On-resonance variable delay multipulse scheme for imaging of fast-exchanging protons and semisolid macromolecules.

PubMed

Xu, Jiadi; Chan, Kannie W Y; Xu, Xiang; Yadav, Nirbhay; Liu, Guanshu; van Zijl, Peter C M

2017-02-01

To develop an on-resonance variable delay multipulse (VDMP) scheme to image magnetization transfer contrast (MTC) and the chemical exchange saturation transfer (CEST) contrast of total fast-exchanging protons (TFP) with exchange rate above approximately 1 kHz. A train of high power binomial pulses was applied at the water resonance. The interpulse delay, called mixing time, was varied to observe its effect on the water signal reduction, allowing separation and quantification of MTC and CEST contributions as a result of their different proton transfer rates. The fast-exchanging protons in CEST and MTC are labeled together with the short T 2 components in MTC and separated out using a variable mixing time. Phantom studies of selected metabolite solutions (glucose, glutamate, creatine, myo-inositol), bovine serum albumin (BSA), and hair conditioner show the capability of on-resonance VDMP to separate out exchangeable protons with exchange rates above 1 kHz. Quantitative MTC and TFP maps were acquired on healthy mouse brains using this method, showing strong gray/white matter contrast for the slowly transferring MTC protons, whereas the TFP map was more uniform across the brain but somewhat higher in gray matter. The new method provides a simple way of imaging fast-exchanging protons and MTC components with a slow transfer rate. Magn Reson Med 77:730-739, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

Emerging MRI and metabolic neuroimaging techniques in mild traumatic brain injury.

PubMed

Lu, Liyan; Wei, Xiaoer; Li, Minghua; Li, Yuehua; Li, Wenbin

2014-01-01

Traumatic brain injury (TBI) is one of the leading causes of death worldwide, and mild traumatic brain injury (mTBI) is the most common traumatic injury. It is difficult to detect mTBI using a routine neuroimaging. Advanced techniques with greater sensitivity and specificity for the diagnosis and treatment of mTBI are required. The aim of this review is to offer an overview of various emerging neuroimaging methodologies that can solve the clinical health problems associated with mTBI. Important findings and improvements in neuroimaging that hold value for better detection, characterization and monitoring of objective brain injuries in patients with mTBI are presented. Conventional computed tomography (CT) and magnetic resonance imaging (MRI) are not very efficient for visualizing mTBI. Moreover, techniques such as diffusion tensor imaging, magnetization transfer imaging, susceptibility-weighted imaging, functional MRI, single photon emission computed tomography, positron emission tomography and magnetic resonance spectroscopy imaging were found to be useful for mTBI imaging.

The Two-Brains Hypothesis: Towards a guide for brain-brain and brain-machine interfaces.

PubMed

Goodman, G; Poznanski, R R; Cacha, L; Bercovich, D

2015-09-01

Great advances have been made in signaling information on brain activity in individuals, or passing between an individual and a computer or robot. These include recording of natural activity using implants under the scalp or by external means or the reverse feeding of such data into the brain. In one recent example, noninvasive transcranial magnetic stimulation (TMS) allowed feeding of digitalized information into the central nervous system (CNS). Thus, noninvasive electroencephalography (EEG) recordings of motor signals at the scalp, representing specific motor intention of hand moving in individual humans, were fed as repetitive transcranial magnetic stimulation (rTMS) at a maximum intensity of 2.0[Formula: see text]T through a circular magnetic coil placed flush on each of the heads of subjects present at a different location. The TMS was said to induce an electric current influencing axons of the motor cortex causing the intended hand movement: the first example of the transfer of motor intention and its expression, between the brains of two remote humans. However, to date the mechanisms involved, not least that relating to the participation of magnetic induction, remain unclear. In general, in animal biology, magnetic fields are usually the poor relation of neuronal current: generally "unseen" and if apparent, disregarded or just given a nod. Niels Bohr searched for a biological parallel to complementary phenomena of physics. Pertinently, the two-brains hypothesis (TBH) proposed recently that advanced animals, especially man, have two brains i.e., the animal CNS evolved as two fundamentally different though interdependent, complementary organs: one electro-ionic (tangible, known and accessible), and the other, electromagnetic (intangible and difficult to access) - a stable, structured and functional 3D compendium of variously induced interacting electro-magnetic (EM) fields. Research on the CNS in health and disease progresses including that on brain-brain, brain-computer and brain-robot engineering. As they grow even closer, these disciplines involve their own unique complexities, including direction by the laws of inductive physics. So the novel TBH hypothesis has wide fundamental implications, including those related to TMS. These require rethinking and renewed research engaging the fully complementary equivalence of mutual magnetic and electric field induction in the CNS and, within this context, a new mathematics of the brain to decipher higher cognitive operations not possible with current brain-brain and brain-machine interfaces. Bohr may now rest.

Accumulation of methylsulfonylmethane in the human brain: identification by multinuclear magnetic resonance spectroscopy.

PubMed

Lin, A; Nguy, C H; Shic, F; Ross, B D

2001-09-15

Methylsulfonylmethane (MSM) is a widely available 'alternative' medicine. In vivo magnetic resonance spectroscopy (MRS) was used to detect and quantify MSM in the brains of four patients with memory loss and in three normal volunteers all of who had ingested MSM at the recommended doses of 1-3 g daily. MSM was detected in all subjects at concentrations of 0.42-3.40 mmole/kg brain and was equally distributed between gray and white matter. MSM was undetectable in drug-naïve normal subjects (N=25), patients screened for 'toxic exposure' (N=50) or patients examined with 1H MRS for the diagnosis of probable Alzheimer Disease (N=520) between 1991 and 2001. No adverse clinical or neurochemical effects were observed. Appearance of MSM in significant concentrations in the human brain indicates ready transfer across the intact blood-brain barrier, of a compound with no known medical benefits.

Early primary biliary cholangitis is characterised by brain abnormalities on cerebral magnetic resonance imaging.

