. In this manuscript, we first provide some technical context for 7 Tesla imaging, including challenges and potential advantages. We then review the major quantitative MRI techniques being applied to musculoskeletal applications on 7 Tesla whole-body systems.

  19. Quantitative techniques for musculoskeletal MRI at 7 Tesla

    PubMed Central

    Taylor, Meredith D.; Tarbox, Grayson J.; Palmer, Antony J.; Park, Daniel J.

    2016-01-01

    Whole-body 7 Tesla MRI scanners have been approved solely for research since they appeared on the market over 10 years ago, but may soon be approved for selected clinical neurological and musculoskeletal applications in both the EU and the United States. There has been considerable research work on musculoskeletal applications at 7 Tesla over the past decade, including techniques for ultra-high resolution morphological imaging, 3D T2 and T2* mapping, ultra-short TE applications, diffusion tensor imaging of cartilage, and several techniques for assessing proteoglycan content in cartilage. Most of this work has been done in the knee or other extremities, due to technical difficulties associated with scanning areas such as the hip and torso at 7 Tesla. In this manuscript, we first provide some technical context for 7 Tesla imaging, including challenges and potential advantages. We then review the major quantitative MRI techniques being applied to musculoskeletal applications on 7 Tesla whole-body systems. PMID:28090448

  20. The effects of the use of piezoelectric motors in a 1.5-Tesla high-field magnetic resonance imaging system (MRI).

    PubMed

    Wendt, O; Oellinger, J; Lüth, T C; Felix, R; Boenick, U

    2000-01-01

    This paper presents the results of an experimental investigation with two different rotatory piezomotors in a closed 1.5 Tesla high-field MRI. The focus of the investigation was on testing the functionality of these motors within the MRI and to determining the image interference they caused. To obtain a differentiated estimate of the interference the motors were tested in both the passive (turned off, i.e. without current flow) and active (turned on, i.e. with current flow) state during MRI scanning. Three different types of sequences were used for the test: Spin-Echo (SE), Gradient-Echo (GE) and Echo-Planar Imaging (EPI). A plastic container filled with a gadolinium-manganese solution was used for representation of the artefacts. The motors investigated were placed parallel to the container at predetermined distances during the experiment. The results show that the motors investigated suffered no functional limitations in the magnetic field of the MRI but, depending on the type of motor, the measurement distance and the state of the motor, the motors had different effects on the sequence images. A motor in the off-state placed immediately next to the object to be measured mainly causes artefacts because of its material properties. If, on the other hand, the piezomotor is in the on-state images with strong noise result when the motor is immediately next to the object being measured. The images regain their normal quality when the motor is approximately at a distance of 1 m from the object being investigated. Driving the motor inside the MRI, therefore, is only to be recommended during the pauses in scanning: this delivers artefact-free images if minimal, motor-specific distances are kept to. With regard to the three different types of sequences it was determined that the SE sequence was the least sensitive and the EPI sequence the most sensitive to disturbance. The GE sequence showed only minimal differences to the SE sequence with regard to signal-to-noise ratios

  1. Ultra-High Temperature Materials Characterization for Propulsion Applications

    NASA Technical Reports Server (NTRS)

    Rogers, Jan; Hyers, Robert

    2007-01-01

    Propulsion system efficiency increases as operating temperatures are increased. Some very high-temperature materials are being developed, including refractory metal alloys, carbides, borides, and silicides. System design requires data for materials properties at operating temperatures. Materials property data are not available for many materials of interest at the desired operating temperatures (up to approx. 3000 K). The objective of this work is to provide important physical property data at ultra-high temperatures. The MSFC Electrostatic levitation (ESL) facility can provide measurements of thermophysical properties which include: creep strength, density and thermal expansion for materials being developed for propulsion applications. The ESL facility uses electrostatic fields to position samples between electrodes during processing and characterization studies. Because the samples float between the electrodes during studies, they are free from any contact with a container or test apparatus. This provides a high purity environment for the study of high-temperature, reactive materials. ESL can be used to process a wide variety of materials including metals, alloys, ceramics, glasses and semiconductors. The MSFC ESL has provided non-contact measurements of properties of materials up to 3400 C. Density and thermal expansion are measured by analyzing digital images of the sample at different temperatures. Our novel, non-contact method for measuring creep uses rapid rotation to deform the sample. Digital images of the deformed samples are analyzed to obtain the creep properties, which match those obtained using ASTM Standard E-139 for Nb at 1985 C. Data from selected ESL-based characterization studies will be presented. The ESL technique could support numerous propulsion technologies by advancing the knowledge base and the technology readiness level for ultra-high temperature materials. Applications include non-eroding nozzle materials and lightweight, high

  2. Modeling of Diamond Field-Emitter-Arrays for high brightness photocathode applications

    NASA Astrophysics Data System (ADS)

    Kwan, Thomas; Huang, Chengkun; Piryatinski, Andrei; Lewellen, John; Nichols, Kimberly; Choi, Bo; Pavlenko, Vitaly; Shchegolkov, Dmitry; Nguyen, Dinh; Andrews, Heather; Simakov, Evgenya

    2017-10-01

    We propose to employ Diamond Field-Emitter-Arrays (DFEAs) as high-current-density ultra-low-emittance photocathodes for compact laser-driven dielectric accelerators capable of generating ultra-high brightness electron beams for advanced applications. We develop a semi-classical Monte-Carlo photoemission model for DFEAs that includes carriers' transport to the emitter surface and tunneling through the surface under external fields. The model accounts for the electronic structure size quantization affecting the transport and tunneling process within the sharp diamond tips. We compare this first principle model with other field emission models, such as the Child-Langmuir and Murphy-Good models. By further including effects of carrier photoexcitation, we perform simulations of the DFEAs' photoemission quantum yield and the emitted electron beam. Details of the theoretical model and validation against preliminary experimental data will be presented. Work ssupported by LDRD program at LANL.

  3. Supercontinuum ultra-high resolution line-field OCT; experimental spectrograph comparison and comparison with current clinical OCT systems by the imaging of a human cornea

    NASA Astrophysics Data System (ADS)

    Lawman, Samuel; Romano, Vito; Madden, Peter W.; Mason, Sharon; Williams, Bryan M.; Zheng, Yalin; Shen, Yao-Chun

    2018-03-01

    Ultra high axial resolution (UHR) was demonstrated early in the development of optical coherence tomography (OCT), but has not yet reached clinical practice. We present the combination of supercontinuum light source and line field (LF-) OCT as a technical and economical route to get UHR-OCT into clinic and other OCT application areas. We directly compare images of a human donor cornea taken with low and high resolution current generation clinical OCT systems with UHR-LF-OCT. These images highlight the massive information increase of UHR-OCT. Application to pharmaceutical pellets, and the functionality and imaging performance of different imaging spectrograph choices for LF- OCT are also demonstrated.

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

    PubMed

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

    1996-01-01

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

  5. Review on the progress of ultra-precision machining technologies

    NASA Astrophysics Data System (ADS)

    Yuan, Julong; Lyu, Binghai; Hang, Wei; Deng, Qianfa

    2017-06-01

    Ultra-precision machining technologies are the essential methods, to obtain the highest form accuracy and surface quality. As more research findings are published, such technologies now involve complicated systems engineering and been widely used in the production of components in various aerospace, national defense, optics, mechanics, electronics, and other high-tech applications. The conception, applications and history of ultra-precision machining are introduced in this article, and the developments of ultra-precision machining technologies, especially ultra-precision grinding, ultra-precision cutting and polishing are also reviewed. The current state and problems of this field in China are analyzed. Finally, the development trends of this field and the coping strategies employed in China to keep up with the trends are discussed.

  6. Compressed Sensing for fMRI: Feasibility Study on the Acceleration of Non-EPI fMRI at 9.4T

    PubMed Central

    Kim, Seong-Gi; Ye, Jong Chul

    2015-01-01

    Conventional functional magnetic resonance imaging (fMRI) technique known as gradient-recalled echo (GRE) echo-planar imaging (EPI) is sensitive to image distortion and degradation caused by local magnetic field inhomogeneity at high magnetic fields. Non-EPI sequences such as spoiled gradient echo and balanced steady-state free precession (bSSFP) have been proposed as an alternative high-resolution fMRI technique; however, the temporal resolution of these sequences is lower than the typically used GRE-EPI fMRI. One potential approach to improve the temporal resolution is to use compressed sensing (CS). In this study, we tested the feasibility of k-t FOCUSS—one of the high performance CS algorithms for dynamic MRI—for non-EPI fMRI at 9.4T using the model of rat somatosensory stimulation. To optimize the performance of CS reconstruction, different sampling patterns and k-t FOCUSS variations were investigated. Experimental results show that an optimized k-t FOCUSS algorithm with acceleration by a factor of 4 works well for non-EPI fMRI at high field under various statistical criteria, which confirms that a combination of CS and a non-EPI sequence may be a good solution for high-resolution fMRI at high fields. PMID:26413503

  7. Computational dosimetry of induced electric fields during realistic movements in the vicinity of a 3 T MRI scanner

    NASA Astrophysics Data System (ADS)

    Laakso, Ilkka; Kännälä, Sami; Jokela, Kari

    2013-04-01

    Medical staff working near magnetic resonance imaging (MRI) scanners are exposed both to the static magnetic field itself and also to electric currents that are induced in the body when the body moves in the magnetic field. However, there are currently limited data available on the induced electric field for realistic movements. This study computationally investigates the movement induced electric fields for realistic movements in the magnetic field of a 3 T MRI scanner. The path of movement near the MRI scanner is based on magnetic field measurements using a coil sensor attached to a human volunteer. Utilizing realistic models for both the motion of the head and the magnetic field of the MRI scanner, the induced fields are computationally determined using the finite-element method for five high-resolution numerical anatomical models. The results show that the time-derivative of the magnetic flux density (dB/dt) is approximately linearly proportional to the induced electric field in the head, independent of the position of the head with respect to the magnet. This supports the use of dB/dt measurements for occupational exposure assessment. For the path of movement considered herein, the spatial maximum of the induced electric field is close to the basic restriction for the peripheral nervous system and exceeds the basic restriction for the central nervous system in the international guidelines. The 99th percentile electric field is a considerably less restrictive metric for the exposure than the spatial maximum electric field; the former is typically 60-70% lower than the latter. However, the 99th percentile electric field may exceed the basic restriction for dB/dt values that can be encountered during tasks commonly performed by MRI workers. It is also shown that the movement-induced eddy currents may reach magnitudes that could electrically stimulate the vestibular system, which could play a significant role in the generation of vertigo-like sensations reported

  8. Real-time 2D spatially selective MRI experiments: Comparative analysis of optimal control design methods

    NASA Astrophysics Data System (ADS)

    Maximov, Ivan I.; Vinding, Mads S.; Tse, Desmond H. Y.; Nielsen, Niels Chr.; Shah, N. Jon

    2015-05-01

    There is an increasing need for development of advanced radio-frequency (RF) pulse techniques in modern magnetic resonance imaging (MRI) systems driven by recent advancements in ultra-high magnetic field systems, new parallel transmit/receive coil designs, and accessible powerful computational facilities. 2D spatially selective RF pulses are an example of advanced pulses that have many applications of clinical relevance, e.g., reduced field of view imaging, and MR spectroscopy. The 2D spatially selective RF pulses are mostly generated and optimised with numerical methods that can handle vast controls and multiple constraints. With this study we aim at demonstrating that numerical, optimal control (OC) algorithms are efficient for the design of 2D spatially selective MRI experiments, when robustness towards e.g. field inhomogeneity is in focus. We have chosen three popular OC algorithms; two which are gradient-based, concurrent methods using first- and second-order derivatives, respectively; and a third that belongs to the sequential, monotonically convergent family. We used two experimental models: a water phantom, and an in vivo human head. Taking into consideration the challenging experimental setup, our analysis suggests the use of the sequential, monotonic approach and the second-order gradient-based approach as computational speed, experimental robustness, and image quality is key. All algorithms used in this work were implemented in the MATLAB environment and are freely available to the MRI community.

  9. [Extreme (complicated, ultra-high) refractive errors: terminological misconceptions!?

    PubMed

    Avetisov, S E

    2018-01-01

    The article reviews development mechanisms of different refractive errors accompanied by marked defocus of light rays reaching the retina. Terminology used for such ametropias includes terms extreme, ultra-high and complicated. Justification of their usage for primary ametropias, whose symptom complex is based on changes in axial eye length, is an ongoing discussion. To comply with thesaurus definitions of 'diagnosis' and 'pathogenesis', to characterize refractive and anatomical-functional disorders in patients with primary ametropias it is proposed to use the terms 'hyperaxial and hypoaxial syndromes' with elaboration of specific symptoms instead of such expressions as extreme (ultra-high) myopia and hypermetropia.

  10. Accuracy of deep learning, a machine-learning technology, using ultra-wide-field fundus ophthalmoscopy for detecting rhegmatogenous retinal detachment.

    PubMed

    Ohsugi, Hideharu; Tabuchi, Hitoshi; Enno, Hiroki; Ishitobi, Naofumi

    2017-08-25

    Rhegmatogenous retinal detachment (RRD) is a serious condition that can lead to blindness; however, it is highly treatable with timely and appropriate treatment. Thus, early diagnosis and treatment of RRD is crucial. In this study, we applied deep learning, a machine-learning technology, to detect RRD using ultra-wide-field fundus images and investigated its performance. In total, 411 images (329 for training and 82 for grading) from 407 RRD patients and 420 images (336 for training and 84 for grading) from 238 non-RRD patients were used in this study. The deep learning model demonstrated a high sensitivity of 97.6% [95% confidence interval (CI), 94.2-100%] and a high specificity of 96.5% (95% CI, 90.2-100%), and the area under the curve was 0.988 (95% CI, 0.981-0.995). This model can improve medical care in remote areas where eye clinics are not available by using ultra-wide-field fundus ophthalmoscopy for the accurate diagnosis of RRD. Early diagnosis of RRD can prevent blindness.

  11. Ultra-long high-sensitivity Φ-OTDR for high spatial resolution intrusion detection of pipelines.

    PubMed

    Peng, Fei; Wu, Han; Jia, Xin-Hong; Rao, Yun-Jiang; Wang, Zi-Nan; Peng, Zheng-Pu

    2014-06-02

    An ultra-long phase-sensitive optical time domain reflectometry (Φ-OTDR) that can achieve high-sensitivity intrusion detection over 131.5km fiber with high spatial resolution of 8m is presented, which is the longest Φ-OTDR reported to date, to the best of our knowledge. It is found that the combination of distributed Raman amplification with heterodyne detection can extend the sensing distance and enhances the sensitivity substantially, leading to the realization of ultra-long Φ-OTDR with high sensitivity and spatial resolution. Furthermore, the feasibility of applying such an ultra-long Φ-OTDR to pipeline security monitoring is demonstrated and the features of intrusion signal can be extracted with improved SNR by using the wavelet detrending/denoising method proposed.

  12. Analysis of trace halocarbon contaminants in ultra high purity helium

    NASA Technical Reports Server (NTRS)

    Fewell, Larry L.

    1994-01-01

    This study describes the analysis of ultra high purity helium. Purification studies were conducted and containment removal was effected by the utilization of solid adsorbent purge-trap systems at cryogenic temperatures. Volatile organic compounds in ultra high purity helium were adsorbed on a solid adsorbent-cryogenic trap, and thermally desorbed trace halocarbon and other contaminants were analyzed by combined gas chromatography-mass spectrometry.

  13. Microchip capillary gel electrophoresis using programmed field strength gradients for the ultra-fast analysis of genetically modified organisms in soybeans.

    PubMed

    Kim, Yun-Jeong; Chae, Joon-Seok; Chang, Jun Keun; Kang, Seong Ho

    2005-08-12

    We have developed a novel method for the ultra-fast analysis of genetically modified organisms (GMOs) in soybeans by microchip capillary gel electrophoresis (MCGE) using programmed field strength gradients (PFSG) in a conventional glass double-T microchip. Under the programmed electric field strength and 0.3% poly(ethylene oxide) sieving matrix, the GMO in soybeans was analyzed within only 11 s of the microchip. The MCGE-PFSG method was a program that changes the electric field strength during GMO analysis, and was also applied to the ultra-fast analysis of PCR products. Compared to MCGE using a conventional and constantly applied electric field, the MCGE-PFSG analysis generated faster results without the loss of resolving power and reproducibility for specific DNA fragments (100- and 250-bp DNA) of GM-soybeans. The MCGE-PFSG technique may prove to be a new tool in the GMO analysis due to its speed, simplicity, and high efficiency.

  14. Quantitative comparison of high-resolution MRI and myelin-stained histology of the human cerebral cortex.

    PubMed

    Osechinskiy, Sergey; Kruggel, Frithjof

    2009-01-01

    The architectonic analysis of the human cerebral cortex is presently based on the examination of stained tissue sections. Recent progress in high-resolution magnetic resonance imaging (MRI) promotes the feasibility of an in vivo architectonic analysis. Since the exact relationship between the laminar fine-structure of a cortical MRI signal and histological cyto-and myeloarchitectonic staining patterns is not known, a quantitative study comparing high-resolution MRI to histological ground truth images is necessary for validating a future MRI based architectonic analysis. This communication describes an ongoing study comparing post mortem MR images to a myelin-stained histology of the brain cortex. After establishing a close spatial correspondence between histological sections and MRI using a slice-to-volume nonrigid registration algorithm, transcortical intensity profiles, extracted from both imaging modalities along curved trajectories of a Laplacian vector field, are compared via a cross-correlational analysis.

  15. An Open-Source Hardware and Software System for Acquisition and Real-Time Processing of Electrophysiology during High Field MRI

    PubMed Central

    Purdon, Patrick L.; Millan, Hernan; Fuller, Peter L.; Bonmassar, Giorgio

    2008-01-01

    Simultaneous recording of electrophysiology and functional magnetic resonance imaging (fMRI) is a technique of growing importance in neuroscience. Rapidly evolving clinical and scientific requirements have created a need for hardware and software that can be customized for specific applications. Hardware may require customization to enable a variety of recording types (e.g., electroencephalogram, local field potentials, or multi-unit activity) while meeting the stringent and costly requirements of MRI safety and compatibility. Real-time signal processing tools are an enabling technology for studies of learning, attention, sleep, epilepsy, neurofeedback, and neuropharmacology, yet real-time signal processing tools are difficult to develop. We describe an open source system for simultaneous electrophysiology and fMRI featuring low-noise (< 0.6 uV p-p input noise), electromagnetic compatibility for MRI (tested up to 7 Tesla), and user-programmable real-time signal processing. The hardware distribution provides the complete specifications required to build an MRI-compatible electrophysiological data acquisition system, including circuit schematics, print circuit board (PCB) layouts, Gerber files for PCB fabrication and robotic assembly, a bill of materials with part numbers, data sheets, and vendor information, and test procedures. The software facilitates rapid implementation of real-time signal processing algorithms. This system has used in human EEG/fMRI studies at 3 and 7 Tesla examining the auditory system, visual system, sleep physiology, and anesthesia, as well as in intracranial electrophysiological studies of the non-human primate visual system during 3 Tesla fMRI, and in human hyperbaric physiology studies at depths of up to 300 feet below sea level. PMID:18761038

  16. An open-source hardware and software system for acquisition and real-time processing of electrophysiology during high field MRI.

    PubMed

    Purdon, Patrick L; Millan, Hernan; Fuller, Peter L; Bonmassar, Giorgio

    2008-11-15

    Simultaneous recording of electrophysiology and functional magnetic resonance imaging (fMRI) is a technique of growing importance in neuroscience. Rapidly evolving clinical and scientific requirements have created a need for hardware and software that can be customized for specific applications. Hardware may require customization to enable a variety of recording types (e.g., electroencephalogram, local field potentials, or multi-unit activity) while meeting the stringent and costly requirements of MRI safety and compatibility. Real-time signal processing tools are an enabling technology for studies of learning, attention, sleep, epilepsy, neurofeedback, and neuropharmacology, yet real-time signal processing tools are difficult to develop. We describe an open-source system for simultaneous electrophysiology and fMRI featuring low-noise (<0.6microV p-p input noise), electromagnetic compatibility for MRI (tested up to 7T), and user-programmable real-time signal processing. The hardware distribution provides the complete specifications required to build an MRI-compatible electrophysiological data acquisition system, including circuit schematics, print circuit board (PCB) layouts, Gerber files for PCB fabrication and robotic assembly, a bill of materials with part numbers, data sheets, and vendor information, and test procedures. The software facilitates rapid implementation of real-time signal processing algorithms. This system has been used in human EEG/fMRI studies at 3 and 7T examining the auditory system, visual system, sleep physiology, and anesthesia, as well as in intracranial electrophysiological studies of the non-human primate visual system during 3T fMRI, and in human hyperbaric physiology studies at depths of up to 300 feet below sea level.

  17. Ultra-High Surface Speed for Metal Removal, Artillery Shell

    DTIC Science & Technology

    1981-07-01

    TECHNICAL LIBRARY "y/a^^cr^ AD-E400 660 CONTRACTOR REPORT ARLCD-CR- 81019 ULTRA-HIGH SURFACE SPEED FOR METAL REMOVAL, ARTILLERY SHELL RICHARD F...Report ARLCD-CR- 81019 2. GOVT ACCESSION NO. 3. RECIPIENT’S CATALOG NUMBER 4. TITLE (and Subtitle) ULTRA-HIGH SURFACE SPEED FOR METAL...UNIT* tuiPPtO 1 MIL -STD-43CA i, ASTM A-274-64 EF A1SI~1340 SEHI FIN FORGING STEEL 6 RC SQ ■ IP 120093* a LIFTS 38 PCS

  18. Ultra-low noise supercontinuum source for ultra-high resolution optical coherence tomography at 1300 nm

    NASA Astrophysics Data System (ADS)

    Gonzalo, I. B.; Maria, M.; Engelsholm, R. D.; Feuchter, T.; Leick, L.; Moselund, P. M.; Podoleanu, A.; Bang, O.

    2018-02-01

    Supercontinuum (SC) sources are of great interest for many applications due to their ultra-broad optical bandwidth, good beam quality and high power spectral density [1]. In particular, the high average power over large bandwidths makes SC light sources excellent candidates for ultra-high resolution optical coherence tomography (UHR-OCT) [2-5]. However, conventional SC sources suffer from high pulse-to-pulse intensity fluctuations as a result of the noise-sensitive nonlinear effects involved in the SC generation process [6-9]. This intensity noise from the SC source can limit the performance of OCT, resulting in a reduced signal-to-noise ratio (SNR) [10-12]. Much work has been done to reduce the noise of the SC sources for instance with fiber tapers [7,8] or increasing the repetition rate of the pump laser for averaging in the spectrometer [10,12]. An alternative approach is to use all-normal dispersion (ANDi) fibers [13,14] to generate SC light from well-known coherent nonlinear processes [15-17]. In fact, reduction of SC noise using ANDi fibers compared to anomalous dispersion SC pumped by sub-picosecond pulses has been recently demonstrated [18], but a cladding mode was used to stabilize the ANDi SC. In this work, we characterize the noise performance of a femtosecond pumped ANDi based SC and a commercial SC source in an UHR-OCT system at 1300 nm. We show that the ANDi based SC presents exceptional noise properties compared to a commercial source. An improvement of 5 dB in SNR is measured in the UHR-OCT system, and the noise behavior resembles that of a superluminiscent diode. This preliminary study is a step forward towards development of an ultra-low noise SC source at 1300 nm for ultra-high resolution OCT.

  19. Assessment of alveolar bone marrow fat content using 15 T MRI.

    PubMed

    Cortes, Arthur Rodriguez Gonzalez; Cohen, Ouri; Zhao, Ming; Aoki, Eduardo Massaharu; Ribeiro, Rodrigo Alves; Abu Nada, Lina; Costa, Claudio; Arita, Emiko Saito; Tamimi, Faleh; Ackerman, Jerome L

    2018-03-01

    Bone marrow fat is inversely correlated with bone mineral density. The aim of this study is to present a method to quantify alveolar bone marrow fat content using a 15 T magnetic resonance imaging (MRI) scanner. A 15 T MRI scanner with a 13-mm inner diameter loop-gap radiofrequency coil was used to scan seven 3-mm diameter alveolar bone biopsy specimens. A 3-D gradient-echo relaxation time (T1)-weighted pulse sequence was chosen to obtain images. All images were obtained with a voxel size (58 µm 3 ) sufficient to resolve trabecular spaces. Automated volume of the bone marrow fat content and derived bone volume fraction (BV/TV) were calculated. Results were compared with actual BV/TV obtained from micro-computed tomography (CT) scans. Mean fat tissue volume was 20.1 ± 11%. There was a significantly strong inverse correlation between fat tissue volume and BV/TV (r = -0.68; P = .045). Furthermore, there was a strong agreement between BV/TV derived from MRI and obtained with micro-CT (interclass correlation coefficient = 0.92; P = .001). Bone marrow fat of small alveolar bone biopsy specimens can be quantified with sufficient spatial resolution using an ultra-high-field MRI scanner and a T1-weighted pulse sequence. Copyright © 2017 Elsevier Inc. All rights reserved.

  20. Imaging Electric Properties of Biological Tissues by RF Field Mapping in MRI

    PubMed Central

    Zhang, Xiaotong; Zhu, Shanan; He, Bin

    2010-01-01

    The electric properties (EPs) of biological tissue, i.e., the electric conductivity and permittivity, can provide important information in the diagnosis of various diseases. The EPs also play an important role in specific absorption rate (SAR) calculation, a major concern in high-field Magnetic Resonance Imaging (MRI), as well as in non-medical areas such as wireless-telecommunications. The high-field MRI system is accompanied by significant wave propagation effects, and the radio frequency (RF) radiation is dependent on the EPs of biological tissue. Based on the measurement of the active transverse magnetic component of the applied RF field (known as B1-mapping technique), we propose a dual-excitation algorithm, which uses two sets of measured B1 data to noninvasively reconstruct the electric properties of biological tissues. The Finite Element Method (FEM) was utilized in three-dimensional (3D) modeling and B1 field calculation. A series of computer simulations were conducted to evaluate the feasibility and performance of the proposed method on a 3D head model within a transverse electromagnetic (TEM) coil and a birdcage (BC) coil. Using a TEM coil, when noise free, the reconstructed EP distribution of tissues in the brain has relative errors of 12% ∼ 28% and correlated coefficients of greater than 0.91. Compared with other B1-mapping based reconstruction algorithms, our approach provides superior performance without the need for iterative computations. The present simulation results suggest that good reconstruction of electric properties from B1 mapping can be achieved. PMID:20129847

  1. 2D and 3D MOCART scoring systems assessed by 9.4 T high-field MRI correlate with elementary and complex histological scoring systems in a translational model of osteochondral repair.

    PubMed

    Goebel, L; Zurakowski, D; Müller, A; Pape, D; Cucchiarini, M; Madry, H

    2014-10-01

    To compare the 2D and 3D MOCART system obtained with 9.4 T high-field magnetic resonance imaging (MRI) for the ex vivo analysis of osteochondral repair in a translational model and to correlate the data with semiquantitative histological analysis. Osteochondral samples representing all levels of repair (sheep medial femoral condyles; n = 38) were scanned in a 9.4 T high-field MRI. The 2D and adapted 3D MOCART systems were used for grading after point allocation to each category. Each score was correlated with corresponding reconstructions between both MOCART systems. Data were next correlated with corresponding categories of an elementary (Wakitani) and a complex (Sellers) histological scoring system as gold standards. Correlations between most 2D and 3D MOCART score categories were high, while mean total point values of 3D MOCART scores tended to be 15.8-16.1 points higher compared to the 2D MOCART scores based on a Bland-Altman analysis. "Defect fill" and "total points" of both MOCART scores correlated with corresponding categories of Wakitani and Sellers scores (all P ≤ 0.05). "Subchondral bone plate" also correlated between 3D MOCART and Sellers scores (P < 0.001). Most categories of the 2D and 3D MOCART systems correlate, while total scores were generally higher using the 3D MOCART system. Structural categories "total points" and "defect fill" can reliably be assessed by 9.4 T MRI evaluation using either system, "subchondral bone plate" using the 3D MOCART score. High-field MRI is valuable to objectively evaluate osteochondral repair in translational settings. Copyright © 2014 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.

  2. Mid-infrared ultra-high-Q resonators based on fluoride crystalline materials

    NASA Astrophysics Data System (ADS)

    Lecaplain, C.; Javerzac-Galy, C.; Gorodetsky, M. L.; Kippenberg, T. J.

    2016-11-01

    The unavailability of highly transparent materials in the mid-infrared has been the main limitation in the development of ultra-sensitive molecular sensors or cavity-based spectroscopy applications. Whispering gallery mode microresonators have attained ultra-high-quality (Q) factor resonances in the near-infrared and visible. Here we report ultra-high Q factors in the mid-infrared using polished alkaline earth metal fluoride crystals. Using an uncoated chalcogenide tapered fibre as a high-ideality coupler in the mid-infrared, we study via cavity ringdown technique the losses of BaF2, CaF2, MgF2 and SrF2 microresonators. We show that MgF2 is limited by multiphonon absorption by studying the temperature dependence of the Q factor. In contrast, in SrF2 and BaF2 the lower multiphonon absorption leads to ultra-high Q factors at 4.5 μm. These values correspond to an optical finesse of , the highest value achieved for any type of mid-infrared resonator to date.

  3. Mid-infrared ultra-high-Q resonators based on fluoride crystalline materials

    PubMed Central

    Lecaplain, C.; Javerzac-Galy, C.; Gorodetsky, M. L.; Kippenberg, T. J.

    2016-01-01

    The unavailability of highly transparent materials in the mid-infrared has been the main limitation in the development of ultra-sensitive molecular sensors or cavity-based spectroscopy applications. Whispering gallery mode microresonators have attained ultra-high-quality (Q) factor resonances in the near-infrared and visible. Here we report ultra-high Q factors in the mid-infrared using polished alkaline earth metal fluoride crystals. Using an uncoated chalcogenide tapered fibre as a high-ideality coupler in the mid-infrared, we study via cavity ringdown technique the losses of BaF2, CaF2, MgF2 and SrF2 microresonators. We show that MgF2 is limited by multiphonon absorption by studying the temperature dependence of the Q factor. In contrast, in SrF2 and BaF2 the lower multiphonon absorption leads to ultra-high Q factors at 4.5 μm. These values correspond to an optical finesse of , the highest value achieved for any type of mid-infrared resonator to date. PMID:27869119

  4. Mid-infrared ultra-high-Q resonators based on fluoride crystalline materials.

    PubMed

    Lecaplain, C; Javerzac-Galy, C; Gorodetsky, M L; Kippenberg, T J

    2016-11-21

    The unavailability of highly transparent materials in the mid-infrared has been the main limitation in the development of ultra-sensitive molecular sensors or cavity-based spectroscopy applications. Whispering gallery mode microresonators have attained ultra-high-quality (Q) factor resonances in the near-infrared and visible. Here we report ultra-high Q factors in the mid-infrared using polished alkaline earth metal fluoride crystals. Using an uncoated chalcogenide tapered fibre as a high-ideality coupler in the mid-infrared, we study via cavity ringdown technique the losses of BaF 2 , CaF 2 , MgF 2 and SrF 2 microresonators. We show that MgF 2 is limited by multiphonon absorption by studying the temperature dependence of the Q factor. In contrast, in SrF 2 and BaF 2 the lower multiphonon absorption leads to ultra-high Q factors at 4.5 μm. These values correspond to an optical finesse of , the highest value achieved for any type of mid-infrared resonator to date.

  5. The ALMA Spectroscopic Survey in the Hubble Ultra Deep Field: Molecular Gas Reservoirs in High-redshift Galaxies

    NASA Astrophysics Data System (ADS)

    Decarli, Roberto; Walter, Fabian; Aravena, Manuel; Carilli, Chris; Bouwens, Rychard; da Cunha, Elisabete; Daddi, Emanuele; Elbaz, David; Riechers, Dominik; Smail, Ian; Swinbank, Mark; Weiss, Axel; Bacon, Roland; Bauer, Franz; Bell, Eric F.; Bertoldi, Frank; Chapman, Scott; Colina, Luis; Cortes, Paulo C.; Cox, Pierre; Gónzalez-López, Jorge; Inami, Hanae; Ivison, Rob; Hodge, Jacqueline; Karim, Alex; Magnelli, Benjamin; Ota, Kazuaki; Popping, Gergö; Rix, Hans-Walter; Sargent, Mark; van der Wel, Arjen; van der Werf, Paul

    2016-12-01

    We study the molecular gas properties of high-z galaxies observed in the ALMA Spectroscopic Survey (ASPECS) that targets an ˜1 arcmin2 region in the Hubble Ultra Deep Field (UDF), a blind survey of CO emission (tracing molecular gas) in the 3 and 1 mm bands. Of a total of 1302 galaxies in the field, 56 have spectroscopic redshifts and correspondingly well-defined physical properties. Among these, 11 have infrared luminosities {L}{IR}\\gt {10}11 {L}⊙ , I.e., a detection in CO emission was expected. Out of these, 7 are detected at various significance in CO, and 4 are undetected in CO emission. In the CO-detected sources, we find CO excitation conditions that are lower than those typically found in starburst/sub-mm galaxy/QSO environments. We use the CO luminosities (including limits for non-detections) to derive molecular gas masses. We discuss our findings in the context of previous molecular gas observations at high redshift (star formation law, gas depletion times, gas fractions): the CO-detected galaxies in the UDF tend to reside on the low-{L}{IR} envelope of the scatter in the {L}{IR}{--}{L}{CO}\\prime relation, but exceptions exist. For the CO-detected sources, we find an average depletion time of ˜1 Gyr, with significant scatter. The average molecular-to-stellar mass ratio ({M}{{H}2}/M *) is consistent with earlier measurements of main-sequence galaxies at these redshifts, and again shows large variations among sources. In some cases, we also measure dust continuum emission. On average, the dust-based estimates of the molecular gas are a factor ˜2-5× smaller than those based on CO. When we account for detections as well as non-detections, we find large diversity in the molecular gas properties of the high-redshift galaxies covered by ASPECS.

  6. Definition and quantification of acute inflammatory white matter injury in the immature brain by MRI/MRS at high magnetic field.

    PubMed

    Lodygensky, Gregory A; Kunz, Nicolas; Perroud, Elodie; Somm, Emmanuel; Mlynarik, Vladimir; Hüppi, Petra S; Gruetter, Rolf; Sizonenko, Stéphane V

    2014-03-01

    Lipopolysaccharide (LPS) injection in the corpus callosum (CC) of rat pups results in diffuse white matter injury similar to the main neuropathology of preterm infants. The aim of this study was to characterize the structural and metabolic markers of acute inflammatory injury by high-field magnetic resonance imaging (MRI) magnetic resonance spectroscopy (MRS) in vivo. Twenty-four hours after a 1-mg/kg injection of LPS in postnatal day 3 rat pups, diffusion tensor imaging and proton nuclear magnetic spectroscopy ((1)H NMR) were analyzed in conjunction to determine markers of cell death and inflammation using immunohistochemistry and gene expression. MRI and MRS in the CC revealed an increase in lactate and free lipids and a decrease of the apparent diffusion coefficient. Detailed evaluation of the CC showed a marked apoptotic response assessed by fractin expression. Interestingly, the degree of reduction in the apparent diffusion coefficient correlated strongly with the natural logarithm of fractin expression, in the same region of interest. LPS injection further resulted in increased activated microglia clustered in the cingulum, widespread astrogliosis, and increased expression of genes for interleukin (IL)-1, IL-6, and tumor necrosis factor. This model was able to reproduce the typical MRI hallmarks of acute diffuse white matter injury seen in preterm infants and allowed the evaluation of in vivo biomarkers of acute neuropathology after inflammatory challenge.

  7. Globally conditioned Granger causality in brain–brain and brain–heart interactions: a combined heart rate variability/ultra-high-field (7 T) functional magnetic resonance imaging study

    PubMed Central

    Passamonti, Luca; Wald, Lawrence L.; Barbieri, Riccardo

    2016-01-01

    The causal, directed interactions between brain regions at rest (brain–brain networks) and between resting-state brain activity and autonomic nervous system (ANS) outflow (brain–heart links) have not been completely elucidated. We collected 7 T resting-state functional magnetic resonance imaging (fMRI) data with simultaneous respiration and heartbeat recordings in nine healthy volunteers to investigate (i) the causal interactions between cortical and subcortical brain regions at rest and (ii) the causal interactions between resting-state brain activity and the ANS as quantified through a probabilistic, point-process-based heartbeat model which generates dynamical estimates for sympathetic and parasympathetic activity as well as sympathovagal balance. Given the high amount of information shared between brain-derived signals, we compared the results of traditional bivariate Granger causality (GC) with a globally conditioned approach which evaluated the additional influence of each brain region on the causal target while factoring out effects concomitantly mediated by other brain regions. The bivariate approach resulted in a large number of possibly spurious causal brain–brain links, while, using the globally conditioned approach, we demonstrated the existence of significant selective causal links between cortical/subcortical brain regions and sympathetic and parasympathetic modulation as well as sympathovagal balance. In particular, we demonstrated a causal role of the amygdala, hypothalamus, brainstem and, among others, medial, middle and superior frontal gyri, superior temporal pole, paracentral lobule and cerebellar regions in modulating the so-called central autonomic network (CAN). In summary, we show that, provided proper conditioning is employed to eliminate spurious causalities, ultra-high-field functional imaging coupled with physiological signal acquisition and GC analysis is able to quantify directed brain–brain and brain–heart interactions

  8. Biological and Health Effects of Electromagnetic Fields Related to the Operation of MRI/TMS

    NASA Astrophysics Data System (ADS)

    Shigemitsu, Tsukasa; Ueno, Shoogo

    This paper reviews issues of biological effects and safety aspects of the electromagnetic fields related to both Magnetic Resonance Imaging (MRI) and Transcranial Magnetic Stimulation (TMS) as a diagnostic technique. The noninvasive character of these diagnostic techniques is based on the utilization of the electromagnetic fields such as the static magnetic field, time-varying magnetic field, and radiofrequency electromagnetic field. Following the short view of the history and the principle of these noninvasive techniques, we review the biological effects of the electromagnetic fields, the health effects and safety issues related to MRI/TMS environments. Through a discussion of biological and health effects, it shows briefly guidelines which provide a consideration in human risk for both patients and medical staff. Finally, safety issues related to MRI/TMS are discussed with the highlighting of the guideline such as the International Commission on NonIonizing Radiation Protection (ICNIRP) and EMF Directive (Directve2013/35/EU) of European Union.

  9. Design Method For Ultra-High Resolution Linear CCD Imagers

    NASA Astrophysics Data System (ADS)

    Sheu, Larry S.; Truong, Thanh; Yuzuki, Larry; Elhatem, Abdul; Kadekodi, Narayan

    1984-11-01

    This paper presents the design method to achieve ultra-high resolution linear imagers. This method utilizes advanced design rules and novel staggered bilinear photo sensor arrays with quadrilinear shift registers. Design constraint in the detector arrays and shift registers are analyzed. Imager architecture to achieve ultra-high resolution is presented. The characteristics of MTF, aliasing, speed, transfer efficiency and fine photolithography requirements associated with this architecture are also discussed. A CCD imager with advanced 1.5 um minimum feature size was fabricated. It is intended as a test vehicle for the next generation small sampling pitch ultra-high resolution CCD imager. Standard double-poly, two-phase shift registers were fabricated at an 8 um pitch using the advanced design rules. A special process step that blocked the source-drain implant from the shift register area was invented. This guaranteed excellent performance of the shift registers regardless of the small poly overlaps. A charge transfer efficiency of better than 0.99995 and maximum transfer speed of 8 MHz were achieved. The imager showed excellent performance. The dark current was less than 0.2 mV/ms, saturation 250 mV, adjacent photoresponse non-uniformity ± 4% and responsivity 0.7 V/ μJ/cm2 for the 8 μm x 6 μm photosensor size. The MTF was 0.6 at 62.5 cycles/mm. These results confirm the feasibility of the next generation ultra-high resolution CCD imagers.

  10. Sterilization of liquid foods by pulsed electric fields-an innovative ultra-high temperature process.

    PubMed

    Reineke, Kai; Schottroff, Felix; Meneses, Nicolas; Knorr, Dietrich

    2015-01-01

    The intention of this study was to investigate the inactivation of endospores by a combined thermal and pulsed electric field (PEF) treatment. Therefore, self-cultivated spores of Bacillus subtilis and commercial Geobacillus stearothermophilus spores with certified heat resistance were utilized. Spores of both strains were suspended in saline water (5.3 mS cm(-1)), skim milk (0.3% fat; 5.3 mS cm(-1)) and fresh prepared carrot juice (7.73 mS cm(-1)). The combination of moderate preheating (70-90°C) and an insulated PEF-chamber, combined with a holding tube (65 cm) and a heat exchanger for cooling, enabled a rapid heat up to 105-140°C (measured above the PEF chamber) within 92.2-368.9 μs. To compare the PEF process with a pure thermal inactivation, each spore suspension was heat treated in thin glass capillaries and D-values from 90 to 130°C and its corresponding z-values were calculated. For a comparison of the inactivation data, F-values for the temperature fields of both processes were calculated by using computational fluid dynamics (CFD). A preheating of saline water to 70°C with a flow rate of 5 l h(-1), a frequency of 150 Hz and an energy input of 226.5 kJ kg(-1), resulted in a measured outlet temperature of 117°C and a 4.67 log10 inactivation of B. subtilis. The thermal process with identical F-value caused only a 3.71 log10 inactivation. This synergism of moderate preheating and PEF was even more pronounced for G. stearothermophilus spores in saline water. A preheating to 95°C and an energy input of 144 kJ kg(-1) resulted in an outlet temperature of 126°C and a 3.28 log10 inactivation, whereas nearly no inactivation (0.2 log10) was achieved during the thermal treatment. Hence, the PEF technology was evaluated as an alternative ultra-high temperature process. However, for an industrial scale application of this process for sterilization, optimization of the treatment chamber design is needed to reduce the occurring inhomogeneous temperature fields.