PubMed

Grover, V P B; Southern, L; Dyson, J K; Kim, J U; Crossey, M M E; Wylezinska-Arridge, M; Patel, N; Fitzpatrick, J A; Bak-Bol, A; Waldman, A D; Alexander, G J; Mells, G F; Chapman, R W; Jones, D E J; Taylor-Robinson, S D

2016-11-01

Brain change can occur in primary biliary cholangitis (PBC), potentially as a result of cholestatic and/or inflammatory processes. This change is linked to systemic symptoms of fatigue and cognitive impairment. To identify whether brain change occurs early in PBC. If the change develops early and is progressive, it may explain the difficulty in treating these symptoms. Early disease brain change was explored in 13 patients with newly diagnosed biopsy-proven precirrhotic PBC using magnetisation transfer, diffusion-weighted imaging and 1 H magnetic resonance spectroscopy. Results were compared to 17 healthy volunteers. Cerebral magnetisation transfer ratios were reduced in early PBC, compared to healthy volunteers, in the thalamus, putamen and head of caudate with no greater reduction in patients with greater symptom severity. Mean apparent diffusion coefficients were increased in the thalamus only. No 1 H magnetic resonance spectroscopy abnormalities were seen. Serum manganese levels were elevated in all PBC patients, but no relationship was seen with imaging or symptom parameters. There were no correlations between neuroimaging data, laboratory data, symptom severity scores or age. This is the first study to be performed in this precirrhotic patient population, and we have highlighted that neuroimaging changes are present at a much earlier stage than previously demonstrated. The neuroimaging abnormalities suggest that the brain changes seen in PBC occur early in the pathological process, even before significant liver damage has occurred. If such changes are linked to symptom pathogenesis, this could have important implications for the timing of second-line-therapy use. © 2016 The Authors. Alimentary Pharmacology & Therapeutics published by John Wiley & Sons Ltd.

T1, diffusion tensor, and quantitative magnetization transfer imaging of the hippocampus in an Alzheimer's disease mouse model.

PubMed

Whittaker, Heather T; Zhu, Shenghua; Di Curzio, Domenico L; Buist, Richard; Li, Xin-Min; Noy, Suzanna; Wiseman, Frances K; Thiessen, Jonathan D; Martin, Melanie

2018-07-01

Alzheimer's disease (AD) pathology causes microstructural changes in the brain. These changes, if quantified with magnetic resonance imaging (MRI), could be studied for use as an early biomarker for AD. The aim of our study was to determine if T 1 relaxation, diffusion tensor imaging (DTI), and quantitative magnetization transfer imaging (qMTI) metrics could reveal changes within the hippocampus and surrounding white matter structures in ex vivo transgenic mouse brains overexpressing human amyloid precursor protein with the Swedish mutation. Delineation of hippocampal cell layers using DTI color maps allows more detailed analysis of T 1 -weighted imaging, DTI, and qMTI metrics, compared with segmentation of gross anatomy based on relaxation images, and with analysis of DTI or qMTI metrics alone. These alterations are observed in the absence of robust intracellular Aβ accumulation or plaque deposition as revealed by histology. This work demonstrates that multiparametric quantitative MRI methods are useful for characterizing changes within the hippocampal substructures and surrounding white matter tracts of mouse models of AD. Copyright © 2018. Published by Elsevier Inc.

An abnormal periventricular magnetization transfer ratio gradient occurs early in multiple sclerosis

PubMed Central

Brown, J William L; Pardini, Matteo; Brownlee, Wallace J; Fernando, Kryshani; Samson, Rebecca S; Prados Carrasco, Ferran; Ourselin, Sebastien; Gandini Wheeler-Kingshott, Claudia A M; Miller, David H; Chard, Declan T

2017-01-01

Abstract In established multiple sclerosis, tissue abnormality—as assessed using magnetization transfer ratio—increases close to the lateral ventricles. We aimed to determine whether or not (i) these changes are present from the earliest clinical stages of multiple sclerosis; (ii) they occur independent of white matter lesions; and (iii) they are associated with subsequent conversion to clinically definite multiple sclerosis and disability. Seventy-one subjects had MRI scanning a median of 4.6 months after a clinically isolated optic neuritis (49 females, mean age 33.5 years) and were followed up clinically 2 and 5 years later. Thirty-seven healthy controls (25 females, mean age 34.4 years) were also scanned. In normal-appearing white matter, magnetization transfer ratio gradients were measured 1–5 mm and 6–10 mm from the lateral ventricles. In control subjects, magnetization transfer ratio was highest adjacent to the ventricles and decreased with distance from them; in optic neuritis, normal-appearing white matter magnetization transfer ratio was lowest adjacent to the ventricles, increased over the first 5 mm, and then paralleled control values. The magnetization transfer ratio gradient over 1–5 mm differed significantly between the optic neuritis and control groups [+0.059 percentage units/mm (pu/mm) versus −0.033 pu/mm, P = 0.010], and was significantly steeper in those developing clinically definite multiple sclerosis within 2 years compared to those who did not (0.132 pu/mm versus 0.016 pu/mm, P = 0.020). In multivariate binary logistic regression the magnetization transfer ratio gradient was independently associated with the development of clinically definite multiple sclerosis within 2 years (magnetization transfer ratio gradient odds ratio 61.708, P = 0.023; presence of T2 lesions odds ratio 8.500, P = 0.071). At 5 years, lesional measures overtook magnetization transfer ratio gradients as significant predictors of conversion to multiple sclerosis. The magnetization transfer ratio gradient was not significantly affected by the presence of brain lesions [T2 lesions (P = 0.918), periventricular T2 lesions (P = 0.580) or gadolinium-enhancing T1 lesions (P = 0.724)]. The magnetization transfer ratio gradient also correlated with Expanded Disability Status Scale score 5 years later (Spearman r = 0.313, P = 0.027). An abnormal periventricular magnetization transfer ratio gradient occurs early in multiple sclerosis, is clinically relevant, and may arise from one or more mechanisms that are at least partly independent of lesion formation. PMID:28043954

Pulsed magnetization transfer imaging with body coil transmission at 3 Tesla: feasibility and application.

PubMed

Smith, Seth A; Farrell, Jonathan A D; Jones, Craig K; Reich, Daniel S; Calabresi, Peter A; van Zijl, Peter C M

2006-10-01

Pulsed magnetization transfer (MT) imaging has been applied to quantitatively assess brain pathology in several diseases, especially multiple sclerosis (MS). To date, however, because of the high power deposition associated with the use of short, rapidly repeating MT prepulses, clinical application has been limited to lower field strengths. The contrast-to-noise ratio (CNR) of MT is limited, and this method would greatly benefit from the use of higher magnetic fields and phased-array coil reception. However, power deposition is proportional to the square of the magnetic field and scales with coil size, and MT experiments are already close to the SAR limit at 1.5T even when smaller transmit coils are used instead of the body coil. Here we show that these seemingly great obstacles can be ameliorated by the increased T(1) of tissue water at higher field, which allows for longer maintenance of sufficiently high saturation levels while using a reduced duty cycle. This enables a fast (5-6 min) high-resolution (1.5 mm isotropic) whole-brain MT acquisition with excellent anatomical visualization of gray matter (GM) and white matter (WM) structures, and even substructures. The method is demonstrated in nine normal volunteers and five patients with relapsing remitting MS (RRMS), and the results show a clear delineation of heterogeneous lesions.

Evidence of demyelination in mild cognitive impairment and dementia using a direct and specific magnetic resonance imaging measure of myelin content.

PubMed

Bouhrara, Mustapha; Reiter, David A; Bergeron, Christopher M; Zukley, Linda M; Ferrucci, Luigi; Resnick, Susan M; Spencer, Richard G

2018-04-18

We investigated brain demyelination in aging, mild cognitive impairment (MCI), and dementia using magnetic resonance imaging of myelin. Brains of young and old controls and old subjects with MCI, Alzheimer's disease, or vascular dementia were scanned using our recently developed myelin water fraction (MWF) mapping technique, which provides greatly improved accuracy over previous comparable methods. Maps of MWF, a direct and specific myelin measure, and relaxation times and magnetization transfer ratio, indirect and nonspecific measures, were constructed. MCI subjects showed decreased MWF compared with old controls. Demyelination was greater in Alzheimer's disease or vascular dementia. As expected, decreased MWF was accompanied by decreased magnetization transfer ratio and increased relaxation times. The young subjects showed greater myelin content than the old subjects. We believe this to be the first demonstration of myelin loss in MCI, Alzheimer's disease, and vascular dementia using a method that provides a quantitative magnetic resonance imaging-based measure of myelin. Our findings add to the emerging evidence that myelination may represent an important biomarker for the pathology of MCI and dementia. This study supports the investigation of the role of myelination in MCI and dementia through use of this quantitative magnetic resonance imaging approach in clinical studies of disease progression, relationship of functional status to myelination status, and therapeutics. Furthermore, mapping MWF may permit myelin to serve as a therapeutic target in clinical trials. Copyright © 2018. Published by Elsevier Inc.

Rapid and quantitative chemical exchange saturation transfer (CEST) imaging with magnetic resonance fingerprinting (MRF).

PubMed

Cohen, Ouri; Huang, Shuning; McMahon, Michael T; Rosen, Matthew S; Farrar, Christian T

2018-05-13

To develop a fast magnetic resonance fingerprinting (MRF) method for quantitative chemical exchange saturation transfer (CEST) imaging. We implemented a CEST-MRF method to quantify the chemical exchange rate and volume fraction of the N α -amine protons of L-arginine (L-Arg) phantoms and the amide and semi-solid exchangeable protons of in vivo rat brain tissue. L-Arg phantoms were made with different concentrations (25-100 mM) and pH (pH 4-6). The MRF acquisition schedule varied the saturation power randomly for 30 iterations (phantom: 0-6 μT; in vivo: 0-4 μT) with a total acquisition time of ≤2 min. The signal trajectories were pattern-matched to a large dictionary of signal trajectories simulated using the Bloch-McConnell equations for different combinations of exchange rate, exchangeable proton volume fraction, and water T 1 and T 2 relaxation times. The chemical exchange rates of the N α -amine protons of L-Arg were significantly (P < 0.0001) correlated with the rates measured with the quantitation of exchange using saturation power method. Similarly, the L-Arg concentrations determined using MRF were significantly (P < 0.0001) correlated with the known concentrations. The pH dependence of the exchange rate was well fit (R 2  = 0.9186) by a base catalyzed exchange model. The amide proton exchange rate measured in rat brain cortex (34.8 ± 11.7 Hz) was in good agreement with that measured previously with the water exchange spectroscopy method (28.6 ± 7.4 Hz). The semi-solid proton volume fraction was elevated in white (12.2 ± 1.7%) compared to gray (8.1 ± 1.1%) matter brain regions in agreement with previous magnetization transfer studies. CEST-MRF provides a method for fast, quantitative CEST imaging. © 2018 International Society for Magnetic Resonance in Medicine.

Whole brain inhomogeneous magnetization transfer (ihMT) imaging: Sensitivity enhancement within a steady-state gradient echo sequence.

PubMed

Mchinda, Samira; Varma, Gopal; Prevost, Valentin H; Le Troter, Arnaud; Rapacchi, Stanislas; Guye, Maxime; Pelletier, Jean; Ranjeva, Jean-Philippe; Alsop, David C; Duhamel, Guillaume; Girard, Olivier M

2018-05-01

To implement, characterize, and optimize an interleaved inhomogeneous magnetization transfer (ihMT) gradient echo sequence allowing for whole-brain imaging within a clinically compatible scan time. A general framework for ihMT modelling was developed based on the Provotorov theory of radiofrequency saturation, which accounts for the dipolar order underpinning the ihMT effect. Experimental studies and numerical simulations were performed to characterize and optimize the ihMT-gradient echo dependency with sequence timings, saturation power, and offset frequency. The protocol was optimized in terms of maximum signal intensity and the reproducibility assessed for a nominal resolution of 1.5 mm isotropic. All experiments were performed on healthy volunteers at 1.5T. An important mechanism driving signal optimization and leading to strong ihMT signal enhancement that relies on the dynamics of radiofrequency energy deposition has been identified. By taking advantage of the delay allowed for readout between ihMT pulse bursts, it was possible to boost the ihMT signal by almost 2-fold compared to previous implementation. Reproducibility of the optimal protocol was very good, with an intra-individual error < 2%. The proposed sensitivity-boosted and time-efficient steady-state ihMT-gradient echo sequence, implemented and optimized at 1.5T, allowed robust high-resolution 3D ihMT imaging of the whole brain within a clinically compatible scan time. Magn Reson Med 79:2607-2619, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

Nonlinear optical and multiphoton processes for in situ manipulation and conversion of photons: applications to energy and healthcare (Conference Presentation)

NASA Astrophysics Data System (ADS)

Prasad, Paras N.

2017-02-01

Chiral control of nonlinear optical functions holds a great promise for a wide range of applications including optical signal processing, bio-sensing and chiral bio-imaging. In chiral polyfluorene thin films, we demonstrated extremely large chiral nonlinearity. The physics of manipulating excitation dynamics for photon transformation will be discussed, along with nanochemistry control of upconversion in hierarchically built organic chromophore coupled-core-multiple shell nanostructures which enable introduce new, organic-inorganic energy transfer routes for broadband light harvesting and increased upconversion efficiency via multistep cascaded energy transfer. We are pursuing the applications of photon conversion technology in IR harvesting for photovoltaics, high contrast bioimaging, photoacoustic imaging, photodynamic therapy, and optogenetics. An important application is in Brain research and Neurophotonics for functional mapping and modulation of brain activities. Another new direction pursued is magnetic field control of light in in a chiral polymer nanocomposite to achieve large magneto-optic coefficient which can enable sensing of extremely weak magnetic field due to brain waves. Finally, we will consider the thought provoking concept of utilizing photons to quantify, through magneto-optics, and augment - through nanoptogenetics, the cognitive states, thus paving the path way to a quantified human paradigm.