  11. Large aperture and wide field of view space telescope for the detection of ultra high energy cosmic rays and neutrinos

    NASA Astrophysics Data System (ADS)

    Mazzinghi, Piero; Bratina, Vojko; Gambicorti, Lisa; Simonetti, Francesca; Zuccaro Marchi, Alessandro

    2017-11-01

    New technologies are proposed for large aperture and wide Field of View (FOV) space telescopes dedicated to detection of Ultra High Energy Cosmic Rays and Neutrinos flux, through observation of fluorescence traces in atmosphere and diffused Cerenkov signals. The presented advanced detection system is a spaceborne LEO telescope, with better performance than ground-based observatories, detecting up to 103 - 104 events/year. Different design approaches are implemented, all with very large FOV and focal surface detectors with sufficient segmentation and time resolution to allow precise reconstructions of the arrival direction. In particular, two Schmidt cameras are suggested as an appropriate solution to match most of the optical and technical requirements: large FOV, low f/#, reduction of stray light, optionally flat focal surface, already proven low-cost construction technologies. Finally, a preliminary proposal of a wideFOV retrofocus catadioptric telescope is explained.

  12. Ultra-High Temperature Materials Characterization for Space and Missile Applications

    NASA Technical Reports Server (NTRS)

    Rogers, Jan; Hyers, Robert

    2007-01-01

    Numerous advanced space and missile technologies including propulsion systems require operations at high temperatures. Some very high-temperature materials are being developed to meet these needs, including refractory metal alloys, carbides, borides, and silicides. System design requires data for materials properties at operating temperatures. Materials property data are not available at the desired operating temperatures for many materials of interest. The objective of this work is to provide important physical property data at ultra-high temperatures. The MSFC Electrostatic Levitation (ESL) facility can provide measurements of thermophysical properties which include: creep strength, emissivity, density and thermal expansion. ESL uses electrostatic fields to position samples between electrodes during processing and characterization experiments. Samples float between the electrodes during studies and are free from any contact with a container or test apparatus. This provides a high purity environment for the study of high-temperature, reactive materials. ESL can be used to process a wide variety of materials including metals, alloys, ceramics, glasses and semiconductors. A system for the determination of total hemispherical emissivity is being developed for the MSFC ESL facility by AZ Technology Inc. The instrument has been designed to provide emissivity measurements for samples during ESL experiments over the temperature range 700-3400K. A novel non-contact technique for the determination of high-temperature creep strength has been developed. Data from selected ESL-based characterization studies will be presented. The ESL technique could advance space and missile technologies by advancing the knowledge base and the technology readiness level for ultra-high temperature materials. Applications include non-eroding nozzle materials and lightweight, high-temperature alloys for turbines and structures.

  13. Precision optical slit for high heat load or ultra high vacuum

    DOEpatents

    Andresen, Nord C.; DiGennaro, Richard S.; Swain, Thomas L.

    1995-01-01

    This invention relates generally to slits used in optics that must be precisely aligned and adjusted. The optical slits of the present invention are useful in x-ray optics, x-ray beam lines, optical systems in which the entrance slit is critical for high wavelength resolution. The invention is particularly useful in ultra high vacuum systems where lubricants are difficult to use and designs which avoid the movement of metal parts against one another are important, such as monochrometers for high wavelength resolution with ultra high vacuum systems. The invention further relates to optical systems in which temperature characteristics of the slit materials is important. The present invention yet additionally relates to precision slits wherein the opposing edges of the slit must be precisely moved relative to a center line between the edges with each edge retaining its parallel orientation with respect to the other edge and/or the center line.

  14. Accelerating parallel transmit array B1 mapping in high field MRI with slice undersampling and interpolation by kriging.

    PubMed

    Ferrand, Guillaume; Luong, Michel; Cloos, Martijn A; Amadon, Alexis; Wackernagel, Hans

    2014-08-01

    Transmit arrays have been developed to mitigate the RF field inhomogeneity commonly observed in high field magnetic resonance imaging (MRI), typically above 3T. To this end, the knowledge of the RF complex-valued B1 transmit-sensitivities of each independent radiating element has become essential. This paper details a method to speed up a currently available B1-calibration method. The principle relies on slice undersampling, slice and channel interleaving and kriging, an interpolation method developed in geostatistics and applicable in many domains. It has been demonstrated that, under certain conditions, kriging gives the best estimator of a field in a region of interest. The resulting accelerated sequence allows mapping a complete set of eight volumetric field maps of the human head in about 1 min. For validation, the accuracy of kriging is first evaluated against a well-known interpolation technique based on Fourier transform as well as to a B1-maps interpolation method presented in the literature. This analysis is carried out on simulated and decimated experimental B1 maps. Finally, the accelerated sequence is compared to the standard sequence on a phantom and a volunteer. The new sequence provides B1 maps three times faster with a loss of accuracy limited potentially to about 5%.

  15. Human brain MRI at 500 MHz, scientific perspectives and technological challenges

    NASA Astrophysics Data System (ADS)

    Le Bihan, Denis; Schild, Thierry

    2017-03-01

    The understanding of the human brain is one of the main scientific challenges of the 21st century. In the early 2000s the French Alternative Energies and Atomic Energy Commission launched a program to conceive and build a ‘human brain explorer’, the first human MRI scanner operating at 11.7 T. This scanner was envisioned to be part of the ambitious French-German project Iseult, bridging together industrial and academic partners to push the limits of molecular neuroimaging, from mouse to man, using ultra-high field MRI. In this article we provide a summary of the main neuroscience and medical targets of the Iseult project, mainly to acquire within timescales compatible with human tolerances images at a scale of 100 μm at which everything remains to discover, and to create new approaches to develop new imaging biomarkers for specific neurological and psychiatric disorders. The system specifications, the technological challenges, in terms of magnet design, winding technology, cryogenics, quench protection, stability control, and the solutions which have been chosen to overcome them and build this outstanding instrument are provided. Lines of the research and development which will be necessary to fully exploit the potential of this and other UHF MRI scanners are also outlined.

  16. Ultrahigh field MRI in clinical neuroimmunology: a potential contribution to improved diagnostics and personalised disease management.

    PubMed

    Sinnecker, Tim; Kuchling, Joseph; Dusek, Petr; Dörr, Jan; Niendorf, Thoralf; Paul, Friedemann; Wuerfel, Jens

    2015-01-01

    Conventional magnetic resonance imaging (MRI) at 1.5 Tesla (T) is limited by modest spatial resolution and signal-to-noise ratio (SNR), impeding the identification and classification of inflammatory central nervous system changes in current clinical practice. Gaining from enhanced susceptibility effects and improved SNR, ultrahigh field MRI at 7 T depicts inflammatory brain lesions in great detail. This review summarises recent reports on 7 T MRI in neuroinflammatory diseases and addresses the question as to whether ultrahigh field MRI may eventually improve clinical decision-making and personalised disease management.

  17. Cortical connective field estimates from resting state fMRI activity.

    PubMed

    Gravel, Nicolás; Harvey, Ben; Nordhjem, Barbara; Haak, Koen V; Dumoulin, Serge O; Renken, Remco; Curčić-Blake, Branislava; Cornelissen, Frans W

    2014-01-01

    One way to study connectivity in visual cortical areas is by examining spontaneous neural activity. In the absence of visual input, such activity remains shaped by the underlying neural architecture and, presumably, may still reflect visuotopic organization. Here, we applied population connective field (CF) modeling to estimate the spatial profile of functional connectivity in the early visual cortex during resting state functional magnetic resonance imaging (RS-fMRI). This model-based analysis estimates the spatial integration between blood-oxygen level dependent (BOLD) signals in distinct cortical visual field maps using fMRI. Just as population receptive field (pRF) mapping predicts the collective neural activity in a voxel as a function of response selectivity to stimulus position in visual space, CF modeling predicts the activity of voxels in one visual area as a function of the aggregate activity in voxels in another visual area. In combination with pRF mapping, CF locations on the cortical surface can be interpreted in visual space, thus enabling reconstruction of visuotopic maps from resting state data. We demonstrate that V1 ➤ V2 and V1 ➤ V3 CF maps estimated from resting state fMRI data show visuotopic organization. Therefore, we conclude that-despite some variability in CF estimates between RS scans-neural properties such as CF maps and CF size can be derived from resting state data.

  18. Length matters: Improved high field EEG-fMRI recordings using shorter EEG cables.

    PubMed

    Assecondi, Sara; Lavallee, Christina; Ferrari, Paolo; Jovicich, Jorge

    2016-08-30

    The use of concurrent EEG-fMRI recordings has increased in recent years, allowing new avenues of medical and cognitive neuroscience research; however, currently used setups present problems with data quality and reproducibility. We propose a compact experimental setup for concurrent EEG-fMRI at 4T and compare it to a more standard reference setup. The compact setup uses short EEG cables connecting to the amplifiers, which are placed right at the back of the head RF coil on a form-fitting extension force-locked to the patient MR bed. We compare the two setups in terms of sensitivity to MR-room environmental noise, interferences between measuring devices (EEG or fMRI), and sensitivity to functional responses in a visual stimulation paradigm. The compact setup reduces the system sensitivity to both external noise and MR-induced artefacts by at least 60%, with negligible EEG noise induced from the mechanical vibrations of the cryogenic cooling compression pump. The compact setup improved EEG data quality and the overall performance of MR-artifact correction techniques. Both setups were similar in terms of the fMRI data, with higher reproducibility for cable placement within the scanner in the compact setup. This improved compact setup may be relevant to MR laboratories interested in reducing the sensitivity of their EEG-fMRI experimental setup to external noise sources, setting up an EEG-fMRI workplace for the first time, or for creating a more reproducible configuration of equipment and cables. Implications for safety and ergonomics are discussed. Copyright © 2016 Elsevier B.V. All rights reserved.

  19. Recent Ultra High Energy neutrino bounds and multimessenger observations with the Pierre Auger Observatory

    NASA Astrophysics Data System (ADS)

    Zas, Enrique

    2018-01-01

    The overall picture of the highest energy particles produced in the Universe is changing because of measurements made with the Pierre Auger Observatory. Composition studies of cosmic rays point towards an unexpected mixed composition of intermediate mass nuclei, more isotropic than anticipated, which is reshaping the future of the field and underlining the priority to understand composition at the highest energies. The Observatory is competitive in the search for neutrinos of all flavors above about 100 PeV by looking for very inclined showers produced deep in the atmosphere by neutrinos interacting either in the atmosphere or in the Earth's crust. It covers a large field of view between -85° and 60° declination in equatorial coordinates. Neutrinos are expected because of the existence of ultra high energy cosmic rays. They provide valuable complementary information, their fluxes being sensitive to the primary cosmic ray masses and their directions reflecting the source positions. We report the results of the neutrino search providing competitive bounds to neutrino production and strong constraints to a number of production models including cosmogenic neutrinos due to ultra high energy protons. We also report on two recent contributions of the Observatory to multimessenger studies by searching for correlations of neutrinos both with cosmic rays and with gravitational waves. The correlations of the directions of the highest energy astrophysical neutrinos discovered with IceCube with the highest energy cosmic rays detected with the Auger Observatory and the Telescope Array revealed an excess that is not statistically significant and is being monitored. The targeted search for neutrinos correlated with the discovery of the gravitational wave events GW150914 and GW151226 with advanced LIGO has led to the first bounds on the energy emitted by black hole mergers in Ultra-High Energy Neutrinos.

  20. Radio astronomy ultra-low-noise amplifier for operation at 91 cm wavelength in high RFI environment

    NASA Astrophysics Data System (ADS)

    Korolev, A. M.; Zakharenko, V. V.; Ulyanov, O. M.

    2016-02-01

    An ultra-low-noise input amplifier intended for a use in a radio telescope operating at 91 cm wavelength is presented. The amplifier noise temperatures are 12.8 ± 1.5 and 10.0 ± 1.5 K at ambient temperatures of 293 and 263 K respectively. The amplifier does not require cryogenic cooling. It can be quickly put in operation thus shortening losses in the telescope observation time. High linearity of the amplifier (output power at 1 dB gain compression P1dB ≥ 22 dBm, output third order intercept point OIP3 ≥ 37 dBm) enables the telescope operation in highly urbanized and industrialized regions. To obtain low noise characteristics along with high linearity, high-electron-mobility field-effect transistors were used in parallel in the circuit developed. The transistors used in the amplifier are cost-effective and commercially available. The circuit solution is recommended for similar devices working in ultra-high frequency band.

  1. One dimensional spatial resolution optimization on a hybrid low field MRI-gamma detector

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Agulles-Pedrós, L., E-mail: lagullesp@unal.edu.co; Abril, A., E-mail: ajabrilf@unal.edu.co

    Hybrid systems like Positron Emission Tomography/Magnetic Resonance Imaging (PET/MRI) and MRI/gamma camera, offer advantages combining the resolution and contrast capability of MRI with the better contrast and functional information of nuclear medicine techniques. However, the radiation detectors are expensive and need an electronic set-up, which can interfere with the MRI acquisition process or viceversa. In order to improve these drawbacks, in this work it is presented the design of a low field NMR system made up of permanent magnets compatible with a gamma radiation detector based on gel dosimetry. The design is performed using the software FEMM for estimation ofmore » the magnetic field, and GEANT4 for the physical process involved in radiation detection and effect of magnetic field. The homogeneity in magnetic field is achieved with an array of NbFeB magnets in a linear configuration with a separation between the magnets, minimizing the effect of Compton back scattering compared with a no-spacing linear configuration. The final magnetic field in the homogeneous zone is ca. 100 mT. In this hybrid proposal, although the gel detector do not have spatial resolution per se, it is possible to obtain a dose profile (1D image) as a function of the position by using a collimator array. As a result, the gamma detector system described allows a complete integrated radiation detector within the low field NMR (lfNMR) system. Finally we present the better configuration for the hybrid system considering the collimator parameters such as height, thickness and distance.« less

  2. Precision optical slit for high heat load or ultra high vacuum

    DOEpatents

    Andresen, N.C.; DiGennaro, R.S.; Swain, T.L.

    1995-01-24

    This invention relates generally to slits used in optics that must be precisely aligned and adjusted. The optical slits of the present invention are useful in x-ray optics, x-ray beam lines, optical systems in which the entrance slit is critical for high wavelength resolution. The invention is particularly useful in ultra high vacuum systems where lubricants are difficult to use and designs which avoid the movement of metal parts against one another are important, such as monochromators for high wavelength resolution with ultra high vacuum systems. The invention further relates to optical systems in which temperature characteristics of the slit materials is important. The present invention yet additionally relates to precision slits wherein the opposing edges of the slit must be precisely moved relative to a center line between the edges with each edge retaining its parallel orientation with respect to the other edge and/or the center line. 21 figures.

  3. Clinical field-strength MRI of amyloid plaques induced by low-level cholesterol feeding in rabbits

    PubMed Central

    Chen, Yuanxin; Bernas, Lisa; Kitzler, Hagen H.; Rogers, Kem A.; Hegele, Robert A.; Rutt, Brian K.

    2009-01-01

    Two significant barriers have limited the development of effective treatment of Alzheimer's disease. First, for many cases the aetiology is unknown and likely multi-factorial. Among these factors, hypercholesterolemia is a known risk predictor and has been linked to the formation of β-amyloid plaques, a pathological hallmark this disease. Second, standardized diagnostic tools are unable to definitively diagnose this disease prior to death; hence new diagnostic tools are urgently needed. Magnetic resonance imaging (MRI) using high field-strength scanners has shown promise for direct visualization of β-amyloid plaques, allowing in vivo longitudinal tracking of disease progression in mouse models. Here, we present a new rabbit model for studying the relationship between cholesterol and Alzheimer's disease development and new tools for direct visualization of β-amyloid plaques using clinical field-strength MRI. New Zealand white rabbits were fed either a low-level (0.125–0.25% w/w) cholesterol diet (n = 5) or normal chow (n = 4) for 27 months. High-resolution (66 × 66 × 100 µm3; scan time = 96 min) ex vivo MRI of brains was performed using a 3-Tesla (T) MR scanner interfaced with customized gradient and radiofrequency coils. β-Amyloid-42 immunostaining and Prussian blue iron staining were performed on brain sections and MR and histological images were manually registered. MRI revealed distinct signal voids throughout the brains of cholesterol-fed rabbits, whereas minimal voids were seen in control rabbit brains. These voids corresponded directly to small clusters of extracellular β-amyloid-positive plaques, which were consistently identified as iron-loaded (the presumed source of MR contrast). Plaques were typically located in the hippocampus, parahippocampal gyrus, striatum, hypothalamus and thalamus. Quantitative analysis of the number of histologically positive β-amyloid plaques (P < 0.0001) and MR-positive signal voids (P < 0.05) found in cholesterol

  4. NMR/MRI with hyperpolarized gas and high Tc SQUID

    DOEpatents

    Schlenga, Klaus; de Souza, Ricardo E.; Wong-Foy, Annjoe; Clarke, John; Pines, Alexander

    2000-01-01

    A method and apparatus for the detection of nuclear magnetic resonance (NMR) signals and production of magnetic resonance imaging (MRI) from samples combines the use of hyperpolarized inert gases to enhance the NMR signals from target nuclei in a sample and a high critical temperature (Tc) superconducting quantum interference device (SQUID) to detect the NMR signals. The system operates in static magnetic fields of 3 mT or less (down to 0.1 mT), and at temperatures from liquid nitrogen (77K) to room temperature. Sample size is limited only by the size of the magnetic field coils and not by the detector. The detector is a high Tc SQUID magnetometer designed so that the SQUID detector can be very close to the sample, which can be at room temperature.

  5. Ultra High Temperature Ceramics' Processing Routes and Microstructures Compared

    NASA Technical Reports Server (NTRS)

    Gusman, Michael; Stackpoole, Mairead; Johnson, Sylvia; Gasch, Matt; Lau, Kai-Hung; Sanjurjo, Angel

    2009-01-01

    Ultra High Temperature Ceramics (UHTCs), such as HfB2 and ZrB2 composites containing SiC, are known to have good thermal shock resistance and high thermal conductivity at elevated temperatures. These UHTCs have been proposed for a number of structural applications in hypersonic vehicles, nozzles, and sharp leading edges. NASA Ames is working on controlling UHTC properties (especially, mechanical properties, thermal conductivity, and oxidation resistance) through processing, composition, and microstructure. In addition to using traditional methods of combining additives to boride powders, we are preparing UHTCs using coat ing powders to produce both borides and additives. These coatings and additions to the powders are used to manipulate and control grain-boundary composition and second- and third-phase variations within the UHTCs. Controlling the composition of high temperature oxidation by-products is also an important consideration. The powders are consolidated by hot-pressing or field-assisted sintering (FAS). Comparisons of microstructures and hardness data will be presented.

  6. Real-time 2D spatially selective MRI experiments: Comparative analysis of optimal control design methods.

    PubMed

    Maximov, Ivan I; Vinding, Mads S; Tse, Desmond H Y; Nielsen, Niels Chr; Shah, N Jon

    2015-05-01

    There is an increasing need for development of advanced radio-frequency (RF) pulse techniques in modern magnetic resonance imaging (MRI) systems driven by recent advancements in ultra-high magnetic field systems, new parallel transmit/receive coil designs, and accessible powerful computational facilities. 2D spatially selective RF pulses are an example of advanced pulses that have many applications of clinical relevance, e.g., reduced field of view imaging, and MR spectroscopy. The 2D spatially selective RF pulses are mostly generated and optimised with numerical methods that can handle vast controls and multiple constraints. With this study we aim at demonstrating that numerical, optimal control (OC) algorithms are efficient for the design of 2D spatially selective MRI experiments, when robustness towards e.g. field inhomogeneity is in focus. We have chosen three popular OC algorithms; two which are gradient-based, concurrent methods using first- and second-order derivatives, respectively; and a third that belongs to the sequential, monotonically convergent family. We used two experimental models: a water phantom, and an in vivo human head. Taking into consideration the challenging experimental setup, our analysis suggests the use of the sequential, monotonic approach and the second-order gradient-based approach as computational speed, experimental robustness, and image quality is key. All algorithms used in this work were implemented in the MATLAB environment and are freely available to the MRI community. Copyright © 2015 Elsevier Inc. All rights reserved.

  7. Ultra-high strain in epitaxial silicon carbide nanostructures utilizing residual stress amplification

    NASA Astrophysics Data System (ADS)

    Phan, Hoang-Phuong; Nguyen, Tuan-Khoa; Dinh, Toan; Ina, Ginnosuke; Kermany, Atieh Ranjbar; Qamar, Afzaal; Han, Jisheng; Namazu, Takahiro; Maeda, Ryutaro; Dao, Dzung Viet; Nguyen, Nam-Trung

    2017-04-01

    Strain engineering has attracted great attention, particularly for epitaxial films grown on a different substrate. Residual strains of SiC have been widely employed to form ultra-high frequency and high Q factor resonators. However, to date, the highest residual strain of SiC was reported to be limited to approximately 0.6%. Large strains induced into SiC could lead to several interesting physical phenomena, as well as significant improvement of resonant frequencies. We report an unprecedented nanostrain-amplifier structure with an ultra-high residual strain up to 8% utilizing the natural residual stress between epitaxial 3C-SiC and Si. In addition, the applied strain can be tuned by changing the dimensions of the amplifier structure. The possibility of introducing such a controllable and ultra-high strain will open the door to investigating the physics of SiC in large strain regimes and the development of ultra sensitive mechanical sensors.

  8. Variable Stars in the Field of the Hydra II Ultra-Faint Dwarf Galaxy

    NASA Astrophysics Data System (ADS)

    Vivas, Anna Katherina; Olsen, Knut A.; Blum, Robert D.; Nidever, David L.; Walker, Alistair R.; Martin, Nicolas; Besla, Gurtina; Gallart, Carme; Van Der Marel, Roeland P.; Majewski, Steven R.; Munoz, Ricardo; Kaleida, Catherine C.; Saha, Abhijit; Conn, Blair; Jin, Shoko

    2016-06-01

    We searched for variable stars in Hydra II, one of the recently discovered ultra-faint dwarf satellites of the Milky Way, using gri time-series obtained with the Dark Energy Camera (DECam) at Cerro Tololo Inter-American Observatory, Chile. We discovered one RR Lyrae star in the galaxy which was used to derive a distance of 154±8 kpc to this system and to re-calculate its absolute magnitude and half-light radius.A comparison with other RR Lyrae stars in ultra-faint systems indicates similar pulsational properties among them, which are different to those found among halo field stars and those in the largest of the Milky Way satellites. We also report the discovery of 31 additional short period variables in the field of view (RR Lyrae, SX Phe, eclipsing binaries, and a likely anomalous cepheid) which are likely not related with Hydra II.

  9. Low-field and high-field magnetic resonance contrast imaging of magnetoferritin as a pathological model system of iron accumulation

    NASA Astrophysics Data System (ADS)

    Strbak, Oliver; Balejcikova, Lucia; Baciak, Ladislav; Kovac, Jozef; Masarova-Kozelova, Marta; Krafcik, Andrej; Dobrota, Dusan; Kopcansky, Peter

    2017-09-01

    Various pathological processes including neurodegenerative disorders are associated with the accumulation of iron, while it is believed that a precursor of iron accumulation is ferritin. Physiological ferritin is due to low relaxivity, which results in only weak detection by magnetic resonance imaging (MRI) techniques. On the other hand, pathological ferritin is associated with disrupted iron homeostasis and structural changes in the mineral core, and should increase the hypointensive artefacts in MRI. On the basis of recent findings in respect to the pathological ferritin structure, we prepared the magnetoferritin particles as a possible pathological ferritin model system. The particles were characterised with dynamic light scattering, as well as with superconducting quantum interference device measurements. With the help of low-field (0.2 T) and high-field (4.7 T) MRI standard T 2-weighted protocols we found that it is possible to clearly distinguish between native ferritin as a physiological model system, and magnetoferritin as a pathological model system. Surprisingly, the T 2-weighted short TI inversion recovery protocol at low-field system showed the optimum contrast differentiation. Such findings are highly promising for exploiting the use of iron accumulation as a noninvasive diagnostics tool of pathological processes, where the magnetoferritin particles could be utilised as MRI iron quantification calibration samples.

  10. High-power all-fiber ultra-low noise laser

    NASA Astrophysics Data System (ADS)

    Zhao, Jian; Guiraud, Germain; Pierre, Christophe; Floissat, Florian; Casanova, Alexis; Hreibi, Ali; Chaibi, Walid; Traynor, Nicholas; Boullet, Johan; Santarelli, Giorgio

    2018-06-01

    High-power ultra-low noise single-mode single-frequency lasers are in great demand for interferometric metrology. Robust, compact all-fiber lasers represent one of the most promising technologies to replace the current laser sources in use based on injection-locked ring resonators or multi-stage solid-state amplifiers. Here, a linearly polarized high-power ultra-low noise all-fiber laser is demonstrated at a power level of 100 W. Special care has been taken in the study of relative intensity noise (RIN) and its reduction. Using an optimized servo actuator to directly control the driving current of the pump laser diode, we obtain a large feedback bandwidth of up to 1.3 MHz. The RIN reaches - 160 dBc/Hz between 3 and 20 kHz.

  11. Ultra high vacuum broad band high power microwave window

    DOEpatents

    Nguyen-Tuong, V.; Dylla, H.F. III

    1997-11-04

    An improved high vacuum microwave window has been developed that utilizes high density polyethylene coated on two sides with SiOx, SiNx, or a combination of the two. The resultant low dielectric and low loss tangent window creates a low outgassing, low permeation seal through which broad band, high power microwave energy may be passed. No matching device is necessary and the sealing technique is simple. The features of the window are broad band transmission, ultra-high vacuum compatibility with a simple sealing technique, low voltage standing wave ratio, high power transmission and low cost. 5 figs.

  12. Ultra high vacuum broad band high power microwave window

    DOEpatents

    Nguyen-Tuong, Viet; Dylla, III, Henry Frederick

    1997-01-01

    An improved high vacuum microwave window has been developed that utilizes high density polyethylene coated on two sides with SiOx, SiNx, or a combination of the two. The resultant low dielectric and low loss tangent window creates a low outgassing, low permeation seal through which broad band, high power microwave energy may be passed. No matching device is necessary and the sealing technique is simple. The features of the window are broad band transmission, ultra-high vacuum compatibility with a simple sealing technique, low voltage standing wave ratio, high power transmission and low cost.

  13. Measurement of ultra-low ion energy of decelerated ion beam using a deflecting electric field

    NASA Astrophysics Data System (ADS)

    Thopan, P.; Suwannakachorn, D.; Tippawan, U.; Yu, L. D.

    2015-12-01

    In investigation on ultra-low-energy ion bombardment effect on DNA, an ion beam deceleration lens was developed for high-quality ultra-low-energy ion beam. Measurement of the ion energy after deceleration was necessary to confirm the ion beam really decelerated as theoretically predicted. In contrast to conventional methods, this work used a simple deflecting electrostatic field after the deceleration lens to bend the ion beam. The beam bending distance depended on the ion energy and was described and simulated. A system for the measurement of the ion beam energy was constructed. It consisted of a pair of parallel electrode plates to generate the deflecting electrical field, a copper rod measurement piece to detect ion beam current, a vernier caliper to mark the beam position, a stepping motor to translate the measurement rod, and a webcam-camera to read the beam bending distance. The entire system was installed after the ion-beam deceleration lens inside the large chamber of the bioengineering vertical ion beam line. Moving the measurement rod across the decelerated ion beam enabled to obtain beam profiles, from which the beam bending distance could be known and the ion beam energy could be calculated. The measurement results were in good agreement with theoretical and simulated results.

  14. Effect of Nb on Delayed Fracture Resistance of Ultra-High Strength Martensitic Steels

    NASA Astrophysics Data System (ADS)

    Song, Rongjie; Fonstein, Nina; Pottore, Narayan; Jun, Hyun Jo; Bhattacharya, Debanshu; Jansto, Steve

    Ultra-high strength steels are materials of considerable interest for automotive and structural applications and are increasingly being used in those areas. Higher strength, however, makes steels more prone to hydrogen embrittlement (HE). The effects of Nb and other alloying elements on the hydrogen-induced delayed fracture resistance of cold rolled martensitic steels with ultra-high strength 2000 MPa were studied using an acid immersion test, thermal desorption analysis (TDA) and measuring of permeation. The microstructure was characterized by high resolution field emission Scanning Electron Microscopy (SEM) with Electron Backscattered Diffraction (EBSD) and Transmission Electron Microscopy (TEM). It was shown that the combined addition of Nb significantly improved the delayed fracture resistance of investigated steel. The addition of Nb to alloyed martensitic steels resulted in very apparent grain refinement of the prior austenite grain size. The Nb microalloyed steel contained a lower diffusible hydrogen content during thermal desorption analysis as compared to the base steel and had a higher trapped hydrogen amount after charging. The reason that Nb improved the delayed fracture resistance of steels can be attributed mostly to both hydrogen trapping and grain refinement.

  15. Disrupted latent inhibition in individuals at ultra high-risk for developing psychosis.

    PubMed

    Kraus, Michael; Rapisarda, Attilio; Lam, Max; Thong, Jamie Y J; Lee, Jimmy; Subramaniam, Mythily; Collinson, Simon L; Chong, Siow Ann; Keefe, Richard S E

    2016-12-01

    The addition of off-the-shelf cognitive measures to established prodromal criteria has resulted in limited improvement in the prediction of conversion to psychosis. Tests that assess cognitive processes central to schizophrenia might better identify those at highest risk. The latent inhibition paradigm assesses a subject's tendency to ignore irrelevant stimuli, a process integral to healthy perceptual and cognitive function that has been hypothesized to be a key deficit underlying the development of schizophrenia. In this study, 142 young people at ultra high-risk for developing psychosis and 105 controls were tested on a within-subject latent inhibition paradigm. Additionally, we later inquired about the strategy that each subject employed to complete the test, and further investigated the relationship between reported strategy and the extent of latent inhibition exhibited. Unlike controls, ultra high-risk subjects did not demonstrate a significant latent inhibition effect. This difference between groups became greater when controlling for strategy. The lack of latent inhibition effect in our ultra high-risk sample suggests that individuals at ultra high-risk for psychosis are impaired in their allocation of attentional resources based on past predictive value of repeated stimuli. This fundamental deficit in the allocation of attention may contribute to the broader array of cognitive impairments and clinical symptoms displayed by individuals at ultra high-risk for psychosis.

  16. Nano-textured high sensitivity ion sensitive field effect transistors

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hajmirzaheydarali, M.; Sadeghipari, M.; Akbari, M.

    2016-02-07

    Nano-textured gate engineered ion sensitive field effect transistors (ISFETs), suitable for high sensitivity pH sensors, have been realized. Utilizing a mask-less deep reactive ion etching results in ultra-fine poly-Si features on the gate of ISFET devices where spacing of the order of 10 nm and less is achieved. Incorporation of these nano-sized features on the gate is responsible for high sensitivities up to 400 mV/pH in contrast to conventional planar structures. The fabrication process for this transistor is inexpensive, and it is fully compatible with standard complementary metal oxide semiconductor fabrication procedure. A theoretical modeling has also been presented to predict themore » extension of the diffuse layer into the electrolyte solution for highly featured structures and to correlate this extension with the high sensitivity of the device. The observed ultra-fine features by means of scanning electron microscopy and transmission electron microscopy tools corroborate the theoretical prediction.« less

  17. Search for ultra high energy astrophysical neutrinos with the ANITA experiment

    NASA Astrophysics Data System (ADS)

    Romero-Wolf, Andrew

    2010-12-01

    This work describes a search for cosmogenic neutrinos at energies above 1018 eV with the Antarctic Impulsive Transient Antenna (ANITA). ANITA is a balloon-borne radio interferometer designed to measure radio impulsive emission from particle showers produced in the Antarctic ice-sheet by ultra-high energy neutrinos (UHEnu). Flying at 37 km altitude the ANITA detector is sensitive to 1M km3 of ice and is expected to produce the highest exposure to ultra high energy neutrinos to date. The design, flight performance, and analysis of the first flight of ANITA in 2006 are the subject of this dissertation. Due to sparse anthropogenic backgrounds throughout the Antarctic continent, the ANITA analysis depends on high resolution directional reconstruction. An interferometric method was developed that not only provides high resolution but is also sensitive to very weak radio emissions. The results of ANITA provide the strongest constraints on current ultra-high energy neutrino models. In addition there was a serendipitous observation of ultra-high energy cosmic ray geosynchrotron emissions that are of distinct character from the expected neutrino signal. This thesis includes a study of the radio Cherenkov emission from ultra-high energy electromagnetic showers in ice in the time-domain. All previous simulations computed the radio pulse frequency spectrum. I developed a purely time-domain algorithm for computing radiation using the vector potentials of charged particle tracks. The results are fully consistent with previous frequency domain calculations and shed new light into the properties of the radio pulse in the time domain. The shape of the pulse in the time domain is directly related to the depth development of the excess charge in the shower and its width to the observation angle with respect to the Cherenkov direction. This information can be of great practical importance for interpreting actual data.

  18. Remarkably high mobility ultra-thin-film metal-oxide transistor with strongly overlapped orbitals

    NASA Astrophysics Data System (ADS)

    Wei Shih, Chen; Chin, Albert; Fu Lu, Chun; Fang Su, Wei

    2016-01-01

    High mobility channel thin-film-transistor (TFT) is crucial for both display and future generation integrated circuit. We report a new metal-oxide TFT that has an ultra-thin 4.5 nm SnO2 thickness for both active channel and source-drain regions, very high 147 cm2/Vs field-effect mobility, high ION/IOFF of 2.3 × 107, small 110 mV/dec sub-threshold slope, and a low VD of 2.5 V for low power operation. This mobility is already better than chemical-vapor-deposition grown multi-layers MoS2 TFT. From first principle quantum-mechanical calculation, the high mobility TFT is due to strongly overlapped orbitals.

  19. Imaging frontostriatal function in ultra-high-risk, early, and chronic schizophrenia during executive processing.

    PubMed

    Morey, Rajendra A; Inan, Seniha; Mitchell, Teresa V; Perkins, Diana O; Lieberman, Jeffrey A; Belger, Aysenil

    2005-03-01

    Individuals experiencing prodromal symptoms of schizophrenia (ultra-high-risk group) demonstrate impaired performance on tasks of executive function, attention, and working memory. The neurobiological underpinnings of such executive deficits in ultra-high-risk individuals remains unclear. We assessed frontal and striatal functions during a visual oddball continuous performance task, in ultra-high-risk, early, and chronic schizophrenic patients with the use of functional magnetic resonance imaging. Cross-sectional case-control design. Community; outpatient clinic. Patients Fifty-two individuals (control, n = 16; ultra-high risk, n = 10; early, n = 15; chronic, n = 11) from a referred clinical sample and age- and sex-matched control volunteers underwent scanning. Percentage of active voxels and percentage signal change calculated for the anterior cingulate gyrus (ACG), middle frontal gyrus (MFG), inferior frontal gyrus (IFG), basal ganglia, and thalamus. Performance on the visual oddball task was measured with percentage of hits and d' (a measure based on the hit rate and the false-alarm rate). The ultra-high-risk group showed significantly smaller differential activation between task-relevant and task-irrelevant stimuli in the frontal regions (ACG, IFG, MFG) than the control group. Frontostriatal activation associated with target stimuli in the early and chronic groups was significantly lower than the control group, while the ultra-high-risk group showed a trend toward the early group. Our findings suggest that prefrontal function begins to decline before the onset of syndromally defined illness and hence may represent a vulnerability marker in assessing the risk of developing psychotic disorders among ultra-high-risk individuals.

  20. Disposable photonic integrated circuits for evanescent wave sensors by ultra-high volume roll-to-roll method.

    PubMed

    Aikio, Sanna; Hiltunen, Jussi; Hiitola-Keinänen, Johanna; Hiltunen, Marianne; Kontturi, Ville; Siitonen, Samuli; Puustinen, Jarkko; Karioja, Pentti

    2016-02-08

    Flexible photonic integrated circuit technology is an emerging field expanding the usage possibilities of photonics, particularly in sensor applications, by enabling the realization of conformable devices and introduction of new alternative production methods. Here, we demonstrate that disposable polymeric photonic integrated circuit devices can be produced in lengths of hundreds of meters by ultra-high volume roll-to-roll methods on a flexible carrier. Attenuation properties of hundreds of individual devices were measured confirming that waveguides with good and repeatable performance were fabricated. We also demonstrate the applicability of the devices for the evanescent wave sensing of ambient refractive index. The production of integrated photonic devices using ultra-high volume fabrication, in a similar manner as paper is produced, may inherently expand methods of manufacturing low-cost disposable photonic integrated circuits for a wide range of sensor applications.

  1. Enhancing thermal reliability of fiber-optic sensors for bio-inspired applications at ultra-high temperatures

    NASA Astrophysics Data System (ADS)

    Kang, Donghoon; Kim, Heon-Young; Kim, Dae-Hyun

    2014-07-01

    The rapid growth of bio-(inspired) sensors has led to an improvement in modern healthcare and human-robot systems in recent years. Higher levels of reliability and better flexibility, essential features of these sensors, are very much required in many application fields (e.g. applications at ultra-high temperatures). Fiber-optic sensors, and fiber Bragg grating (FBG) sensors in particular, are being widely studied as suitable sensors for improved structural health monitoring (SHM) due to their many merits. To enhance the thermal reliability of FBG sensors, thermal sensitivity, generally expressed as αf + ξf and considered a constant, should be investigated more precisely. For this purpose, the governing equation of FBG sensors is modified using differential derivatives between the wavelength shift and the temperature change in this study. Through a thermal test ranging from RT to 900 °C, the thermal sensitivity of FBG sensors is successfully examined and this guarantees thermal reliability of FBG sensors at ultra-high temperatures. In detail, αf + ξf has a non-linear dependence on temperature and varies from 6.0 × 10-6 °C-1 (20 °C) to 10.6 × 10-6 °C-1 (650 °C). Also, FBGs should be carefully used for applications at ultra-high temperatures due to signal disappearance near 900 °C.

  2. Near field plasmonic gradient effects on high vacuum tip-enhanced Raman spectroscopy.

    PubMed

    Fang, Yurui; Zhang, Zhenglong; Chen, Li; Sun, Mengtao

    2015-01-14

    Near field gradient effects in high vacuum tip-enhanced Raman spectroscopy (HV-TERS) are a recent developing ultra-sensitive optical and spectral analysis technology on the nanoscale, based on the plasmons and plasmonic gradient enhancement in the near field and under high vacuum. HV-TERS can not only be used to detect ultra-sensitive Raman spectra enhanced by surface plasmon, but also to detect clear molecular IR-active modes enhanced by strongly plasmonic gradient. Furthermore, the molecular overtone modes and combinational modes can also be experimentally measured, where the Fermi resonance and Darling-Dennison resonance were successfully observed in HV-TERS. Theoretical calculations using electromagnetic field theory firmly supported experimental observation. The intensity ratio of the plasmon gradient term over the linear plasmon term can reach values greater than 1. Theoretical calculations also revealed that with the increase in gap distance between tip and substrate, the decrease in the plasmon gradient was more significant than the decrease in plasmon intensity, which is the reason that the gradient Raman can be only observed in the near field. Recent experimental results of near field gradient effects on HV-TERS were summarized, following the section of the theoretical analysis.

  3. High power radiators of ultra-short electromagnetic quasi-unipolar pulses

    NASA Astrophysics Data System (ADS)

    Fedorov, V. M.; Ostashev, V. E.; Tarakanov, V. P.; Ul'yanov, A. V.

    2017-05-01

    Results of creation, operation, and diagnostics of the high power radiators for ultra-short length electromagnetic pulses (USEMPs) with a quasi-unipolar profile, which have been developed in our laboratory, are presented. The radiating module contains: the ultra-wideband (UWB) antenna array, the exciting high voltage pulse semiconductor generator (a pulser), the power source and the control unit. The principles of antenna array with a high efficiency aperture about 0.9 were developed using joint four TEM-horns with shielding electrodes in every TEM-horn. Sizes of the antenna apertures were (16-60) cm. The pulsers produced by “FID Technology” company had the following parameters: 50 Ohm connector impedance, unipolar pulses voltages (10-100) kV, the rise-time (0.04-0.15) ns, and the width (0.2-1) ns. The modules radiate the USEMPs of (0.1-10) GHz spectrum, their repetition rate is (1-100) kHz, and the effective potential is E*R = (20-400) kV, producing the peak E-field into the far-zone of R-distance. Parameters of the USEMP waves were measured by a calibrated sensor with the following characteristics: the sensitivity 0.32V/(kV/m), the rise-time 0.03 ns, the duration up to 7 ns. The measurements were in agreement with the simulation results, which were obtained using the 3-D code “KARAT”. The USEMP waves with amplitudes (1-10) kV/m and the pulse repetition rate (0.5-100) kHz were successfully used to examine various electronic devices for an electromagnetic immunity.