Hyperpolarized xenon magnetic resonance of the lung and the brain

NASA Astrophysics Data System (ADS)

Venkatesh, Arvind Krishnamachari

2001-04-01

Hyperpolarized noble gas Magnetic Resonance Imaging (MRI) is a new diagnostic modality that has been used successfully for lung imaging. Xenon is soluble in blood and inhaled xenon is transported to the brain via circulating blood. Xenon also accumulates in the lipid rich white matter of the brain. Hyperpolarized xenon can hence be used as a tissue- sensitive probe of brain function. The goals of this study were to identify the NMR resonances of xenon in the rat brain and evaluate the role of hyperpolarized xenon for brain MRI. We have developed systems to produce sufficient volumes of hyperpolarized xenon for in vivo brain experiments. The specialized instrumentation developed include an apparatus for optical pump-cell manufacture and high purity gas manifolds for filling cells. A hyperpolarized gas delivery system was designed to ventilate small animals with hyperpolarized xenon for transport to the brain. The T1 of xenon dissolved in blood indicates that the lifetime of xenon in the blood is sufficient for significant magnetization to be transferred to distal tissues. A variety of carrier agents for intravenous delivery of hyperpolarized xenon were tested for transport to distal tissues. Using our new gas delivery system, high SNR 129Xe images of rat lungs were obtained. Spectroscopy with hyperpolarized xenon indicated that xenon was transported from the lungs to the blood and tissues with intact magnetization. After preliminary studies that indicated the feasibility for in vivo rat brain studies, experiments were performed with adult rats and young rats with different stages of white matter development. Both in vivo and in vitro experiments showed the prominence of one peak from xenon in the rat brain, which was assigned to brain lipids. Cerebral brain perfusion was calculated from the wash-out of the hyperpolarized xenon signal in the brain. An increase in brain perfusion during maturation was observed. These experiments showed that hyperpolarized xenon MRI can be used to develop unique approaches to studying white matter and gray matter in the brain. Some of the possible applications of hyperpolarized xenon MRI in the brain are clinical diagnosis of white matter diseases, functional MRI (fMRI) and measurement of cerebral blood perfusion.

Item-Specific and Generalization Effects on Brain Activation when Learning Chinese Characters

ERIC Educational Resources Information Center

Deng, Yuan; Booth, James R.; Chou, Tai-Li; Ding, Guo-Sheng; Peng, Dan-Ling

2008-01-01

Neural changes related to learning of the meaning of Chinese characters in English speakers were examined using functional magnetic resonance imaging (fMRI). We examined item specific learning effects for trained characters, but also the generalization of semantic knowledge to novel transfer characters that shared a semantic radical (part of a…

Simultaneous mapping of water shift and B1 (WASABI)-Application to field-Inhomogeneity correction of CEST MRI data.

PubMed

Schuenke, Patrick; Windschuh, Johannes; Roeloffs, Volkert; Ladd, Mark E; Bachert, Peter; Zaiss, Moritz

2017-02-01

Together with the development of MRI contrasts that are inherently small in their magnitude, increased magnetic field accuracy is also required. Hence, mapping of the static magnetic field (B 0 ) and the excitation field (B 1 ) is not only important to feedback shim algorithms, but also for postprocess contrast-correction procedures. A novel field-inhomogeneity mapping method is presented that allows simultaneous mapping of the water shift and B 1 (WASABI) using an off-resonant rectangular preparation pulse. The induced Rabi oscillations lead to a sinc-like spectrum in the frequency-offset dimension and allow for determination of B 0 by its symmetry axis and of B 1 by its oscillation frequency. Stability of the WASABI method with regard to the influences of T 1 , T 2 , magnetization transfer, and repetition time was investigated and its convergence interval was verified. B 0 and B 1 maps obtained simultaneously by means of WASABI in the human brain at 3 T and 7 T can compete well with maps obtained by standard methods. Finally, the method was applied successfully for B 0 and B 1 correction of chemical exchange saturation transfer MRI (CEST-MRI) data of the human brain. The proposed WASABI method yields a novel simultaneous B 0 and B 1 mapping within 1 min that is robust and easy to implement. Magn Reson Med 77:571-580, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

Magnetic Transfer Contrast Accurately Localizes Substantia Nigra Confirmed by Histology

PubMed Central

Bolding, Mark S.; Reid, Meredith A.; Avsar, Kathy B.; Roberts, Rosalinda C.; Gamlin, Paul D.; Gawne, Timothy J.; White, David M.; den Hollander, Jan A.; Lahti, Adrienne C.

2012-01-01

Background Magnetic Resonance Imaging (MRI) has multiple contrast mechanisms. Like various staining techniques in histology, each contrast type reveals different information about the structure of the brain. However, it is not always clear how structures visible in MRI correspond to structures previously identified by histology. The purpose of this study was to determine if magnetic transfer contrast (MTC) or T2 contrast MRI was better at delineating the substantia nigra. Methods MRI scans were acquired in-vivo from two non-human primates (NHPs). The NHPs were subsequently euthanized, perfused, and their brains sectioned for histological analyses. Each slice was photographed prior to sectioning. Each brain was sectioned into approximately 500, 40-micron sections, encompassing most of the cortex, midbrain, and dorsal parts of the hindbrain. Levels corresponding to anatomical MRI images were selected. From these, adjacent sections were stained using Kluver Barrera (myelin and cell bodies) or tyrosine hydroxylase (TH) (dopaminergic neurons) immunohistochemistry. The resulting images were coregistered to the block-face images using a moving least squares algorithm with similarity transformations. MR images were similarly coregistered to the block-face images, allowing the structures in the MRI to be identified with structures in the histological images. Results We found that hyperintense (light) areas in MTC images were coextensive with the SN as delineated histologically. The hypointense (dark) areas in T2-weighted images were not coextensive with the SN, but extended partially into the SN and partially into the cerebral peduncles. Conclusions MTC is a more accurate contrast mechanism than T2-weighting for localizing the SN in vivo. PMID:22981657

Measurement of creatine kinase reaction rate in human brain using magnetization transfer image-selected in vivo spectroscopy (MT-ISIS) and a volume ³¹P/¹H radiofrequency coil in a clinical 3-T MRI system.

PubMed

Jeong, Eun-Kee; Sung, Young-Hoon; Kim, Seong-Eun; Zuo, Chun; Shi, Xianfeng; Mellon, Eric A; Renshaw, Perry F

2011-08-01

High-energy phosphate metabolism, which allows the synthesis and regeneration of adenosine triphosphate (ATP), is a vital process for neuronal survival and activity. In particular, creatine kinase (CK) serves as an energy reservoir for the rapid buffering of ATP levels. Altered CK enzyme activity, reflecting compromised high-energy phosphate metabolism or mitochondrial dysfunction in the brain, can be assessed using magnetization transfer (MT) MRS. MT (31)P MRS has been used to measure the forward CK reaction rate in animal and human brain, employing a surface radiofrequency coil. However, long acquisition times and excessive radiofrequency irradiation prevent these methods from being used routinely for clinical evaluations. In this article, a new MT (31)P MRS method is presented, which can be practically used to measure the CK forward reaction rate constant in a clinical MRI system employing a volume head (31)P coil for spatial localization, without contamination from the scalp muscle, and an acquisition time of 30 min. Other advantages associated with the method include radiofrequency homogeneity within the regions of interest of the brain using a volume coil with image-selected in vivo spectroscopy localization, and reduction of the specific absorption rate using nonadiabatic radiofrequency pulses for MT saturation. The mean value of k(f) was measured as 0.320 ± 0.075 s(-1) from 10 healthy volunteers with an age range of 18-40 years. These values are consistent with those obtained using earlier methods, and the technique may be used routinely to evaluate energetic processes in the brain on a clinical MRI system. Copyright © 2010 John Wiley & Sons, Ltd.

Methods for Dichoptic Stimulus Presentation in Functional Magnetic Resonance Imaging - A Review

PubMed Central

Choubey, Bhaskar; Jurcoane, Alina; Muckli, Lars; Sireteanu, Ruxandra

2009-01-01

Dichoptic stimuli (different stimuli displayed to each eye) are increasingly being used in functional brain imaging experiments using visual stimulation. These studies include investigation into binocular rivalry, interocular information transfer, three-dimensional depth perception as well as impairments of the visual system like amblyopia and stereodeficiency. In this paper, we review various approaches of displaying dichoptic stimulus used in functional magnetic resonance imaging experiments. These include traditional approaches of using filters (red-green, red-blue, polarizing) with optical assemblies as well as newer approaches of using bi-screen goggles. PMID:19526076

Parietal plasticity after training with a complex video game is associated with individual differences in improvements in an untrained working memory task

PubMed Central

Nikolaidis, Aki; Voss, Michelle W.; Lee, Hyunkyu; Vo, Loan T. K.; Kramer, Arthur F.

2014-01-01

Researchers have devoted considerable attention and resources to cognitive training, yet there have been few examinations of the relationship between individual differences in patterns of brain activity during the training task and training benefits on untrained tasks (i.e., transfer). While a predominant hypothesis suggests that training will transfer if there is training-induced plasticity in brain regions important for the untrained task, this theory lacks sufficient empirical support. To address this issue we investigated the relationship between individual differences in training-induced changes in brain activity during a cognitive training videogame, and whether those changes explained individual differences in the resulting changes in performance in untrained tasks. Forty-five young adults trained with a videogame that challenges working memory, attention, and motor control for 15 2-h sessions. Before and after training, all subjects received neuropsychological assessments targeting working memory, attention, and procedural learning to assess transfer. Subjects also underwent pre- and post-functional magnetic resonance imaging (fMRI) scans while they played the training videogame to assess how these patterns of brain activity change in response to training. For regions implicated in working memory, such as the superior parietal lobe (SPL), individual differences in the post-minus-pre changes in activation predicted performance changes in an untrained working memory task. These findings suggest that training-induced plasticity in the functional representation of a training task may play a role in individual differences in transfer. Our data support and extend previous literature that has examined the association between training related cognitive changes and associated changes in underlying neural networks. We discuss the role of individual differences in brain function in training generalizability and make suggestions for future cognitive training research. PMID:24711792

Parietal plasticity after training with a complex video game is associated with individual differences in improvements in an untrained working memory task.

PubMed

Nikolaidis, Aki; Voss, Michelle W; Lee, Hyunkyu; Vo, Loan T K; Kramer, Arthur F

2014-01-01

Researchers have devoted considerable attention and resources to cognitive training, yet there have been few examinations of the relationship between individual differences in patterns of brain activity during the training task and training benefits on untrained tasks (i.e., transfer). While a predominant hypothesis suggests that training will transfer if there is training-induced plasticity in brain regions important for the untrained task, this theory lacks sufficient empirical support. To address this issue we investigated the relationship between individual differences in training-induced changes in brain activity during a cognitive training videogame, and whether those changes explained individual differences in the resulting changes in performance in untrained tasks. Forty-five young adults trained with a videogame that challenges working memory, attention, and motor control for 15 2-h sessions. Before and after training, all subjects received neuropsychological assessments targeting working memory, attention, and procedural learning to assess transfer. Subjects also underwent pre- and post-functional magnetic resonance imaging (fMRI) scans while they played the training videogame to assess how these patterns of brain activity change in response to training. For regions implicated in working memory, such as the superior parietal lobe (SPL), individual differences in the post-minus-pre changes in activation predicted performance changes in an untrained working memory task. These findings suggest that training-induced plasticity in the functional representation of a training task may play a role in individual differences in transfer. Our data support and extend previous literature that has examined the association between training related cognitive changes and associated changes in underlying neural networks. We discuss the role of individual differences in brain function in training generalizability and make suggestions for future cognitive training research.

Chemical exchange rotation transfer (CERT) on human brain at 3 Tesla.

PubMed

Lin, Eugene C; Li, Hua; Zu, Zhongliang; Louie, Elizabeth A; Lankford, Christopher L; Dortch, Richard D; Does, Mark D; Gore, John C; Gochberg, Daniel F

2018-05-25

To test the ability of a novel pulse sequence applied in vivo at 3 Tesla to separate the contributions to the water signal from amide proton transfer (APT) and relayed nuclear Overhauser enhancement (rNOE) from background direct water saturation and semisolid magnetization transfer (MT). The lack of such signal source isolation has confounded conventional chemical exchange saturation transfer (CEST) imaging. We quantified APT and rNOE signals using a chemical exchange rotation transfer (CERT) metric, MTR double . A range of duty cycles and average irradiation powers were applied, and results were compared with conventional CEST analyses using asymmetry (MTR asym ) and extrapolated magnetization transfer (EMR). Our results indicate that MTR double is more specific than MTR asym and, because it requires as few as 3 data points, is more rapid than methods requiring a complete Z-spectrum, such as EMR. In white matter, APT (1.5 ± 0.5%) and rNOE (2.1 ± 0.7%) were quantified by using MTR double with a 30% duty cycle and a 0.5-µT average power. In addition, our results suggest that MTR double is insensitive to B 0 inhomogeneity, further magnifying its speed advantage over CEST metrics that require a separate B 0 measurement. However, MTR double still has nontrivial sensitivity to B 1 inhomogeneities. We demonstrated that MTR double is an alternative metric to evaluate APT and rNOE, which is fast, robust to B 0 inhomogeneity, and easy to process. © 2018 International Society for Magnetic Resonance in Medicine.