  4. Ultra Fast, High Rep Rate, High Voltage Spark Gap Pulser

    DTIC Science & Technology

    1995-07-01

    current rise time. The spark gap was designed to have a coaxial geometry reducing its inductance. Provisions were made to pass flowing gas between the...ULTRA FAST, HIGH REP RATE, HIGH VOLTAGE SPARK GAP PULSER Robert A. Pastore Jr., Lawrence E. Kingsley, Kevin Fonda, Erik Lenzing Electrophysics and...Modeling Branch AMSRL-PS-EA Tel.: (908)-532-0271 FAX: (908)-542-3348 U.S. Army Research Laboratory Physical Sciences Directorate Ft. Monmouth

  5. Fast and sensitive analysis of beta blockers by ultra-high-performance liquid chromatography coupled with ultra-high-resolution TOF mass spectrometry.

    PubMed

    Tomková, Jana; Ondra, Peter; Kocianová, Eva; Václavík, Jan

    2017-07-01

    This paper presents a method for the determination of acebutolol, betaxolol, bisoprolol, metoprolol, nebivolol and sotalol in human serum by liquid-liquid extraction and ultra-high-performance liquid chromatography coupled with ultra-high-resolution TOF mass spectrometry. After liquid-liquid extraction, beta blockers were separated on a reverse-phase analytical column (Acclaim RS 120; 100 × 2.1 mm, 2.2 μm). The total run time was 6 min for each sample. Linearity, limit of detection, limit of quantification, matrix effects, specificity, precision, accuracy, recovery and sample stability were evaluated. The method was successfully applied to the therapeutic drug monitoring of 108 patients with hypertension. This method was also used for determination of beta blockers in 33 intoxicated patients. Copyright © 2016 John Wiley & Sons, Ltd.

  6. Compressed perovskite aqueous mixtures near their phase transitions show very high permittivities: New prospects for high-field MRI dielectric shimming.

    PubMed

    Neves, Ana L; Leroi, Lisa; Raolison, Zo; Cochinaire, Nicolas; Letertre, Thibaut; Abdeddaïm, Redha; Enoch, Stefan; Wenger, Jerome; Berthelot, Johann; Adenot-Engelvin, Anne-Lise; Malléjac, Nicolas; Mauconduit, Franck; Vignaud, Alexandre; Sabouroux, Pierre

    2018-03-01

    Perovskites are greatly used nowadays in many technological applications because of their high permittivity, more specifically in the form of aqueous solutions, for MRI dielectric shimming. In this study, full dielectric characterizations of highly concentrated CaTiO 3 /BaTiO 3 water mixtures were carried out and new permittivity maxima was reached. Permittivity measurements were done on aqueous solutions from 0%v/v to dry powder. The permittivity dependence with pressure was investigated. Scanning electron microscopy images were performed on a few representative solutions. BaTiO 3 pressed pads of different thicknesses, permittivities, and distances to the head were compared in a 7T MRI scanner. Perovskite aqueous mixtures undergo a pressure-dependent phase transition in terms of permittivity, with increasing water content. A new relative permittivity maximum of 475 was achieved. Microscopic images revealed structural differences between phases. A B1+ improvement in the temporal lobe was obtained with thin, high permittivity BaTiO 3 head. This new preparation method allows improved pad geometry and placement, as a result of the high relative permittivity values achieved. This method has great significance for medical applications of MRI dielectric shimming, being easy to replicate and implement on a large scale. Magn Reson Med 79:1753-1765, 2018. © 2017 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes. © 2017 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine.

  7. High-field modulated ion-selective field-effect-transistor (FET) sensors with sensitivity higher than the ideal Nernst sensitivity.

    PubMed

    Chen, Yi-Ting; Sarangadharan, Indu; Sukesan, Revathi; Hseih, Ching-Yen; Lee, Geng-Yen; Chyi, Jen-Inn; Wang, Yu-Lin

    2018-05-29

    Lead ion selective membrane (Pb-ISM) coated AlGaN/GaN high electron mobility transistors (HEMT) was used to demonstrate a whole new methodology for ion-selective FET sensors, which can create ultra-high sensitivity (-36 mV/log [Pb 2+ ]) surpassing the limit of ideal sensitivity (-29.58 mV/log [Pb 2+ ]) in a typical Nernst equation for lead ion. The largely improved sensitivity has tremendously reduced the detection limit (10 -10  M) for several orders of magnitude of lead ion concentration compared to typical ion-selective electrode (ISE) (10 -7  M). The high sensitivity was obtained by creating a strong filed between the gate electrode and the HEMT channel. Systematical investigation was done by measuring different design of the sensor and gate bias, indicating ultra-high sensitivity and ultra-low detection limit obtained only in sufficiently strong field. Theoretical study in the sensitivity consistently agrees with the experimental finding and predicts the maximum and minimum sensitivity. The detection limit of our sensor is comparable to that of Inductively-Coupled-Plasma Mass Spectrum (ICP-MS), which also has detection limit near 10 -10  M.

  8. BAKABLE ULTRA-HIGH VACUUM VALVE

    DOEpatents

    Mark, J.T.; Gantz, I.H.

    1962-07-10

    S>This patent relates to a valve useful in applications involving successively closing and opening a communication between a chamber evacuated to an ultra-high vacuum condition of the order of 10/sup -10/ millimeters of mercury and another chamber or the ambient. The valve is capable of withstanding extended baking at 450 deg C and repeated opening and closing without repiacement of the valve seat (approximately 200 cycle limit). The seal is formed by mutual interdiffusion weld, coerced by a pneumatic actuator. (AEC)

  9. Spacewalking_in_Ultra_High_Definition

    NASA Image and Video Library

    2017-07-21

    Ever wonder what the spacewalker sees while you’re looking at him or her? Here’s your answer, courtesy of NASA astronaut Jack Fischer. This Ultra High Definition clip shows Fischer outside the International Space Station during a spacewalk on Expedition 51 in May 2017, and the view from a small camera attached to his spacesuit at the same time. Music by Joakim Karud. _______________________________________ FOLLOW THE SPACE STATION! Twitter: https://twitter.com/Space_Station Facebook: https://www.facebook.com/ISS Instagram: https://instagram.com/iss/

  10. "Ultra High Dilution 1994" revisited 2015--the state of follow-up research.

    PubMed

    Endler, P Christian; Schulte, Jurgen; Stock-Schroeer, Beate; Stephen, Saundra

    2015-10-01

    The "Ultra High Dilution 1994" project was an endeavour to take stock of the findings and theories on homeopathic extreme dilutions that were under research at the time in areas of biology, biophysics, physics and medicine. The project finally materialized into an anthology assembling contributions of leading scientists in the field. Over the following two decades, it became widely quoted within the homeopathic community and also known in other research communities. The aim of the present project was to re-visit and review the 1994 studies from the perspective of 2015. The original authors from 1994 or close laboratory colleagues were asked to contribute papers covering their research efforts and learnings in the period from 1994 up to 2015. These contributions were edited and cross-referenced, and a selection of further contributions was added. About a dozen contributions reported on follow-up experiments and studies, including further developments in theory. Only few of the models that had seemed promising in 1994 had not been followed up later. Most models presented in the original publication had meanwhile been submitted to intra-laboratory, multicentre or independent scrutiny. The results of the follow-up research seemed to have rewarded the efforts. Furthermore, contributions were provided on new models that had been inspired by the original ones or that may be candidates for further in-depth ultra high dilution (UHD) research. The project "Ultra High Dilution 1994 revisited 2015" is the latest output of what might be considered the "buena vista social club" of homeopathy research. However, it presents new developments and results of the older, established experimental models as well as a general survey of the state of UHD research. Copyright © 2015 The Faculty of Homeopathy. Published by Elsevier Ltd. All rights reserved.

  11. Mechanical flip-chip for ultra-high electron mobility devices

    DOE PAGES

    Bennaceur, Keyan; Schmidt, Benjamin A.; Gaucher, Samuel; ...

    2015-09-22

    In this study, electrostatic gates are of paramount importance for the physics of devices based on high-mobility two-dimensional electron gas (2DEG) since they allow depletion of electrons in selected areas. This field-effect gating enables the fabrication of a wide range of devices such as, for example, quantum point contacts (QPC), electron interferometers and quantum dots. To fabricate these gates, processing is usually performed on the 2DEG material, which is in many cases detrimental to its electron mobility. Here we propose an alternative process which does not require any processing of the 2DEG material other than for the ohmic contacts. Thismore » approach relies on processing a separate wafer that is then mechanically mounted on the 2DEG material in a flip-chip fashion. This technique proved successful to fabricate quantum point contacts on both GaAs/AlGaAs materials with both moderate and ultra-high electron mobility.« less

  12. Second order nonlinear QED processes in ultra-strong laser fields

    NASA Astrophysics Data System (ADS)

    Mackenroth, Felix

    2017-10-01

    In the interaction of ultra-intense laser fields with matter the ever increasing peak laser intensities render nonlinear QED effects ever more important. For long, ultra-intense laser pulses scattering large systems, like a macroscopic plasma, the interaction time can be longer than the scattering time, leading to multiple scatterings. These are usually approximated as incoherent cascades of single-vertex processes. Under certain conditions, however, this common cascade approximation may be insufficient, as it disregards several effects such as coherent processes, quantum interferences or pulse shape effects. Quantifying deviations of the full amplitude of multiple scatterings from the commonly employed cascade approximations is a formidable, yet unaccomplished task. In this talk we are going to discuss how to compute second order nonlinear QED amplitudes and relate them to the conventional cascade approximation. We present examples for typical second order processes and benchmark the full result against common approximations. We demonstrate that the approximation of multiple nonlinear QED scatterings as a cascade of single interactions has certain limitations and discuss these limits in light of upcoming experimental tests.

  13. Herpin effective media resonant underlayers and resonant overlayer designs for ultra-high NA interference lithography.

    PubMed

    Bourke, Levi; Blaikie, Richard J

    2017-12-01

    Dielectric waveguide resonant underlayers are employed in ultra-high NA interference photolithography to effectively double the depth of field. Generally a single high refractive index waveguiding layer is employed. Here multilayer Herpin effective medium methods are explored to develop equivalent multilayer waveguiding layers. Herpin equivalent resonant underlayers are shown to be suitable replacements provided at least one layer within the Herpin trilayer supports propagating fields. In addition, a method of increasing the intensity incident upon the photoresist using resonant overlayers is also developed. This method is shown to greatly enhance the intensity within the photoresist making the use of thicker, safer, non-absorbing, low refractive index matching liquids potentially suitable for large-scale applications.

  14. WE-G-BRD-09: Novel MRI Compatible Electron Accelerator for MRI-Linac Radiotherapy

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Whelan, B; Keall, P; Gierman, S

    Purpose: MRI guided radiotherapy is a rapidly growing field; however current linacs are not designed to operate in MRI fringe fields. As such, current MRI- Linac systems require magnetic shielding, impairing MR image quality and system flexibility. Here, we present a bespoke electron accelerator concept with robust operation in in-line magnetic fields. Methods: For in-line MRI-Linac systems, electron gun performance is the major constraint on accelerator performance. To overcome this, we propose placing a cathode directly within the first accelerating cavity. Such a configuration is used extensively in high energy particle physics, but not previously for radiotherapy. Benchmarked computational modellingmore » (CST, Darmstadt, Germany) was employed to design and assess a 5.5 cell side coupled accelerator with a temperature limited thermionic cathode in the first accelerating cell. This simulation was coupled to magnetic fields from a 1T MRI model to assess robustness in magnetic fields for Source to Isocenter Distance between 1 and 2 meters. Performance was compared to a conventional electron gun based system in the same magnetic field. Results: A temperature limited cathode (work function 1.8eV, temperature 1245K, emission constant 60A/K/cm{sup 2}) will emit a mean current density of 24mA/mm{sup 2} (Richardson’s Law). We modeled a circular cathode with radius 2mm and mean current 300mA. Capture efficiency of the device was 43%, resulting in target current of 130 mA. The electron beam had a FWHM of 0.2mm, and mean energy of 5.9MeV (interquartile spread of 0.1MeV). Such an electron beam is suitable for radiotherapy, comparing favourably to conventional systems. This model was robust to operation the MRI fringe field, with a maximum current loss of 6% compared to 85% for the conventional system. Conclusion: The bespoke electron accelerator is robust to operation in in-line magnetic fields. This will enable MRI-Linacs with no accelerator magnetic shielding, and

  15. Mapping three-dimensional oil distribution with π-EPI MRI measurements at low magnetic field

    NASA Astrophysics Data System (ADS)

    Li, Ming; Xiao, Dan; Romero-Zerón, Laura; Marica, Florea; MacMillan, Bryce; Balcom, Bruce J.

    2016-08-01

    Magnetic resonance imaging (MRI) is a robust tool to image oil saturation distribution in rock cores during oil displacement processes. However, a lengthy measurement time for 3D measurements at low magnetic field can hinder monitoring the displacement. 1D and 2D MRI measurements are instead often undertaken to monitor the oil displacement since they are faster. However, 1D and 2D images may not completely reflect the oil distribution in heterogeneous rock cores. In this work, a high-speed 3D MRI technique, π Echo Planar Imaging (π-EPI), was employed at 0.2 T to monitor oil displacement. Centric scan interleaved sampling with view sharing in k-t space was employed to improve the temporal resolution of the π-EPI measurements. A D2O brine was employed to distinguish the hydrocarbon and water phases. A relatively homogenous glass bead pack and a heterogeneous Spynie core plug were employed to show different oil displacement behaviors. High quality 3D images were acquired with π-EPI MRI measurements. Fluid quantification with π-EPI compared favorably with FID, CPMG, 1D-DHK-SPRITE, 3D Fast Spin Echo (FSE) and 3D Conical SPRITE measurements. π-EPI greatly reduced the gradient duty cycle and improved sensitivity, compared to FSE and Conical SPRITE measurements, enabling dynamic monitoring of oil displacement processes. For core plug samples with sufficiently long lived T2, T2∗, π-EPI is an ideal method for rapid 3D saturation imaging.

  16. A continuous tensor field approximation of discrete DT-MRI data for extracting microstructural and architectural features of tissue.

    PubMed

    Pajevic, Sinisa; Aldroubi, Akram; Basser, Peter J

    2002-01-01

    The effective diffusion tensor of water, D, measured by diffusion tensor MRI (DT-MRI), is inherently a discrete, noisy, voxel-averaged sample of an underlying macroscopic effective diffusion tensor field, D(x). Within fibrous tissues this field is presumed to be continuous and smooth at a gross anatomical length scale. Here a new, general mathematical framework is proposed that uses measured DT-MRI data to produce a continuous approximation to D(x). One essential finding is that the continuous tensor field representation can be constructed by repeatedly performing one-dimensional B-spline transforms of the DT-MRI data. The fidelity and noise-immunity of this approximation are tested using a set of synthetically generated tensor fields to which background noise is added via Monte Carlo methods. Generally, these tensor field templates are reproduced faithfully except at boundaries where diffusion properties change discontinuously or where the tensor field is not microscopically homogeneous. Away from such regions, the tensor field approximation does not introduce bias in useful DT-MRI parameters, such as Trace(D(x)). It also facilitates the calculation of several new parameters, particularly differential quantities obtained from the tensor of spatial gradients of D(x). As an example, we show that they can identify tissue boundaries across which diffusion properties change rapidly using in vivo human brain data. One important application of this methodology is to improve the reliability and robustness of DT-MRI fiber tractography.

  17. Quantifying the ultrastructure of carotid arteries using high-resolution micro-diffusion tensor imaging—comparison of intact versus open cut tissue

    NASA Astrophysics Data System (ADS)

    Salman Shahid, Syed; Gaul, Robert T.; Kerskens, Christian; Flamini, Vittoria; Lally, Caitríona

    2017-12-01

    Diffusion magnetic resonance imaging (dMRI) can provide insights into the microstructure of intact arterial tissue. The current study employed high magnetic field MRI to obtain ultra-high resolution dMRI at an isotropic voxel resolution of 117 µm3 in less than 2 h of scan time. A parameter selective single shell (128 directions) diffusion-encoding scheme based on Stejskel-Tanner sequence with echo-planar imaging (EPI) readout was used. EPI segmentation was used to reduce the echo time (TE) and to minimise the susceptibility-induced artefacts. The study utilised the dMRI analysis with diffusion tensor imaging (DTI) framework to investigate structural heterogeneity in intact arterial tissue and to quantify variations in tissue composition when the tissue is cut open and flattened. For intact arterial samples, the region of interest base comparison showed significant differences in fractional anisotropy and mean diffusivity across the media layer (p  <  0.05). For open cut flat samples, DTI based directionally invariant indices did not show significant differences across the media layer. For intact samples, fibre tractography based indices such as calculated helical angle and fibre dispersion showed near circumferential alignment and a high degree of fibre dispersion, respectively. This study demonstrates the feasibility of fast dMRI acquisition with ultra-high spatial and angular resolution at 7 T. Using the optimised sequence parameters, this study shows that DTI based markers are sensitive to local structural changes in intact arterial tissue samples and these markers may have clinical relevance in the diagnosis of atherosclerosis and aneurysm.

  18. Intraoperative high-field magnetic resonance imaging, multimodal neuronavigation, and intraoperative electrophysiological monitoring-guided surgery for treating supratentorial cavernomas.

    PubMed

    Li, Fang-Ye; Chen, Xiao-Lei; Xu, Bai-Nan

    2016-09-01

    To determine the beneficial effects of intraoperative high-field magnetic resonance imaging (MRI), multimodal neuronavigation, and intraoperative electrophysiological monitoring-guided surgery for treating supratentorial cavernomas. Twelve patients with 13 supratentorial cavernomas were prospectively enrolled and operated while using a 1.5 T intraoperative MRI, multimodal neuronavigation, and intraoperative electrophysiological monitoring. All cavernomas were deeply located in subcortical areas or involved critical areas. Intraoperative high-field MRIs were obtained for the intraoperative "visualization" of surrounding eloquent structures, "brain shift" corrections, and navigational plan updates. All cavernomas were successfully resected with guidance from intraoperative MRI, multimodal neuronavigation, and intraoperative electrophysiological monitoring. In 5 cases with supratentorial cavernomas, intraoperative "brain shift" severely deterred locating of the lesions; however, intraoperative MRI facilitated precise locating of these lesions. During long-term (>3 months) follow-up, some or all presenting signs and symptoms improved or resolved in 4 cases, but were unchanged in 7 patients. Intraoperative high-field MRI, multimodal neuronavigation, and intraoperative electrophysiological monitoring are helpful in surgeries for the treatment of small deeply seated subcortical cavernomas.

  19. Operation of a 400MHz NMR magnet using a (RE:Rare Earth)Ba2Cu3O7-x high-temperature superconducting coil: Towards an ultra-compact super-high field NMR spectrometer operated beyond 1GHz.

    PubMed

    Yanagisawa, Y; Piao, R; Iguchi, S; Nakagome, H; Takao, T; Kominato, K; Hamada, M; Matsumoto, S; Suematsu, H; Jin, X; Takahashi, M; Yamazaki, T; Maeda, H

    2014-12-01

    High-temperature superconductors (HTS) are the key technology to achieve super-high magnetic field nuclear magnetic resonance (NMR) spectrometers with an operating frequency far beyond 1GHz (23.5T). (RE)Ba 2 Cu 3 O 7- x (REBCO, RE: rare earth) conductors have an advantage over Bi 2 Sr 2 Ca 2 Cu 3 O 10- x (Bi-2223) and Bi 2 Sr 2 CaCu 2 O 8- x (Bi-2212) conductors in that they have very high tensile strengths and tolerate strong electromagnetic hoop stress, thereby having the potential to act as an ultra-compact super-high field NMR magnet. As a first step, we developed the world's first NMR magnet comprising an inner REBCO coil and outer low-temperature superconducting (LTS) coils. The magnet was successfully charged without degradation and mainly operated at 400MHz (9.39T). Technical problems for the NMR magnet due to screening current in the REBCO coil were clarified and solved as follows: (i) A remarkable temporal drift of the central magnetic field was suppressed by a current sweep reversal method utilizing ∼10% of the peak current. (ii) A Z2 field error harmonic of the main coil cannot be compensated by an outer correction coil and therefore an additional ferromagnetic shim was used. (iii) Large tesseral harmonics emerged that could not be corrected by cryoshim coils. Due to those harmonics, the resolution and sensitivity of NMR spectra are ten-fold lower than those for a conventional LTS NMR magnet. As a result, a HSQC spectrum could be achieved for a protein sample, while a NOESY spectrum could not be obtained. An ultra-compact 1.2GHz NMR magnet could be realized if we effectively take advantage of REBCO conductors, although this will require further research to suppress the effect of the screening current. Copyright © 2014 Elsevier Inc. All rights reserved.

  20. Ultra-high-field magnetic resonance spectroscopy in non-alcoholic fatty liver disease: Novel mechanistic and diagnostic insights of energy metabolism in non-alcoholic steatohepatitis and advanced fibrosis.

    PubMed

    Traussnigg, Stefan; Kienbacher, Christian; Gajdošík, Martin; Valkovič, Ladislav; Halilbasic, Emina; Stift, Judith; Rechling, Christian; Hofer, Harald; Steindl-Munda, Petra; Ferenci, Peter; Wrba, Fritz; Trattnig, Siegfried; Krššák, Martin; Trauner, Michael

    2017-10-01

    With the rising prevalence of non-alcoholic fatty liver disease (NAFLD) and steatohepatitis (NASH) non-invasive tools obtaining pathomechanistic insights to improve risk stratification are urgently needed. We therefore explored high- and ultra-high-field magnetic resonance spectroscopy (MRS) to obtain novel mechanistic and diagnostic insights into alterations of hepatic lipid, cell membrane and energy metabolism across the spectrum of NAFLD. MRS and liver biopsy were performed in 30 NAFLD patients with NAFL (n=8) or NASH (n=22). Hepatic lipid content and composition were measured using 3-Tesla proton ( 1 H)-MRS. 7-Tesla phosphorus ( 31 P)-MRS was applied to determine phosphomonoester (PME) including phosphoethanolamine (PE), phosphodiester (PDE) including glycerophosphocholine (GPC), phosphocreatine (PCr), nicotinamide adenine dinucleotide phosphate (NADPH), inorganic phosphate (Pi), γ-ATP and total phosphorus (TP). Saturation transfer technique was used to quantify hepatic ATP flux. Hepatic steatosis in 1 H-MRS highly correlated with histology (P<.001) showing higher values in NASH than NAFL (P<.001) without differences in saturated or unsaturated fatty acid indices. PE/TP ratio increased with advanced fibrosis (F3/4) (P=.002) whereas GPC/PME+PDE decreased (P=.05) compared to no/mild fibrosis (F0-2). γ-ATP/TP was lower in advanced fibrosis (P=.049), while PCr/TP increased (P=.01). NADPH/TP increased with higher grades of ballooning (P=.02). Pi-to-ATP exchange rate constant (P=.003) and ATP flux (P=.001) were lower in NASH than NAFL. Ultra-high-field MRS, especially saturation transfer technique uncovers changes in energy metabolism including dynamic ATP flux in inflammation and fibrosis in NASH. Non-invasive profiling by MRS appears feasible and may assist further mechanistic and therapeutic studies in NAFLD/NASH. © 2017 The Authors Liver International Published by John Wiley & Sons Ltd.

  1. Nano-thermometers with thermo-sensitive polymer grafted USPIOs behaving as positive contrast agents in low-field MRI

    NASA Astrophysics Data System (ADS)

    Hannecart, Adeline; Stanicki, Dimitri; Vander Elst, Luce; Muller, Robert N.; Lecommandoux, Sébastien; Thévenot, Julie; Bonduelle, Colin; Trotier, Aurélien; Massot, Philippe; Miraux, Sylvain; Sandre, Olivier; Laurent, Sophie

    2015-02-01

    Two commercial statistical copolymers of ethylene oxide and propylene oxide, Jeffamine® M-2005 (PEO5-st-PPO37) and M-2070 (PEO46-st-PPO13), exhibiting lower critical solution temperature (LCST) in water, were grafted onto the surface of ultra-small superparamagnetic iron oxide nanoparticles (USPIOs) using silanization and amide-bond coupling reactions. The LCSTs of the polymers in solution were measured by dynamic light scattering (DLS) and nuclear magnetic resonance (NMR). In accordance with the compositions of EO vs. PO, the transition temperature was measured to be 22 +/- 2 °C for M-2005 by both DLS and NMR, while the LCST was much higher, 52 +/- 2 °C, for M-2070 (a second transition was also detected above 80 °C by NMR in that case, ascribed to the full dehydration of chains at the molecular level). The resulting polymer-grafted USPIOs exhibit a temperature-responsive colloidal behaviour, their surface reversibly changing from hydrophilic below LCST to hydrophobic above it. This phenomenon was utilised to design thermo-sensitive contrast agents for MRI. Transverse relaxivities (r2) of the USPIO@PEO5-st-PPO37 core-shell nanoparticles were measured at 8.25, 20, 60, and 300 MHz. Nuclear magnetic resonance dispersion (NMRD) profiles, giving longitudinal relaxivities (r1) between 0.01 and 60 MHz, were acquired at temperatures ranging from 15 to 50 °C. For all tested frequencies except 300 MHz, both r1 and r2 decrease with temperature and show an inflection point at 25 °C, near the LCST. To illustrate the interest of such polymer-coated USPIOs for MRI thermometry, sample tubes were imaged on both low-field (8.25 MHz/0.194 Tesla) and high-field (300 MHz/7.05 Tesla) MRI scanners with either T1- or T2*-weighted spin echo sequences. The positive contrast on low-field MR images and the perfect linearity of the signal with a T2*-weighted sequence over the entire temperature range 15-50 °C render these LCST polymer coated USPIOs interesting positive contrast agents

  2. Ultra-high-energy cosmic rays from radio galaxies

    NASA Astrophysics Data System (ADS)

    Eichmann, B.; Rachen, J. P.; Merten, L.; van Vliet, A.; Becker Tjus, J.

    2018-02-01

    Radio galaxies are intensively discussed as the sources of cosmic rays observed above about 3 × 1018 eV, called ultra-high energy cosmic rays (UHECRs). We present a first, systematic approach that takes the individual characteristics of these sources into account, as well as the impact of the extragalactic magnetic-field structures up to a distance of 120 Mpc. We use a mixed simulation setup, based on 3D simulations of UHECRs ejected by observed, individual radio galaxies taken out to a distance of 120 Mpc, and on 1D simulations over a continuous source distribution contributing from beyond 120 Mpc. Additionally, we include the ultra-luminous radio galaxy Cygnus A at a distance of about 250 Mpc, as its contribution is so strong that it must be considered as an individual point source. The implementation of the UHECR ejection in our simulation setup, both that of individual radio galaxies and the continuous source function, is based on a detailed consideration of the physics of radio jets and standard first-order Fermi acceleration. This allows to derive the spectrum of ejected UHECR as a function of radio luminosity, and at the same time provides an absolute normalization of the problem involving only a small set of parameters adjustable within narrow constraints. We show that the average contribution of radio galaxies taken over a very large volume cannot explain the observed features of UHECRs measured at Earth. However, we obtain excellent agreement with the spectrum, composition, and arrival-direction distribution of UHECRs measured by the Pierre Auger Observatory, if we assume that most UHECRs observed arise from only two sources: the ultra-luminous radio galaxy Cygnus A, providing a mostly light composition of nuclear species dominating up to about 6 × 1019 eV, and the nearest radio galaxy Centaurus A, providing a heavy composition dominating above 6 × 1019 eV . Here we have to assume that extragalactic magnetic fields out to 250 Mpc, which we did not

  3. Ultra-broadband and planar sound diffuser with high uniformity of reflected intensity

    NASA Astrophysics Data System (ADS)

    Fan, Xu-Dong; Zhu, Yi-Fan; Liang, Bin; Yang, Jing; Yang, Jun; Cheng, Jian-Chun

    2017-09-01

    Schroeder diffusers, as a classical design of acoustic diffusers proposed over 40 years ago, play key roles in many practical scenarios ranging from architectural acoustics to noise control to particle manipulation. Despite the great success of conventional acoustic diffusers, it is still worth pursuing ideal acoustic diffusers that are essentially expected to produce perfect sound diffuse reflection within the unlimited bandwidth. Here, we propose a different mechanism for designing acoustic diffusers to overcome the basic limits in intensity uniformity and working bandwidth in the previous designs and demonstrate a practical implementation by acoustic metamaterials with dispersionless phase-steering capability. In stark contrast to the existing production of diffuse fields relying on random scattering of sound energy by using a specific mathematical number sequence of periodically distributed unit cells, we directly mold the reflected wavefront into the desired shape by precisely manipulating the local phases of individual subwavelength metastructures. We also benchmark our design via numerical simulation with a commercially available Schroeder diffuser, and the results verify that our proposed diffuser scatters incident acoustic energy into all directions more uniformly within an ultra-broad band regardless of the incident angle. Furthermore, our design enables further improvement of the working bandwidth just by simply downscaling each individual element. With ultra-broadband functionality and high uniformity of reflected intensity, our metamaterial-based production of the diffusive field opens a route to the design and application of acoustic diffusers and may have a significant impact on various fields such as architectural acoustics and medical ultrasound imaging/treatment.

  4. Simultaneously driven linear and nonlinear spatial encoding fields in MRI.

    PubMed

    Gallichan, Daniel; Cocosco, Chris A; Dewdney, Andrew; Schultz, Gerrit; Welz, Anna; Hennig, Jürgen; Zaitsev, Maxim

    2011-03-01

    Spatial encoding in MRI is conventionally achieved by the application of switchable linear encoding fields. The general concept of the recently introduced PatLoc (Parallel Imaging Technique using Localized Gradients) encoding is to use nonlinear fields to achieve spatial encoding. Relaxing the requirement that the encoding fields must be linear may lead to improved gradient performance or reduced peripheral nerve stimulation. In this work, a custom-built insert coil capable of generating two independent quadratic encoding fields was driven with high-performance amplifiers within a clinical MR system. In combination with the three linear encoding fields, the combined hardware is capable of independently manipulating five spatial encoding fields. With the linear z-gradient used for slice-selection, there remain four separate channels to encode a 2D-image. To compare trajectories of such multidimensional encoding, the concept of a local k-space is developed. Through simulations, reconstructions using six gradient-encoding strategies were compared, including Cartesian encoding separately or simultaneously on both PatLoc and linear gradients as well as two versions of a radial-based in/out trajectory. Corresponding experiments confirmed that such multidimensional encoding is practically achievable and demonstrated that the new radial-based trajectory offers the PatLoc property of variable spatial resolution while maintaining finite resolution across the entire field-of-view. Copyright © 2010 Wiley-Liss, Inc.

  5. High-resolution MRI in detecting subareolar breast abscess.

    PubMed

    Fu, Peifen; Kurihara, Yasuyuki; Kanemaki, Yoshihide; Okamoto, Kyoko; Nakajima, Yasuo; Fukuda, Mamoru; Maeda, Ichiro

    2007-06-01

    Because subareolar breast abscess has a high recurrence rate, a more effective imaging technique is needed to comprehensively visualize the lesions and guide surgery. We performed a high-resolution MRI technique using a microscopy coil to reveal the characteristics and extent of subareolar breast abscess. High-resolution MRI has potential diagnostic value in subareolar breast abscess. This technique can be used to guide surgery with the aim of reducing the recurrence rate.

  6. Remarkably high mobility ultra-thin-film metal-oxide transistor with strongly overlapped orbitals

    PubMed Central

    Wei Shih, Chen; Chin, Albert; Fu Lu, Chun; Fang Su, Wei

    2016-01-01

    High mobility channel thin-film-transistor (TFT) is crucial for both display and future generation integrated circuit. We report a new metal-oxide TFT that has an ultra-thin 4.5 nm SnO2 thickness for both active channel and source-drain regions, very high 147 cm2/Vs field-effect mobility, high ION/IOFF of 2.3 × 107, small 110 mV/dec sub-threshold slope, and a low VD of 2.5 V for low power operation. This mobility is already better than chemical-vapor-deposition grown multi-layers MoS2 TFT. From first principle quantum-mechanical calculation, the high mobility TFT is due to strongly overlapped orbitals. PMID:26744240

  7. MR-compatibility of a high-resolution small animal PET insert operating inside a 7 T MRI.

    PubMed

    Thiessen, J D; Shams, E; Stortz, G; Schellenberg, G; Bishop, D; Khan, M S; Kozlowski, P; Retière, F; Sossi, V; Thompson, C J; Goertzen, A L

    2016-11-21

    A full-ring PET insert consisting of 16 PET detector modules was designed and constructed to fit within the 114 mm diameter gradient bore of a Bruker 7 T MRI. The individual detector modules contain two silicon photomultiplier (SiPM) arrays, dual-layer offset LYSO crystal arrays, and high-definition multimedia interface (HDMI) cables for both signal and power transmission. Several different RF shielding configurations were assessed prior to construction of a fully assembled PET insert using a combination of carbon fibre and copper foil for RF shielding. MR-compatibility measurements included field mapping of the static magnetic field (B 0 ) and the time-varying excitation field (B 1 ) as well as acquisitions with multiple pulse sequences: spin echo (SE), rapid imaging with refocused echoes (RARE), fast low angle shot (FLASH) gradient echo, and echo planar imaging (EPI). B 0 field maps revealed a small degradation in the mean homogeneity (+0.1 ppm) when the PET insert was installed and operating. No significant change was observed in the B 1 field maps or the image homogeneity of various MR images, with a 9% decrease in the signal-to-noise ratio (SNR) observed only in EPI images acquired with the PET insert installed and operating. PET detector flood histograms, photopeak amplitudes, and energy resolutions were unchanged in individual PET detector modules when acquired during MRI operation. There was a small baseline shift on the PET detector signals due to the switching amplifiers used to power MRI gradient pulses. This baseline shift was observable when measured with an oscilloscope and varied as a function of the gradient duty cycle, but had no noticeable effect on the performance of the PET detector modules. Compact front-end electronics and effective RF shielding led to minimal cross-interference between the PET and MRI systems. Both PET detector and MRI performance was excellent, whether operating as a standalone system or a hybrid PET/MRI.

  8. MR-compatibility of a high-resolution small animal PET insert operating inside a 7 T MRI

    NASA Astrophysics Data System (ADS)

    Thiessen, J. D.; Shams, E.; Stortz, G.; Schellenberg, G.; Bishop, D.; Khan, M. S.; Kozlowski, P.; Retière, F.; Sossi, V.; Thompson, C. J.; Goertzen, A. L.

    2016-11-01

    A full-ring PET insert consisting of 16 PET detector modules was designed and constructed to fit within the 114 mm diameter gradient bore of a Bruker 7 T MRI. The individual detector modules contain two silicon photomultiplier (SiPM) arrays, dual-layer offset LYSO crystal arrays, and high-definition multimedia interface (HDMI) cables for both signal and power transmission. Several different RF shielding configurations were assessed prior to construction of a fully assembled PET insert using a combination of carbon fibre and copper foil for RF shielding. MR-compatibility measurements included field mapping of the static magnetic field (B 0) and the time-varying excitation field (B 1) as well as acquisitions with multiple pulse sequences: spin echo (SE), rapid imaging with refocused echoes (RARE), fast low angle shot (FLASH) gradient echo, and echo planar imaging (EPI). B 0 field maps revealed a small degradation in the mean homogeneity (+0.1 ppm) when the PET insert was installed and operating. No significant change was observed in the B 1 field maps or the image homogeneity of various MR images, with a 9% decrease in the signal-to-noise ratio (SNR) observed only in EPI images acquired with the PET insert installed and operating. PET detector flood histograms, photopeak amplitudes, and energy resolutions were unchanged in individual PET detector modules when acquired during MRI operation. There was a small baseline shift on the PET detector signals due to the switching amplifiers used to power MRI gradient pulses. This baseline shift was observable when measured with an oscilloscope and varied as a function of the gradient duty cycle, but had no noticeable effect on the performance of the PET detector modules. Compact front-end electronics and effective RF shielding led to minimal cross-interference between the PET and MRI systems. Both PET detector and MRI performance was excellent, whether operating as a standalone system or a hybrid PET/MRI.

  9. Ultra-high vacuum compatible induction-heated rod casting furnace

    NASA Astrophysics Data System (ADS)

    Bauer, A.; Neubauer, A.; Münzer, W.; Regnat, A.; Benka, G.; Meven, M.; Pedersen, B.; Pfleiderer, C.

    2016-06-01

    We report the design of a radio-frequency induction-heated rod casting furnace that permits the preparation of polycrystalline ingots of intermetallic compounds under ultra-high vacuum compatible conditions. The central part of the system is a bespoke water-cooled Hukin crucible supporting a casting mold. Depending on the choice of the mold, typical rods have a diameter between 6 mm and 10 mm and a length up to 90 mm, suitable for single-crystal growth by means of float-zoning. The setup is all-metal sealed and may be baked out. We find that the resulting ultra-high vacuum represents an important precondition for processing compounds with high vapor pressures under a high-purity argon atmosphere up to 3 bars. Using the rod casting furnace, we succeeded to prepare large high-quality single crystals of two half-Heusler compounds, namely, the itinerant antiferromagnet CuMnSb and the half-metallic ferromagnet NiMnSb.

  10. Ultra-high vacuum compatible induction-heated rod casting furnace.

    PubMed

    Bauer, A; Neubauer, A; Münzer, W; Regnat, A; Benka, G; Meven, M; Pedersen, B; Pfleiderer, C

    2016-06-01

    We report the design of a radio-frequency induction-heated rod casting furnace that permits the preparation of polycrystalline ingots of intermetallic compounds under ultra-high vacuum compatible conditions. The central part of the system is a bespoke water-cooled Hukin crucible supporting a casting mold. Depending on the choice of the mold, typical rods have a diameter between 6 mm and 10 mm and a length up to 90 mm, suitable for single-crystal growth by means of float-zoning. The setup is all-metal sealed and may be baked out. We find that the resulting ultra-high vacuum represents an important precondition for processing compounds with high vapor pressures under a high-purity argon atmosphere up to 3 bars. Using the rod casting furnace, we succeeded to prepare large high-quality single crystals of two half-Heusler compounds, namely, the itinerant antiferromagnet CuMnSb and the half-metallic ferromagnet NiMnSb.

  11. Evaluation of preprocessing steps to compensate for magnetic field distortions due to body movements in BOLD fMRI

    PubMed Central

    Barry, Robert L.; Williams, Joy M.; Klassen, L. Martyn; Gallivan, Jason P.; Culham, Jody C.

    2009-01-01

    Blood-oxygenation-level-dependent (BOLD) functional magnetic resonance imaging (fMRI) is currently the dominant technique for non-invasive investigation of brain functions. One of the challenges with BOLD fMRI, particularly at high fields, is compensation for the effects of spatiotemporally varying magnetic field inhomogeneities (ΔB0) caused by normal subject respiration, and in some studies, movement of the subject during the scan to perform tasks related to the functional paradigm. The presence of ΔB0 during data acquisition distorts reconstructed images and introduces extraneous fluctuations in the fMRI time series that decrease the BOLD contrast-to-noise ratio. Optimization of the fMRI data-processing pipeline to compensate for geometric distortions is of paramount importance to ensure high quality of fMRI data. To investigate ΔB0 caused by subject movement, echo-planar imaging scans were collected with and without concurrent motion of a phantom arm. The phantom arm was constructed and moved by the experimenter to emulate forearm motions while subjects remained still and observed a visual stimulation paradigm. These data were then subjected to eight different combinations of preprocessing steps. The best preprocessing pipeline included navigator correction, a complex phase regressor, and spatial smoothing. The synergy between navigator correction and phase regression reduced geometric distortions better than either step in isolation, and preconditioned the data to make them more amenable to the benefits of spatial smoothing. The combination of these steps provided a 10% increase in t-statistics compared to only navigator correction and spatial smoothing, and reduced the noise and false activations in regions where no legitimate effects would occur. PMID:19695810

  12. Novel planar field emission of ultra-thin individual carbon nanotubes.

    PubMed

    Song, Xuefeng; Gao, Jingyun; Fu, Qiang; Xu, Jun; Zhao, Qing; Yu, Dapeng

    2009-10-07

    In this work, we proposed and realized a new prototype of planar field emission device based on as-grown individual carbon nanotubes (CNTs) on the surface of a Si-SiO2 substrate. The anode, cathode and the CNT tip all lie on the same surface, so the electron emission is reduced from three-dimensional to two-dimensional. The benefits of such a design include usage of thinner CNT emitters, integrity with planar technology, stable construction, better heat dissipation, etc. A tip-to-tip field emission device was presented besides the tip-to-electrode one. Real-time, in situ observation of the planar field emission was realized in a scanning electron microscope (SEM). Measurements showed that the minimum voltage for 10 nA field emission current was only 8.0 V and the maximum emission current density in an individual CNT emitter (1.0 nm in diameter) exceeded 5.7 x 10(8) A cm(-2). These results stand out in the comparison with recent works on individual CNT field emission, indicating that the planar devices based on ultra-thin individual CNTs are more competitive candidates for next-generation electron field emitters.