A Nested Phosphorus and Proton Coil Array for Brain Magnetic Resonance Imaging and Spectroscopy

PubMed Central

Brown, Ryan; Lakshmanan, Karthik; Madelin, Guillaume; Parasoglou, Prodromos

2015-01-01

A dual-nuclei radiofrequency coil array was constructed for phosphorus and proton magnetic resonance imaging and spectroscopy of the human brain at 7 Tesla. An eight-channel transceive degenerate birdcage phosphorus module was implemented to provide whole-brain coverage and significant sensitivity improvement over a standard dual-tuned loop coil. A nested eight-channel proton module provided adequate sensitivity for anatomical localization without substantially sacrificing performance on the phosphorus module. The developed array enabled phosphorus spectroscopy, a saturation transfer technique to calculate the global creatine kinase forward reaction rate, and single-metabolite whole-brain imaging with 1.4 cm nominal isotropic resolution in 15 min (2.3 cm actual resolution), while additionally enabling 1 mm isotropic proton imaging. This study demonstrates that a multi-channel array can be utilized for phosphorus and proton applications with improved coverage and/or sensitivity over traditional single-channel coils. The efficient multi-channel coil array, time-efficient pulse sequences, and the enhanced signal strength available at ultra-high fields can be combined to allow volumetric assessment of the brain and could provide new insights into the underlying energy metabolism impairment in several neurodegenerative conditions, such as Alzheimer’s and Parkinson’s diseases, as well as mental disorders such as schizophrenia. PMID:26375209

A nested phosphorus and proton coil array for brain magnetic resonance imaging and spectroscopy.

PubMed

Brown, Ryan; Lakshmanan, Karthik; Madelin, Guillaume; Parasoglou, Prodromos

2016-01-01

A dual-nuclei radiofrequency coil array was constructed for phosphorus and proton magnetic resonance imaging and spectroscopy of the human brain at 7T. An eight-channel transceive degenerate birdcage phosphorus module was implemented to provide whole-brain coverage and significant sensitivity improvement over a standard dual-tuned loop coil. A nested eight-channel proton module provided adequate sensitivity for anatomical localization without substantially sacrificing performance on the phosphorus module. The developed array enabled phosphorus spectroscopy, a saturation transfer technique to calculate the global creatine kinase forward reaction rate, and single-metabolite whole-brain imaging with 1.4cm nominal isotropic resolution in 15min (2.3cm actual resolution), while additionally enabling 1mm isotropic proton imaging. This study demonstrates that a multi-channel array can be utilized for phosphorus and proton applications with improved coverage and/or sensitivity over traditional single-channel coils. The efficient multi-channel coil array, time-efficient pulse sequences, and the enhanced signal strength available at ultra-high fields can be combined to allow volumetric assessment of the brain and could provide new insights into the underlying energy metabolism impairment in several neurodegenerative conditions, such as Alzheimer's and Parkinson's diseases, as well as mental disorders such as schizophrenia. Copyright © 2015 Elsevier Inc. All rights reserved.

Magnetic resonance spectroscopy of fiber tracts in children with traumatic brain injury: A combined MRS - Diffusion MRI study.

PubMed

Dennis, Emily L; Babikian, Talin; Alger, Jeffry; Rashid, Faisal; Villalon-Reina, Julio E; Jin, Yan; Olsen, Alexander; Mink, Richard; Babbitt, Christopher; Johnson, Jeffrey; Giza, Christopher C; Thompson, Paul M; Asarnow, Robert F

2018-05-10

Traumatic brain injury can cause extensive damage to the white matter (WM) of the brain. These disruptions can be especially damaging in children, whose brains are still maturing. Diffusion magnetic resonance imaging (dMRI) is the most commonly used method to assess WM organization, but it has limited resolution to differentiate causes of WM disruption. Magnetic resonance spectroscopy (MRS) yields spectra showing the levels of neurometabolites that can indicate neuronal/axonal health, inflammation, membrane proliferation/turnover, and other cellular processes that are on-going post-injury. Previous analyses on this dataset revealed a significant division within the msTBI patient group, based on interhemispheric transfer time (IHTT); one subgroup of patients (TBI-normal) showed evidence of recovery over time, while the other showed continuing degeneration (TBI-slow). We combined dMRI with MRS to better understand WM disruptions in children with moderate-severe traumatic brain injury (msTBI). Tracts with poorer WM organization, as shown by lower FA and higher MD and RD, also showed lower N-acetylaspartate (NAA), a marker of neuronal and axonal health and myelination. We did not find lower NAA in tracts with normal WM organization. Choline, a marker of inflammation, membrane turnover, or gliosis, did not show such associations. We further show that multi-modal imaging can improve outcome prediction over a single modality, as well as over earlier cognitive function measures. Our results suggest that demyelination plays an important role in WM disruption post-injury in a subgroup of msTBI children and indicate the utility of multi-modal imaging. © 2018 Wiley Periodicals, Inc.

Higher-order Brain Areas Associated with Real-time Functional MRI Neurofeedback Training of the Somato-motor Cortex.

PubMed

Auer, Tibor; Dewiputri, Wan Ilma; Frahm, Jens; Schweizer, Renate

2018-05-15

Neurofeedback (NFB) allows subjects to learn self-regulation of neuronal brain activation based on information about the ongoing activation. The implementation of real-time functional magnetic resonance imaging (rt-fMRI) for NFB training now facilitates the investigation into underlying processes. Our study involved 16 control and 16 training right-handed subjects, the latter performing an extensive rt-fMRI NFB training using motor imagery. A previous analysis focused on the targeted primary somato-motor cortex (SMC). The present study extends the analysis to the supplementary motor area (SMA), the next higher brain area within the hierarchy of the motor system. We also examined transfer-related functional connectivity using a whole-volume psycho-physiological interaction (PPI) analysis to reveal brain areas associated with learning. The ROI analysis of the pre- and post-training fMRI data for motor imagery without NFB (transfer) resulted in a significant training-specific increase in the SMA. It could also be shown that the contralateral SMA exhibited a larger increase than the ipsilateral SMA in the training and the transfer runs, and that the right-hand training elicited a larger increase in the transfer runs than the left-hand training. The PPI analysis revealed a training-specific increase in transfer-related functional connectivity between the left SMA and frontal areas as well as the anterior midcingulate cortex (aMCC) for right- and left-hand trainings. Moreover, the transfer success was related with training-specific increase in functional connectivity between the left SMA and the target area SMC. Our study demonstrates that NFB training increases functional connectivity with non-targeted brain areas. These are associated with the training strategy (i.e., SMA) as well as with learning the NFB skill (i.e., aMCC and frontal areas). This detailed description of both the system to be trained and the areas involved in learning can provide valuable information for further optimization of NFB trainings. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

Advances in the Neuroscience of Intelligence: from Brain Connectivity to Brain Perturbation.

PubMed

Santarnecchi, Emiliano; Rossi, Simone

2016-12-06

Our view is that intelligence, as expression of the complexity of the human brain and of its evolutionary path, represents an intriguing example of "system level brain plasticity": tangible proofs of this assertion lie in the strong links intelligence has with vital brain capacities as information processing (i.e., pure, rough capacity to transfer information in an efficient way), resilience (i.e., the ability to cope with loss of efficiency and/or loss of physical elements in a network) and adaptability (i.e., being able to efficiently rearrange its dynamics in response to environmental demands). Current evidence supporting this view move from theoretical models correlating intelligence and individual response to systematic "lesions" of brain connectivity, as well as from the field of Noninvasive Brain Stimulation (NiBS). Perturbation-based approaches based on techniques as transcranial magnetic stimulation (TMS) and transcranial alternating current stimulation (tACS), are opening new in vivo scenarios which could allow to disclose more causal relationship between intelligence and brain plasticity, overcoming the limitations of brain-behavior correlational evidence.

[Initial diagnosis of Parkinson's disease - neuroradiological diagnosis].

PubMed

Orimo, Satoshi

2013-01-01

Brain MRI is essential for differentiating Parkinson's disease (PD) from other parkinsonian syndromes. The purpose of performing brain MRI is not to make a diagnosis of PD but is to exclude other parkinsonian syndromes. Recently, several new MRI techniques such as voxel based morphometry, relaxometry, magnetization transfer, spectroscopy, tractography, and functional MRI have been introduced in the diagnosis of PD. Neuromelanin imaging is one of the new techniques and can be useful to make an initial diagnosis of PD. MIBG myocardial scintigraphy is a sensitive imaging tool to differentiate PD from other parkinsonian syndromes and is one of the good tools to make an initial diagnosis of PD. Brain perfusion imaging is sometimes useful to make an initial diagnosis of PD, because reduced brain perfusion area can be detected before brain MRI detects morphological changes of the brain. Dopamine transporter imaging, not available in Japan, is a sensitive tool to detect very early parkinsonism and is useful to make an initial diagnosis of PD. However, it is difficult to differentiate PD from other parkinsonian syndromes.

Detecting functional magnetic resonance imaging activation in white matter: Interhemispheric transfer across the corpus callosum

PubMed Central

Mazerolle, Erin L; D'Arcy, Ryan CN; Beyea, Steven D

2008-01-01

Background It is generally believed that activation in functional magnetic resonance imaging (fMRI) is restricted to gray matter. Despite this, a number of studies have reported white matter activation, particularly when the corpus callosum is targeted using interhemispheric transfer tasks. These findings suggest that fMRI signals may not be neatly confined to gray matter tissue. In the current experiment, 4 T fMRI was employed to evaluate whether it is possible to detect white matter activation. We used an interhemispheric transfer task modelled after neurological studies of callosal disconnection. It was hypothesized that white matter activation could be detected using fMRI. Results Both group and individual data were considered. At liberal statistical thresholds (p < 0.005, uncorrected), group level activation was detected in the isthmus of the corpus callosum. This region connects the superior parietal cortices, which have been implicated previously in interhemispheric transfer. At the individual level, five of the 24 subjects (21%) had activation clusters that were located primarily within the corpus callosum. Consistent with the group results, the clusters of all five subjects were located in posterior callosal regions. The signal time courses for these clusters were comparable to those observed for task related gray matter activation. Conclusion The findings support the idea that, despite the inherent challenges, fMRI activation can be detected in the corpus callosum at the individual level. Future work is needed to determine whether the detection of this activation can be improved by utilizing higher spatial resolution, optimizing acquisition parameters, and analyzing the data with tissue specific models of the hemodynamic response. The ability to detect white matter fMRI activation expands the scope of basic and clinical brain mapping research, and provides a new approach for understanding brain connectivity. PMID:18789154

Magnetic resonance techniques for investigation of multiple sclerosis

NASA Astrophysics Data System (ADS)

MacKay, Alex; Laule, Cornelia; Li, David K. B.; Meyers, Sandra M.; Russell-Schulz, Bretta; Vavasour, Irene M.

2014-11-01

Multiple sclerosis (MS) is a common neurological disease which can cause loss of vision and balance, muscle weakness, impaired speech, fatigue, cognitive dysfunction and even paralysis. The key pathological processes in MS are inflammation, edema, myelin loss, axonal loss and gliosis. Unfortunately, the cause of MS is still not understood and there is currently no cure. Magnetic resonance imaging (MRI) is an important clinical and research tool for MS. 'Conventional' MRI images of MS brain reveal bright lesions, or plaques, which demark regions of severe tissue damage. Conventional MRI has been extremely valuable for the diagnosis and management of people who have MS and also for the assessment of therapies designed to reduce inflammation and promote repair. While conventional MRI is clearly valuable, it lack pathological specificity and, in some cases, sensitivity to non-lesional pathology. Advanced MR techniques have been developed to provide information that is more sensitive and specific than what is available with clinical scanning. Diffusion tensor imaging and magnetization transfer provide a general but non-specific measure of the pathological state of brain tissue. MR spectroscopy provides concentrations of brain metabolites which can be related to specific pathologies. Myelin water imaging was designed to assess brain myelination and has proved useful for measuring myelin loss in MS. To combat MS, it is crucial that the pharmaceutical industry finds therapies which can reverse the neurodegenerative processes which occur in the disease. The challenge for magnetic resonance researchers is to design imaging techniques which can provide detailed pathological information relating to the mechanisms of MS therapies. This paper briefly describes the pathologies of MS and demonstrates how MS-associated pathologies can be followed using both conventional and advanced MR imaging protocols.

Variable Delay Multi-Pulse Train for Fast Chemical Exchange Saturation Transfer and Relayed-Nuclear Overhauser Enhancement MRI

PubMed Central

Xu, Jiadi; Yadav, Nirbhay N.; Bar-Shir, Amnon; Jones, Craig K.; Chan, Kannie W. Y.; Zhang, Jiangyang; Walczak, P.; McMahon, Michael T.; van Zijl, Peter C. M.