  13. Preliminary experience with 4K ultra-high definition endoscope: analysis of pros and cons in skull base surgery.

    PubMed

    Rigante, M; La Rocca, G; Lauretti, L; D'Alessandris, G Q; Mangiola, A; Anile, C; Olivi, A; Paludetti, G

    2017-06-01

    During the last two decades endoscopic skull base surgery observed a continuous technical and technological development 3D endoscopy and ultra High Definition (HD) endoscopy have provided great advances in terms of visualisation and spatial resolution. Ultra-high definition (UHD) 4K systems, recently introduced in the clinical practice, will shape next steps forward especially in skull base surgery field. Patients were operated on through transnasal transsphenoidal endoscopic approaches performed using Olympus NBI 4K UHD endoscope with a 4 mm 0° Ultra Telescope, 300 W xenon lamp (CLV-S400) predisposed for narrow band imaging (NBI) technology connected through a camera head to a high-quality control unit (OTV-S400 - VISERA 4K UHD) (Olympus Corporation, Tokyo, Japan). Two screens are used, one 31" Monitor - (LMD-X310S) and one main ultra-HD 55" screen optimised for UHD image reproduction (LMD-X550S). In selected cases, we used a navigation system (Stealthstation S7, Medtronic, Minneapolis, MN, US). We evaluated 22 pituitary adenomas (86.3% macroadenomas; 13.7% microadenomas). 50% were not functional (NF), 22.8% GH, 18.2% ACTH, 9% PRL-secreting. Three of 22 were recurrences. In 91% of cases we achieved total removal, while in 9% near total resection. A mean follow-up of 187 days and average length of hospitalisation was 3.09 ± 0.61 days. Surgical duration was 128.18± 30.74 minutes. We experienced only 1 case of intraoperative low flow fistula with no further complications. None of the cases required any post- or intraoperative blood transfusion. The visualisation and high resolution of the operative field provided a very detailed view of all anatomical structures and pathologies allowing an improvement in safety and efficacy of the surgical procedure. The operative time was similar to the standard 2D HD and 3D procedures and the physical strain was also comparable to others in terms of ergonomics and weight. © Copyright by Società Italiana di Otorinolaringologia

  14. Advances in indirect detector systems for ultra high-speed hard X-ray imaging with synchrotron light

    NASA Astrophysics Data System (ADS)

    Olbinado, M. P.; Grenzer, J.; Pradel, P.; De Resseguier, T.; Vagovic, P.; Zdora, M.-C.; Guzenko, V. A.; David, C.; Rack, A.

    2018-04-01

    We report on indirect X-ray detector systems for various full-field, ultra high-speed X-ray imaging methodologies, such as X-ray phase-contrast radiography, diffraction topography, grating interferometry and speckle-based imaging performed at the hard X-ray imaging beamline ID19 of the European Synchrotron—ESRF. Our work highlights the versatility of indirect X-ray detectors to multiple goals such as single synchrotron pulse isolation, multiple-frame recording up to millions frames per second, high efficiency, and high spatial resolution. Besides the technical advancements, potential applications are briefly introduced and discussed.

  15. Search for Ultra-High Energy Photons with the Pierre Auger Observatory

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Homola, Piotr

    One of key scientific objectives of the Pierre Auger Observatory is the search for ultra-high energy photons. Such photons could originate either in the interactions of energetic cosmic-ray nuclei with the cosmic microwave background (so-called cosmogenic photons) or in the exotic scenarios, e.g. those assuming a production and decay of some hypothetical super-massive particles. The latter category of models would imply relatively large fluxes of photons with ultra-high energies at Earth, while the former, involving interactions of cosmic-ray nuclei with the microwave background - just the contrary: very small fractions. The investigations on the data collected so far in themore » Pierre Auger Observatory led to placing very stringent limits to ultra-high energy photon fluxes: below the predictions of the most of the exotic models and nearing the predicted fluxes of the cosmogenic photons. In this paper the status of these investigations and perspectives for further studies are summarized.« less

  16. Numerical investigations of MRI RF field induced heating for external fixation devices

    PubMed Central

    2013-01-01

    Background The magnetic resonance imaging (MRI) radio frequency (RF) field induced heating on external fixation devices can be very high in the vicinity of device screws. Such induced RF heating is related to device constructs, device placements, as well as the device insertion depth into human subjects. In this study, computational modeling is performed to determine factors associated with such induced heating. Methods Numerical modeling, based on the finite-difference time-domain (FDTD) method, is used to evaluate the temperature rises near external device screw tips inside the ASTM phantom for both 1.5-T and 3-T MRI systems. The modeling approach consists of 1) the development of RF coils for 1.5-T and 3-T, 2) the electromagnetic simulations of energy deposition near the screw tips of external fixation devices, and 3) the thermal simulations of temperature rises near the tips of these devices. Results It is found that changing insertion depth and screw spacing could largely affect the heating of these devices. In 1.5-T MRI system, smaller insertion depth and larger pin spacing will lead to higher temperature rise. However, for 3-T MRI system, the relation is not very clear when insertion depth is larger than 5 cm or when pin spacing became larger than 20 cm. The effect of connection bar material on device heating is also studied and the heating mechanism of the device is analysed. Conclusions Numerical simulation is used to study RF heating for external fixation devices in both 1.5-T and 3-T MRI coils. Typically, shallower insertion depth and larger pin spacing with conductive bar lead to higher RF heating. The heating mechanism is explained using induced current along the device and power decay inside ASTM phantom. PMID:23394173

  17. The MUSE Hubble Ultra Deep Field Survey. VIII. Extended Lyman-α haloes around high-z star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Leclercq, Floriane; Bacon, Roland; Wisotzki, Lutz; Mitchell, Peter; Garel, Thibault; Verhamme, Anne; Blaizot, Jérémy; Hashimoto, Takuya; Herenz, Edmund Christian; Conseil, Simon; Cantalupo, Sebastiano; Inami, Hanae; Contini, Thierry; Richard, Johan; Maseda, Michael; Schaye, Joop; Marino, Raffaella Anna; Akhlaghi, Mohammad; Brinchmann, Jarle; Carollo, Marcella

    2017-11-01

    We report the detection of extended Lyα haloes around 145 individual star-forming galaxies at redshifts 3 ≤ z ≤ 6 in the Hubble Ultra Deep Field observed with the Multi-Unit Spectroscopic Explorer (MUSE) at ESO-VLT. Our sample consists of continuum-faint (- 15 ≥ MUV ≥ -22) Lyα emitters (LAEs). Using a 2D, two-component (continuum-like and halo) decomposition of Lyα emission assuming circular exponential distributions, we measure scale lengths and luminosities of Lyα haloes. We find that 80% of our objects having reliable Lyα halo measurements show Lyα emission that is significantly more extended than the UV continuum detected by HST (by a factor ≈4 to >20). The median exponential scale length of the Lyα haloes in our sample is ≈4.5 kpc with a few haloes exceeding 10 kpc. By comparing the maximal detected extent of the Lyα emission with the predicted dark matter halo virial radii of simulated galaxies, we show that the detected Lyα emission of our selected sample of Lyα emitters probes a significant portion of the cold circum-galactic medium of these galaxies (>50% in average). This result therefore shows that there must be significant HI reservoirs in the circum-galactic medium and reinforces the idea that Lyα haloes are ubiquitous around high-redshift Lyα emitting galaxies. Our characterization of the Lyα haloes indicates that the majority of the Lyα flux comes from the halo (≈65%) and that their scale lengths seem to be linked to the UV properties of the galaxies (sizes and magnitudes). We do not observe a significant Lyα halo size evolution with redshift, although our sample for z> 5 is very small. We also explore the diversity of the Lyα line profiles in our sample and we find that the Lyα lines cover a large range of full width at half maximum (FWHM) from 118 to 512 km s-1. While the FWHM does not seem to be correlated to the Lyα scale length, most compact Lyα haloes and those that are not detected with high significance tend

  18. Tests of a Prototype for Assessing the Field Homogeneity of the Iseult/Inumac 11.7T Whole Body MRI Magnet

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Quettier, Lionel

    A neuroscience research center with very high field MRI equipments has been opened in November 2006 by the CEA life science division. One of the imaging systems will require a 11.75 T magnet with a 900 mm warm bore, the so-call Iseult/Inumac magnet. Regarding the large aperture and field strength, this magnet is a challenge as compared to the largest MRI systems ever built, and is then developed within an ambitious R&D program. With the objective of demonstrating the possibility of achieving field homogeneity better than 1 ppm using double pancake windings, a 24 double pancakes model coil, working atmore » 1.5 T has been designed. This model magnet has been manufactured by Alstom MSA and tested at CEA. It has been measured with a very high precision, in order to fully characterize the field homogeneity, and then to investigate and discriminate the parameters that influence the field map. This magnet has reached the bare magnet field homogeneity specification expected for Iseult and thus successfully demonstrated the feasibility of building a homogenous magnet with the double pancake winding technique.« less

  19. High spatial resolution compressed sensing (HSPARSE) functional MRI.

    PubMed

    Fang, Zhongnan; Van Le, Nguyen; Choy, ManKin; Lee, Jin Hyung

    2016-08-01

    To propose a novel compressed sensing (CS) high spatial resolution functional MRI (fMRI) method and demonstrate the advantages and limitations of using CS for high spatial resolution fMRI. A randomly undersampled variable density spiral trajectory enabling an acceleration factor of 5.3 was designed with a balanced steady state free precession sequence to achieve high spatial resolution data acquisition. A modified k-t SPARSE method was then implemented and applied with a strategy to optimize regularization parameters for consistent, high quality CS reconstruction. The proposed method improves spatial resolution by six-fold with 12 to 47% contrast-to-noise ratio (CNR), 33 to 117% F-value improvement and maintains the same temporal resolution. It also achieves high sensitivity of 69 to 99% compared the original ground-truth, small false positive rate of less than 0.05 and low hemodynamic response function distortion across a wide range of CNRs. The proposed method is robust to physiological noise and enables detection of layer-specific activities in vivo, which cannot be resolved using the highest spatial resolution Nyquist acquisition. The proposed method enables high spatial resolution fMRI that can resolve layer-specific brain activity and demonstrates the significant improvement that CS can bring to high spatial resolution fMRI. Magn Reson Med 76:440-455, 2016. © 2015 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made. © 2015 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine.

  20. Large-Scale, High-Resolution Neurophysiological Maps Underlying fMRI of Macaque Temporal Lobe

    PubMed Central

    Papanastassiou, Alex M.; DiCarlo, James J.

    2013-01-01

    Maps obtained by functional magnetic resonance imaging (fMRI) are thought to reflect the underlying spatial layout of neural activity. However, previous studies have not been able to directly compare fMRI maps to high-resolution neurophysiological maps, particularly in higher level visual areas. Here, we used a novel stereo microfocal x-ray system to localize thousands of neural recordings across monkey inferior temporal cortex (IT), construct large-scale maps of neuronal object selectivity at subvoxel resolution, and compare those neurophysiology maps with fMRI maps from the same subjects. While neurophysiology maps contained reliable structure at the sub-millimeter scale, fMRI maps of object selectivity contained information at larger scales (>2.5 mm) and were only partly correlated with raw neurophysiology maps collected in the same subjects. However, spatial smoothing of neurophysiology maps more than doubled that correlation, while a variety of alternative transforms led to no significant improvement. Furthermore, raw spiking signals, once spatially smoothed, were as predictive of fMRI maps as local field potential signals. Thus, fMRI of the inferior temporal lobe reflects a spatially low-passed version of neurophysiology signals. These findings strongly validate the widespread use of fMRI for detecting large (>2.5 mm) neuronal domains of object selectivity but show that a complete understanding of even the most pure domains (e.g., faces vs nonface objects) requires investigation at fine scales that can currently only be obtained with invasive neurophysiological methods. PMID:24048850

  1. Manganese oxide micro-supercapacitors with ultra-high areal capacitance

    NASA Astrophysics Data System (ADS)

    Wang, Xu; Myers, Benjamin D.; Yan, Jian; Shekhawat, Gajendra; Dravid, Vinayak; Lee, Pooi See

    2013-05-01

    A symmetric micro-supercapacitor is constructed by electrochemically depositing manganese oxide onto micro-patterned current collectors. High surface-to-volume ratio of manganese oxide and short diffusion distance between electrodes give an ultra-high areal capacitance of 56.3 mF cm-2 at a current density of 27.2 μA cm-2.A symmetric micro-supercapacitor is constructed by electrochemically depositing manganese oxide onto micro-patterned current collectors. High surface-to-volume ratio of manganese oxide and short diffusion distance between electrodes give an ultra-high areal capacitance of 56.3 mF cm-2 at a current density of 27.2 μA cm-2. Electronic supplementary information (ESI) available: Experimental procedures; optical images of micro-supercapacitors; areal capacitances of samples M-0.3C, M-0.6C and M-0.9C; illustration of interdigital finger electrodes; Nyquist plot of Co(OH)2 deposited on micro-electrodes. See DOI: 10.1039/c3nr00210a

  2. SQUIDs vs. Faraday coils for ultlra-low field nuclear magnetic resonance: experimental and simulation comparison

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Matlashov, Andrei N; Espy, Michelle A; Kraus, Robert H

    2010-01-01

    Nuclear magnetic resonance (NMR) methods are widely used in medicine, chemistry and industry. One application area is magnetic resonance imaging or MRI. Recently it has become possible to perform NMR and MRI in ultra-low field (ULF) regime that requires measurement field strengths only of the order of 1 Gauss. These techniques exploit the advantages offered by superconducting quantum interference devices or SQUIDs. Our group at LANL has built SQUID based MRI systems for brain imaging and for liquid explosives detection at airports security checkpoints. The requirement for liquid helium cooling limits potential applications of ULF MRI for liquid identification andmore » security purposes. Our experimental comparative investigation shows that room temperature inductive magnetometers provide enough sensitivity in the 3-10 kHz range and can be used for fast liquid explosives detection based on ULF NMR/MRI technique. We describe an experimental and computer simulation comparison of the world's first multichannel SQUID based and Faraday coils based instruments that are capable of performing ULF MRI for liquids identification.« less

  3. Further demonstration of the VRLA-type UltraBattery under medium-HEV duty and development of the flooded-type UltraBattery for micro-HEV applications

    NASA Astrophysics Data System (ADS)

    Furukawa, J.; Takada, T.; Monma, D.; Lam, L. T.

    The UltraBattery has been invented by the CSIRO Energy Technology in Australia and has been developed and produced by the Furukawa Battery Co., Ltd., Japan. This battery is a hybrid energy storage device which combines a super capacitor and a lead-acid battery in single unit cells, taking the best from both technologies without the need of extra, expensive electronic controls. The capacitor enhances the power and lifespan of the lead-acid battery as it acts as a buffer during high-rate discharging and charging, thus enabling it to provide and absorb charge rapidly during vehicle acceleration and braking. The laboratory results of the prototype valve-regulated UltraBatteries show that the capacity, power, available energy, cold cranking and self-discharge of these batteries have met, or exceeded, all the respective performance targets set for both minimum and maximum power-assist HEVs. The cycling performance of the UltraBatteries under micro-, mild- and full-HEV duties is at least four times longer than that of the state-of-the-art lead-acid batteries. Importantly, the cycling performance of UltraBatteries is proven to be comparable or even better than that of the Ni-MH cells. On the other hand, the field trial of UltraBatteries in the Honda Insight HEV shows that the vehicle has surpassed 170,000 km and the batteries are still in a healthy condition. Furthermore, the UltraBatteries demonstrate very good acceptance of the charge from regenerative braking even at high state-of-charge, e.g., 70% during driving. Therefore, no equalization charge is required for the UltraBatteries during field trial. The HEV powered by UltraBatteries gives slightly higher fuel consumption (cf., 4.16 with 4.05 L/100 km) and CO 2 emissions (cf., 98.8 with 96 g km -1) compared with that by Ni-MH cells. There are no differences in driving experience between the Honda Insight powered by UltraBatteries and by Ni-MH cells. Given such comparable performance, the UltraBattery pack costs

  4. Ultra-wideband high-efficiency reflective linear-to-circular polarization converter based on metasurface at terahertz frequencies.

    PubMed

    Jiang, Yannan; Wang, Lei; Wang, Jiao; Akwuruoha, Charles Nwakanma; Cao, Weiping

    2017-10-30

    The polarization conversion of electromagnetic (EM) waves, especially linear-to-circular (LTC) polarization conversion, is of great significance in practical applications. In this study, we propose an ultra-wideband high-efficiency reflective LTC polarization converter based on a metasurface in the terahertz regime. It consists of periodic unit cells, each cell of which is formed by a double split resonant square ring, dielectric layer, and fully reflective gold mirror. In the frequency range of 0.60 - 1.41 THz, the magnitudes of the reflection coefficients reach approximately 0.7, and the phase difference between the two orthogonal electric field components of the reflected wave is close to 90° or -270°. The results indicate that the relative bandwidth reaches 80% and the efficiency is greater than 88%, thus, ultra-wideband high-efficiency LTC polarization conversion has been realized. Finally, the physical mechanism of the polarization conversion is revealed. This converter has potential applications in antenna design, EM measurement, and stealth technology.

  5. Sodium MRI: Methods and applications

    PubMed Central

    Madelin, Guillaume; Lee, Jae-Seung; Regatte, Ravinder R.; Jerschow, Alexej

    2014-01-01

    Sodium NMR spectroscopy and MRI have become popular in recent years through the increased availability of high-field MRI scanners, advanced scanner hardware and improved methodology. Sodium MRI is being evaluated for stroke and tumor detection, for breast cancer studies, and for the assessment of osteoarthritis and muscle and kidney functions, to name just a few. In this article, we aim to present an up-to-date review of the theoretical background, the methodology, the challenges and limitations, and current and potential new applications of sodium MRI. PMID:24815363

  6. New-type steel plate with ultra high crack-arrestability

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ishikawa, T.; Nomiyama, Y.; Hagiwara, Y.

    1995-12-31

    A new-type steel plate has been developed by controlling the microstructure of the surface layers. The surface layer consists of ultra fine grain ferrite microstructure, which provides excellent fracture toughness even at cryogenic temperature. When an unstable brittle crack propagates in the developed steel plate, shear-lips can be easily formed due to the surface layers with ultra fine grain microstructure. Since unstable running crack behavior is strongly affected by side-ligaments (shear-lips), which are associated with extensive plastic deformation, enhanced formation of the shear-lips can improve crack arrestability. This paper describes the developed steel plates of HT500MPa tensile strength class formore » shipbuilding use. Fracture mechanics investigations using large-scale fracture testings (including ultrawide duplex ESSO tests) clarified that the developed steel plates have ultra high crack-arrestability. It was also confirmed that the plates possess sufficient properties, including weldability and workability, for ship building use.« less

  7. Application of ultra-high performance concrete to bridge girders.

    DOT National Transportation Integrated Search

    2009-02-01

    "Ultra-High Performance Concrete (UHPC) is a new class of concrete that has superior performance characteristics : compared to conventional concrete. The enhanced strength and durability properties of UHPC are mainly due to optimized : particle grada...

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

    NASA Astrophysics Data System (ADS)

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

    2018-03-01

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

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

    PubMed

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

    2018-03-01

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

  10. Study on creep of fiber reinforced ultra-high strength concrete based on strength

    NASA Astrophysics Data System (ADS)

    Peng, Wenjun; Wang, Tao

    2018-04-01

    To complement the creep performance of ultra-high strength concrete, the long creep process of fiber reinforced concrete was studied in this paper. The long-term creep process and regularity of ultra-high strength concrete with 0.5% PVA fiber under the same axial compression were analyzed by using concrete strength (C80/C100/C120) as a variable. The results show that the creep coefficient of ultra-high strength concrete decreases with the increase of concrete strength. Compared with ACI209R (92), GL2000 models, it is found that the predicted value of ACI209R (92) are close to the experimental value, and the creep prediction model suitable for this experiment is proposed based on ACI209R (92).

  11. Detailed T1-Weighted Profiles from the Human Cortex Measured in Vivo at 3 Tesla MRI.

    PubMed

    Ferguson, Bart; Petridou, Natalia; Fracasso, Alessio; van den Heuvel, Martijn P; Brouwer, Rachel M; Hulshoff Pol, Hilleke E; Kahn, René S; Mandl, René C W

    2018-04-01

    Studies into cortical thickness in psychiatric diseases based on T1-weighted MRI frequently report on aberrations in the cerebral cortex. Due to limitations in image resolution for studies conducted at conventional MRI field strengths (e.g. 3 Tesla (T)) this information cannot be used to establish which of the cortical layers may be implicated. Here we propose a new analysis method that computes one high-resolution average cortical profile per brain region extracting myeloarchitectural information from T1-weighted MRI scans that are routinely acquired at a conventional field strength. To assess this new method, we acquired standard T1-weighted scans at 3 T and compared them with state-of-the-art ultra-high resolution T1-weighted scans optimised for intracortical myelin contrast acquired at 7 T. Average cortical profiles were computed for seven different brain regions. Besides a qualitative comparison between the 3 T scans, 7 T scans, and results from literature, we tested if the results from dynamic time warping-based clustering are similar for the cortical profiles computed from 7 T and 3 T data. In addition, we quantitatively compared cortical profiles computed for V1, V2 and V7 for both 7 T and 3 T data using a priori information on their relative myelin concentration. Although qualitative comparisons show that at an individual level average profiles computed for 7 T have more pronounced features than 3 T profiles the results from the quantitative analyses suggest that average cortical profiles computed from T1-weighted scans acquired at 3 T indeed contain myeloarchitectural information similar to profiles computed from the scans acquired at 7 T. The proposed method therefore provides a step forward to study cortical myeloarchitecture in vivo at conventional magnetic field strength both in health and disease.

  12. Advances in Ultra High Temperature Ceramics for Hot Structures

    NASA Astrophysics Data System (ADS)

    Scatteia, Luigi; Monteverde, Federico; Alfano, Davide; Cantoni, Stefania

    The objective of this paper is to describe the current state of the art of the research on Ultra High Temperature Ceramic materials with particular reference to their space applications, and also to report on the activities performed on UHTC in the past decade by the Italian Aerospace Research Centre in the specific technological field of structural thermal protection systems. Within several internal research project, various UHTC composition, mainly based upon Zirconium Diboride and Hafnium Diboride with added secondary phases and sintering aid were examined characterized in their mechanical properties and oxidation resistance. Two main composition were selected as the most promising for hot structure manufacturing: these materials were extensively characterized in order to obtain a comprehensive database of properties to feed the thermomechanical design of prototype hot structures. Technological demonstrators were manufactured by hot pressing followed by further fine machining with Electrical Discharge methods, and then tested at high temperature for long times in a plasma torch facility. The main outstanding results obtained are discussed in this paper. Future outlooks related to the UHTC technology and its further development are also provided.

  13. Restoration of MRI data for intensity non-uniformities using local high order intensity statistics

    PubMed Central

    Hadjidemetriou, Stathis; Studholme, Colin; Mueller, Susanne; Weiner, Michael; Schuff, Norbert

    2008-01-01

    MRI at high magnetic fields (>3.0 T) is complicated by strong inhomogeneous radio-frequency fields, sometimes termed the “bias field”. These lead to non-biological intensity non-uniformities across the image. They can complicate further image analysis such as registration and tissue segmentation. Existing methods for intensity uniformity restoration have been optimized for 1.5 T, but they are less effective for 3.0 T MRI, and not at all satisfactory for higher fields. Also, many of the existing restoration algorithms require a brain template or use a prior atlas, which can restrict their practicalities. In this study an effective intensity uniformity restoration algorithm has been developed based on non-parametric statistics of high order local intensity co-occurrences. These statistics are restored with a non-stationary Wiener filter. The algorithm also assumes a smooth non-uniformity and is stable. It does not require a prior atlas and is robust to variations in anatomy. In geriatric brain imaging it is robust to variations such as enlarged ventricles and low contrast to noise ratio. The co-occurrence statistics improve robustness to whole head images with pronounced non-uniformities present in high field acquisitions. Its significantly improved performance and lower time requirements have been demonstrated by comparing it to the very commonly used N3 algorithm on BrainWeb MR simulator images as well as on real 4 T human head images. PMID:18621568

  14. Ultra high vacuum test setup for electron gun

    NASA Astrophysics Data System (ADS)

    Pandiyar, M. L.; Prasad, M.; Jain, S. K.; Kumar, R.; Hannurkar, P. R.

    2008-05-01

    Ultra High Vacuum (UHV) test setup for electron gun testing has been developed. The development of next generation light sources and accelerators require development of klystron as a radio frequency power source, and in turn electron gun. This UHV electron gun test setup can be used to test the electron guns ranging from high average current, quasi-continuous wave to high peak current, single pulse etc. An electron gun has been designed, fabricated, assembled and tested for insulation up to 80 kV under the programme to develop high power klystron for future accelerators. Further testing includes the electron emission parameters characterization of the cathode, as it determines the development of a reliable and efficient electron gun with high electron emission current and high life time as well. This needs a clean ultra high vacuum to study these parameters particularly at high emission current. The cathode emission current, work function and vapour pressure of cathode surface material at high temperature studies will further help in design and development of high power electron gun The UHV electron gun test setup consists of Turbo Molecular Pump (TMP), Sputter Ion Pump (SIP), pressure gauge, high voltage and cathode power supplies, current measurement device, solenoid magnet and its power supply, residual gas analyser etc. The ultimate vacuum less than 2×10-9 mbar was achieved. This paper describes the UHV test setup for electron gun testing.

  15. Bond behavior of reinforcing steel in ultra-high performance concrete.

    DOT National Transportation Integrated Search

    2014-10-01

    Ultra-High Performance Concrete (UHPC) is a relatively new class of advanced cementitious composite : materials, which exhibits high compressive [above 21.7 ksi (150 MPa)] and tensile [above 0.72 ksi (5 MPa)] : strengths. The discrete steel fiber rei...

  16. Brain structure in people at ultra-high risk of psychosis, patients with first-episode schizophrenia, and healthy controls: a VBM study.

    PubMed

    Nenadic, Igor; Dietzek, Maren; Schönfeld, Nils; Lorenz, Carsten; Gussew, Alexander; Reichenbach, Jürgen R; Sauer, Heinrich; Gaser, Christian; Smesny, Stefan

    2015-02-01

    Early intervention research in schizophrenia has suggested that brain structural alterations might be present in subjects at high risk of developing psychosis. The heterogeneity of regional effects of these changes, which is established in schizophrenia, however, has not been explored in prodromal or high-risk populations. We used high-resolution MRI and voxel-based morphometry (VBM8) to analyze grey matter differences in 43 ultra high-risk subjects for psychosis (meeting ARMS criteria, identified through CAARMS interviews), 24 antipsychotic-naïve first-episode schizophrenia patients and 49 healthy controls (groups matched for age and gender). Compared to healthy controls, resp., first-episode schizophrenia patients had reduced regional grey matter in left prefrontal, insula, right parietal and left temporal cortices, while the high-risk group showed reductions in right middle temporal and left anterior frontal cortices. When dividing the ultra-high-risk group in those with a genetic risk vs. those with attenuated psychotic symptoms, the former showed left anterior frontal, right caudate, as well as a smaller right hippocampus, and amygdala reduction, while the latter subgroup showed right middle temporal cortical reductions (each compared to healthy controls). Our findings in a clinical psychosis high-risk cohort demonstrate variability of brain structural changes according to subgroup and background of elevated risk, suggesting frontal and possibly also hippocampal/amygdala changes in individuals with genetic susceptibility. Heterogeneity of structural brain changes (as seen in schizophrenia) appears evident even at high-risk stage, prior to potential onset of psychosis. Copyright © 2014 Elsevier B.V. All rights reserved.

  17. Thermal ablation system using high intensity focused ultrasound (HIFU) and guided by MRI

    NASA Astrophysics Data System (ADS)

    Damianou, C.; Ioannides, K.; HadjiSavas, V.; Milonas, N.; Couppis, A.; Iosif, D.; Komodromos, M.; Vrionides, F.

    2009-04-01

    In this paper magnetic resonance imaging (MRI) is investigated for monitoring lesions created by high intensity focused ultrasound (HIFU) in kidney, liver and brain in vitro and in vivo. Spherically focused transducers of 4 cm diameter, focusing at 10 cm and operating at 1 and 4 MHz were used. An MRI compatible positioning device was developed in order to scan the HIFU transducer. The MRI compatibility of the system was successfully demonstrated in a clinical high-field MRI scanner. The ability of the positioning device to accurately move the transducer thus creating discrete and overlapping lesions in biological tissue was tested successfully. A simple, cost effective, portable positioning device has been developed which can be used in virtually any clinical MRI scanner since it can be sited on the scanner's table. The propagation of HIFU can use either a lateral or superior-inferior approach. Both T1-w FSE and T2-w FSE imaged successfully lesions in kidney and liver. T1-w FSE and T2-w FSE and FLAIR shows better anatomical details in brain than T1-w FSE, but with T1-w FSE the contrast between lesion and brain is higher for both thermal and bubbly lesion. With this system we were able to create large lesions (by producing overlapping lesions). The length of the lesions in vivo brain was much higher than the length in vitro, proving that the penetration in the in vitro brain is limited by reflection due to trapped bubbles in the blood vessels.

  18. Assessment of the metrological performance of an in situ storage image sensor ultra-high speed camera for full-field deformation measurements

    NASA Astrophysics Data System (ADS)

    Rossi, Marco; Pierron, Fabrice; Forquin, Pascal

    2014-02-01

    Ultra-high speed (UHS) cameras allow us to acquire images typically up to about 1 million frames s-1 for a full spatial resolution of the order of 1 Mpixel. Different technologies are available nowadays to achieve these performances, an interesting one is the so-called in situ storage image sensor architecture where the image storage is incorporated into the sensor chip. Such an architecture is all solid state and does not contain movable devices as occurs, for instance, in the rotating mirror UHS cameras. One of the disadvantages of this system is the low fill factor (around 76% in the vertical direction and 14% in the horizontal direction) since most of the space in the sensor is occupied by memory. This peculiarity introduces a series of systematic errors when the camera is used to perform full-field strain measurements. The aim of this paper is to develop an experimental procedure to thoroughly characterize the performance of such kinds of cameras in full-field deformation measurement and identify the best operative conditions which minimize the measurement errors. A series of tests was performed on a Shimadzu HPV-1 UHS camera first using uniform scenes and then grids under rigid movements. The grid method was used as full-field measurement optical technique here. From these tests, it has been possible to appropriately identify the camera behaviour and utilize this information to improve actual measurements.

  19. Rats avoid high magnetic fields: dependence on an intact vestibular system

    PubMed Central

    Houpt, Thomas A.; Cassell, Jennifer A.; Riccardi, Christina; DenBleyker, Megan D.; Hood, Alison; Smith, James C.

    2009-01-01

    Summary HOUPT, T.A., J.A. CASSELL, C. RICCARDI, M.D. DENBLEYKER, A. HOOD, AND J.C. SMITH. Rats avoid high magnetic fields: dependence on an intact vestibular system. PHYSIOL BEHAV 00(0)000-000, 2006. High strength static magnetic fields are thought to be benign and largely undetectable by mammals. As magnetic resonance imaging (MRI) machines increase in strength, however, potential aversive effects may become clinically relevant. Here we report that rats find entry into a 14.1 T magnet aversive, and that they can detect and avoid entry into the magnet at a point where the magnetic field is 2 T or lower. Rats were trained to climb a ladder through the bore of a 14.1 T superconducting magnet. After their first climb into 14.1 T, most rats refused to re-enter the magnet or climb past the 2 T field line. This result was confirmed in a resistive magnet in which the magnetic field was varied from 1 to 14 T. Detection and avoidance required the vestibular apparatus of the inner ear, because labyrinthectomized rats readily traversed the magnet. The inner ear is a novel site for magnetic field transduction in mammals, but perturbation of the vestibular apparatus would be consistent with human reports of vertigo and nausea around high strength MRI machines. PMID:17585969

  20. Local and global thermoregulatory responses to MRI electromagnetic fields: Biological effects and safety aspects of nuclear magnetic resonance imaging and spectroscopy

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Gordon, C.J.

    1991-01-01

    During magnetic resonance imaging (MRI) procedures, a subject is exposed to three novel environmental stimuli which have drawn attention over the past decade as potential health hazards: (1) a relatively intense static magnetic field; (2) a time-varying magnetic field, and (3) a radiofrequency (RF) field. Thermoregulation is one of many physiological systems that can be affected by MRI, specifically by the RF radiation absorbed by the subject during MRI. While there is some sparse, albeit controversial data on the possible effects of static magnetic fields on thermoregulation, the major concern regarding potential health hazards of the MRI-induced thermal effects centersmore » on the RF radiation absorbed by a subject during a scan. The purpose of the paper is to review the studies that have impacted on understanding the thermoregulatory effects of MRI with special emphasis on the problems of selecting appropriate animal models for assessing the potential risk of RF radiation exposure during MRI.« less

  1. Ultra-high sensitivity Fabry-Perot interferometer gas refractive index fiber sensor based on photonic crystal fiber and Vernier effect.

    PubMed

    Quan, Mingran; Tian, Jiajun; Yao, Yong

    2015-11-01

    An ultra-high sensitivity open-cavity Fabry-Perot interferometer (FPI) gas refractive index (RI) sensor based on the photonic crystal fiber (PCF) and Vernier effect is proposed and demonstrated. The sensor is prepared by splicing a section of PCF to a section of fiber tube fused with a section of single mode fiber. The air holes running along the cladding of the PCF enable the gas to enter or leave the cavity freely. The reflection beam from the last end face of the PCF is used to generate the Vernier effect, which significantly improves the sensitivity of the sensor. Experimental results show that the proposed sensor can provide an ultra-high RI sensitivity of 30899 nm/RIU. This sensor has potential applications in fields such as gas concentration analyzing and humidity monitoring.

  2. SMALLER FOOTPRINT DRILLING SYSTEM FOR DEEP AND HARD ROCK ENVIRONMENTS; FEASIBILITY OF ULTRA-HIGH SPEED DIAMOND DRILLING

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Alan Black; Arnis Judzis

    2004-10-01

    The two phase program addresses long-term developments in deep well and hard rock drilling. TerraTek believes that significant improvements in drilling deep hard rock will be obtained by applying ultra-high (greater than 10,000 rpm) rotational speeds. The work includes a feasibility of concept research effort aimed at development and test results that will ultimately result in the ability to reliably drill ''faster and deeper'' possibly with rigs having a smaller footprint to be more mobile. The principle focus is on demonstration testing of diamond bits rotating at speeds in excess of 10,000 rpm to achieve high rate of penetration rockmore » cutting with substantially lower inputs of energy and loads. The project draws on TerraTek results submitted to NASA's ''Drilling on Mars'' program. The objective of that program was to demonstrate miniaturization of a robust and mobile drilling system that expends small amounts of energy. TerraTek successfully tested ultrahigh speed ({approx}40,000 rpm) small kerf diamond coring. Adaptation to the oilfield will require innovative bit designs for full hole drilling or continuous coring and the eventual development of downhole ultra-high speed drives. For domestic operations involving hard rock and deep oil and gas plays, improvements in penetration rates is an opportunity to reduce well costs and make viable certain field developments. An estimate of North American hard rock drilling costs is in excess of $1,200 MM. Thus potential savings of $200 MM to $600 MM are possible if drilling rates are doubled [assuming bit life is reasonable]. The net result for operators is improved profit margin as well as an improved position on reserves. The significance of the ''ultra-high rotary speed drilling system'' is the ability to drill into rock at very low weights on bit and possibly lower energy levels. The drilling and coring industry today does not practice this technology. The highest rotary speed systems in oil field and mining

  3. SMALLER FOOTPRINT DRILLING SYSTEM FOR DEEP AND HARD ROCK ENVIRONMENTS; FEASIBILITY OF ULTRA-HIGH SPEED DIAMOND DRILLING

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Alan Black; Arnis Judzis

    2004-10-01

    The two phase program addresses long-term developments in deep well and hard rock drilling. TerraTek believes that significant improvements in drilling deep hard rock will be obtained by applying ultra-high (greater than 10,000 rpm) rotational speeds. The work includes a feasibility of concept research effort aimed at development and test results that will ultimately result in the ability to reliably drill ''faster and deeper'' possibly with rigs having a smaller footprint to be more mobile. The principle focus is on demonstration testing of diamond bits rotating at speeds in excess of 10,000 rpm to achieve high rate of penetration rockmore » cutting with substantially lower inputs of energy and loads. The project draws on TerraTek results submitted to NASA's ''Drilling on Mars'' program. The objective of that program was to demonstrate miniaturization of a robust and mobile drilling system that expends small amounts of energy. TerraTek successfully tested ultrahigh speed ({approx}40,000 rpm) small kerf diamond coring. Adaptation to the oilfield will require innovative bit designs for full hole drilling or continuous coring and the eventual development of downhole ultra-high speed drives. For domestic operations involving hard rock and deep oil and gas plays, improvements in penetration rates is an opportunity to reduce well costs and make viable certain field developments. An estimate of North American hard rock drilling costs is in excess of $1,200 MM. Thus potential savings of $200 MM to $600 MM are possible if drilling rates are doubled [assuming bit life is reasonable]. The net result for operators is improved profit margin as well as an improved position on reserves. The significance of the ''ultra-high rotary speed drilling system'' is the ability to drill into rock at very low weights on bit and possibly lower energy levels. The drilling and coring industry today does not practice this technology. The highest rotary speed systems in oil field and mining

  4. Impact of magnetic field strength and receiver coil in ocular MRI: a phantom and patient study.

    PubMed

    Erb-Eigner, K; Warmuth, C; Taupitz, M; Willerding, G; Bertelmann, E; Asbach, P

    2013-09-01

    Generally, high-resolution MRI of the eye is performed with small loop surface coils. The purpose of this phantom and patient study was to investigate the influence of magnetic field strength and receiver coils on image quality in ocular MRI. The eyeball and the complex geometry of the facial bone were simulated by a skull phantom with swine eyes. MR images were acquired with two small loop surface coils with diameters of 4 cm and 7 cm and with a multi-channel head coil at 1.5 and 3 Tesla, respectively. Furthermore, MRI of the eye was performed prospectively in 20 patients at 1.5 Tesla (7 cm loop surface coil) and 3 Tesla (head coil). These images were analysed qualitatively and quantitatively and statistical significance was tested using the Wilcoxon-signed-rank test (a p-value of less than 0.05 was considered to indicate statistical significance). The analysis of the phantom images yielded the highest mean signal-to-noise ratio (SNR) at 3 Tesla with the use of the 4 cm loop surface coil. In the phantom experiment as well as in the patient studies the SNR was higher at 1.5 Tesla by applying the 7 cm surface coil than at 3 Tesla by applying the head coil. Concerning the delineation of anatomic structures no statistically significant differences were found. Our results show that the influence of small loop surface coils on image quality (expressed in SNR) in ocular MRI is higher than the influence of the magnetic field strength. The similar visibility of detailed anatomy leads to the conclusion that the image quality of ocular MRI at 3 Tesla remains acceptable by applying the head coil as a receiver coil. © Georg Thieme Verlag KG Stuttgart · New York.

  5. Ultra-fast magnetic vortex core reversal by a local field pulse

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Rückriem, R.; Albrecht, M., E-mail: manfred.albrecht@physik.uni-augsburg.de; Schrefl, T.

    2014-02-03

    Magnetic vortex core reversal of a 20-nm-thick permalloy disk with a diameter of 100 nm was studied by micromagnetic simulations. By applying a global out-of-plane magnetic field pulse, it turned out that the final core polarity is very sensitive to pulse width and amplitude, which makes it hard to control. The reason for this phenomenon is the excitation of radial spin waves, which dominate the reversal process. The excitation of spin waves can be strongly suppressed by applying a local field pulse within a small area at the core center. With this approach, ultra-short reversal times of about 15 ps weremore » achieved, which are ten times faster compared to a global pulse.« less

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

    PubMed

    Krug, Johannes W; Rose, Georg; Clifford, Gari D; Oster, Julien

    2013-11-19

    In Cardiovascular Magnetic Resonance (CMR), the synchronization of image acquisition with heart motion is performed in clinical practice by processing the electrocardiogram (ECG). The ECG-based synchronization is well established for MR scanners with magnetic fields up to 3 T. However, this technique is prone to errors in ultra high field environments, e.g. in 7 T MR scanners as used in research applications. The high magnetic fields cause severe magnetohydrodynamic (MHD) effects which disturb the ECG signal. Image synchronization is thus less reliable and yields artefacts in CMR images. A strategy based on Independent Component Analysis (ICA) was pursued in this work to enhance the ECG contribution and attenuate the MHD effect. ICA was applied to 12-lead ECG signals recorded inside a 7 T MR scanner. An automatic source identification procedure was proposed to identify an independent component (IC) dominated by the ECG signal. The identified IC was then used for detecting the R-peaks. The presented ICA-based method was compared to other R-peak detection methods using 1) the raw ECG signal, 2) the raw vectorcardiogram (VCG), 3) the state-of-the-art gating technique based on the VCG, 4) an updated version of the VCG-based approach and 5) the ICA of the VCG. ECG signals from eight volunteers were recorded inside the MR scanner. Recordings with an overall length of 87 min accounting for 5457 QRS complexes were available for the analysis. The records were divided into a training and a test dataset. In terms of R-peak detection within the test dataset, the proposed ICA-based algorithm achieved a detection performance with an average sensitivity (Se) of 99.2%, a positive predictive value (+P) of 99.1%, with an average trigger delay and jitter of 5.8 ms and 5.0 ms, respectively. Long term stability of the demixing matrix was shown based on two measurements of the same subject, each being separated by one year, whereas an averaged detection performance of Se = 99.4% and +P

  7. Optimizing MRI for imaging peripheral arthritis.

    PubMed

    Hodgson, Richard J; O'Connor, Philip J; Ridgway, John P

    2012-11-01

    MRI is increasingly used for the assessment of both inflammatory arthritis and osteoarthritis. The wide variety of MRI systems in use ranges from low-field, low-cost extremity units to whole-body high-field 7-T systems, each with different strengths for specific applications. The availability of dedicated radiofrequency phased-array coils allows the rapid acquisition of high-resolution images of one or more peripheral joints. MRI is uniquely flexible in its ability to manipulate image contrast, and individual MR sequences may be combined into protocols to sensitively visualize multiple features of arthritis including synovitis, bone marrow lesions, erosions, cartilage changes, and tendinopathy. Careful choice of the imaging parameters allows images to be generated with optimal quality while minimizing unwanted artifacts. Finally, there are many novel MRI techniques that can quantify disease levels in arthritis in tissues including synovitis and cartilage. Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

  8. [Effect of vibration caused by time-varying magnetic fields on diffusion-weighted MRI].

    PubMed

    Ogura, Akio; Maeda, Fumie; Miyai, Akira; Hayashi, Kohji; Hongoh, Takaharu

    2006-04-20

    Diffusion-weighted images (DWIs) with high b-factor in the body are often used to detect and diagnose cancer at MRI. The echo planar imaging (EPI) sequence and high motion probing gradient pulse are used at diffusion weighted imaging, causing high table vibration. The purpose of this study was to assess whether the diffusion signal and apparent diffusion coefficient (ADC) values are influenced by this vibration because of time-varying magnetic fields. Two DWIs were compared. In one, phantoms were fixed on the MRI unit's table transmitting the vibration. In the other, phantoms were supported in air, in the absence of vibration. The phantoms called "solution phantoms" were made from agarose of a particular density. The phantoms called "jelly phantoms" were made from agarose that was heated. The diffusion signal and ADC value of each image were compared. The results showed that the signal of DWI units using the solution phantom was not affected by vibration. However, the signal of DWI and ADC were increased in the low-density jelly phantom as a result of vibration, causing the jelly phantom to vibrate. The DWIs of vibrating regions such as the breast maybe be subject to error. A countermeasure seems to be to support the region adequately.

  9. The active modulation of drug release by an ionic field effect transistor for an ultra-low power implantable nanofluidic system.

    PubMed

    Bruno, Giacomo; Canavese, Giancarlo; Liu, Xuewu; Filgueira, Carly S; Sacco, Adriano; Demarchi, Danilo; Ferrari, Mauro; Grattoni, Alessandro

    2016-11-10

    We report an electro-nanofluidic membrane for tunable, ultra-low power drug delivery employing an ionic field effect transistor. Therapeutic release from a drug reservoir was successfully modulated, with high energy efficiency, by actively adjusting the surface charge of slit-nanochannels 50, 110, and 160 nm in size, by the polarization of a buried gate electrode and the consequent variation of the electrical double layer in the nanochannel. We demonstrated control over the transport of ionic species, including two relevant hypertension drugs, atenolol and perindopril, that could benefit from such modulation. By leveraging concentration-driven diffusion, we achieve a 2 to 3 order of magnitude reduction in power consumption as compared to other electrokinetic phenomena. The application of a small gate potential (±5 V) in close proximity (150 nm) of 50 nm nanochannels generated a sufficiently strong electric field, which doubled or blocked the ionic flux depending on the polarity of the voltage applied. These compelling findings can lead to next generation, more reliable, smaller, and longer lasting drug delivery implants with ultra-low power consumption.

  10. Quantitative imaging of brain energy metabolisms and neuroenergetics using in vivo X-nuclear 2H, 17O and 31P MRS at ultra-high field.

    PubMed

    Zhu, Xiao-Hong; Lu, Ming; Chen, Wei

    2018-07-01

    Brain energy metabolism relies predominantly on glucose and oxygen utilization to generate biochemical energy in the form of adenosine triphosphate (ATP). ATP is essential for maintaining basal electrophysiological activities in a resting brain and supporting evoked neuronal activity under an activated state. Studying complex neuroenergetic processes in the brain requires sophisticated neuroimaging techniques enabling noninvasive and quantitative assessment of cerebral energy metabolisms and quantification of metabolic rates. Recent state-of-the-art in vivo X-nuclear MRS techniques, including 2 H, 17 O and 31 P MRS have shown promise, especially at ultra-high fields, in the quest for understanding neuroenergetics and brain function using preclinical models and in human subjects under healthy and diseased conditions. Copyright © 2018 Elsevier Inc. All rights reserved.

  11. HST/ACS Observations of RR Lyrae Stars in Six Ultra-Deep Fields of M31

    NASA Technical Reports Server (NTRS)

    Jeffery, E. J.; Smith, E.; Brown, T. M.; Sweigart, A. V.; Kalirai, J. S.; Ferguson, H. C.; Guhathakurta, P.; Renzini, A.; Rich, R. M.

    2010-01-01

    We present HST/ACS observations of RR Lyrae variable stars in six ultra deep fields of the Andromeda galaxy (M31), including parts of the halo, disk, and giant stellar stream. Past work on the RR Lyrae stars in M31 has focused on various aspects of the stellar populations that make up the galaxy s halo, including their distances and metallicities. This study builds upon this previous work by increasing the spatial coverage (something that has been lacking in previous studies) and by searching for these variable stars in constituents of the galaxy not yet explored. Besides the 55 RR Lyrae stars we found in our initial field located 11kpc from the galactic nucleus, we find additional RR Lyrae stars in four of the remaining five ultra deep fields as follows: 21 in the disk, 24 in the giant stellar stream, 3 in the halo field 21kpc from the galactic nucleus, and 5 in one of the halo fields at 35kpc. No RR Lyrae were found in the second halo field at 35kpc. The RR Lyrae populations of these fields appear to mostly be of Oosterhoff I type, although the 11kpc field appears to be intermediate or mixed. We will discuss the properties of these stars including period and reddening distributions. We calculate metallicities and distances for the stars in each of these fields using different methods and compare the results, to an extent that has not yet been done. We compare these methods not just on RR Lyrae in our M31 fields, but also on a data set of Milky Way field RR Lyrae stars.

  12. Ultra high vacuum seal arrangement

    DOEpatents

    Flaherty, Robert

    1981-01-01

    Arrangement for demountably sealing two concentric metallic tubes in an ultra high vacuum system which facilitates remote actuation. A tubular seal includes integral spaced lips which circumferentially engage the metallic tubes. The lips plastically deform the metallic tubes by mechanical forces resulting from a martensite to austenite transformation of the tubular seal upon application of a predetermined temperature. The sealing force is released upon application of another temperature which causes a transformation from the stronger austenite to the weaker martensite. Use of a dual acting sealing ring and driving ring circumferentially contacting the sealing ring is particularly applicable to sealing larger diameter concentric metallic members.

  13. WE-DE-206-00: MRI Physics

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    NONE

    Magnetic resonance imaging (MRI) has become an essential part of clinical imaging due to its ability to render high soft tissue contrast. Instead of ionizing radiation, MRI use strong magnetic field, radio frequency waves and field gradients to create diagnostic useful images. It can be used to image the anatomy and also functional and physiological activities within the human body. Knowledge of the basic physical principles underlying MRI acquisition is vitally important to successful image production and proper image interpretation. This lecture will give an overview of the spin physics, imaging principle of MRI, the hardware of the MRI scanner,more » and various pulse sequences and their applications. It aims to provide a conceptual foundation to understand the image formation process of a clinical MRI scanner. Learning Objectives: Understand the origin of the MR signal and contrast from the spin physics level. Understand the main hardware components of a MRI scanner and their purposes Understand steps for MR image formation including spatial encoding and image reconstruction Understand the main kinds of MR pulse sequences and their characteristics.« less

  14. Future ultra-speed tube-flight

    NASA Astrophysics Data System (ADS)

    Salter, Robert M.

    1994-05-01

    Future long-link, ultra-speed, surface transport systems will require electromagnetically (EM) driven and restrained vehicles operating under reduced-atmosphere in very straight tubes. Such tube-flight trains will be safe, energy conservative, pollution-free, and in a protected environment. Hypersonic (and even hyperballistic) speeds are theoretically achievable. Ultimate system choices will represent tradeoffs between amoritized capital costs (ACC) and operating costs. For example, long coasting links might employ aerodynamic lift coupled with EM restraint and drag make-up. Optimized, combined EM lift, and thrust vectors could reduce energy costs but at increased ACC. (Repulsive levitation can produce lift-over-drag l/d ratios a decade greater than aerodynamic), Alternatively, vehicle-emanated, induced-mirror fields in a conducting (aluminum sheet) road bed could reduce ACC but at substantial energy costs. Ultra-speed tube flight will demand fast-acting, high-precision sensors and computerized magnetic shimming. This same control system can maintain a magnetic 'guide way' invariant in inertial space with inertial detectors imbedded in tube structures to sense and correct for earth tremors. Ultra-speed tube flight can complete with aircraft for transit time and can provide even greater passenger convenience by single-model connections with local subways and feeder lines. Although cargo transport generally will not need to be performed at ultra speeds, such speeds may well be desirable for high throughput to optimize channel costs. Thus, a large and expensive pipeline might be replaced with small EM-driven pallets at high speeds.

  15. Future ultra-speed tube-flight

    NASA Technical Reports Server (NTRS)

    Salter, Robert M.

    1994-01-01

    Future long-link, ultra-speed, surface transport systems will require electromagnetically (EM) driven and restrained vehicles operating under reduced-atmosphere in very straight tubes. Such tube-flight trains will be safe, energy conservative, pollution-free, and in a protected environment. Hypersonic (and even hyperballistic) speeds are theoretically achievable. Ultimate system choices will represent tradeoffs between amoritized capital costs (ACC) and operating costs. For example, long coasting links might employ aerodynamic lift coupled with EM restraint and drag make-up. Optimized, combined EM lift, and thrust vectors could reduce energy costs but at increased ACC. (Repulsive levitation can produce lift-over-drag l/d ratios a decade greater than aerodynamic), Alternatively, vehicle-emanated, induced-mirror fields in a conducting (aluminum sheet) road bed could reduce ACC but at substantial energy costs. Ultra-speed tube flight will demand fast-acting, high-precision sensors and computerized magnetic shimming. This same control system can maintain a magnetic 'guide way' invariant in inertial space with inertial detectors imbedded in tube structures to sense and correct for earth tremors. Ultra-speed tube flight can complete with aircraft for transit time and can provide even greater passenger convenience by single-model connections with local subways and feeder lines. Although cargo transport generally will not need to be performed at ultra speeds, such speeds may well be desirable for high throughput to optimize channel costs. Thus, a large and expensive pipeline might be replaced with small EM-driven pallets at high speeds.

  16. Design of Ultra-High-Power-Density Machine Optimized for Future Aircraft

    NASA Technical Reports Server (NTRS)

    Choi, Benjamin B.

    2004-01-01

    The NASA Glenn Research Center's Structural Mechanics and Dynamics Branch is developing a compact, nonpolluting, bearingless electric machine with electric power supplied by fuel cells for future "more-electric" aircraft with specific power in the projected range of 50 hp/lb, whereas conventional electric machines generate usually 0.2 hp/lb. The use of such electric drives for propulsive fans or propellers depends on the successful development of ultra-high-power-density machines. One possible candidate for such ultra-high-power-density machines, a round-rotor synchronous machine with an engineering current density as high as 20,000 A/sq cm, was selected to investigate how much torque and power can be produced.

  17. Population receptive field (pRF) measurements of chromatic responses in human visual cortex using fMRI.

    PubMed

    Welbourne, Lauren E; Morland, Antony B; Wade, Alex R

    2018-02-15

    The spatial sensitivity of the human visual system depends on stimulus color: achromatic gratings can be resolved at relatively high spatial frequencies while sensitivity to isoluminant color contrast tends to be more low-pass. Models of early spatial vision often assume that the receptive field size of pattern-sensitive neurons is correlated with their spatial frequency sensitivity - larger receptive fields are typically associated with lower optimal spatial frequency. A strong prediction of this model is that neurons coding isoluminant chromatic patterns should have, on average, a larger receptive field size than neurons sensitive to achromatic patterns. Here, we test this assumption using functional magnetic resonance imaging (fMRI). We show that while spatial frequency sensitivity depends on chromaticity in the manner predicted by behavioral measurements, population receptive field (pRF) size measurements show no such dependency. At any given eccentricity, the mean pRF size for neuronal populations driven by luminance, opponent red/green and S-cone isolating contrast, are identical. Changes in pRF size (for example, an increase with eccentricity and visual area hierarchy) are also identical across the three chromatic conditions. These results suggest that fMRI measurements of receptive field size and spatial resolution can be decoupled under some circumstances - potentially reflecting a fundamental dissociation between these parameters at the level of neuronal populations. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

  18. Fast Room Temperature Very Low Field-Magnetic Resonance Imaging System Compatible with MagnetoEncephaloGraphy Environment

    PubMed Central

    Galante, Angelo; Sinibaldi, Raffaele; Conti, Allegra; De Luca, Cinzia; Catallo, Nadia; Sebastiani, Piero; Pizzella, Vittorio; Romani, Gian Luca; Sotgiu, Antonello; Della Penna, Stefania

    2015-01-01

    In recent years, ultra-low field (ULF)-MRI is being given more and more attention, due to the possibility of integrating ULF-MRI and Magnetoencephalography (MEG) in the same device. Despite the signal-to-noise ratio (SNR) reduction, there are several advantages to operating at ULF, including increased tissue contrast, reduced cost and weight of the scanners, the potential to image patients that are not compatible with clinical scanners, and the opportunity to integrate different imaging modalities. The majority of ULF-MRI systems are based, until now, on magnetic field pulsed techniques for increasing SNR, using SQUID based detectors with Larmor frequencies in the kHz range. Although promising results were recently obtained with such systems, it is an open question whether similar SNR and reduced acquisition time can be achieved with simpler devices. In this work a room-temperature, MEG-compatible very-low field (VLF)-MRI device working in the range of several hundred kHz without sample pre-polarization is presented. This preserves many advantages of ULF-MRI, but for equivalent imaging conditions and SNR we achieve reduced imaging time based on preliminary results using phantoms and ex-vivo rabbits heads. PMID:26630172

  19. Optogenetic Functional MRI

    PubMed Central

    Lin, Peter; Fang, Zhongnan; Liu, Jia; Lee, Jin Hyung

    2016-01-01

    The investigation of the functional connectivity of precise neural circuits across the entire intact brain can be achieved through optogenetic functional magnetic resonance imaging (ofMRI), which is a novel technique that combines the relatively high spatial resolution of high-field fMRI with the precision of optogenetic stimulation. Fiber optics that enable delivery of specific wavelengths of light deep into the brain in vivo are implanted into regions of interest in order to specifically stimulate targeted cell types that have been genetically induced to express light-sensitive trans-membrane conductance channels, called opsins. fMRI is used to provide a non-invasive method of determining the brain's global dynamic response to optogenetic stimulation of specific neural circuits through measurement of the blood-oxygen-level-dependent (BOLD) signal, which provides an indirect measurement of neuronal activity. This protocol describes the construction of fiber optic implants, the implantation surgeries, the imaging with photostimulation and the data analysis required to successfully perform ofMRI. In summary, the precise stimulation and whole-brain monitoring ability of ofMRI are crucial factors in making ofMRI a powerful tool for the study of the connectomics of the brain in both healthy and diseased states. PMID:27167840

  20. High-energy ultra-short pulse thin-disk lasers: new developments and applications

    NASA Astrophysics Data System (ADS)

    Michel, Knut; Klingebiel, Sandro; Schultze, Marcel; Tesseit, Catherine Y.; Bessing, Robert; Häfner, Matthias; Prinz, Stefan; Sutter, Dirk; Metzger, Thomas

    2016-03-01

    We report on the latest developments at TRUMPF Scientific Lasers in the field of ultra-short pulse lasers with highest output energies and powers. All systems are based on the mature and industrialized thin-disk technology of TRUMPF. Thin Yb:YAG disks provide a reliable and efficient solution for power and energy scaling to Joule- and kW-class picosecond laser systems. Due to its efficient one dimensional heat removal, the thin-disk exhibits low distortions and thermal lensing even when pumped under extremely high pump power densities of 10kW/cm². Currently TRUMPF Scientific Lasers develops regenerative amplifiers with highest average powers, optical parametric amplifiers and synchronization schemes. The first few-ps kHz multi-mJ thin-disk regenerative amplifier based on the TRUMPF thindisk technology was developed at the LMU Munich in 20081. Since the average power and energy have continuously been increased, reaching more than 300W (10kHz repetition rate) and 200mJ (1kHz repetition rate) at pulse durations below 2ps. First experiments have shown that the current thin-disk technology supports ultra-short pulse laser solutions >1kW of average power. Based on few-picosecond thin-disk regenerative amplifiers few-cycle optical parametric chirped pulse amplifiers (OPCPA) can be realized. These systems have proven to be the only method for scaling few-cycle pulses to the multi-mJ energy level. OPA based few-cycle systems will allow for many applications such as attosecond spectroscopy, THz spectroscopy and imaging, laser wake field acceleration, table-top few-fs accelerators and laser-driven coherent X-ray undulator sources. Furthermore, high-energy picosecond sources can directly be used for a variety of applications such as X-ray generation or in atmospheric research.

  1. Spatially-Resolved Characterization Techniques to Investigate Impact Damage in Ultra-High Performance Concretes

    DTIC Science & Technology

    2013-04-01

    Concretes G eo te ch n ic al a n d S tr u ct u re s La b or at or y Robert D. Moser, Paul G. Allison, and Mei Q. Chandler April 2013 Approved...Impact Damage in Ultra-High Performance Concretes Robert D. Moser, Paul G. Allison, and Mei Q. Chandler Geotechnical and Structures Laboratory US...Portland Cement concrete (OPC) and Ultra-High Performance Concretes (UHPCs) under high-strain impact and penetration loads at lower length scales

  2. Lensfree fluorescent on-chip imaging of transgenic Caenorhabditis elegans over an ultra-wide field-of-view.

    PubMed

    Coskun, Ahmet F; Sencan, Ikbal; Su, Ting-Wei; Ozcan, Aydogan

    2011-01-06

    We demonstrate lensfree on-chip fluorescent imaging of transgenic Caenorhabditis elegans (C. elegans) over an ultra-wide field-of-view (FOV) of e.g., >2-8 cm(2) with a spatial resolution of ∼10 µm. This is the first time that a lensfree on-chip platform has successfully imaged fluorescent C. elegans samples. In our wide-field lensfree imaging platform, the transgenic samples are excited using a prism interface from the side, where the pump light is rejected through total internal reflection occurring at the bottom facet of the substrate. The emitted fluorescent signal from C. elegans samples is then recorded on a large area opto-electronic sensor-array over an FOV of e.g., >2-8 cm(2), without the use of any lenses, thin-film interference filters or mechanical scanners. Because fluorescent emission rapidly diverges, such lensfree fluorescent images recorded on a chip look blurred due to broad point-spread-function of our platform. To combat this resolution challenge, we use a compressive sampling algorithm to uniquely decode the recorded lensfree fluorescent patterns into higher resolution images, demonstrating ∼10 µm resolution. We tested the efficacy of this compressive decoding approach with different types of opto-electronic sensors to achieve a similar resolution level, independent of the imaging chip. We further demonstrate that this wide FOV lensfree fluorescent imaging platform can also perform sequential bright-field imaging of the same samples using partially-coherent lensfree digital in-line holography that is coupled from the top facet of the same prism used in fluorescent excitation. This unique combination permits ultra-wide field dual-mode imaging of C. elegans on a chip which could especially provide a useful tool for high-throughput screening applications in biomedical research.

  3. Lensfree Fluorescent On-Chip Imaging of Transgenic Caenorhabditis elegans Over an Ultra-Wide Field-of-View

    PubMed Central

    Ozcan, Aydogan

    2011-01-01

    We demonstrate lensfree on-chip fluorescent imaging of transgenic Caenorhabditis elegans (C. elegans) over an ultra-wide field-of-view (FOV) of e.g., >2–8 cm2 with a spatial resolution of ∼10µm. This is the first time that a lensfree on-chip platform has successfully imaged fluorescent C. elegans samples. In our wide-field lensfree imaging platform, the transgenic samples are excited using a prism interface from the side, where the pump light is rejected through total internal reflection occurring at the bottom facet of the substrate. The emitted fluorescent signal from C. elegans samples is then recorded on a large area opto-electronic sensor-array over an FOV of e.g., >2–8 cm2, without the use of any lenses, thin-film interference filters or mechanical scanners. Because fluorescent emission rapidly diverges, such lensfree fluorescent images recorded on a chip look blurred due to broad point-spread-function of our platform. To combat this resolution challenge, we use a compressive sampling algorithm to uniquely decode the recorded lensfree fluorescent patterns into higher resolution images, demonstrating ∼10 µm resolution. We tested the efficacy of this compressive decoding approach with different types of opto-electronic sensors to achieve a similar resolution level, independent of the imaging chip. We further demonstrate that this wide FOV lensfree fluorescent imaging platform can also perform sequential bright-field imaging of the same samples using partially-coherent lensfree digital in-line holography that is coupled from the top facet of the same prism used in fluorescent excitation. This unique combination permits ultra-wide field dual-mode imaging of C. elegans on a chip which could especially provide a useful tool for high-throughput screening applications in biomedical research. PMID:21253611

  4. Ultra-sensitive speciation analysis of mercury by CE-ICP-MS together with field-amplified sample stacking injection and dispersive solid-phase extraction.

    PubMed

    Chen, YiQuan; Cheng, Xian; Mo, Fan; Huang, LiMei; Wu, Zujian; Wu, Yongning; Xu, LiangJun; Fu, FengFu

    2016-04-01

    A simple dispersive solid-phase extraction (DSPE) used to extract and preconcentrate ultra-trace MeHg, EtHg and Hg(2+) from water sample, and a sensitive method for the simultaneous analysis of MeHg, EtHg and Hg(2+) by using capillary electrophoresis-inductively coupled plasma mass spectrometry (CE-ICP-MS) with field-amplified sample stacking injection (FASI) were first reported in this study. The DSPE used thiol cotton particles as adsorbent, and is simple and effective. It can be used to extract and preconcentrate ultra-trace mercury compounds in water samples within 30 min with a satisfied recovery and no mercury species alteration during the process. The FASI enhanced the sensitivity of CE-ICP-MS with 25-fold, 29-fold and 27-fold for MeHg, EtHg and Hg(2+) , respectively. Using FASI-CE-ICP-MS together with DSPE, we have successfully determined ultra-trace MeHg, EtHg and Hg(2+) in tap water with a limits of quantification (LOQs) of 0.26-0.45 pg/mL, an RSD (n = 3) < 6% and a recovery of 92-108%. Ultra-high sensitivity, as well as much less sample and reagent consumption and low operating cost, make our method a valuable technique to the speciation analysis of ultra-trace mercury. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. A diamond-based scanning probe spin sensor operating at low temperature in ultra-high vacuum

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Schaefer-Nolte, E.; Wrachtrup, J.; 3rd Institute of Physics and Research Center SCoPE, University Stuttgart, 70569 Stuttgart

    2014-01-15

    We present the design and performance of an ultra-high vacuum (UHV) low temperature scanning probe microscope employing the nitrogen-vacancy color center in diamond as an ultrasensitive magnetic field sensor. Using this center as an atomic-size scanning probe has enabled imaging of nanoscale magnetic fields and single spins under ambient conditions. In this article we describe an experimental setup to operate this sensor in a cryogenic UHV environment. This will extend the applicability to a variety of molecular systems due to the enhanced target spin lifetimes at low temperature and the controlled sample preparation under UHV conditions. The instrument combines amore » tuning-fork based atomic force microscope (AFM) with a high numeric aperture confocal microscope and the facilities for application of radio-frequency (RF) fields for spin manipulation. We verify a sample temperature of <50 K even for strong laser and RF excitation and demonstrate magnetic resonance imaging with a magnetic AFM tip.« less

  6. Effects of magnetic field strength and particle aggregation on relaxivity of ultra-small dual contrast iron oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Ta, Hang T.; Li, Zhen; Wu, Yuao; Cowin, Gary; Zhang, Shaohua; Yago, Anya; Whittaker, Andrew K.; Xu, Zhi Ping

    2017-11-01

    This study aims to compare the relaxivities of ultra-small dual positive and negative contrast iron oxide nanoparticles (DCION) at different magnetic field strengths ranging from 4.7 to 16.4 T at physiological temperatures; and to investigate the effect of particle aggregation on relaxivities. Relaxivities of DCIONs were determined by magnetic resonance imaging scanners at 4.7, 7, 9.4, and 16.4 T. Both longitudinal (T 1) and transverse relaxation times (T 2) were measured by appropriate spin-echo sequences. It has been found that both longitudinal and transverse relaxivities are significantly dependent on the magnetic field strength. Particle aggregation also strongly affects the relaxivities. Awareness of the field strength and particle colloid stability is crucial for the comparison and evaluation of relaxivity values of these ultra-small iron oxide nanoparticles, and also for their medical applications as contrast agents.

  7. High Spatiotemporal Resolution Prostate MRI

    DTIC Science & Technology

    2017-09-01

    AWARD NUMBER: W81XWH-15-1-0341 TITLE: High Spatiotemporal Resolution Prostate MRI PRINCIPAL INVESTIGATOR: Stephen J. Riederer, Ph.D...views, opinions and/or findings contained in this report are those of the author(s) and should not be construed as an official Department of the Army...ADDRESS. 1. REPORT DATE September 2017 2. REPORT TYPE Annual 3. DATES COVERED 15 Aug 2016 - 14 Aug 2017 4. TITLE AND SUBTITLE High Spatiotemporal

  8. Ultra-high density diffraction grating

    DOEpatents

    Padmore, Howard A.; Voronov, Dmytro L.; Cambie, Rossana; Yashchuk, Valeriy V.; Gullikson, Eric M.

    2012-12-11

    A diffraction grating structure having ultra-high density of grooves comprises an echellette substrate having periodically repeating recessed features, and a multi-layer stack of materials disposed on the echellette substrate. The surface of the diffraction grating is planarized, such that layers of the multi-layer stack form a plurality of lines disposed on the planarized surface of the structure in a periodical fashion, wherein lines having a first property alternate with lines having a dissimilar property on the surface of the substrate. For example, in one embodiment, lines comprising high-Z and low-Z materials alternate on the planarized surface providing a structure that is suitable as a diffraction grating for EUV and soft X-rays. In some embodiments, line density of between about 10,000 lines/mm to about 100,000 lines/mm is provided.

  9. Transient line starting analysis of the ultra-high speed PMSM

    PubMed Central

    Cheng, Wenjie; Li, Wei; Xiao, ling; Li, Ming; Tian, Yongsheng; Sun, Yanhua; Yu, Lie

    2017-01-01

    Aiming at the ultra high speed permanent magnet synchronous motor (PMSM) supported by gas foil bearings (GFBs), this paper calculates the transient line starting of the motor. Firstly, the start effect of the rotor composed of cylindrical PM and stainless steel sleeve is studied. Then, in order to enhance the start torque, copper ring, nickel ring and copper squirrel-cage are introduced in the rotor and their start effect are analysed, respectively. It can be found that the rotor including nickel ring can be accelerated to set speed, but all the other rotors are failed due to the higher PM and braking torques. It can be concluded that some material owning slight large relative permeability can be applied in the rotor to reduce the PM field and contribute to start by using the line-start method. PMID:28105384

  10. Higher order reconstruction for MRI in the presence of spatiotemporal field perturbations.

    PubMed

    Wilm, Bertram J; Barmet, Christoph; Pavan, Matteo; Pruessmann, Klaas P

    2011-06-01

    Despite continuous hardware advances, MRI is frequently subject to field perturbations that are of higher than first order in space and thus violate the traditional k-space picture of spatial encoding. Sources of higher order perturbations include eddy currents, concomitant fields, thermal drifts, and imperfections of higher order shim systems. In conventional MRI with Fourier reconstruction, they give rise to geometric distortions, blurring, artifacts, and error in quantitative data. This work describes an alternative approach in which the entire field evolution, including higher order effects, is accounted for by viewing image reconstruction as a generic inverse problem. The relevant field evolutions are measured with a third-order NMR field camera. Algebraic reconstruction is then formulated such as to jointly minimize artifacts and noise in the resulting image. It is solved by an iterative conjugate-gradient algorithm that uses explicit matrix-vector multiplication to accommodate arbitrary net encoding. The feasibility and benefits of this approach are demonstrated by examples of diffusion imaging. In a phantom study, it is shown that higher order reconstruction largely overcomes variable image distortions that diffusion gradients induce in EPI data. In vivo experiments then demonstrate that the resulting geometric consistency permits straightforward tensor analysis without coregistration. Copyright © 2011 Wiley-Liss, Inc.

  11. The Effect of Magnetic Field on Positron Range and Spatial Resolution in an Integrated Whole-Body Time-Of-Flight PET/MRI System.

    PubMed

    Huang, Shih-Ying; Savic, Dragana; Yang, Jaewon; Shrestha, Uttam; Seo, Youngho

    2014-11-01

    Simultaneous imaging systems combining positron emission tomography (PET) and magnetic resonance imaging (MRI) have been actively investigated. A PET/MR imaging system (GE Healthcare) comprised of a time-of-flight (TOF) PET system utilizing silicon photomultipliers (SiPMs) and 3-tesla (3T) MRI was recently installed at our institution. The small-ring (60 cm diameter) TOF PET subsystem of this PET/MRI system can generate images with higher spatial resolution compared with conventional PET systems. We have examined theoretically and experimentally the effect of uniform magnetic fields on the spatial resolution for high-energy positron emitters. Positron emitters including 18 F, 124 I, and 68 Ga were simulated in water using the Geant4 Monte Carlo toolkit in the presence of a uniform magnetic field (0, 3, and 7 Tesla). The positron annihilation position was tracked to determine the 3D spatial distribution of the 511-keV gammy ray emission. The full-width at tenth maximum (FWTM) of the positron point spread function (PSF) was determined. Experimentally, 18 F and 68 Ga line source phantoms in air and water were imaged with an investigational PET/MRI system and a PET/CT system to investigate the effect of magnetic field on the spatial resolution of PET. The full-width half maximum (FWHM) of the line spread function (LSF) from the line source was determined as the system spatial resolution. Simulations and experimental results show that the in-plane spatial resolution was slightly improved at field strength as low as 3 Tesla, especially when resolving signal from high-energy positron emitters in the air-tissue boundary.

  12. High-energy green supercapacitor driven by ionic liquid electrolytes as an ultra-high stable next-generation energy storage device

    NASA Astrophysics Data System (ADS)

    Thangavel, Ranjith; Kannan, Aravindaraj G.; Ponraj, Rubha; Thangavel, Vigneysh; Kim, Dong-Won; Lee, Yun-Sung

    2018-04-01

    Development of supercapacitors with high energy density and long cycle life using sustainable materials for next-generation applications is of paramount importance. The ongoing challenge is to elevate the energy density of supercapacitors on par with batteries, while upholding the power and cyclability. In addition, attaining such superior performance with green and sustainable bio-mass derived compounds is very crucial to address the rising environmental concerns. Herein, we demonstrate the use of watermelon rind, a bio-waste from watermelons, towards high energy, and ultra-stable high temperature green supercapacitors with a high-voltage ionic liquid electrolyte. Supercapacitors assembled with ultra-high surface area, hierarchically porous carbon exhibits a remarkable performance both at room temperature and at high temperature (60 °C) with maximum energy densities of ∼174 Wh kg-1 (25 °C), and 177 Wh kg-1 (60 °C) - based on active mass of both electrodes. Furthermore, an ultra-high specific power of ∼20 kW kg-1 along with an ultra-stable cycling performance with 90% retention over 150,000 cycles has been achieved even at 60 °C, outperforming supercapacitors assembled with other carbon based materials. These results demonstrate the potential to develop high-performing, green energy storage devices using eco-friendly materials for next generation electric vehicles and other advanced energy storage systems.

  13. Monte Carlo study of the impact of a magnetic field on the dose distribution in MRI-guided HDR brachytherapy using Ir-192

    NASA Astrophysics Data System (ADS)

    Beld, E.; Seevinck, P. R.; Lagendijk, J. J. W.; Viergever, M. A.; Moerland, M. A.

    2016-09-01

    In the process of developing a robotic MRI-guided high-dose-rate (HDR) prostate brachytherapy treatment, the influence of the MRI scanner’s magnetic field on the dose distribution needs to be investigated. A magnetic field causes a deflection of electrons in the plane perpendicular to the magnetic field, and it leads to less lateral scattering along the direction parallel with the magnetic field. Monte Carlo simulations were carried out to determine the influence of the magnetic field on the electron behavior and on the total dose distribution around an Ir-192 source. Furthermore, the influence of air pockets being present near the source was studied. The Monte Carlo package Geant4 was utilized for the simulations. The simulated geometries consisted of a simplified point source inside a water phantom. Magnetic field strengths of 0 T, 1.5 T, 3 T, and 7 T were considered. The simulation results demonstrated that the dose distribution was nearly unaffected by the magnetic field for all investigated magnetic field strengths. Evidence was found that, from a dose perspective, the HDR prostate brachytherapy treatment using Ir-192 can be performed safely inside the MRI scanner. No need was found to account for the magnetic field during treatment planning. Nevertheless, the presence of air pockets in close vicinity to the source, particularly along the direction parallel with the magnetic field, appeared to be an important point for consideration.

  14. Monte Carlo study of the impact of a magnetic field on the dose distribution in MRI-guided HDR brachytherapy using Ir-192.

    PubMed

    Beld, E; Seevinck, P R; Lagendijk, J J W; Viergever, M A; Moerland, M A

    2016-09-21

    In the process of developing a robotic MRI-guided high-dose-rate (HDR) prostate brachytherapy treatment, the influence of the MRI scanner's magnetic field on the dose distribution needs to be investigated. A magnetic field causes a deflection of electrons in the plane perpendicular to the magnetic field, and it leads to less lateral scattering along the direction parallel with the magnetic field. Monte Carlo simulations were carried out to determine the influence of the magnetic field on the electron behavior and on the total dose distribution around an Ir-192 source. Furthermore, the influence of air pockets being present near the source was studied. The Monte Carlo package Geant4 was utilized for the simulations. The simulated geometries consisted of a simplified point source inside a water phantom. Magnetic field strengths of 0 T, 1.5 T, 3 T, and 7 T were considered. The simulation results demonstrated that the dose distribution was nearly unaffected by the magnetic field for all investigated magnetic field strengths. Evidence was found that, from a dose perspective, the HDR prostate brachytherapy treatment using Ir-192 can be performed safely inside the MRI scanner. No need was found to account for the magnetic field during treatment planning. Nevertheless, the presence of air pockets in close vicinity to the source, particularly along the direction parallel with the magnetic field, appeared to be an important point for consideration.

  15. High Efficient Ultra-Thin Flat Optics Based on Dielectric Metasurfaces

    NASA Astrophysics Data System (ADS)

    Ozdemir, Aytekin

    Metasurfaces which emerged as two-dimensional counterparts of metamaterials, facilitate the realization of arbitrary phase distributions using large arrays with subwavelength and ultra-thin features. Even if metasurfaces are ultra-thin, they still effectively manipulate the phase, amplitude, and polarization of light in transmission or reflection mode. In contrast, conventional optical components are bulky, and they lose their functionality at sub-wavelength scales, which requires conceptually new types of nanoscale optical devices. On the other hand, as the optical systems shrink in size day by day, conventional bulky optical components will have tighter alignment and fabrication tolerances. Since metasurfaces can be fabricated lithographically, alignment can be done during lithographic fabrication, thus eliminating the need for post-fabrication alignments. In this work, various types of metasurface applications are thoroughly investigated for robust wavefront engineering with enhanced characteristics in terms of broad bandwidth, high efficiency and active tunability, while beneficial for application. Plasmonic metasurfaces are not compatible with the CMOS process flow, and, additionally their high absorption and ohmic loss is problematic in transmission based applications. Dielectric metasurfaces, however, offer a strong magnetic response at optical frequencies, and thus they can offer great opportunities for interacting not only with the electric component of a light field, but also with its magnetic component. They show great potential to enable practical device functionalities at optical frequencies, which motivates us to explore them one step further on wavefront engineering and imaging sensor platforms. Therefore, we proposed an efficient ultra-thin flat metalens at near-infrared regime constituted by silicon nanodisks which can support both electric and magnetic dipolar Mie-type resonances. These two dipole resonances can be overlapped at the same frequency

  16. Value of Endorectal MRI in Romanian Men for High Risk of Prostate Cancer: MRI Findings Compared with Saturation Biopsy.

    PubMed

    Lebovici, A; Sfrangeu, S A; Caraiani, C; Lucan, C; Suciu, M; Elec, F; Iacob, Gh; Buruian, M

    2015-01-01

    To evaluate the potentials of T2 weighted (T2W)MRI and diffusion weighted (DW) MRI for prostate cancer(PCa) detection, local staging and treatment planning in high-risk group. Endorectal MRI was performed in 17 Romanian men (median age: 66 years; range: 58 75 years), prostate specific antigen (PSA) serum levels (median: 20 ng mL; range: 8.6 100 ng mL) with positive findings for PCa(median Gleason score: 8; range: 7 - 9). Imaging findings were compared to standarised 20-core transperineal saturation biopsy. The prostate was divided into 16 standart sectors(10 posterior and 6 anterior). Overall, prostate cancer was detected in 16 patients(94%) on DW-MRI alone and in all 17 patients (100%) on T2W-MRI alone, and on combined imaging. On T2W-MRI165 sectors out of 272 were suspicious for PCa and 124 (75%)were cancer positive. On DW-MRI 126 sectors out of 272 were suspicious for PCa and 118 (95%) were cancer positive. On the combined imaging approach 134 sectors out of 272 were suspicious for PCa and 126 (94%) were cancer positive. This resulted in diagnostic accuracies per sector of 76% for T2WMRI, 86% for DW-MRI and 89% for combined imaging. Multifocal PCa was confirmed both on MR imaging and by biopsy in 8 of the 17 men (47%) Extra capsular extension(ECE) or seminal vesicles invasion (SVI) was highly suspected in 8 (47%) respectively 7 (41%) of the 17 patients. 6 patients(35%) presented both ECE and SVI. MRI findings were taken into account for treatment planning and none of these patients underwent radical prostatectomy and instead was treated with palliative cryotherapy, radiotherapy and hormone therapy. Endorectal MRI is highly accurate in PCa detection in the high-risk group and seems to have an important role in local staging and treatment planning for Romanian population. Celsius.

  17. Link and Network Layers Design for Ultra-High-Speed Terahertz-Band Communications Networks

    DTIC Science & Technology

    2017-01-01

    throughput, and identify the optimal parameter values for their design (Sec. 6.2.3). Moreover, we validate and test the scheme with experimental data obtained...LINK AND NETWORK LAYERS DESIGN FOR ULTRA-HIGH- SPEED TERAHERTZ-BAND COMMUNICATIONS NETWORKS STATE UNIVERSITY OF NEW YORK (SUNY) AT BUFFALO JANUARY...TYPE FINAL TECHNICAL REPORT 3. DATES COVERED (From - To) FEB 2015 – SEP 2016 4. TITLE AND SUBTITLE LINK AND NETWORK LAYERS DESIGN FOR ULTRA-HIGH

  18. Adaptive sensor-based ultra-high accuracy solar concentrator tracker

    NASA Astrophysics Data System (ADS)

    Brinkley, Jordyn; Hassanzadeh, Ali

    2017-09-01

    Conventional solar trackers use information of the sun's position, either by direct sensing or by GPS. Our method uses the shading of the receiver. This, coupled with nonimaging optics design allows us to achieve ultra-high concentration. Incorporating a sensor based shadow tracking method with a two stage concentration solar hybrid parabolic trough allows the system to maintain high concentration with acute accuracy.

  19. Development of an MRI-compatible digital SiPM detector stack for simultaneous PET/MRI.

    PubMed

    Düppenbecker, Peter M; Weissler, Bjoern; Gebhardt, Pierre; Schug, David; Wehner, Jakob; Marsden, Paul K; Schulz, Volkmar

    2016-02-01

    Advances in solid-state photon detectors paved the way to combine positron emission tomography (PET) and magnetic resonance imaging (MRI) into highly integrated, truly simultaneous, hybrid imaging systems. Based on the most recent digital SiPM technology, we developed an MRI-compatible PET detector stack, intended as a building block for next generation simultaneous PET/MRI systems. Our detector stack comprises an array of 8 × 8 digital SiPM channels with 4 mm pitch using Philips Digital Photon Counting DPC 3200-22 devices, an FPGA for data acquisition, a supply voltage control system and a cooling infrastructure. This is the first detector design that allows the operation of digital SiPMs simultaneously inside an MRI system. We tested and optimized the MRI-compatibility of our detector stack on a laboratory test bench as well as in combination with a Philips Achieva 3 T MRI system. Our design clearly reduces distortions of the static magnetic field compared to a conventional design. The MRI static magnetic field causes weak and directional drift effects on voltage regulators, but has no direct impact on detector performance. MRI gradient switching initially degraded energy and timing resolution. Both distortions could be ascribed to voltage variations induced on the bias and the FPGA core voltage supply respectively. Based on these findings, we improved our detector design and our final design shows virtually no energy or timing degradations, even during heavy and continuous MRI gradient switching. In particular, we found no evidence that the performance of the DPC 3200-22 digital SiPM itself is degraded by the MRI system.

  20. High-efficiency water-loaded microwave antenna in ultra-high-frequency band

    NASA Astrophysics Data System (ADS)

    Gong, Zilun; Bartone, Chris; Yang, Fuyi; Yao, Jie

    2018-03-01

    High-index dielectrics are widely used in microwave antennas to control the radiation characteristics. Liquid water, with a high dielectric index at microwave frequency, is an interesting material to achieving tunable functionalities. Here, we demonstrate a water-loaded microwave antenna system that has high loss-tolerance and wideband tunability enabled by fluidity. Our simulation and experimental results show that the resonance frequency can be effectively tuned by the size of loading water. Furthermore, the antenna systems with water loading can achieve high radiation efficiency (>90%) in the ultra-high-frequency (0.3-3 GHz) band. This work brings about opportunities in realistic tunable microwave antenna designs enabled by liquid.

  1. MRI breast screening in high-risk women: cancer detection and survival analysis.

    PubMed

    Evans, D Gareth; Gareth, Evans D; Kesavan, Nisha; Nisha, Kesavan; Lim, Yit; Yit, Lim; Gadde, Soujanye; Soujanye, Gadde; Hurley, Emma; Emma, Hurley; Massat, Nathalie J; Maxwell, Anthony J; Ingham, Sarah; Sarah, Ingham; Eeles, Rosalind; Rosalind, Eeles; Leach, Martin O; Howell, Anthony; Anthony, Howell; Duffy, Stephen W; Stephen, Duffy

    2014-06-01

    Women with a genetic predisposition to breast cancer tend to develop the disease at a younger age with denser breasts making mammography screening less effective. The introduction of magnetic resonance imaging (MRI) for familial breast cancer screening programs in recent years was intended to improve outcomes in these women. We aimed to assess whether introduction of MRI surveillance improves 5- and 10-year survival of high-risk women and determine the accuracy of MRI breast cancer detection compared with mammography-only or no enhanced surveillance and compare size and pathology of cancers detected in women screened with MRI + mammography and mammography only. We used data from two prospective studies where asymptomatic women with a very high breast cancer risk were screened by either mammography alone or with MRI also compared with BRCA1/2 carriers with no intensive surveillance. 63 cancers were detected in women receiving MRI + mammography and 76 in women receiving mammography only. Sensitivity of MRI + mammography was 93 % with 63 % specificity. Fewer cancers detected on MRI were lymph node positive compared to mammography/no additional screening. There were no differences in 10-year survival between the MRI + mammography and mammography-only groups, but survival was significantly higher in the MRI-screened group (95.3 %) compared to no intensive screening (73.7 %; p = 0.002). There were no deaths among the 21 BRCA2 carriers receiving MRI. There appears to be benefit from screening with MRI, particularly in BRCA2 carriers. Extended follow-up of larger numbers of high-risk women is required to assess long-term survival.

  2. Measuring functional connectivity using MEG: Methodology and comparison with fcMRI

    PubMed Central

    Brookes, Matthew J.; Hale, Joanne R.; Zumer, Johanna M.; Stevenson, Claire M.; Francis, Susan T.; Barnes, Gareth R.; Owen, Julia P.; Morris, Peter G.; Nagarajan, Srikantan S.

    2011-01-01

    Functional connectivity (FC) between brain regions is thought to be central to the way in which the brain processes information. Abnormal connectivity is thought to be implicated in a number of diseases. The ability to study FC is therefore a key goal for neuroimaging. Functional connectivity (fc) MRI has become a popular tool to make connectivity measurements but the technique is limited by its indirect nature. A multimodal approach is therefore an attractive means to investigate the electrodynamic mechanisms underlying hemodynamic connectivity. In this paper, we investigate resting state FC using fcMRI and magnetoencephalography (MEG). In fcMRI, we exploit the advantages afforded by ultra high magnetic field. In MEG we apply envelope correlation and coherence techniques to source space projected MEG signals. We show that beamforming provides an excellent means to measure FC in source space using MEG data. However, care must be taken when interpreting these measurements since cross talk between voxels in source space can potentially lead to spurious connectivity and this must be taken into account in all studies of this type. We show good spatial agreement between FC measured independently using MEG and fcMRI; FC between sensorimotor cortices was observed using both modalities, with the best spatial agreement when MEG data are filtered into the β band. This finding helps to reduce the potential confounds associated with each modality alone: while it helps reduce the uncertainties in spatial patterns generated by MEG (brought about by the ill posed inverse problem), addition of electrodynamic metric confirms the neural basis of fcMRI measurements. Finally, we show that multiple MEG based FC metrics allow the potential to move beyond what is possible using fcMRI, and investigate the nature of electrodynamic connectivity. Our results extend those from previous studies and add weight to the argument that neural oscillations are intimately related to functional

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

    PubMed Central

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

    2013-01-01

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

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

    PubMed

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

    2013-12-01

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

  5. Imaging interactions of metal oxide nanoparticles with macrophage cells by ultra-high resolution scanning electron microscopy techniques.

    PubMed

    Plascencia-Villa, Germán; Starr, Clarise R; Armstrong, Linda S; Ponce, Arturo; José-Yacamán, Miguel

    2012-11-01

    Use of engineered metal oxide nanoparticles in a plethora of biological applications and custom products has warned about some possible dose-dependent cytotoxic effects. Macrophages are key components of the innate immune system used to study possible toxic effects and internalization of different nanoparticulate materials. In this work, ultra-high resolution field emission scanning electron microscopy (FE-SEM) was used to offer new insights into the dynamical processes of interaction of nanomaterials with macrophage cells dosed with different concentrations of metal oxide nanoparticles (CeO(2), TiO(2) and ZnO). The versatility of FE-SEM has allowed obtaining a detailed characterization of processes of adsorption and endocytosis of nanoparticles, by using advanced analytical and imaging techniques on complete unstained uncoated cells, including secondary electron imaging, high-sensitive backscattered electron imaging, X-ray microanalysis and stereoimaging. Low voltage BF/DF-STEM confirmed nanoparticle adsorption and internalization into endosomes of CeO(2) and TiO(2), whereas ZnO develop apoptosis after 24 h of interaction caused by dissolution and invasion of cell nucleus. Ultra-high resolution scanning electron microscopy techniques provided new insights into interactions of inorganic nanoparticles with macrophage cells with high spatial resolution.

  6. Imaging interactions of metal oxide nanoparticles with macrophage cells by ultra-high resolution scanning electron microscopy techniques†

    PubMed Central

    Plascencia-Villa, Germán; Starr, Clarise R.; Armstrong, Linda S.; Ponce, Arturo

    2016-01-01

    Use of engineered metal oxide nanoparticles in a plethora of biological applications and custom products has warned about some possible dose-dependent cytotoxic effects. Macrophages are key components of the innate immune system used to study possible toxic effects and internalization of different nanoparticulate materials. In this work, ultra-high resolution field emission scanning electron microscopy (FE-SEM) was used to offer new insights into the dynamical processes of interaction of nanomaterials with macrophage cells dosed with different concentrations of metal oxide nanoparticles (CeO2, TiO2 and ZnO). The versatility of FE-SEM has allowed obtaining a detailed characterization of processes of adsorption and endocytosis of nanoparticles, by using advanced analytical and imaging techniques on complete unstained uncoated cells, including secondary electron imaging, high-sensitive backscattered electron imaging, X-ray microanalysis and stereoimaging. Low voltage BF/DF-STEM confirmed nanoparticle adsorption and internalization into endosomes of CeO2 and TiO2, whereas ZnO develop apoptosis after 24 h of interaction caused by dissolution and invasion of cell nucleus. Ultra-high resolution scanning electron microscopy techniques provided new insights into interactions of inorganic nanoparticles with macrophage cells with high spatial resolution. PMID:23023106

  7. Bond Behavior of Reinforcing Steel in Ultra-High Performance Concrete

    DOT National Transportation Integrated Search

    2014-11-01

    Ultra-high performance concrete (UHPC) has garnered interest from the highway infrastructure community for its greatly enhanced mechanical and durability properties. The objective of this research is to extensively evaluate the factors that affect bo...

  8. Molecular MRI in the Earth's Magnetic Field Using Continuous Hyperpolarization of a Biomolecule in Water.

    PubMed

    Rovedo, Philipp; Knecht, Stephan; Bäumlisberger, Tim; Cremer, Anna Lena; Duckett, Simon B; Mewis, Ryan E; Green, Gary G R; Burns, Michael; Rayner, Peter J; Leibfritz, Dieter; Korvink, Jan G; Hennig, Jürgen; Pütz, Gerhard; von Elverfeldt, Dominik; Hövener, Jan-Bernd

    2016-06-30

    In this work, we illustrate a method to continuously hyperpolarize a biomolecule, nicotinamide, in water using parahydrogen and signal amplification by reversible exchange (SABRE). Building on the preparation procedure described recently by Truong et al. [ J. Phys. Chem. B , 2014 , 118 , 13882 - 13889 ], aqueous solutions of nicotinamide and an Ir-IMes catalyst were prepared for low-field NMR and MRI. The (1)H-polarization was continuously renewed and monitored by NMR experiments at 5.9 mT for more than 1000 s. The polarization achieved corresponds to that induced by a 46 T magnet (P = 1.6 × 10(-4)) or an enhancement of 10(4). The polarization persisted, although reduced, if cell culture medium (DPBS with Ca(2+) and Mg(2+)) or human cells (HL-60) were added, but was no longer observable after the addition of human blood. Using a portable MRI unit, fast (1)H-MRI was enabled by cycling the magnetic field between 5 mT and the Earth's field for hyperpolarization and imaging, respectively. A model describing the underlying spin physics was developed that revealed a polarization pattern depending on both contact time and magnetic field. Furthermore, the model predicts an opposite phase of the dihydrogen and substrate signal after one exchange, which is likely to result in the cancelation of some signal at low field.

  9. Waste heat recovery with ultra high-speed turbomachinery

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Vakkilainen, E.; Larjola, J.; Lindgren, O.

    1984-08-01

    A new ORC heat recovery system which converts waste heat to electricity has been developed in Lappeenranta University of Technology with support from Department of Energy in Finnish Ministry of Trade and Industry. Use of ultra high-speed turbomachinery (10 000 rpm - 200 000 rpm) promises lower unit costs, higher efficiencies and fast amortization rate, 2,4 - 3,0 years.

  10. Remotely detected high-field MRI of porous samples

    NASA Astrophysics Data System (ADS)

    Seeley, Juliette A.; Han, Song-I.; Pines, Alexander

    2004-04-01

    Remote detection of NMR is a novel technique in which an NMR-active sensor surveys an environment of interest and retains memory of that environment to be recovered at a later time in a different location. The NMR or MRI information about the sensor nucleus is encoded and stored as spin polarization at the first location and subsequently moved to a different physical location for optimized detection. A dedicated probe incorporating two separate radio frequency (RF)—circuits was built for this purpose. The encoding solenoid coil was large enough to fit around the bulky sample matrix, while the smaller detection solenoid coil had not only a higher quality factor, but also an enhanced filling factor since the coil volume comprised purely the sensor nuclei. We obtained two-dimensional (2D) void space images of two model porous samples with resolution less than 1.4 mm 2. The remotely reconstructed images demonstrate the ability to determine fine structure with image quality superior to their directly detected counterparts and show the great potential of NMR remote detection for imaging applications that suffer from low sensitivity due to low concentrations and filling factor.

  11. [Reparative Osteogenesis and Angiogenesis in Low Intensity Electromagnetic Radiation of Ultra-High Frequency].

    PubMed

    Iryanov, Y M; Kiryanov, N A

    2015-01-01

    Non-drug correction of reparative bone tissue regeneration in different pathological states - one of the most actual problems of modern medicine. Our aim was to conduct morphological analysis of the influence of electromagnetic radiation of ultra-high frequency and low intensity on reparative osteogenesis and angiogenesis in fracture treatment under transosseous osteosynthesis. A controlled nonrandomized study was carried out. In the experiment conducted on rats we modeled tibial fracture with reposition and fixation of the bone fragments both in control and experimental groups. In the animals of the experimental group the fracture zone was exposed to low intensity electromagnetic radiation of ultra-high frequency. Exposure simulation was performed in the control group. The operated bones were examined using radiography, light and electronic microscopy, X-ray electronic probe microanalysis. It has been established that electromagnetic radiation of ultra-high frequency sessions in fracture treatment stimulate secretory activity and degranulation of mast cells, produce microcirculatory bed vascular permeability increase, endotheliocyte migration phenotype expression, provide endovascular endothelial outgrowth formation, activate reparative osteogenesis and angiogenesis while fracture reparation becomes the one of the primary type. The full periosteal, intermediary and intraosteal bone union was defined in 28 days. Among the therapeutic benefits of electromagnetic radiation of ultra-high frequency in fracture treatment we can detect mast cell secretorv activity stimulation and endovascular anziozenesis activation.

  12. Development of Non-Proprietary Ultra-High Performance Concrete : Final Report

    DOT National Transportation Integrated Search

    2017-12-01

    Ultra-high performance concrete (UHPC) has mechanical and durability properties that far exceed those of conventional concrete. Particularly, UHPC has compressive and post-cracking tensile strengths of around 20 ksi and 0.72 ksi, respectively. Thus, ...

  13. Prostate cancer localization with multispectral MRI using cost-sensitive support vector machines and conditional random fields.

    PubMed

    Artan, Yusuf; Haider, Masoom A; Langer, Deanna L; van der Kwast, Theodorus H; Evans, Andrew J; Yang, Yongyi; Wernick, Miles N; Trachtenberg, John; Yetik, Imam Samil

    2010-09-01

    Prostate cancer is a leading cause of cancer death for men in the United States. Fortunately, the survival rate for early diagnosed patients is relatively high. Therefore, in vivo imaging plays an important role for the detection and treatment of the disease. Accurate prostate cancer localization with noninvasive imaging can be used to guide biopsy, radiotherapy, and surgery as well as to monitor disease progression. Magnetic resonance imaging (MRI) performed with an endorectal coil provides higher prostate cancer localization accuracy, when compared to transrectal ultrasound (TRUS). However, in general, a single type of MRI is not sufficient for reliable tumor localization. As an alternative, multispectral MRI, i.e., the use of multiple MRI-derived datasets, has emerged as a promising noninvasive imaging technique for the localization of prostate cancer; however almost all studies are with human readers. There is a significant inter and intraobserver variability for human readers, and it is substantially difficult for humans to analyze the large dataset of multispectral MRI. To solve these problems, this study presents an automated localization method using cost-sensitive support vector machines (SVMs) and shows that this method results in improved localization accuracy than classical SVM. Additionally, we develop a new segmentation method by combining conditional random fields (CRF) with a cost-sensitive framework and show that our method further improves cost-sensitive SVM results by incorporating spatial information. We test SVM, cost-sensitive SVM, and the proposed cost-sensitive CRF on multispectral MRI datasets acquired from 21 biopsy-confirmed cancer patients. Our results show that multispectral MRI helps to increase the accuracy of prostate cancer localization when compared to single MR images; and that using advanced methods such as cost-sensitive SVM as well as the proposed cost-sensitive CRF can boost the performance significantly when compared to SVM.

  14. Inactivation of Bacillus spores inoculated in milk by Ultra High Pressure Homogenization.

    PubMed

    Amador Espejo, Genaro Gustavo; Hernández-Herrero, M M; Juan, B; Trujillo, A J

    2014-12-01

    Ultra High-Pressure Homogenization treatments at 300 MPa with inlet temperatures (Ti) of 55, 65, 75 and 85 °C were applied to commercial Ultra High Temperature treated whole milk inoculated with Bacillus cereus, Bacillus licheniformis, Bacillus sporothermodurans, Bacillus coagulans, Geobacillus stearothermophilus and Bacillus subtilis spores in order to evaluate the inactivation level achieved. Ultra High-Pressure Homogenization conditions at 300 MPa with Ti = 75 and 85 °C were capable of a spore inactivation of ∼5 log CFU/mL. Furthermore, under these processing conditions, commercial sterility (evaluated as the complete inactivation of the inoculated spores) was obtained in milk, with the exception of G. stearothermophilus and B. subtilis treated at 300 MPa with Ti = 75 °C. The results showed that G. stearothermophilus and B. subtilis have higher resistance to the Ultra High-Pressure Homogenization treatments applied than the other microorganisms inoculated and that a treatment performed at 300 MPa with Ti = 85 °C was necessary to completely inactivate these microorganisms at the spore level inoculated (∼1 × 10(6) CFU/mL). Besides, a change in the resistance of B. licheniformis, B. sporothermodurans, G. stearothermophilus and B. subtilis spores was observed as the inactivation obtained increased remarkably in treatments performed with Ti between 65 and 75 °C. This study provides important evidence of the suitability of UHPH technology for the inactivation of spores in high numbers, leading to the possibility of obtaining commercially sterile milk. Copyright © 2014 Elsevier Ltd. All rights reserved.

  15. Performance of a clinical gridded electron gun in magnetic fields: Implications for MRI-linac therapy.

    PubMed

    Whelan, Brendan; Holloway, Lois; Constantin, Dragos; Oborn, Brad; Bazalova-Carter, Magdalena; Fahrig, Rebecca; Keall, Paul

    2016-11-01

    MRI-linac therapy is a rapidly growing field, and requires that conventional linear accelerators are operated with the fringe field of MRI magnets. One of the most sensitive accelerator components is the electron gun, which serves as the source of the beam. The purpose of this work was to develop a validated finite element model (FEM) model of a clinical triode (or gridded) electron gun, based on accurate geometric and electrical measurements, and to characterize the performance of this gun in magnetic fields. The geometry of a Varian electron gun was measured using 3D laser scanning and digital calipers. The electric potentials and emission current of these guns were measured directly from six dose matched true beam linacs for the 6X, 10X, and 15X modes of operation. Based on these measurements, a finite element model (FEM) of the gun was developed using the commercial software opera/scala. The performance of the FEM model in magnetic fields was characterized using parallel fields ranging from 0 to 200 G in the in-line direction, and 0-35 G in the perpendicular direction. The FEM model matched the average measured emission current to within 5% across all three modes of operation. Different high voltage settings are used for the different modes; the 6X, 10X, and 15X modes have an average high voltage setting of 15, 10, and 11 kV. Due to these differences, different operating modes show different sensitivities in magnetic fields. For in line fields, the first current loss occurs at 40, 20, and 30 G for each mode. This is a much greater sensitivity than has previously been observed. For perpendicular fields, first beam loss occurred at 8, 5, and 5 G and total beam loss at 27, 22, and 20 G. A validated FEM model of a clinical triode electron gun has been developed based on accurate geometric and electrical measurements. Three different operating modes were simulated, with a maximum mean error of 5%. This gun shows greater sensitivity to in-line magnetic fields than

  16. Performance of a clinical gridded electron gun in magnetic fields: Implications for MRI-linac therapy

    PubMed Central

    Whelan, Brendan; Holloway, Lois; Constantin, Dragos; Oborn, Brad; Bazalova-Carter, Magdalena; Fahrig, Rebecca; Keall, Paul

    2016-01-01

    Purpose: MRI-linac therapy is a rapidly growing field, and requires that conventional linear accelerators are operated with the fringe field of MRI magnets. One of the most sensitive accelerator components is the electron gun, which serves as the source of the beam. The purpose of this work was to develop a validated finite element model (FEM) model of a clinical triode (or gridded) electron gun, based on accurate geometric and electrical measurements, and to characterize the performance of this gun in magnetic fields. Methods: The geometry of a Varian electron gun was measured using 3D laser scanning and digital calipers. The electric potentials and emission current of these guns were measured directly from six dose matched true beam linacs for the 6X, 10X, and 15X modes of operation. Based on these measurements, a finite element model (FEM) of the gun was developed using the commercial software opera/scala. The performance of the FEM model in magnetic fields was characterized using parallel fields ranging from 0 to 200 G in the in-line direction, and 0–35 G in the perpendicular direction. Results: The FEM model matched the average measured emission current to within 5% across all three modes of operation. Different high voltage settings are used for the different modes; the 6X, 10X, and 15X modes have an average high voltage setting of 15, 10, and 11 kV. Due to these differences, different operating modes show different sensitivities in magnetic fields. For in line fields, the first current loss occurs at 40, 20, and 30 G for each mode. This is a much greater sensitivity than has previously been observed. For perpendicular fields, first beam loss occurred at 8, 5, and 5 G and total beam loss at 27, 22, and 20 G. Conclusions: A validated FEM model of a clinical triode electron gun has been developed based on accurate geometric and electrical measurements. Three different operating modes were simulated, with a maximum mean error of 5%. This gun shows greater

  17. Lesion detection in ultra-wide field retinal images for diabetic retinopathy diagnosis

    NASA Astrophysics Data System (ADS)

    Levenkova, Anastasia; Sowmya, Arcot; Kalloniatis, Michael; Ly, Angelica; Ho, Arthur

    2018-02-01

    Diabetic retinopathy (DR) leads to irreversible vision loss. Diagnosis and staging of DR is usually based on the presence, number, location and type of retinal lesions. Ultra-wide field (UWF) digital scanning laser technology provides an opportunity for computer-aided DR lesion detection. High-resolution UWF images (3078×2702 pixels) may allow detection of more clinically relevant retinopathy in comparison with conventional retinal images as UWF imaging covers a 200° retinal area, versus 45° by conventional cameras. Current approaches to DR diagnosis that analyze 7-field Early Treatment Diabetic Retinopathy Study (ETDRS) retinal images provide similar results to UWF imaging. However, in 40% of cases, more retinopathy was found outside the 7- field ETDRS fields by UWF and in 10% of cases, retinopathy was reclassified as more severe. The reason is that UWF images examine both the central retina and more peripheral regions. We propose an algorithm for automatic detection and classification of DR lesions such as cotton wool spots, exudates, microaneurysms and haemorrhages in UWF images. The algorithm uses convolutional neural network (CNN) as a feature extractor and classifies the feature vectors extracted from colour-composite UWF images using a support vector machine (SVM). The main contribution includes detection of four types of DR lesions in the peripheral retina for diagnostic purposes. The evaluation dataset contains 146 UWF images. The proposed method for detection of DR lesion subtypes in UWF images using two scenarios for transfer learning achieved AUC ≈ 80%. Data was split at the patient level to validate the proposed algorithm.

  18. The effect of cognitive remediation in individuals at ultra-high risk for psychosis: a systematic review.

    PubMed

    Glenthøj, Louise Birkedal; Hjorthøj, Carsten; Kristensen, Tina Dam; Davidson, Charlie Andrew; Nordentoft, Merete

    2017-01-01

    Cognitive deficits are prominent features of the ultra-high risk state for psychosis that are known to impact functioning and course of illness. Cognitive remediation appears to be the most promising treatment approach to alleviate the cognitive deficits, which may translate into functional improvements. This study systematically reviewed the evidence on the effectiveness of cognitive remediation in the ultra-high risk population. The electronic databases MEDLINE, PsycINFO, and Embase were searched using keywords related to cognitive remediation and the UHR state. Studies were included if they were peer-reviewed, written in English, and included a population meeting standardized ultra-high risk criteria. Six original research articles were identified. All the studies provided computerized, bottom-up-based cognitive remediation, predominantly targeting neurocognitive function. Four out of five studies that reported a cognitive outcome found cognitive remediation to improve cognition in the domains of verbal memory, attention, and processing speed. Two out of four studies that reported on functional outcome found cognitive remediation to improve the functional outcome in the domains of social functioning and social adjustment. Zero out of the five studies that reported such an outcome found cognitive remediation to affect the magnitude of clinical symptoms. Research on the effect of cognitive remediation in the ultra-high risk state is still scarce. The current state of evidence indicates an effect of cognitive remediation on cognition and functioning in ultra-high risk individuals. More research on cognitive remediation in ultra-high risk is needed, notably in large-scale trials assessing the effect of neurocognitive and/or social cognitive remediation on multiple outcomes.

  19. Development of an MRI-compatible digital SiPM detector stack for simultaneous PET/MRI

    PubMed Central

    Düppenbecker, Peter M; Weissler, Bjoern; Gebhardt, Pierre; Schug, David; Wehner, Jakob; Marsden, Paul K; Schulz, Volkmar

    2016-01-01

    Abstract Advances in solid-state photon detectors paved the way to combine positron emission tomography (PET) and magnetic resonance imaging (MRI) into highly integrated, truly simultaneous, hybrid imaging systems. Based on the most recent digital SiPM technology, we developed an MRI-compatible PET detector stack, intended as a building block for next generation simultaneous PET/MRI systems. Our detector stack comprises an array of 8 × 8 digital SiPM channels with 4 mm pitch using Philips Digital Photon Counting DPC 3200-22 devices, an FPGA for data acquisition, a supply voltage control system and a cooling infrastructure. This is the first detector design that allows the operation of digital SiPMs simultaneously inside an MRI system. We tested and optimized the MRI-compatibility of our detector stack on a laboratory test bench as well as in combination with a Philips Achieva 3 T MRI system. Our design clearly reduces distortions of the static magnetic field compared to a conventional design. The MRI static magnetic field causes weak and directional drift effects on voltage regulators, but has no direct impact on detector performance. MRI gradient switching initially degraded energy and timing resolution. Both distortions could be ascribed to voltage variations induced on the bias and the FPGA core voltage supply respectively. Based on these findings, we improved our detector design and our final design shows virtually no energy or timing degradations, even during heavy and continuous MRI gradient switching. In particular, we found no evidence that the performance of the DPC 3200-22 digital SiPM itself is degraded by the MRI system. PMID:28458919

  20. MRI differentiation of low-grade from high-grade appendicular chondrosarcoma.

    PubMed

    Douis, Hassan; Singh, Leanne; Saifuddin, Asif

    2014-01-01

    To identify magnetic resonance imaging (MRI) features which differentiate low-grade chondral lesions (atypical cartilaginous tumours/grade 1 chondrosarcoma) from high-grade chondrosarcomas (grade 2, grade 3 and dedifferentiated chondrosarcoma) of the major long bones. We identified all patients treated for central atypical cartilaginous tumours and central chondrosarcoma of major long bones (humerus, femur, tibia) over a 13-year period. The MRI studies were assessed for the following features: bone marrow oedema, soft tissue oedema, bone expansion, cortical thickening, cortical destruction, active periostitis, soft tissue mass and tumour length. The MRI-features were compared with the histopathological tumour grading using univariate, multivariate logistic regression and receiver operating characteristic curve (ROC) analyses. One hundred and seventy-nine tumours were included in this retrospective study. There were 28 atypical cartilaginous tumours, 79 grade 1 chondrosarcomas, 36 grade 2 chondrosarcomas, 13 grade 3 chondrosarcomas and 23 dedifferentiated chondrosarcomas. Multivariate analysis demonstrated that bone expansion (P = 0.001), active periostitis (P = 0.001), soft tissue mass (P < 0.001) and tumour length (P < 0.001) were statistically significant differentiating factors between low-grade and high-grade chondral lesions with an area under the ROC curve of 0.956. On MRI, bone expansion, active periostitis, soft tissue mass and tumour length can reliably differentiate high-grade chondrosarcomas from low-grade chondral lesions of the major long bones. • Accurate differentiation of low-grade from high-grade chondrosarcomas is essential before surgery • MRI can reliably differentiate high-grade from low-grade chondrosarcomas of long bone • Differentiating features are bone expansion, periostitis, soft tissue mass and tumour length • Presence of these four MRI features demonstrated a diagnostic accuracy (AUC) of 95.6 % • The findings

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

    NASA Astrophysics Data System (ADS)

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

    2004-11-01

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

  2. Gas-Enhanced Ultra-High Shear Mixing: A Concept and Applications

    NASA Astrophysics Data System (ADS)

    Czerwinski, Frank; Birsan, Gabriel

    2017-04-01

    The processes of mixing, homogenizing, and deagglomeration are of paramount importance in many industries for modifying properties of liquids or liquid-based dispersions at room temperature and treatment of molten or semi-molten alloys at high temperatures, prior to their solidification. To implement treatments, a variety of technologies based on mechanical, electromagnetic, and ultrasonic principles are used commercially or tested at the laboratory scale. In a large number of techniques, especially those tailored toward metallurgical applications, the vital role is played by cavitation, generation of gas bubbles, and their interaction with the melt. This paper describes a novel concept exploring an integration of gas injection into the shear zone with ultra-high shear mixing. As revealed via experiments with a prototype of the cylindrical rotor-stator apparatus and transparent media, gases injected radially through the high-speed rotor generate highly refined bubbles of high concentration directly in the shear zone of the mixer. It is believed that an interaction of large volume of fine gas bubbles with the liquid, superimposed on ultra-high shear, will enhance mixing capabilities and cause superior refining and homogenizing of the liquids or solid-liquid slurries, thus allowing their effective property modification.

  3. Correction of MRI-induced geometric distortions in whole-body small animal PET-MRI

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Frohwein, Lynn J., E-mail: frohwein@uni-muenster.de; Schäfers, Klaus P.; Hoerr, Verena

    Purpose: The fusion of positron emission tomography (PET) and magnetic resonance imaging (MRI) data can be a challenging task in whole-body PET-MRI. The quality of the registration between these two modalities in large field-of-views (FOV) is often degraded by geometric distortions of the MRI data. The distortions at the edges of large FOVs mainly originate from MRI gradient nonlinearities. This work describes a method to measure and correct for these kind of geometric distortions in small animal MRI scanners to improve the registration accuracy of PET and MRI data. Methods: The authors have developed a geometric phantom which allows themore » measurement of geometric distortions in all spatial axes via control points. These control points are detected semiautomatically in both PET and MRI data with a subpixel accuracy. The spatial transformation between PET and MRI data is determined with these control points via 3D thin-plate splines (3D TPS). The transformation derived from the 3D TPS is finally applied to real MRI mouse data, which were acquired with the same scan parameters used in the phantom data acquisitions. Additionally, the influence of the phantom material on the homogeneity of the magnetic field is determined via field mapping. Results: The spatial shift according to the magnetic field homogeneity caused by the phantom material was determined to a mean of 0.1 mm. The results of the correction show that distortion with a maximum error of 4 mm could be reduced to less than 1 mm with the proposed correction method. Furthermore, the control point-based registration of PET and MRI data showed improved congruence after correction. Conclusions: The developed phantom has been shown to have no considerable negative effect on the homogeneity of the magnetic field. The proposed method yields an appropriate correction of the measured MRI distortion and is able to improve the PET and MRI registration. Furthermore, the method is applicable to whole-body small

  4. Variable Stars in the Field of the Hydra II Ultra-faint Dwarf Galaxy

    NASA Astrophysics Data System (ADS)

    Vivas, A. Katherina; Olsen, Knut; Blum, Robert; Nidever, David L.; Walker, Alistair R.; Martin, Nicolas F.; Besla, Gurtina; Gallart, Carme; van der Marel, Roeland P.; Majewski, Steven R.; Kaleida, Catherine C.; Muñoz, Ricardo R.; Saha, Abhijit; Conn, Blair C.; Jin, Shoko

    2016-05-01

    We report the discovery of one RR Lyrae star in the ultra-faint satellite galaxy Hydra II based on time series photometry in the g, r and I bands obtained with the Dark Energy Camera at Cerro Tololo Inter-American Observatory, Chile. The association of the RR Lyrae star discovered here with Hydra II is clear because is located at 42\\prime\\prime from the center of the dwarf, well within its half-light radius of 102\\prime\\prime . The RR Lyrae star has a mean magnitude of I=21.30+/- 0.04 which is too faint to be a field halo star. This magnitude translates to a heliocentric distance of 151 ± 8 kpc for Hydra II; this value is ˜ 13% larger than the estimate from the discovery paper based on the average magnitude of several blue horizontal branch star candidates. The new distance implies a slightly larger half-light radius of {76}-10+12 pc and a brighter absolute magnitude of {M}V=-5.1+/- 0.3, which keeps this object within the realm of the dwarf galaxies. A comparison with other RR Lyrae stars in ultra-faint systems indicates similar pulsational properties among them, which are different to those found among halo field stars and those in the largest of the Milky Way satellites. We also report the discovery of 31 additional short period variables in the field of view (RR Lyrae, SX Phe, eclipsing binaries, and a likely anomalous cepheid) which are likely not related with Hydra II.

  5. On the maximum energy of shock-accelerated cosmic rays at ultra-relativistic shocks

    NASA Astrophysics Data System (ADS)

    Reville, B.; Bell, A. R.

    2014-04-01

    The maximum energy to which cosmic rays can be accelerated at weakly magnetised ultra-relativistic shocks is investigated. We demonstrate that for such shocks, in which the scattering of energetic particles is mediated exclusively by ion skin-depth scale structures, as might be expected for a Weibel-mediated shock, there is an intrinsic limit on the maximum energy to which particles can be accelerated. This maximum energy is determined from the requirement that particles must be isotropized in the downstream plasma frame before the mean field transports them far downstream, and falls considerably short of what is required to produce ultra-high-energy cosmic rays. To circumvent this limit, a highly disorganized field is required on larger scales. The growth of cosmic ray-induced instabilities on wavelengths much longer than the ion-plasma skin depth, both upstream and downstream of the shock, is considered. While these instabilities may play an important role in magnetic field amplification at relativistic shocks, on scales comparable to the gyroradius of the most energetic particles, the calculated growth rates have insufficient time to modify the scattering. Since strong modification is a necessary condition for particles in the downstream region to re-cross the shock, in the absence of an alternative scattering mechanism, these results imply that acceleration to higher energies is ruled out. If weakly magnetized ultra-relativistic shocks are disfavoured as high-energy particle accelerators in general, the search for potential sources of ultra-high-energy cosmic rays can be narrowed.

  6. Ultra-high speed vacuum pump system with first stage turbofan and second stage turbomolecular pump

    DOEpatents

    Jostlein, Hans

    2006-04-04

    An ultra-high speed vacuum pump evacuation system includes a first stage ultra-high speed turbofan and a second stage conventional turbomolecular pump. The turbofan is either connected in series to a chamber to be evacuated, or is optionally disposed entirely within the chamber. The turbofan employs large diameter rotor blades operating at high linear blade velocity to impart an ultra-high pumping speed to a fluid. The second stage turbomolecular pump is fluidly connected downstream from the first stage turbofan. In operation, the first stage turbofan operates in a pre-existing vacuum, with the fluid asserting only small axial forces upon the rotor blades. The turbofan imparts a velocity to fluid particles towards an outlet at a high volume rate, but moderate compression ratio. The second stage conventional turbomolecular pump then compresses the fluid to pressures for evacuation by a roughing pump.

  7. Ultra high energy gamma rays, cosmic rays and neutrinos from accreting degenerate stars

    NASA Technical Reports Server (NTRS)

    Brecher, K.; Chanmugam, G.

    1985-01-01

    Super-Eddington accretion for a recently proposed unipolar induction model of cosmic ray acceleration in accreting binary star systems containing magnetic white dwarfs or neutron stars is considered. For sufficiently high accretion rates and low magnetic fields, the model can account for: (1) acceleration of cosmic ray nuclei up to energies of 10 to the 19th power eV; (2) production of more or less normal solar cosmic ray composition; (3) the bulk of cosmic rays observed with energies above 1 TeV, and probably even down to somewhat lower energies as well; and (4) possibly the observed antiproton cosmic ray flux. It can also account for the high ultra high energy (UHE) gamma ray flux observed from several accreting binary systems (including Cygnus X-3), while allowing the possibility of an even higher neutrino flux from these sources, with L sub nu/L sub gamma is approximately 100.

  8. A deep ALMA image of the Hubble Ultra Deep Field

    NASA Astrophysics Data System (ADS)

    Dunlop, J. S.; McLure, R. J.; Biggs, A. D.; Geach, J. E.; Michałowski, M. J.; Ivison, R. J.; Rujopakarn, W.; van Kampen, E.; Kirkpatrick, A.; Pope, A.; Scott, D.; Swinbank, A. M.; Targett, T. A.; Aretxaga, I.; Austermann, J. E.; Best, P. N.; Bruce, V. A.; Chapin, E. L.; Charlot, S.; Cirasuolo, M.; Coppin, K.; Ellis, R. S.; Finkelstein, S. L.; Hayward, C. C.; Hughes, D. H.; Ibar, E.; Jagannathan, P.; Khochfar, S.; Koprowski, M. P.; Narayanan, D.; Nyland, K.; Papovich, C.; Peacock, J. A.; Rieke, G. H.; Robertson, B.; Vernstrom, T.; Werf, P. P. van der; Wilson, G. W.; Yun, M.

    2017-04-01

    We present the results of the first, deep Atacama Large Millimeter Array (ALMA) imaging covering the full ≃4.5 arcmin2 of the Hubble Ultra Deep Field (HUDF) imaged with Wide Field Camera 3/IR on HST. Using a 45-pointing mosaic, we have obtained a homogeneous 1.3-mm image reaching σ1.3 ≃ 35 μJy, at a resolution of ≃0.7 arcsec. From an initial list of ≃50 > 3.5σ peaks, a rigorous analysis confirms 16 sources with S1.3 > 120 μJy. All of these have secure galaxy counterparts with robust redshifts ( = 2.15). Due to the unparalleled supporting data, the physical properties of the ALMA sources are well constrained, including their stellar masses (M*) and UV+FIR star formation rates (SFR). Our results show that stellar mass is the best predictor of SFR in the high-redshift Universe; indeed at z ≥ 2 our ALMA sample contains seven of the nine galaxies in the HUDF with M* ≥ 2 × 1010 M⊙, and we detect only one galaxy at z > 3.5, reflecting the rapid drop-off of high-mass galaxies with increasing redshift. The detections, coupled with stacking, allow us to probe the redshift/mass distribution of the 1.3-mm background down to S1.3 ≃ 10 μJy. We find strong evidence for a steep star-forming 'main sequence' at z ≃ 2, with SFR ∝M* and a mean specific SFR ≃ 2.2 Gyr-1. Moreover, we find that ≃85 per cent of total star formation at z ≃ 2 is enshrouded in dust, with ≃65 per cent of all star formation at this epoch occurring in high-mass galaxies (M* > 2 × 1010 M⊙), for which the average obscured:unobscured SF ratio is ≃200. Finally, we revisit the cosmic evolution of SFR density; we find this peaks at z ≃ 2.5, and that the star-forming Universe transits from primarily unobscured to primarily obscured at z ≃ 4.

  9. Silicon-graphene conductive photodetector with ultra-high responsivity

    PubMed Central

    Liu, Jingjing; Yin, Yanlong; Yu, Longhai; Shi, Yaocheng; Liang, Di; Dai, Daoxin

    2017-01-01

    Graphene is attractive for realizing optoelectronic devices, including photodetectors because of the unique advantages. It can easily co-work with other semiconductors to form a Schottky junction, in which the photo-carrier generated by light absorption in the semiconductor might be transported to the graphene layer efficiently by the build-in field. It changes the graphene conduction greatly and provides the possibility of realizing a graphene-based conductive-mode photodetector. Here we design and demonstrate a silicon-graphene conductive photodetector with improved responsivity and response speed. An electrical-circuit model is established and the graphene-sheet pattern is designed optimally for maximizing the responsivity. The fabricated silicon-graphene conductive photodetector shows a responsivity of up to ~105 A/W at room temperature (27 °C) and the response time is as short as ~30 μs. The temperature dependence of the silicon-graphene conductive photodetector is studied for the first time. It is shown that the silicon-graphene conductive photodetector has ultra-high responsivity when operating at low temperature, which provides the possibility to detect extremely weak optical power. For example, the device can detect an input optical power as low as 6.2 pW with the responsivity as high as 2.4 × 107 A/W when operating at −25 °C in our experiment. PMID:28106084

  10. On the Contribution of Curl-Free Current Patterns to the Ultimate Intrinsic Signal-to-Noise Ratio at Ultra-High Field Strength.

    PubMed

    Pfrommer, Andreas; Henning, Anke

    2017-05-01

    The ultimate intrinsic signal-to-noise ratio (SNR) is a coil independent performance measure to compare different receive coil designs. To evaluate this benchmark in a sample, a complete electromagnetic basis set is required. The basis set can be obtained by curl-free and divergence-free surface current distributions, which excite linearly independent solutions to Maxwell's equations. In this work, we quantitatively investigate the contribution of curl-free current patterns to the ultimate intrinsic SNR in a spherical head-sized model at 9.4 T. Therefore, we compare the ultimate intrinsic SNR obtained with having only curl-free or divergence-free current patterns, with the ultimate intrinsic SNR obtained from a combination of curl-free and divergence-free current patterns. The influence of parallel imaging is studied for various acceleration factors. Moreover results for different field strengths (1.5 T up to 11.7 T) are presented at specific voxel positions and acceleration factors. The full-wave electromagnetic problem is analytically solved using dyadic Green's functions. We show, that at ultra-high field strength (B 0 ⩾7T) a combination of curl-free and divergence-free current patterns is required to achieve the best possible SNR at any position in a spherical head-sized model. On 1.5- and 3T platforms, divergence-free current patterns are sufficient to cover more than 90% of the ultimate intrinsic SNR. Copyright © 2017 John Wiley & Sons, Ltd.

  11. Ultra low-level measurements of actinides by sector field ICP-MS.

    PubMed

    Pointurier, F; Baglan, N; Hémet, P

    2004-01-01

    In the present work, a double-focusing sector field inductively coupled plasma-mass spectrometer was optimised for ultra trace and isotopic analyses of actinide long-lived isotopes in low concentration solutions of the fgml(-1) to the ngml(-1) range. Sensitivities of about 3GHz/(microgml(-1)), with as low a background as 0.1cps, were obtained for U using a conventional concentric pneumatic nebuliser. Detection limits are below the fg range for 239Pu and 240Pu. With natural U, a precision lower than 0.5% RSD is currently obtained for 235U/238U isotopic ratio at the 200pgml(-1) level.

  12. Simultaneous Multi-Slice fMRI using Spiral Trajectories

    PubMed Central

    Zahneisen, Benjamin; Poser, Benedikt A.; Ernst, Thomas; Stenger, V. Andrew

    2014-01-01

    Parallel imaging methods using multi-coil receiver arrays have been shown to be effective for increasing MRI acquisition speed. However parallel imaging methods for fMRI with 2D sequences show only limited improvements in temporal resolution because of the long echo times needed for BOLD contrast. Recently, Simultaneous Multi-Slice (SMS) imaging techniques have been shown to increase fMRI temporal resolution by factors of four and higher. In SMS fMRI multiple slices can be acquired simultaneously using Echo Planar Imaging (EPI) and the overlapping slices are un-aliased using a parallel imaging reconstruction with multiple receivers. The slice separation can be further improved using the “blipped-CAIPI” EPI sequence that provides a more efficient sampling of the SMS 3D k-space. In this paper a blipped-spiral SMS sequence for ultra-fast fMRI is presented. The blipped-spiral sequence combines the sampling efficiency of spiral trajectories with the SMS encoding concept used in blipped-CAIPI EPI. We show that blipped spiral acquisition can achieve almost whole brain coverage at 3 mm isotropic resolution in 168 ms. It is also demonstrated that the high temporal resolution allows for dynamic BOLD lag time measurement using visual/motor and retinotopic mapping paradigms. The local BOLD lag time within the visual cortex following the retinotopic mapping stimulation of expanding flickering rings is directly measured and easily translated into an eccentricity map of the cortex. PMID:24518259

  13. Design of Ultra-High Temperature Ceramics for Improved Performance

    DTIC Science & Technology

    2009-02-28

    e.g., grain boundary chemistry or change in impurity concentrations) or physical (e.g., residual stress) effects. 600 co 500 a. oi400 c CD i...SA037 Effects of oxygen content on the properties of supcr-high-teiiiperature resistant Si-AI- C fibers D.f. Zhao (National University of Defense...of Technology, China) 15:05 S A034 Oxyacetylene ablation behavior of carbon fibers reinforced carbon matrix and ultra-high temperature

  14. mrsFAST-Ultra: a compact, SNP-aware mapper for high performance sequencing applications.

    PubMed

    Hach, Faraz; Sarrafi, Iman; Hormozdiari, Farhad; Alkan, Can; Eichler, Evan E; Sahinalp, S Cenk

    2014-07-01

    High throughput sequencing (HTS) platforms generate unprecedented amounts of data that introduce challenges for processing and downstream analysis. While tools that report the 'best' mapping location of each read provide a fast way to process HTS data, they are not suitable for many types of downstream analysis such as structural variation detection, where it is important to report multiple mapping loci for each read. For this purpose we introduce mrsFAST-Ultra, a fast, cache oblivious, SNP-aware aligner that can handle the multi-mapping of HTS reads very efficiently. mrsFAST-Ultra improves mrsFAST, our first cache oblivious read aligner capable of handling multi-mapping reads, through new and compact index structures that reduce not only the overall memory usage but also the number of CPU operations per alignment. In fact the size of the index generated by mrsFAST-Ultra is 10 times smaller than that of mrsFAST. As importantly, mrsFAST-Ultra introduces new features such as being able to (i) obtain the best mapping loci for each read, and (ii) return all reads that have at most n mapping loci (within an error threshold), together with these loci, for any user specified n. Furthermore, mrsFAST-Ultra is SNP-aware, i.e. it can map reads to reference genome while discounting the mismatches that occur at common SNP locations provided by db-SNP; this significantly increases the number of reads that can be mapped to the reference genome. Notice that all of the above features are implemented within the index structure and are not simple post-processing steps and thus are performed highly efficiently. Finally, mrsFAST-Ultra utilizes multiple available cores and processors and can be tuned for various memory settings. Our results show that mrsFAST-Ultra is roughly five times faster than its predecessor mrsFAST. In comparison to newly enhanced popular tools such as Bowtie2, it is more sensitive (it can report 10 times or more mappings per read) and much faster (six times or

  15. MDOT aims for lower-cost ultra-high performance concrete : research spotlight.

    DOT National Transportation Integrated Search

    2016-08-01

    In recent years, several vendors have developed ultra-high performance : concrete (UHPC) that surpasses traditional concrete mixes by offering : exceptional freeze-thaw resistance, reduced susceptibility to cracking : and far less reinforcement corro...

  16. A brain MRI bias field correction method created in the Gaussian multi-scale space

    NASA Astrophysics Data System (ADS)

    Chen, Mingsheng; Qin, Mingxin

    2017-07-01

    A pre-processing step is needed to correct for the bias field signal before submitting corrupted MR images to such image-processing algorithms. This study presents a new bias field correction method. The method creates a Gaussian multi-scale space by the convolution of the inhomogeneous MR image with a two-dimensional Gaussian function. In the multi-Gaussian space, the method retrieves the image details from the differentiation of the original image and convolution image. Then, it obtains an image whose inhomogeneity is eliminated by the weighted sum of image details in each layer in the space. Next, the bias field-corrected MR image is retrieved after the Υ correction, which enhances the contrast and brightness of the inhomogeneity-eliminated MR image. We have tested the approach on T1 MRI and T2 MRI with varying bias field levels and have achieved satisfactory results. Comparison experiments with popular software have demonstrated superior performance of the proposed method in terms of quantitative indices, especially an improvement in subsequent image segmentation.

  17. Ultrastructural Study on Ultra-Low Frequency Electromagnetic Fields and Transfer Factor Effects on Skin Ulcers

    NASA Astrophysics Data System (ADS)

    Cadena, M. S. Reyes; Chapul, L. Sánchez; Pérez, Javiér; García, M. N. Jiménez; López, M. A. Jiménez; Espíndola, M. E. Sánchez; Perez, R. Paniagua; Hernández, N. A.; Paniagua, G.; Uribe, F.; Nava, J. J. Godina; Segura, M. A. Rodríguez

    2008-08-01

    We determined the effect of 120Hz ultra low frequency electromagnetic field (ELF) on the healing process of skin in 20 Wistar rats distributed in four groups in which chronic dermal ulcers had been produced. The first two groups received a dose of the transfer factor and interferon-beta (IFN-β) every 24 h during 12 days. The third group (positive control) received only electromagnetic field (ELF) sessions, and in the fourth group (negative control), no treatment was applied. The electromagnetic field was applied through a Helmholtz coils; 30 Gauss of intensity. Results shown histological changes that improve the healing process in animals subjected to ELF together with the transfer factor.

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

    DOEpatents

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

    2013-03-05

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

  19. Backscatter dose effects for high atomic number materials being irradiated in the presence of a magnetic field: A Monte Carlo study for the MRI linac

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ahmad, Syed Bilal

    Purpose: To quantify and explain the backscatter dose effects for clinically relevant high atomic number materials being irradiated in the presence of a 1.5 T transverse magnetic field. Methods: Interface effects were investigated using Monte Carlo simulation techniques. We used GPUMCD (v5.1) and GEANT4 (v10.1) for this purpose. GPUMCD is a commercial software written for the Elekta AB, MRI linac. Dose was scored using GPUMCD in cubic voxels of side 1 and 0.5 mm, in two different virtual phantoms of dimensions 20 × 20 × 20 cm and 5 × 5 × 13.3 cm, respectively. A photon beam was generatedmore » from a point 143.5 cm away from the isocenter with energy distribution sampled from a histogram representing the true Elekta, MRI linac photon spectrum. A slab of variable thickness and position containing either bone, aluminum, titanium, stainless steel, or one of the two different dental filling materials was inserted as an inhomogeneity in the 20 × 20 × 20 cm phantom. The 5 × 5 × 13.3 cm phantom was used as a clinical test case in order to explain the dose perturbation effects for a head and neck cancer patient. The back scatter dose factor (BSDF) was defined as the ratio of the doses at a given depth with and without the presence of the inhomogeneity. Backscattered electron fluence was calculated at the inhomogeneity interface using GEANT4. A 1.5 T magnetic field was applied perpendicular to the direction of the beam in both phantoms, identical to the geometry in the Elekta MRI linac. Results: With the application of a 1.5 T magnetic field, all the BSDF’s were reduced by 12%–47%, compared to the no magnetic field case. The corresponding backscattered electron fluence at the interface was also reduced by 45%–64%. The reduction in the BSDF at the interface, due to the application of the magnetic field, is manifested in a different manner for each material. In the case of bone, the dose drops at the interface contrary to the expected increase when no magnetic

  20. Multilayer ultra-high-temperature ceramic coatings

    DOEpatents

    Loehman, Ronald E [Albuquerque, NM; Corral, Erica L [Tucson, AZ

    2012-03-20

    A coated carbon-carbon composite material with multiple ceramic layers to provide oxidation protection from ultra-high-temperatures, where if the carbon-carbon composite material is uninhibited with B.sub.4C particles, then the first layer on the composite material is selected from ZrB.sub.2 and HfB.sub.2, onto which is coated a layer of SiC coated and if the carbon-carbon composite material is inhibited with B.sub.4C particles, then protection can be achieved with a layer of SiC and a layer of either ZrB.sub.2 and HfB.sub.2 in any order.

  1. Simulation of concomitant magnetic fields on fast switched gradient coils used in advanced application of MRI

    NASA Astrophysics Data System (ADS)

    Salinas-Muciño, G.; Torres-García, E.; Hidalgo-Tobon, S.

    2012-10-01

    The process to produce an MR image includes nuclear alignment, RF excitation, spatial encoding, and image formation. To form an image, it is necessary to perform spatial localization of the MR signals, which is achieved using gradient coils. MRI requires the use of gradient coils that generate magnetic fields, which vary linearly with position over the imaging volume. Safety issues have been a motivation to study deeply the relation between the interaction of gradient magnetic field and the peripheral nerve stimulation. In this work is presented a numerical modeling between the concomitant magnetic fields produced by the gradient coils and the electric field induced in a cube with σ conductivity by the gradient field switching in pulse sequences as Eco planar Imaging (EPI), due to this kind of sequence is the most used in advance applications of magnetic resonance imaging as functional MRI, cardiac imaging or diffusion.

  2. Passive magnetic shielding in MRI-Linac systems.

    PubMed

    Whelan, Brendan; Kolling, Stefan; Oborn, Brad M; Keall, Paul

    2018-03-26

    Passive magnetic shielding refers to the use of ferromagnetic materials to redirect magnetic field lines away from vulnerable regions. An application of particular interest to the medical physics community is shielding in MRI systems, especially integrated MRI-linear accelerator (MRI-Linac) systems. In these systems, the goal is not only to minimize the magnetic field in some volume, but also to minimize the impact of the shield on the magnetic fields within the imaging volume of the MRI scanner. In this work, finite element modelling was used to assess the shielding of a side coupled 6 MV linac and resultant heterogeneity induced within the 30 cm diameter of spherical volume (DSV) of a novel 1 Tesla split bore MRI magnet. A number of different shield parameters were investigated; distance between shield and magnet, shield shape, shield thickness, shield length, openings in the shield, number of concentric layers, spacing between each layer, and shield material. Both the in-line and perpendicular MRI-Linac configurations were studied. By modifying the shield shape around the linac from the starting design of an open ended cylinder, the shielding effect was boosted by approximately 70% whilst the impact on the magnet was simultaneously reduced by approximately 10%. Openings in the shield for the RF port and beam exit were substantial sources of field leakage; however it was demonstrated that shielding could be added around these openings to compensate for this leakage. Layering multiple concentric shield shells was highly effective in the perpendicular configuration, but less so for the in-line configuration. Cautious use of high permeability materials such as Mu-metal can greatly increase the shielding performance in some scenarios. In the perpendicular configuration, magnetic shielding was more effective and the impact on the magnet lower compared with the in-line configuration.

  3. Passive magnetic shielding in MRI-Linac systems

    NASA Astrophysics Data System (ADS)

    Whelan, Brendan; Kolling, Stefan; Oborn, Brad M.; Keall, Paul

    2018-04-01

    Passive magnetic shielding refers to the use of ferromagnetic materials to redirect magnetic field lines away from vulnerable regions. An application of particular interest to the medical physics community is shielding in MRI systems, especially integrated MRI-linear accelerator (MRI-Linac) systems. In these systems, the goal is not only to minimize the magnetic field in some volume, but also to minimize the impact of the shield on the magnetic fields within the imaging volume of the MRI scanner. In this work, finite element modelling was used to assess the shielding of a side coupled 6 MV linac and resultant heterogeneity induced within the 30 cm diameter of spherical volume (DSV) of a novel 1 Tesla split bore MRI magnet. A number of different shield parameters were investigated; distance between shield and magnet, shield shape, shield thickness, shield length, openings in the shield, number of concentric layers, spacing between each layer, and shield material. Both the in-line and perpendicular MRI-Linac configurations were studied. By modifying the shield shape around the linac from the starting design of an open ended cylinder, the shielding effect was boosted by approximately 70% whilst the impact on the magnet was simultaneously reduced by approximately 10%. Openings in the shield for the RF port and beam exit were substantial sources of field leakage; however it was demonstrated that shielding could be added around these openings to compensate for this leakage. Layering multiple concentric shield shells was highly effective in the perpendicular configuration, but less so for the in-line configuration. Cautious use of high permeability materials such as Mu-metal can greatly increase the shielding performance in some scenarios. In the perpendicular configuration, magnetic shielding was more effective and the impact on the magnet lower compared with the in-line configuration.

  4. Ultra-high-speed variable focus optics for novel applications in advanced imaging

    NASA Astrophysics Data System (ADS)

    Kang, S.; Dotsenko, E.; Amrhein, D.; Theriault, C.; Arnold, C. B.

    2018-02-01

    With the advancement of ultra-fast manufacturing technologies, high speed imaging with high 3D resolution has become increasingly important. Here we show the use of an ultra-high-speed variable focus optical element, the TAG Lens, to enable new ways to acquire 3D information from an object. The TAG Lens uses sound to adjust the index of refraction profile in a liquid and thereby can achieve focal scanning rates greater than 100 kHz. When combined with a high-speed pulsed LED and a high-speed camera, we can exploit this phenomenon to achieve high-resolution imaging through large depths. By combining the image acquisition with digital image processing, we can extract relevant parameters such as tilt and angle information from objects in the image. Due to the high speeds at which images can be collected and processed, we believe this technique can be used as an efficient method of industrial inspection and metrology for high throughput applications.

  5. Application of Quantitative MRI for Brain Tissue Segmentation at 1.5 T and 3.0 T Field Strengths

    PubMed Central

    West, Janne; Blystad, Ida; Engström, Maria; Warntjes, Jan B. M.; Lundberg, Peter

    2013-01-01

    Background Brain tissue segmentation of white matter (WM), grey matter (GM), and cerebrospinal fluid (CSF) are important in neuroradiological applications. Quantitative Mri (qMRI) allows segmentation based on physical tissue properties, and the dependencies on MR scanner settings are removed. Brain tissue groups into clusters in the three dimensional space formed by the qMRI parameters R1, R2 and PD, and partial volume voxels are intermediate in this space. The qMRI parameters, however, depend on the main magnetic field strength. Therefore, longitudinal studies can be seriously limited by system upgrades. The aim of this work was to apply one recently described brain tissue segmentation method, based on qMRI, at both 1.5 T and 3.0 T field strengths, and to investigate similarities and differences. Methods In vivo qMRI measurements were performed on 10 healthy subjects using both 1.5 T and 3.0 T MR scanners. The brain tissue segmentation method was applied for both 1.5 T and 3.0 T and volumes of WM, GM, CSF and brain parenchymal fraction (BPF) were calculated on both field strengths. Repeatability was calculated for each scanner and a General Linear Model was used to examine the effect of field strength. Voxel-wise t-tests were also performed to evaluate regional differences. Results Statistically significant differences were found between 1.5 T and 3.0 T for WM, GM, CSF and BPF (p<0.001). Analyses of main effects showed that WM was underestimated, while GM and CSF were overestimated on 1.5 T compared to 3.0 T. The mean differences between 1.5 T and 3.0 T were -66 mL WM, 40 mL GM, 29 mL CSF and -1.99% BPF. Voxel-wise t-tests revealed regional differences of WM and GM in deep brain structures, cerebellum and brain stem. Conclusions Most of the brain was identically classified at the two field strengths, although some regional differences were observed. PMID:24066153

  6. NASA / Pratt and Whitney Collaborative Partnership Research in Ultra High Bypass Cycle Propulsion Concepts

    NASA Technical Reports Server (NTRS)

    Hughes, Chris; Lord, Wed

    2008-01-01

    Current collaborative research with Pratt & Whitney on Ultra High Bypass Engine Cycle noise, performance and emissions improvements as part of the Subsonic Fixed Wing Project Ultra High Bypass Engine Partnership Element is discussed. The Subsonic Fixed Wing Project goals are reviewed, as well as their relative technology level compared to previous NASA noise program goals. Progress toward achieving the Subsonic Fixed Wing Project goals over the 2008 fiscal year by the UHB Partnership in this area of research are reviewed. The current research activity in Ultra High Bypass Engine Cycle technology, specifically the Pratt & Whitney Geared Turbofan, at NASA and Pratt & Whitney are discussed including the contributions each entity bring toward the research project, and technical plans and objectives. Pratt & Whitney Geared Turbofan current and future technology and business plans are also discussed, including the role the NASA SFW UHB partnership plays toward achieving those goals.

  7. On magnetic field strength effect on velocity and turbulence characterization using Phase-Contrast Magnetic Resonance Imaging (PC-MRI)

    NASA Astrophysics Data System (ADS)

    van de Moortele, Pierre-Francois; Amili, Omid; Coletti, Filippo; Toloui, Mostafa

    2017-11-01

    Cardiovascular flows are predominantly laminar. Nevertheless, transient and even turbulent flows have been observed in the vicinity of the heart (e.g. valves, ascending aorta, valvular/vascular stenosis). Effective in-vivo hemodynamic-based diagnostics in these sites require both high-resolution velocity measurements (especially in the near-vessel wall regions) and accurate evaluation of blood flow turbulence level (e.g. in terms of TKE). In addition to phase contrast (PC), appropriately designed PC-MRI sequences provide intravoxel incoherent motion encoding, a unique tool for simultaneous, non-invasive evaluation of velocity 3D vector fields and Reynolds stresses in cardiovascular flows in vivo. However, limited spatial and temporal resolution of PC-MRI result in inaccuracies in the estimation of hemodynamics (e.g. WSS) and of flow turbulence characteristics. This study aims to assess whether SNR gains at higher magnetic field could overcome these limits, providing more accurate velocity and turbulence characterization at higher spatial resolution. Experiments are conducted on MR Scanners at 3 and 7 Tesla with a U-bent pipe flow shaped phantom. 3D velocity fields, Reynolds stresses and TKE are analyzed and compared to a reference PIV experiments.

  8. Ring-like spatial distribution of laser accelerated protons in the ultra-high-contrast TNSA-regime

    NASA Astrophysics Data System (ADS)

    Becker, G. A.; Tietze, S.; Keppler, S.; Reislöhner, J.; Bin, J. H.; Bock, L.; Brack, F.-E.; Hein, J.; Hellwing, M.; Hilz, P.; Hornung, M.; Kessler, A.; Kraft, S. D.; Kuschel, S.; Liebetrau, H.; Ma, W.; Polz, J.; Schlenvoigt, H.-P.; Schorcht, F.; Schwab, M. B.; Seidel, A.; Zeil, K.; Schramm, U.; Zepf, M.; Schreiber, J.; Rykovanov, S.; Kaluza, M. C.

    2018-05-01

    The spatial distribution of protons accelerated from submicron-thick plastic foil targets using multi-terawatt, frequency-doubled laser pulses with ultra-high temporal contrast has been investigated experimentally. A very stable, ring-like beam profile of the accelerated protons, oriented around the target’s normal direction has been observed. The ring’s opening angle has been found to decrease with increasing foil thicknesses. Two-dimensional particle-in-cell simulations reproduce our results indicating that the ring is formed during the expansion of the proton density distribution into the vacuum as described by the mechanism of target-normal sheath acceleration. Here—in addition to the longitudinal electric fields responsible for the forward acceleration of the protons—a lateral charge separation leads to transverse field components accelerating the protons in the lateral direction.

  9. An improved cylindrical FDTD method and its application to field-tissue interaction study in MRI.

    PubMed

    Chi, Jieru; Liu, Feng; Xia, Ling; Shao, Tingting; Mason, David G; Crozier, Stuart

    2010-01-01

    This paper presents a three dimensional finite-difference time-domain (FDTD) scheme in cylindrical coordinates with an improved algorithm for accommodating the numerical singularity associated with the polar axis. The regularization of this singularity problem is entirely based on Ampere's law. The proposed algorithm has been detailed and verified against a problem with a known solution obtained from a commercial electromagnetic simulation package. The numerical scheme is also illustrated by modeling high-frequency RF field-human body interactions in MRI. The results demonstrate the accuracy and capability of the proposed algorithm.

  10. An in vivo MRI Template Set for Morphometry, Tissue Segmentation, and fMRI Localization in Rats

    PubMed Central

    Valdés-Hernández, Pedro Antonio; Sumiyoshi, Akira; Nonaka, Hiroi; Haga, Risa; Aubert-Vásquez, Eduardo; Ogawa, Takeshi; Iturria-Medina, Yasser; Riera, Jorge J.; Kawashima, Ryuta

    2011-01-01

    Over the last decade, several papers have focused on the construction of highly detailed mouse high field magnetic resonance image (MRI) templates via non-linear registration to unbiased reference spaces, allowing for a variety of neuroimaging applications such as robust morphometric analyses. However, work in rats has only provided medium field MRI averages based on linear registration to biased spaces with the sole purpose of approximate functional MRI (fMRI) localization. This precludes any morphometric analysis in spite of the need of exploring in detail the neuroanatomical substrates of diseases in a recent advent of rat models. In this paper we present a new in vivo rat T2 MRI template set, comprising average images of both intensity and shape, obtained via non-linear registration. Also, unlike previous rat template sets, we include white and gray matter probabilistic segmentations, expanding its use to those applications demanding prior-based tissue segmentation, e.g., statistical parametric mapping (SPM) voxel-based morphometry. We also provide a preliminary digitalization of latest Paxinos and Watson atlas for anatomical and functional interpretations within the cerebral cortex. We confirmed that, like with previous templates, forepaw and hindpaw fMRI activations can be correctly localized in the expected atlas structure. To exemplify the use of our new MRI template set, were reported the volumes of brain tissues and cortical structures and probed their relationships with ontogenetic development. Other in vivo applications in the near future can be tensor-, deformation-, or voxel-based morphometry, morphological connectivity, and diffusion tensor-based anatomical connectivity. Our template set, freely available through the SPM extension website, could be an important tool for future longitudinal and/or functional extensive preclinical studies. PMID:22275894

  11. Multiple imputation of missing fMRI data in whole brain analysis

    PubMed Central

    Vaden, Kenneth I.; Gebregziabher, Mulugeta; Kuchinsky, Stefanie E.; Eckert, Mark A.

    2012-01-01

    anticipated to be particularly useful for 1) large fMRI data sets with inconsistent missing voxels across subjects and 2) addressing the problem of increased artifact at ultra-high field, which significantly limit the extent of whole brain coverage and interpretations of results. PMID:22500925

  12. 'Squeezing' near-field thermal emission for ultra-efficient high-power thermophotovoltaic conversion.

    PubMed

    Karalis, Aristeidis; Joannopoulos, J D

    2016-07-01

    We numerically demonstrate near-field planar ThermoPhotoVoltaic systems with very high efficiency and output power, at large vacuum gaps. Example performances include: at 1200 °K emitter temperature, output power density 2 W/cm(2) with ~47% efficiency at 300 nm vacuum gap; at 2100 °K, 24 W/cm(2) with ~57% efficiency at 200 nm gap; and, at 3000 °K, 115 W/cm(2) with ~61% efficiency at 140 nm gap. Key to this striking performance is a novel photonic design forcing the emitter and cell single modes to cros resonantly couple and impedance-match just above the semiconductor bandgap, creating there a 'squeezed' narrowband near-field emission spectrum. Specifically, we employ surface-plasmon-polariton thermal emitters and silver-backed semiconductor-thin-film photovoltaic cells. The emitter planar plasmonic nature allows for high-power and stable high-temperature operation. Our simulations include modeling of free-carrier absorption in both cell electrodes and temperature dependence of the emitter properties. At high temperatures, the efficiency enhancement via resonant mode cross-coupling and matching can be extended to even higher power, by appropriately patterning the silver back electrode to enforce also an absorber effective surface-plasmon-polariton mode. Our proposed designs can therefore lead the way for mass-producible and low-cost ThermoPhotoVoltaic micro-generators and solar cells.

  13. Advanced optical systems for ultra high energy cosmic rays detection

    NASA Astrophysics Data System (ADS)

    Gambicorti, L.; Pace, E.; Mazzinghi, P.

    2017-11-01

    A new advanced optical system is proposed and analysed in this work with the purpose to improve the photons collection efficiency of Multi-AnodePhotoMultipliers (MAPMT) detectors, which will be used to cover large focal surface of instruments dedicated to the Ultra High Energy Cosmic Rays (UHECRs, above 1019eV) and Ultra High Energy Neutrino (UHEN) detection. The employment of the advanced optical system allows to focus all photons inside the sensitive area of detectors and to improve the signal-to-noise ratios in the wavelength range of interest (300-400nm), thus coupling imaging and filtering capability. Filter is realised with a multilayer coating to reach high transparency in UV range and with a sharp cut-off outside. In this work the applications on different series of PMTs have been studied and results of simulations are shown. First prototypes have been realised. Finally, this paper proposes another class of adapters to be optically coupled on each pixel of MAPMT detector selected, consisting of non-imaging concentrators as Winston cones.

  14. Examining the association between social cognition and functioning in individuals at ultra-high risk for psychosis.

    PubMed

    Cotter, Jack; Bartholomeusz, Cali; Papas, Alicia; Allott, Kelly; Nelson, Barnaby; Yung, Alison R; Thompson, Andrew

    2017-01-01

    Social and role functioning are compromised for the majority of individuals at ultra-high risk of psychosis, and it is important to identify factors that contribute to this functional decline. This study aimed to investigate social cognitive abilities, which have previously been linked to functioning in schizophrenia, as potential factors that impact social, role and global functioning in ultra-high risk patients. A total of 30 ultra-high risk patients were recruited from an established at-risk clinical service in Melbourne, Australia, and completed a battery of social cognitive, neurocognitive, clinical and functioning measures. We examined the relationships between all four core domains of social cognition (emotion recognition, theory of mind, social perception and attributional style), neurocognitive, clinical and demographic variables with three measures of functioning (the Global Functioning Social and Role scales and the Social and Occupational Functioning Assessment Scale) using correlational and multiple regression analyses. Performance on a visual theory of mind task (visual jokes task) was significantly correlated with both concurrent role ( r = 0.425, p = 0.019) and global functioning ( r = 0.540, p = 0.002). In multivariate analyses, it also accounted for unique variance in global, but not role functioning after adjusting for negative symptoms and stress. Social functioning was not associated with performance on any of the social cognition tasks. Among specific social cognitive abilities, only a test of theory of mind was associated with functioning in our ultra-high risk sample. Further longitudinal research is needed to examine the impact of social cognitive deficits on long-term functional outcome in the ultra-high risk group. Identifying social cognitive abilities that significantly impact functioning is important to inform the development of targeted intervention programmes for ultra-high risk individuals.

  15. High-performance radial AMTEC cell design for ultra-high-power solar AMTEC systems

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hendricks, T.J.; Huang, C.

    1999-07-01

    Alkali Metal Thermal to Electric Conversion (AMTEC) technology is rapidly maturing for potential application in ultra-high-power solar AMTEC systems required by potential future US Air Force (USAF) spacecraft missions in medium-earth and geosynchronous orbits (MEO and GEO). Solar thermal AMTEC power systems potentially have several important advantages over current solar photovoltaic power systems in ultra-high-power spacecraft applications for USAF MEO and GEO missions. This work presents key aspects of radial AMTEC cell design to achieve high cell performance in solar AMTEC systems delivering larger than 50 kW(e) to support high power USAF missions. These missions typically require AMTEC cell conversionmore » efficiency larger than 25%. A sophisticated design parameter methodology is described and demonstrated which establishes optimum design parameters in any radial cell design to satisfy high-power mission requirements. Specific relationships, which are distinct functions of cell temperatures and pressures, define critical dependencies between key cell design parameters, particularly the impact of parasitic thermal losses on Beta Alumina Solid Electrolyte (BASE) area requirements, voltage, number of BASE tubes, and system power production for both maximum power-per-BASE-area and optimum efficiency conditions. Finally, some high-level system tradeoffs are demonstrated using the design parameter methodology to establish high-power radial cell design requirements and philosophy. The discussion highlights how to incorporate this methodology with sophisticated SINDA/FLUINT AMTEC cell modeling capabilities to determine optimum radial AMTEC cell designs.« less

  16. MRI-Compatible Pneumatic Robot for Transperineal Prostate Needle Placement.

    PubMed

    Fischer, Gregory S; Iordachita, Iulian; Csoma, Csaba; Tokuda, Junichi; Dimaio, Simon P; Tempany, Clare M; Hata, Nobuhiko; Fichtinger, Gabor

    2008-06-01

    Magnetic resonance imaging (MRI) can provide high-quality 3-D visualization of prostate and surrounding tissue, thus granting potential to be a superior medical imaging modality for guiding and monitoring prostatic interventions. However, the benefits cannot be readily harnessed for interventional procedures due to difficulties that surround the use of high-field (1.5T or greater) MRI. The inability to use conventional mechatronics and the confined physical space makes it extremely challenging to access the patient. We have designed a robotic assistant system that overcomes these difficulties and promises safe and reliable intraprostatic needle placement inside closed high-field MRI scanners. MRI compatibility of the robot has been evaluated under 3T MRI using standard prostate imaging sequences and average SNR loss is limited to 5%. Needle alignment accuracy of the robot under servo pneumatic control is better than 0.94 mm rms per axis. The complete system workflow has been evaluated in phantom studies with accurate visualization and targeting of five out of five 1 cm targets. The paper explains the robot mechanism and controller design, the system integration, and presents results of preliminary evaluation of the system.

  17. MRI-Compatible Pneumatic Robot for Transperineal Prostate Needle Placement

    PubMed Central

    Fischer, Gregory S.; Iordachita, Iulian; Csoma, Csaba; Tokuda, Junichi; DiMaio, Simon P.; Tempany, Clare M.; Hata, Nobuhiko; Fichtinger, Gabor

    2010-01-01

    Magnetic resonance imaging (MRI) can provide high-quality 3-D visualization of prostate and surrounding tissue, thus granting potential to be a superior medical imaging modality for guiding and monitoring prostatic interventions. However, the benefits cannot be readily harnessed for interventional procedures due to difficulties that surround the use of high-field (1.5T or greater) MRI. The inability to use conventional mechatronics and the confined physical space makes it extremely challenging to access the patient. We have designed a robotic assistant system that overcomes these difficulties and promises safe and reliable intraprostatic needle placement inside closed high-field MRI scanners. MRI compatibility of the robot has been evaluated under 3T MRI using standard prostate imaging sequences and average SNR loss is limited to 5%. Needle alignment accuracy of the robot under servo pneumatic control is better than 0.94 mm rms per axis. The complete system workflow has been evaluated in phantom studies with accurate visualization and targeting of five out of five 1 cm targets. The paper explains the robot mechanism and controller design, the system integration, and presents results of preliminary evaluation of the system. PMID:21057608

  18. Battlefield MRI

    DOE PAGES

    Espy, Michelle

    2015-06-01

    Magnetic Resonance Imaging is the best method for non-invasive imaging of soft tissue anatomy, saving countless lives each year. It is regarded as the gold standard for diagnosis of mild to moderate traumatic brain injuries. Furthermore, conventional MRI relies on very high, fixed strength magnetic fields (> 1.5 T) with parts-per-million homogeneity, which requires very large and expensive magnets.

  19. Battlefield MRI

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Espy, Michelle

    Magnetic Resonance Imaging is the best method for non-invasive imaging of soft tissue anatomy, saving countless lives each year. It is regarded as the gold standard for diagnosis of mild to moderate traumatic brain injuries. Furthermore, conventional MRI relies on very high, fixed strength magnetic fields (> 1.5 T) with parts-per-million homogeneity, which requires very large and expensive magnets.

  20. Electric fields induced in the human body by time-varying magnetic field gradients in MRI: numerical calculations and correlation analysis.

    PubMed

    Bencsik, Martin; Bowtell, Richard; Bowley, Roger

    2007-05-07

    The spatial distributions of the electric fields induced in the human body by switched magnetic field gradients in MRI have been calculated numerically using the commercial software package, MAFIA, and the three-dimensional, HUGO body model that comprises 31 different tissue types. The variation of |J|, |E| and |B| resulting from exposure of the body model to magnetic fields generated by typical whole-body x-, y- and z-gradient coils has been analysed for three different body positions (head-, heart- and hips-centred). The magnetic field varied at 1 kHz, so as to produce a rate of change of gradient of 100 T m(-1) s(-1) at the centre of each coil. A highly heterogeneous pattern of induced electric field and current density was found to result from the smoothly varying magnetic field in all cases, with the largest induced electric fields resulting from application of the y-gradient, in agreement with previous studies. By applying simple statistical analysis to electromagnetic quantities within axial planes of the body model, it is shown that the induced electric field is strongly correlated to the local value of resistivity, and the induced current density exhibits even stronger correlation with the local conductivity. The local values of the switched magnetic field are however shown to bear little relation to the local values of the induced electric field or current density.

  1. Development of Non-Proprietary Ultra-High Performance Concrete : Project Summary Report

    DOT National Transportation Integrated Search

    2017-12-01

    Ultra-high performance concrete (UHPC) has mechanical and durability properties that far exceed those of conventional concrete. Thus, elements made with UHPC can be thinner/lighter than elements made with conventional concrete. The enhanced durabilit...

  2. A novel high temperature superconducting magnetic flux pump for MRI magnets

    NASA Astrophysics Data System (ADS)

    Bai, Zhiming; Yan, Guo; Wu, Chunli; Ding, Shufang; Chen, Chuan

    2010-10-01

    This paper presents a kind of minitype magnetic flux pump made of high temperature superconductor. This kind of novel high temperature superconducting (HTS) flux pump has not any mechanical revolving parts or thermal switches. The excitation current of copper coils in magnetic pole system is controlled by a singlechip. The structure design and operational principle have been described. The operating performance of the new model magnetic flux pump has been preliminarily tested. The experiments show that the maximum pumping current is approximately 200 A for Bi2223 flux pump and 80 A for MgB 2 flux pump operating at 20 K. By comparison, it is discovered that the operating temperature range is wider, the ripple is smaller and the pumping frequency is higher in Bi2223 flux pump than those in MgB 2 flux pump. These results indicate that the newly developed Bi2223 magnetic flux pump may efficiently compensate the magnetic field decay in HTS magnet and make the magnet operate in persistent current mode, this point is significant to the magnetic resonance imaging (MRI) magnets. This new flux pump is under construction presently. It is expected that the Bi2223 flux pump would be applied to the superconducting MRI magnets by further optimizing structure and improving working process.

  3. Enantioselective ultra high performance liquid and supercritical fluid chromatography: The race to the shortest chromatogram.

    PubMed

    Ciogli, Alessia; Ismail, Omar H; Mazzoccanti, Giulia; Villani, Claudio; Gasparrini, Francesco

    2018-03-01

    The ever-increasing need for enantiomerically pure chiral compounds has greatly expanded the number of enantioselective separation methods available for the precise and accurate measurements of the enantiomeric purity. The introduction of chiral stationary phases for liquid chromatography in the last decades has revolutionized the routine methods to determine enantiomeric purity of chiral drugs, agrochemicals, fragrances, and in general of organic and organometallic compounds. In recent years, additional efforts have been placed on faster, enantioselective analytical methods capable to fulfill the high throughput requirements of modern screening procedures. Efforts in this field, capitalizing on improved chromatographic particle technology and dedicated instrumentation, have led to highly efficient separations that are routinely completed on the seconds time scale. An overview of the recent achievements in the field of ultra-high-resolution chromatography on column packed with chiral stationary phases, both based on sub-2 μm fully porous and sub-3 μm superficially porous particles, will be given, with an emphasis on very recent studies on ultrafast chiral separations. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. TH-CD-BRA-07: MRI-Linac Dosimetry: Parameters That Change in a Magnetic Field

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    O’Brien, D. J.; Sawakuchi, G. O.

    Purpose: In MRI-linac integrated systems, the presence of the magnetic (B-)field has a large impact of the dose-distribution and the dose-responses of detectors; yet established protocols and previous experience may lead to assumptions about the commissioning process that are no longer valid. This study quantifies parameters that change when performing dosimetry with an MRI-linac including beam quality specifiers and the effective-point-of-measurement (EPOM) of ionization chambers. Methods: We used the Geant4 Monte Carlo code for this work with physics parameters that pass the Fano cavity test to within 0.1% for the simulated conditions with and without a 1.5 T B-field. Amore » point source model with the energy distribution of an MRI-linac beam was used with and without the B-field to calculate the beam quality specifiers %dd(10)× and TPR{sup 20}{sub 10}, the variation of chamber response with orientation and the how the B-field affects the EPOM of ionization chambers by comparing depth-dose curves calculated in water to those generated by a model PTW30013 Farmer chamber. Results: The %dd(10)× changes by over 2% in the presence of the B-field while the TPR{sup 20}{sub 10} is unaffected. Ionization chamber dose-response is known to depend on the orientation w.r.t. the B-field, but two alternative perpendicular orientations (anti-parallel to each other) also differ in dose-response by over 1%. The B-field shifts the EPOM downstream (closer to the chamber center) but it is also shifted laterally by 0.27 times the chamber’s cavity radius. Conclusion: The EPOM is affected by the B-field and it even shifts laterally. The relationship between %dd(10)× and the Spencer-Attix stopping powers is also changed. Care must be taken when using chambers perpendicular to the field as the dose-response changes depending on which perpendicular orientation is used. All of these effects must be considered when performing dosimetry in B-fields and should be accounted for in

  5. Device for wavefront correction in an ultra high power laser

    DOEpatents

    Ault, Earl R.; Comaskey, Brian J.; Kuklo, Thomas C.

    2002-01-01

    A system for wavefront correction in an ultra high power laser. As the laser medium flows past the optical excitation source and the fluid warms its index of refraction changes creating an optical wedge. A system is provided for correcting the thermally induced optical phase errors.

  6. High-power ultra-broadband frequency comb from ultraviolet to infrared by high-power fiber amplifiers.

    PubMed

    Yang, Kangwen; Li, Wenxue; Yan, Ming; Shen, Xuling; Zhao, Jian; Zeng, Heping

    2012-06-04

    A high-power ultra-broadband frequency comb covering the spectral range from ultraviolet to infrared was generated directly by nonlinear frequency conversion of a multi-stage high-power fiber comb amplifier. The 1030-nm infrared spectral fraction of a broadband Ti:sapphire femtosecond frequency comb was power-scaled up to 100 W average power by using a large-mode-area fiber chirped-pulse amplifier. We obtained a frequency-doubled green comb at 515 nm and frequency-quadrupled ultraviolet pulses at 258 nm with the average power of 12.8 and 1.62 W under the input infrared power of 42.2 W, respectively. The carrier envelope phase stabilization was accomplished with an ultra-narrow line-width of 1.86 mHz and a quite low accumulated phase jitter of 0.41 rad, corresponding to a timing jitter of 143 as.

  7. The use of ultra-high pressure liquid chromatography with tandem mass spectrometric detection of analysis of agrochemical residues and mycotoxines in food - challenges and applications

    USDA-ARS?s Scientific Manuscript database

    In the field of food contaminant analysis, the most significant development of recent years has been the integration of ultra-high pressure liquid chromatography (UHPLC), coupled to tandem quadrupole mass spectrometry (MS/MS), into analytical applications. In this review, we describe the emergence o...

  8. Visual analytics of inherently noisy crowdsourced data on ultra high resolution displays

    NASA Astrophysics Data System (ADS)

    Huynh, Andrew; Ponto, Kevin; Lin, Albert Yu-Min; Kuester, Falko

    The increasing prevalence of distributed human microtasking, crowdsourcing, has followed the exponential increase in data collection capabilities. The large scale and distributed nature of these microtasks produce overwhelming amounts of information that is inherently noisy due to the nature of human input. Furthermore, these inputs create a constantly changing dataset with additional information added on a daily basis. Methods to quickly visualize, filter, and understand this information over temporal and geospatial constraints is key to the success of crowdsourcing. This paper present novel methods to visually analyze geospatial data collected through crowdsourcing on top of remote sensing satellite imagery. An ultra high resolution tiled display system is used to explore the relationship between human and satellite remote sensing data at scale. A case study is provided that evaluates the presented technique in the context of an archaeological field expedition. A team in the field communicated in real-time with and was guided by researchers in the remote visual analytics laboratory, swiftly sifting through incoming crowdsourced data to identify target locations that were identified as viable archaeological sites.

  9. A non-invasive approach to monitor chronic lymphocytic leukemia engraftment in a xenograft mouse model using ultra-small superparamagnetic iron oxide-magnetic resonance imaging (USPIO-MRI).

    PubMed

    Valdora, Francesca; Cutrona, Giovanna; Matis, Serena; Morabito, Fortunato; Massucco, Carlotta; Emionite, Laura; Boccardo, Simona; Basso, Luca; Recchia, Anna Grazia; Salvi, Sandra; Rosa, Francesca; Gentile, Massimo; Ravina, Marco; Pace, Daniele; Castronovo, Angela; Cilli, Michele; Truini, Mauro; Calabrese, Massimo; Neri, Antonino; Neumaier, Carlo Emanuele; Fais, Franco; Baio, Gabriella; Ferrarini, Manlio

    2016-11-01

    Chronic lymphocytic leukemia (CLL) is the most prevalent leukemia among adults. Despite its indolent nature, CLL remains an incurable disease. Herein we aimed to monitor CLL disease engraftment and, progression/regression in a xenograft CLL mouse model using ultra-small superparamagnetic iron oxide-magnetic resonance imaging (USPIO-MRI). Spleen contrast enhancement, quantified as percentage change in signal intensity upon USPIO administration, demonstrated a difference due to a reduced USPIO uptake, in the spleens of mice injected with CLL cells (NSG-CLL, n=71) compared to controls (NSG-CTR, n=17). These differences were statistically significant both after 2 and 4weeks from CLL cells injection. In addition comparison of mice treated with rituximab with untreated controls for changes in spleen iron uptake confirmed that it is possible to monitor treatment efficacy in this mouse model of CLL using USPIO-enhanced MRI. Further applications could include the preclinical in vivo monitoring of new therapies and the clinical evaluation of CLL patients. Copyright © 2016 Elsevier Inc. All rights reserved.

  10. Ultra-high density aligned Carbon-nanotube with controled nano-morphology for supercapacitors

    NASA Astrophysics Data System (ADS)

    Ghaffari, Mehdi; Zhao, Ran; Liu, Yang; Zhou, Yue; Cheng, Jiping; Guzman de Villoria, Roberto; Wardle, B. L.; Zhang, Q. M.

    2012-02-01

    Recent advances in fabricating controlled-morphology vertically aligned carbon nanotubes (VA-CNTs) with ultrahigh volume fractioncreate unique opportunities for developing unconventional supercapacitors with ultra-high energy density, power density, and long charge/discharge cycle life.Continuous paths through inter-VA-CNT channels allow fast ion transport, and high electrical conduction of the aligned CNTs in the composite electrodes lead to fast discharge speed. We investigate the charge-discharge characteristics of VA-CNTs with >20 vol% of CNT and ionic liquids as electrolytes. By employing both the electric and electromechanical spectroscopes, as well as nanostructured materials characterization, the ion transport and storage behaviors in porous electrodes are studied. The results suggest pathways for optimizing the electrode morphology in supercapacitorsusing ultra-high volume fraction VA-CNTs to further enhance performance.

  11. Development of a Family of Ultra-High Performance Concrete Pi-Girders

    DOT National Transportation Integrated Search

    2014-01-01

    Ultra-high performance concrete (UHPC) is an advanced cementitious composite material, which tends to exhibit superior properties such as exceptional durability, increased strength, and long-term stability. (See references 1-4.) The use of existing s...

  12. Ultra-high performance concrete for Michigan bridges, material performance : phase I.

    DOT National Transportation Integrated Search

    2008-10-13

    One of the latest advancements in concrete technology is Ultra-High Performance Concrete (UHPC). UHPC is : defined as concretes attaining compressive strengths exceeding 25 ksi (175 MPa). It is a fiber-reinforced, denselypacked : concrete material wh...

  13. 7T MRI in focal epilepsy with unrevealing conventional field strength imaging.

    PubMed

    De Ciantis, Alessio; Barba, Carmen; Tassi, Laura; Cosottini, Mirco; Tosetti, Michela; Costagli, Mauro; Bramerio, Manuela; Bartolini, Emanuele; Biagi, Laura; Cossu, Massimo; Pelliccia, Veronica; Symms, Mark R; Guerrini, Renzo

    2016-03-01

    To assess the diagnostic yield of 7T magnetic resonance imaging (MRI) in detecting and characterizing structural lesions in patients with intractable focal epilepsy and unrevealing conventional (1.5 or 3T) MRI. We conducted an observational clinical imaging study on 21 patients (17 adults and 4 children) with intractable focal epilepsy, exhibiting clinical and electroencephalographic features consistent with a single seizure-onset zone (SOZ) and unrevealing conventional MRI. Patients were enrolled at two tertiary epilepsy surgery centers and imaged at 7T, including whole brain (three-dimensional [3D] T1 -weighted [T1W] fast-spoiled gradient echo (FSPGR), 3D susceptibility-weighted angiography [SWAN], 3D fluid-attenuated inversion recovery [FLAIR]) and targeted imaging (2D T2*-weighted dual-echo gradient-recalled echo [GRE] and 2D gray-white matter tissue border enhancement [TBE] fast spin echo inversion recovery [FSE-IR]). MRI studies at 1.5 or 3T deemed unrevealing at the referral center were reviewed by three experts in epilepsy imaging. Reviewers were provided information regarding the suspected localization of the SOZ. The same team subsequently reviewed 7T images. Agreement in imaging interpretation was reached through consensus-based discussions based on visual identification of structural abnormalities and their likely correlation with clinical and electrographic data. 7T MRI revealed structural lesions in 6 (29%) of 21 patients. The diagnostic gain in detection was obtained using GRE and FLAIR images. Four of the six patients with abnormal 7T underwent epilepsy surgery. Histopathology revealed focal cortical dysplasia (FCD) in all. In the remaining 15 patients (71%), 7T MRI remained unrevealing; 4 of the patients underwent epilepsy surgery and histopathologic evaluation revealed gliosis. 7T MRI improves detection of epileptogenic FCD that is not visible at conventional field strengths. A dedicated protocol including whole brain FLAIR and GRE images at 7T

  14. CNR considerations for rapid real-time MRI tumor tracking in radiotherapy hybrid devices: Effects of B{sub 0} field strength

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wachowicz, K., E-mail: keith.wachowicz@albertaheal

    2016-08-15

    Purpose: This work examines the subject of contrast-to-noise ratio (CNR), specifically between tumor and tissue background, and its dependence on the MRI field strength, B{sub 0}. This examination is motivated by the recent interest and developments in MRI/radiotherapy hybrids where real-time imaging can be used to guide treatment beams. The ability to distinguish a tumor from background tissue is of primary importance in this field, and this work seeks to elucidate the complex relationship between the CNR and B{sub 0} that is too often assumed to be purely linear. Methods: Experimentally based models of B{sub 0}-dependant relaxation for various tumormore » and normal tissues from the literature were used in conjunction with signal equations for MR sequences suitable for rapid real-time imaging to develop field-dependent predictions for CNR. These CNR models were developed for liver, lung, breast, glioma, and kidney tumors for spoiled gradient-echo, balanced steady-state free precession (bSSFP), and single-shot half-Fourier fast spin echo sequences. Results: Due to the pattern in which the relaxation properties of tissues are found to vary over B{sub 0} field (specifically the T{sub 1} time), there was always an improved CNR at lower fields compared to linear dependency. Further, in some tumor sites, the CNR at lower fields was found to be comparable to, or sometimes higher than those at higher fields (i.e., bSSFP CNR for glioma, kidney, and liver tumors). Conclusions: In terms of CNR, lower B{sub 0} fields have been shown to perform as well or better than higher fields for some tumor sites due to superior T{sub 1} contrast. In other sites this effect was less pronounced, reversing the CNR advantage. This complex relationship between CNR and B{sub 0} reveals both low and high magnetic fields as viable options for tumor tracking in MRI/radiotherapy hybrids.« less

  15. High resolution MRI of the normal finger at 0.1 T: anatomic correlations.

    PubMed

    Drapé, J L; Constantinesco, A; Arbogast, S; Sick, H; Wolfram-Gabel, R; Brunot, B

    1992-01-01

    MR images of the fingers are obtained in a 128 x 128 or 256 x 256 matrix format using a prototype of a mini imager dedicated to the hand. The vertical field of 0.1 T is provided by an electro-magnet with an air gap of 15 cm equipped with a single solenoidal coil. No Faraday cage is used. The maximum in plane pixel resolution of 100 mu is obtained for a field of view of 2.5 cm with a slice thickness of 2 mm. The identification of fine structures of the finger is demonstrated by the anatomical and histological correlations. This type of imager which is adapted to very limited field of views demonstrate that high resolution MRI of limb extremities can be achieved at 0.1 T.

  16. Integrated computational study of ultra-high heat flux cooling using cryogenic micro-solid nitrogen spray

    NASA Astrophysics Data System (ADS)

    Ishimoto, Jun; Oh, U.; Tan, Daisuke

    2012-10-01

    A new type of ultra-high heat flux cooling system using the atomized spray of cryogenic micro-solid nitrogen (SN2) particles produced by a superadiabatic two-fluid nozzle was developed and numerically investigated for application to next generation super computer processor thermal management. The fundamental characteristics of heat transfer and cooling performance of micro-solid nitrogen particulate spray impinging on a heated substrate were numerically investigated and experimentally measured by a new type of integrated computational-experimental technique. The employed Computational Fluid Dynamics (CFD) analysis based on the Euler-Lagrange model is focused on the cryogenic spray behavior of atomized particulate micro-solid nitrogen and also on its ultra-high heat flux cooling characteristics. Based on the numerically predicted performance, a new type of cryogenic spray cooling technique for application to a ultra-high heat power density device was developed. In the present integrated computation, it is clarified that the cryogenic micro-solid spray cooling characteristics are affected by several factors of the heat transfer process of micro-solid spray which impinges on heated surface as well as by atomization behavior of micro-solid particles. When micro-SN2 spraying cooling was used, an ultra-high cooling heat flux level was achieved during operation, a better cooling performance than that with liquid nitrogen (LN2) spray cooling. As micro-SN2 cooling has the advantage of direct latent heat transport which avoids the film boiling state, the ultra-short time scale heat transfer in a thin boundary layer is more possible than in LN2 spray. The present numerical prediction of the micro-SN2 spray cooling heat flux profile can reasonably reproduce the measurement results of cooling wall heat flux profiles. The application of micro-solid spray as a refrigerant for next generation computer processors is anticipated, and its ultra-high heat flux technology is expected

  17. Caveats when Analyzing Ultra-high Molar Mass Polymers by SEC

    USDA-ARS?s Scientific Manuscript database

    The analysis of ultra-high molar mass (M > 1 million g/mol) polymers via size-exclusion chromatography (SEC) presents a number of non-trivial challenges. Dissolution and full solvation may take days, as is the case for cellulose dissolution in non-complexing non degrading solvents; very low concent...

  18. Ultrastructural Study on Ultra-Low Frequency Electromagnetic Fields and Transfer Factor Effects on Skin Ulcers

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Cadena, M. S. Reyes; Chapul, L. Sanchez; Perez, Javier

    2008-08-11

    We determined the effect of 120Hz ultra low frequency electromagnetic field (ELF) on the healing process of skin in 20 Wistar rats distributed in four groups in which chronic dermal ulcers had been produced. The first two groups received a dose of the transfer factor and interferon-beta (IFN-{beta}) every 24 h during 12 days. The third group (positive control) received only electromagnetic field (ELF) sessions, and in the fourth group (negative control), no treatment was applied. The electromagnetic field was applied through a Helmholtz coils; 30 Gauss of intensity. Results shown histological changes that improve the healing process in animalsmore » subjected to ELF together with the transfer factor.« less

  19. Wave-induced loss of ultra-relativistic electrons in the Van Allen radiation belts.

    PubMed

    Shprits, Yuri Y; Drozdov, Alexander Y; Spasojevic, Maria; Kellerman, Adam C; Usanova, Maria E; Engebretson, Mark J; Agapitov, Oleksiy V; Zhelavskaya, Irina S; Raita, Tero J; Spence, Harlan E; Baker, Daniel N; Zhu, Hui; Aseev, Nikita A

    2016-09-28

    The dipole configuration of the Earth's magnetic field allows for the trapping of highly energetic particles, which form the radiation belts. Although significant advances have been made in understanding the acceleration mechanisms in the radiation belts, the loss processes remain poorly understood. Unique observations on 17 January 2013 provide detailed information throughout the belts on the energy spectrum and pitch angle (angle between the velocity of a particle and the magnetic field) distribution of electrons up to ultra-relativistic energies. Here we show that although relativistic electrons are enhanced, ultra-relativistic electrons become depleted and distributions of particles show very clear telltale signatures of electromagnetic ion cyclotron wave-induced loss. Comparisons between observations and modelling of the evolution of the electron flux and pitch angle show that electromagnetic ion cyclotron waves provide the dominant loss mechanism at ultra-relativistic energies and produce a profound dropout of the ultra-relativistic radiation belt fluxes.

  20. Wave-induced loss of ultra-relativistic electrons in the Van Allen radiation belts

    PubMed Central

    Shprits, Yuri Y.; Drozdov, Alexander Y.; Spasojevic, Maria; Kellerman, Adam C.; Usanova, Maria E.; Engebretson, Mark J.; Agapitov, Oleksiy V.; Zhelavskaya, Irina S.; Raita, Tero J.; Spence, Harlan E.; Baker, Daniel N.; Zhu, Hui; Aseev, Nikita A.

    2016-01-01

    The dipole configuration of the Earth's magnetic field allows for the trapping of highly energetic particles, which form the radiation belts. Although significant advances have been made in understanding the acceleration mechanisms in the radiation belts, the loss processes remain poorly understood. Unique observations on 17 January 2013 provide detailed information throughout the belts on the energy spectrum and pitch angle (angle between the velocity of a particle and the magnetic field) distribution of electrons up to ultra-relativistic energies. Here we show that although relativistic electrons are enhanced, ultra-relativistic electrons become depleted and distributions of particles show very clear telltale signatures of electromagnetic ion cyclotron wave-induced loss. Comparisons between observations and modelling of the evolution of the electron flux and pitch angle show that electromagnetic ion cyclotron waves provide the dominant loss mechanism at ultra-relativistic energies and produce a profound dropout of the ultra-relativistic radiation belt fluxes. PMID:27678050

  1. Novel Diffusion-Weighted MRI for High-Grade Prostate Cancer Detection

    DTIC Science & Technology

    2017-10-01

    AWARD NUMBER: W81XWH-15-1-0346 TITLE: Novel Diffusion-Weighted MRI for High -Grade Prostate Cancer Detection PRINCIPAL INVESTIGATOR: Michael Abern...Unlimited The views, opinions and/or findings contained in this report are those of the author(s) and should not be construed as an official Department of...Diffusion-Weighted MRI for High -Grade Prostate Cancer Detection 5a. CONTRACT NUMBER 5b. GRANT NUMBER W81XWH-15-1-0346 5c. PROGRAM ELEMENT NUMBER 6

  2. Study of Volumetrically Heated Ultra-High Energy Density Plasmas

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Rocca, Jorge J.

    2016-10-27

    Heating dense matter to millions of degrees is important for applications, but requires complex and expensive methods. The major goal of the project was to demonstrate using a compact laser the creation of a new ultra-high energy density plasma regime characterized by simultaneous extremely high temperature and high density, and to study it combining experimental measurements and advanced simulations. We have demonstrated that trapping of intense femtosecond laser pulses deep within ordered nanowire arrays can heat near solid density matter into a new ultra hot plasma regime. Extreme electron densities, and temperatures of several tens of million degrees were achievedmore » using laser pulses of only 0.5 J energy from a compact laser. Our x-ray spectra and simulations showed that extremely highly ionized plasma volumes several micrometers in depth are generated by irradiation of gold and Nickel nanowire arrays with femtosecond laser pulses of relativistic intensities. We obtained extraordinarily high degrees of ionization (e.g. we peeled 52 electrons from gold atoms, and up to 26 electrons from nickel atoms). In the process we generated Gigabar pressures only exceeded in the central hot spot of highly compressed thermonuclear fusion plasmas.. The plasma created after the dissolved wires expand, collide, and thermalize, is computed to have a thermal energy density of 0.3 GJ cm -3 and a pressure of 1-2 Gigabar. These are pressures only exceeded in highly compressed thermonuclear fusion plasmas. Scaling these results to higher laser intensities promises to create plasmas with temperatures and pressures exceeding those in the center of the sun.« less

  3. Differential renal effects of candesartan at high and ultra-high doses in diabetic mice–potential role of the ACE2/AT2R/Mas axis

    PubMed Central

    Callera, Glaucia E.; Antunes, Tayze T.; Correa, Jose W.; Moorman, Danielle; Gutsol, Alexey; He, Ying; Cat, Aurelie Nguyen Dinh; Briones, Ana M.; Montezano, Augusto C.; Burns, Kevin D.; Touyz, Rhian M.

    2016-01-01

    High doses of Ang II receptor (AT1R) blockers (ARBs) are renoprotective in diabetes. Underlying mechanisms remain unclear. We evaluated whether high/ultra-high doses of candesartan (ARB) up-regulate angiotensin-converting enzyme 2 (ACE2)/Ang II type 2 receptor (AT2R)/Mas receptor [protective axis of the of the renin–angiotensin system (RAS)] in diabetic mice. Systolic blood pressure (SBP), albuminuria and expression/activity of RAS components were assessed in diabetic db/db and control db/+ mice treated with increasing candesartan doses (intermediate, 1 mg/kg/d; high, 5 mg/kg/d; ultra-high, 25 and 75 mg/kg/d; 4 weeks). Lower doses candesartan did not influence SBP, but ultra-high doses reduced SBP in both groups. Plasma glucose and albuminuria were increased in db/db compared with db/+ mice. In diabetic mice treated with intermediate dose candesartan, renal tubular damage and albuminuria were ameliorated and expression of ACE2, AT2R and Mas and activity of ACE2 were increased, effects associated with reduced ERK1/2 phosphorylation, decreased fibrosis and renal protection. Ultra-high doses did not influence the ACE2/AT2R/Mas axis and promoted renal injury with increased renal ERK1/2 activation and exaggerated fibronectin expression in db/db mice. Our study demonstrates dose-related effects of candesartan in diabetic nephropathy: intermediate–high dose candesartan is renoprotective, whereas ultra-high dose candesartan induces renal damage. Molecular processes associated with these effects involve differential modulation of the ACE2/AT2R/Mas axis: intermediate–high dose candesartan up-regulating RAS protective components and attenuating pro-fibrotic processes, and ultra-high doses having opposite effects. These findings suggest novel mechanisms through the protective RAS axis, whereby candesartan may ameliorate diabetic nephropathy. Our findings also highlight potential injurious renal effects of ultra-high dose candesartan in diabetes. PMID:27612496

  4. Feasibility and clinical utility of ultra-widefield indocyanine green angiography.

    PubMed

    Klufas, Michael A; Yannuzzi, Nicolas A; Pang, Claudine E; Srinivas, Sowmya; Sadda, Srinivas R; Freund, K Bailey; Kiss, Szilárd

    2015-03-01

    To evaluate the feasibility and clinical utility of a novel noncontact scanning laser ophthalmoscope-based ultra-widefield indocyanine green angiographic system. Ultra-widefield indocyanine green angiographic images were captured using a modified Optos P200Tx that produced high-resolution images of the choroidal vasculature with up to a 200° field. Ultra-widefield indocyanine green angiography was performed on patients with a variety of retinal conditions to assess utility of this imaging technique for diagnostic purposes and disease treatment monitoring. Ultra-widefield indocyanine green angiography was performed on 138 eyes of 69 patients. Mean age was 58 ± 16.9 years (range, 24-85 years). The most common ocular pathologies imaged included central serous chorioretinopathy (24 eyes), uveitis (various subtypes, 16 eyes), age-related macular degeneration (12 eyes), and polypoidal choroidal vasculopathy (4 eyes). In all eyes evaluated with ultra-widefield indocyanine green angiography, high-resolution images of choroidal and retinal circulation were obtained with sufficient detail out to 200° of the fundus. In this series of 138 eyes, scanning laser ophthalmoscope-based ultra-widefield indocyanine green angiography was clinically practical and provided detailed images of both the central and peripheral choroidal circulation. Future studies are needed to refine the clinical value of this imaging modality and the significance of peripheral choroidal vascular changes in the diagnosis, monitoring, and treatment of ocular diseases.

  5. Activated iron-containing microglia in the human hippocampus identified by magnetic resonance imaging in Alzheimer disease

    PubMed Central

    Zeineh, Michael M.; Chen, Yuanxin; Kitzler, Hagen H.; Hammond, Robert; Vogel, Hannes; Rutt, Brian K.

    2016-01-01

    Although amyloid plaques and neurofibrillary pathology play important roles in Alzheimer disease (AD), our understanding of AD is incomplete, and the contribution of microglia and iron to neurodegeneration is unknown. High-field magnetic resonance imaging (MRI) is exquisitely sensitive to microscopic iron. To explore iron-associated neuroinflammatory AD pathology, we studied AD and control human brain specimens by (1) performing ultra-high resolution ex vivo 7 Tesla MRI, (2) coregistering the MRI with successive histologic staining for iron, microglia, amyloid beta, and tau, and (3) quantifying the relationship between magnetic resonance signal intensity and histological staining. In AD, we identified numerous small MR hypointensities primarily within the subiculum that were best explained by the combination of microscopic iron and activated microglia (p = 0.025), in contradistinction to the relatively lesser contribution of tau or amyloid. Neuropathologically, this suggests that microglial-mediated neurodegeneration may occur in the hippocampal formation in AD and is detectable by ultra-high resolution MRI. PMID:26190634

  6. Activated iron-containing microglia in the human hippocampus identified by magnetic resonance imaging in Alzheimer disease.

    PubMed

    Zeineh, Michael M; Chen, Yuanxin; Kitzler, Hagen H; Hammond, Robert; Vogel, Hannes; Rutt, Brian K

    2015-09-01

    Although amyloid plaques and neurofibrillary pathology play important roles in Alzheimer disease (AD), our understanding of AD is incomplete, and the contribution of microglia and iron to neurodegeneration is unknown. High-field magnetic resonance imaging (MRI) is exquisitely sensitive to microscopic iron. To explore iron-associated neuroinflammatory AD pathology, we studied AD and control human brain specimens by (1) performing ultra-high resolution ex vivo 7 Tesla MRI, (2) coregistering the MRI with successive histologic staining for iron, microglia, amyloid beta, and tau, and (3) quantifying the relationship between magnetic resonance signal intensity and histological staining. In AD, we identified numerous small MR hypointensities primarily within the subiculum that were best explained by the combination of microscopic iron and activated microglia (p = 0.025), in contradistinction to the relatively lesser contribution of tau or amyloid. Neuropathologically, this suggests that microglial-mediated neurodegeneration may occur in the hippocampal formation in AD and is detectable by ultra-high resolution MRI. Copyright © 2015 Elsevier Inc. All rights reserved.

  7. CFRP composite optical telescope assembly for the 1 m ULTRA project

    NASA Astrophysics Data System (ADS)

    Martin, Robert N.; Romeo, Robert C.

    2006-06-01

    The focus of the ULTRA Project is to develop and test Ultra-Lightweight Technology for Research applications in Astronomy. The ULTRA project is a collaborative effort involving the private firm Composite Mirror Applications, Inc (CMA) and 3 universities: University of Kansas, San Diego State University, and Dartmouth College. Funding for ULTRA is predominately from a NSF three year MRI program grant to CMA and KU with additional support from CMA, KU and SDSU. The goal of the ULTRA program is to demonstrate that a viable alternative exists to traditional glass mirror and steel telescope technology by designing, fabricating and testing a research telescope constructed from carbon fiber reinforced plastic (CFRP) materials. In particular, a 1m diameter, Cassegrain telescope optics set and optical tube assembly (OTA) are being designed and fabricated by CMA. The completed telescope will be deployed at SDSU's Mt Laguna Observatory in a refurbished structure (new dome and mount provided via KU and SDSU). We expect that a successful completion and testing of this project will lead to future use of CFRP technology in larger telescopes and segmented telescopes. This paper describes the OTA (optical tube assembly) that has been developed for the ULTRA project. The mirror technology is described in another paper in this conference. A poster describes the ULTRA project overview in more detail.

  8. Reliability of high- and low-field magnetic resonance imaging systems for detection of cartilage and bone lesions in the equine cadaver fetlock.

    PubMed

    Smith, M A; Dyson, S J; Murray, R C

    2012-11-01

    To determine the reliability of 2 magnetic resonance imaging (MRI) systems for detection of cartilage and bone lesions of the equine fetlock. To test the hypotheses that lesions in cartilage, subchondral and trabecular bone of the equine fetlock verified using histopathology can be detected on high- and low-field MR images with a low incidence of false positive or negative results; that low-field images are less reliable than high-field images for detection of cartilage lesions; and that combining results of interpretation from different pulse sequences increases detection of cartilage lesions. High- and low-field MRI was performed on 19 limbs from horses identified with fetlock lameness prior to euthanasia. Grading systems were used to score cartilage, subchondral and trabecular bone on MR images and histopathology. Sensitivity and specificity were calculated for images. High-field T2*-weighted gradient echo (T2*W-GRE) and low-field T2-weighted fast spin echo (T2W-FSE) images had high sensitivity but low specificity for detection of cartilage lesions. All pulse sequences had high sensitivity and low-moderate specificity for detection of subchondral bone lesions and moderate sensitivity and moderate-high specificity for detection of trabecular bone lesions (histopathology as gold standard). For detection of lesions of trabecular bone low-field T2*W-GRE images had higher sensitivity and specificity than T2W-FSE images. There is high likelihood of false positive results using high- or low-field MRI for detection of cartilage lesions and moderate-high likelihood of false positive results for detection of subchondral bone lesions compared with histopathology. Combining results of interpretation from different pulse sequences did not increase detection of cartilage lesions. MRI interpretation of trabecular bone was more reliable than cartilage or subchondral bone in both MR systems. Independent interpretation of a variety of pulse sequences may maximise detection of

  9. Ultra-modular 500m2 heliostat field for high flux/high temperature solar-driven processes

    NASA Astrophysics Data System (ADS)

    Romero, Manuel; González-Aguilar, José; Luque, Salvador

    2017-06-01

    The main objective of the European Project SUN-to-LIQUID is the scale-up and experimental demonstration of the complete process chain to solar liquid fuels from H2O and CO2. This implies moving from a 4 kW laboratory setup to a pre-commercial plant including a heliostat field. The small power and high irradiance onto the focal spot is forcing the optical design to behave half way between a large solar furnace and an extremely small central receiver system. The customized heliostat field makes use of the most recent developments on small size heliostats and a tower with reduced optical height (15 m) to minimize visual impact. A heliostat field of 250kWth (500 m2 reflective surface) has been built adjacent to IMDEA Energy premises at the Technology Park of Móstoles, Spain, and consists of 169 small size heliostats (1.9 m × 1.6 m). In spite of the small size and compactness of the field, when all heliostats are aligned, it is possible to fulfil the specified flux above 2500 kW/m2 for at least 50 kW and an aperture of 16 cm, with a peak flux of 3000 kW/m2.

  10. Characterization of the blood-oxygen level-dependent (BOLD) response in cat auditory cortex using high-field fMRI.

    PubMed

    Brown, Trecia A; Joanisse, Marc F; Gati, Joseph S; Hughes, Sarah M; Nixon, Pam L; Menon, Ravi S; Lomber, Stephen G

    2013-01-01

    Much of what is known about the cortical organization for audition in humans draws from studies of auditory cortex in the cat. However, these data build largely on electrophysiological recordings that are both highly invasive and provide less evidence concerning macroscopic patterns of brain activation. Optical imaging, using intrinsic signals or dyes, allows visualization of surface-based activity but is also quite invasive. Functional magnetic resonance imaging (fMRI) overcomes these limitations by providing a large-scale perspective of distributed activity across the brain in a non-invasive manner. The present study used fMRI to characterize stimulus-evoked activity in auditory cortex of an anesthetized (ketamine/isoflurane) cat, focusing specifically on the blood-oxygen-level-dependent (BOLD) signal time course. Functional images were acquired for adult cats in a 7 T MRI scanner. To determine the BOLD signal time course, we presented 1s broadband noise bursts between widely spaced scan acquisitions at randomized delays (1-12 s in 1s increments) prior to each scan. Baseline trials in which no stimulus was presented were also acquired. Our results indicate that the BOLD response peaks at about 3.5s in primary auditory cortex (AI) and at about 4.5 s in non-primary areas (AII, PAF) of cat auditory cortex. The observed peak latency is within the range reported for humans and non-human primates (3-4 s). The time course of hemodynamic activity in cat auditory cortex also occurs on a comparatively shorter scale than in cat visual cortex. The results of this study will provide a foundation for future auditory fMRI studies in the cat to incorporate these hemodynamic response properties into appropriate analyses of cat auditory cortex. Copyright © 2012 Elsevier Inc. All rights reserved.

  11. The Attentional Field Revealed by Single-Voxel Modeling of fMRI Time Courses

    PubMed Central

    DeYoe, Edgar A.

    2015-01-01

    The spatial topography of visual attention is a distinguishing and critical feature of many theoretical models of visuospatial attention. Previous fMRI-based measurements of the topography of attention have typically been too crude to adequately test the predictions of different competing models. This study demonstrates a new technique to make detailed measurements of the topography of visuospatial attention from single-voxel, fMRI time courses. Briefly, this technique involves first estimating a voxel's population receptive field (pRF) and then “drifting” attention through the pRF such that the modulation of the voxel's fMRI time course reflects the spatial topography of attention. The topography of the attentional field (AF) is then estimated using a time-course modeling procedure. Notably, we are able to make these measurements in many visual areas including smaller, higher order areas, thus enabling a more comprehensive comparison of attentional mechanisms throughout the full hierarchy of human visual cortex. Using this technique, we show that the AF scales with eccentricity and varies across visual areas. We also show that voxels in multiple visual areas exhibit suppressive attentional effects that are well modeled by an AF having an enhancing Gaussian center with a suppressive surround. These findings provide extensive, quantitative neurophysiological data for use in modeling the psychological effects of visuospatial attention. PMID:25810532

  12. Distinguishing the Magnetorotational Instability (MRI) from Magnetized Ekman Flows in the PPPL MRI Experiment

    NASA Astrophysics Data System (ADS)

    Gilson, Erik; Caspary, Kyle; Goodman, Jeremy; Ji, Hantao; Schartman, Ethan; Wei, Xing

    2015-11-01

    Results are presented from initial experiments on the upgraded Magnetorotational Instability (MRI) experiment that uses GaInSn as the working fluid and now operates with conductive end caps to improve the coupling of angular momentum to the fluid to increase the saturation amplitude of the MRI signal. Measurements of the fluid velocity field and perturbed magnetic field over a range of magnetic Reynolds numbers, Rm , and Lundquist numbers, S, are compared with results from the SFEMaNS code in order to separate the effects of MRI on the system from effects such as Ekman flows and Shercliff layer instabilities. The MRI can be identified by observing its growth rate, noting the relative magnitudes and spatial distributions of the perturbed radial flow velocity ur and radial magnetic field Br, and measuring the scaling of ur and Br with Rm . The clear identification of the onset of MRI in the apparatus is complicated by the geometry and boundary conditions creating an imperfect supercritical pitchfork bifurcation. Nevertheless, a stability diagram can be created that shows that MRI is a weak-field instability that occurs only below a certain value of the normalized magnetic field S / Rm but above a threshold where viscous effects damps the growth of the instability.

  13. Structural Analysis of Titan's Tholins by Ultra-High Resolution Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Vuitton, V.; Frisari, M.; Thissen, R.; Dutuit, O.; Bonnet, J.-Y.; Quirico, E.; Sciamma O'Brien, E.; Szopa, C.; Carrasco, N.; Somogyi, A.; Smith, M.; Hörst, S. M.; Yelle, R.

    2010-04-01

    We propose here a systematic ultra-high resolution mass spectrometry and MS/MS study in order to provide a more coherent and complete characterization of the structure of the molecules making up the soluble fraction of the Titan tholins.

  14. A strategy to unveil transient sources of ultra-high-energy cosmic rays

    NASA Astrophysics Data System (ADS)

    Takami, Hajime

    2013-06-01

    Transient generation of ultra-high-energy cosmic rays (UHECRs) has been motivated from promising candidates of UHECR sources such as gamma-ray bursts, flares of active galactic nuclei, and newly born neutron stars and magnetars. Here we propose a strategy to unveil transient sources of UHECRs from UHECR experiments. We demonstrate that the rate of UHECR bursts and/or flares is related to the apparent number density of UHECR sources, which is the number density estimated on the assumption of steady sources, and the time-profile spread of the bursts produced by cosmic magnetic fields. The apparent number density strongly depends on UHECR energies under a given rate of the bursts, which becomes observational evidence of transient sources. It is saturated at the number density of host galaxies of UHECR sources. We also derive constraints on the UHECR burst rate and/or energy budget of UHECRs per source as a function of the apparent source number density by using models of cosmic magnetic fields. In order to obtain a precise constraint of the UHECR burst rate, high event statistics above ˜ 1020 eV for evaluating the apparent source number density at the highest energies and better knowledge on cosmic magnetic fields by future observations and/or simulations to better estimate the time-profile spread of UHECR bursts are required. The estimated rate allows us to constrain transient UHECR sources by being compared with the occurrence rates of known energetic transient phenomena.

  15. An MRI-Compatible High Frequency AC Resistive Heating System for Homeothermic Maintenance in Small Animals

    PubMed Central

    Gomes, Ana L.; Kinchesh, Paul; Kersemans, Veerle; Allen, Philip D.; Smart, Sean C.

    2016-01-01

    Purpose To develop an MRI-compatible resistive heater, using high frequency alternating current (AC), for temperature maintenance of anaesthetised animals. Materials and Methods An MRI-compatible resistive electrical heater was formed from narrow gauge wire connected to a high frequency (10–100 kHz) AC power source. Multiple gradient echo images covering a range of echo times, and pulse-acquire spectra were acquired with the wire heater powered using high frequency AC or DC power sources and without any current flowing in order to assess the sensitivity of the MRI acquisitions to the presence of current flow through the heater wire. The efficacy of temperature maintenance using the AC heater was assessed by measuring rectal temperature immediately following induction of general anaesthesia for a period of 30 minutes in three different mice. Results Images and spectra acquired in the presence and absence of 50–100 kHz AC through the wire heater were indistinguishable, whereas DC power created field shifts and lineshape distortions. Temperature lost during induction of anaesthesia was recovered within approximately 20 minutes and a stable temperature was reached as the mouse’s temperature approached the set target. Conclusion The AC-powered wire heater maintains adequate heat input to the animal to maintain body temperature, and does not compromise image quality. PMID:27806062

  16. Use of high-field and low-field magnetic resonance imaging to describe the anatomy of the proximal portion of the tarsal region of nonlame horses.

    PubMed

    Biggi, Marianna; Dyson, Sue J

    2018-03-01

    OBJECTIVE To use high-field and low-field MRI to describe the anatomy of the proximal portion of the tarsal region (proximal tarsal region) of nonlame horses. SAMPLE 25 cadaveric equine tarsi. PROCEDURES The proximal portion of 1 tarsus from each of 25 nonlame horses with no history of tarsal lameness underwent high-field (1.5-T) and low-field (0.27-T) MRI. Resulting images were used to subjectively describe the anatomy of that region and obtain measurements of the collateral ligaments of the tarsocrural joint. RESULTS Long and short components of the lateral and medial collateral ligaments of the tarsocrural joint were identified. Various bundles of the short collateral ligaments were difficult to delineate on low-field images. Ligaments typically had low signal intensity in all sequences; however, multiple areas of increased signal intensity were identified at specific locations in most tarsi. This signal intensity was attributed to focal magic angle effect associated with orientation of collagen fibers within the ligaments at those locations. Subchondral bone of the distal aspect of the tibia was uniform in thickness, whereas that of the medial trochlear ridge of the talus was generally thicker than that of the lateral trochlear ridge. In most tarsi, subchondral bone of the talocalcaneal joint decreased in thickness from proximal to distal. CONCLUSIONS AND CLINICAL RELEVANCE Results generated in this study can be used as a reference for interpretation of MRI images of the proximal tarsal region in horses.

  17. Ex vivo assessment of polyol coated-iron oxide nanoparticles for MRI diagnosis applications: toxicological and MRI contrast enhancement effects

    NASA Astrophysics Data System (ADS)

    Bomati-Miguel, Oscar; Miguel-Sancho, Nuria; Abasolo, Ibane; Candiota, Ana Paula; Roca, Alejandro G.; Acosta, Milena; Schwartz, Simó; Arus, Carles; Marquina, Clara; Martinez, Gema; Santamaria, Jesus

    2014-03-01

    Polyol synthesis is a promising method to obtain directly pharmaceutical grade colloidal dispersion of superparamagnetic iron oxide nanoparticles (SPIONs). Here, we study the biocompatibility and performance as T2-MRI contrast agents (CAs) of high quality magnetic colloidal dispersions (average hydrodynamic aggregate diameter of 16-27 nm) consisting of polyol-synthesized SPIONs (5 nm in mean particle size) coated with triethylene glycol (TEG) chains (TEG-SPIONs), which were subsequently functionalized to carboxyl-terminated meso-2-3-dimercaptosuccinic acid (DMSA) coated-iron oxide nanoparticles (DMSA-SPIONs). Standard MTT assays on HeLa, U87MG, and HepG2 cells revealed that colloidal dispersions of TEG-coated iron oxide nanoparticles did not induce any loss of cell viability after 3 days incubation with dose concentrations below 50 μg Fe/ml. However, after these nanoparticles were functionalized with DMSA molecules, an increase on their cytotoxicity was observed, so that particles bearing free terminal carboxyl groups on their surface were not cytotoxic only at low concentrations (<10 μg Fe/ml). Moreover, cell uptake assays on HeLa and U87MG and hemolysis tests have demonstrated that TEG-SPIONs and DMSA-SPIONs were well internalized by the cells and did not induce any adverse effect on the red blood cells at the tested concentrations. Finally, in vitro relaxivity measurements and post mortem MRI studies in mice indicated that both types of coated-iron oxide nanoparticles produced higher negative T2-MRI contrast enhancement than that measured for a similar commercial T2-MRI CAs consisting in dextran-coated ultra-small iron oxide nanoparticles (Ferumoxtran-10). In conclusion, the above attributes make both types of as synthesized coated-iron oxide nanoparticles, but especially DMSA-SPIONs, promising candidates as T2-MRI CAs for nanoparticle-enhanced MRI diagnosis applications.

  18. Dual-TRACER: High resolution fMRI with constrained evolution reconstruction.

    PubMed

    Li, Xuesong; Ma, Xiaodong; Li, Lyu; Zhang, Zhe; Zhang, Xue; Tong, Yan; Wang, Lihong; Sen Song; Guo, Hua

    2018-01-01

    fMRI with high spatial resolution is beneficial for studies in psychology and neuroscience, but is limited by various factors such as prolonged imaging time, low signal to noise ratio and scarcity of advanced facilities. Compressed Sensing (CS) based methods for accelerating fMRI data acquisition are promising. Other advanced algorithms like k-t FOCUSS or PICCS have been developed to improve performance. This study aims to investigate a new method, Dual-TRACER, based on Temporal Resolution Acceleration with Constrained Evolution Reconstruction (TRACER), for accelerating fMRI acquisitions using golden angle variable density spiral. Both numerical simulations and in vivo experiments at 3T were conducted to evaluate and characterize this method. Results show that Dual-TRACER can provide functional images with a high spatial resolution (1×1mm 2 ) under an acceleration factor of 20 while maintaining hemodynamic signals well. Compared with other investigated methods, dual-TRACER provides a better signal recovery, higher fMRI sensitivity and more reliable activation detection. Copyright © 2017 Elsevier Inc. All rights reserved.

  19. 2D dose distribution images of a hybrid low field MRI-γ detector

    NASA Astrophysics Data System (ADS)

    Abril, A.; Agulles-Pedrós, L.

    2016-07-01

    The proposed hybrid system is a combination of a low field MRI and dosimetric gel as a γ detector. The readout system is based on the polymerization process induced by the gel radiation. A gel dose map is obtained which represents the functional part of hybrid image alongside with the anatomical MRI one. Both images should be taken while the patient with a radiopharmaceutical is located inside the MRI system with a gel detector matrix. A relevant aspect of this proposal is that the dosimetric gel has never been used to acquire medical images. The results presented show the interaction of the 99mTc source with the dosimetric gel simulated in Geant4. The purpose was to obtain the planar γ 2D-image. The different source configurations are studied to explore the ability of the gel as radiation detector through the following parameters; resolution, shape definition and radio-pharmaceutical concentration.

  20. The Bendability of Ultra High strength Steels

    NASA Astrophysics Data System (ADS)

    Hazra, S. K.; Efthymiadis, P.; Alamoudi, A.; Kumar, R. L. V.; Shollock, B.; Dashwood, R.

    2016-08-01

    Automotive manufacturers have been reducing the weight of their vehicles to meet increasingly stringent environmental legislation that reflects public demand. A strategy is to use higher strength materials for parts with reduced cross-sections. However, such materials are less formable than traditional grades. The frequent result is increased processing and piece costs. 3D roll forming is a novel and flexible process: it is estimated that a quarter of the structure of a vehicle can be made with a single set of tooling. Unlike stamping, this process requires material with low work hardening rates. In this paper, we present results of ultra high strength steels that have low elongation in a tension but display high formability in bending through the suppression of the necking response.