2013-01-01

Purpose Chemical exchange saturation transfer (CEST) imaging is a new MRI technology allowing the detection of low concentration endogenous cellular proteins and metabolites indirectly through their exchangeable protons. A new technique, variable delay multi-pulse CEST (VDMP-CEST), is proposed to eliminate the need for recording full Z-spectra and performing asymmetry analysis to obtain CEST contrast. Methods The VDMP-CEST scheme involves acquiring images with two (or more) delays between radiofrequency saturation pulses in pulsed CEST, producing a series of CEST images sensitive to the speed of saturation transfer. Subtracting two images or fitting a time series produces CEST and relayed-nuclear Overhauser enhancement CEST maps without effects of direct water saturation and, when using low radiofrequency power, minimal magnetization transfer contrast interference. Results When applied to several model systems (bovine serum albumin, crosslinked bovine serum albumin, l-glutamic acid) and in vivo on healthy rat brain, VDMP-CEST showed sensitivity to slow to intermediate range magnetization transfer processes (rate < 100–150 Hz), such as amide proton transfer and relayed nuclear Overhauser enhancement-CEST. Images for these contrasts could be acquired in short scan times by using a single radiofrequency frequency. Conclusions VDMP-CEST provides an approach to detect CEST effect by sensitizing saturation experiments to slower exchange processes without interference of direct water saturation and without need to acquire Z-spectra and perform asymmetry analysis. PMID:23813483

Investigating dynamical information transfer in the brain following a TMS pulse: Insights from structural architecture.

PubMed

Amico, Enrico; Van Mierlo, Pieter; Marinazzo, Daniele; Laureys, Steven

2015-01-01

Transcranial magnetic stimulation (TMS) has been used for more than 20 years to investigate connectivity and plasticity in the human cortex. By combining TMS with high-density electroencephalography (hd-EEG), one can stimulate any cortical area and measure the effects produced by this perturbation in the rest of the cerebral cortex. The purpose of this paper is to investigate changes of information flow in the brain after TMS from a functional and structural perspective, using multimodal modeling of source reconstructed TMS/hd-EEG recordings and DTI tractography. We prove how brain dynamics induced by TMS is constrained and driven by its structure, at different spatial and temporal scales, especially when considering cross-frequency interactions. These results shed light on the function-structure organization of the brain network at the global level, and on the huge variety of information contained in it.

Assignment of the molecular origins of CEST signals at 2 ppm in rat brain.

PubMed

Zhang, Xiao-Yong; Xie, Jingping; Wang, Feng; Lin, Eugene C; Xu, Junzhong; Gochberg, Daniel F; Gore, John C; Zu, Zhongliang

2017-09-01

Chemical exchange saturation transfer effects at 2 ppm (CEST@2ppm) in brain have previously been interpreted as originating from creatine. However, protein guanidino amine protons may also contribute to CEST@2ppm. This study aims to investigate the molecular origins and specificity of CEST@2ppm in brain. Two experiments were performed: (i) samples containing egg white albumin and creatine were dialyzed using a semipermeable membrane to demonstrate that proteins and creatine can be separated by this method; and (ii) tissue homogenates of rat brain with and without dialysis to remove creatine were studied to measure the relative contributions of proteins and creatine to CEST@2ppm. The experiments indicate that dialysis can successfully remove creatine from proteins. Measurements on tissue homogenates show that, with the removal of creatine via dialysis, CEST@2ppm decreases to approximately 34% of its value before dialysis, which indicates that proteins and creatine have comparable contribution to the CEST@2ppm in brain. However, considering the contribution from peptides and amino acids to CEST@2ppm, creatine may have much less contribution to CEST@2ppm. The contribution of proteins, peptides, and amino acids to CEST@2ppm cannot be neglected. The CEST@2ppm measurements of creatine in rat brain should be interpreted with caution. Magn Reson Med 78:881-887, 2017. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

Effect of intravascular-to-extravascular water exchange on the determination of blood-to-tissue transfer constant by magnetic resonance imaging.

PubMed

Cao, Y; Brown, S L; Knight, R A; Fenstermacher, J D; Ewing, J R

2005-02-01

Water exchange across capillary walls couples intra- and extravascular (IV-EV) protons and their magnetization. A bolus i.v. injection of an extracellular MRI contrast agent (MRCA) causes a large increase in the spin-lattice relaxation rate, R1, of water protons in the plasma and blood cells within the capillaries and changes the effective relaxation rate R1eff in tissue via IV-EV water exchange. An analysis of the effect of plasma-red cell and IV-EV water exchange on the MRI-measured influx and permeability of capillaries to the MRCA is presented and focused on the brain and the blood-brain barrier. The effect of arrival of a bolus of an MRCA in the capillary on the relaxation rate R1eff in tissue via IV-EV water exchange occurs more rapidly than the MRCA uptake in tissue and can dominate the initial time curve of the R1eff change before the MRCA uptake in tissue becomes significant. This raises the possibility that (tissue dependent) IV-EV rate of exchange of water molecules can affect estimates of MRCA transfer constant. We demonstrate that an approach that considers IV-EV water exchange and uses the theoretical model of blood-brain tracer distribution developed by Patlak et al. (J Cereb Blood Flow Metab 1983;3:1-7) can lead to an accurate estimate of the MRI-determined influx rate constant of the MRCA and to an underestimation of the tissue blood volume.

Delineation of early brain development from fetuses to infants with diffusion MRI and beyond.

PubMed

Ouyang, Minhui; Dubois, Jessica; Yu, Qinlin; Mukherjee, Pratik; Huang, Hao

2018-04-12

Dynamic macrostructural and microstructural changes take place from the mid-fetal stage to 2 years after birth. Delineating structural changes of the brain during early development provides new insights into the complicated processes of both typical development and the pathological mechanisms underlying various psychiatric and neurological disorders including autism, attention deficit hyperactivity disorder and schizophrenia. Decades of histological studies have identified strong spatial and functional maturation gradients in human brain gray and white matter. The recent improvements in magnetic resonance imaging (MRI) techniques, especially diffusion MRI (dMRI), relaxometry imaging, and magnetization transfer imaging (MTI) have provided unprecedented opportunities to non-invasively quantify and map the early developmental changes at whole brain and regional levels. Here, we review the recent advances in understanding early brain structural development during the second half of gestation and the first two postnatal years using modern MR techniques. Specifically, we review studies that delineate the emergence and microstructural maturation of white matter tracts, as well as dynamic mapping of inhomogeneous cortical microstructural organization unique to fetuses and infants. These imaging studies converge into maturational curves of MRI measurements that are distinctive across different white matter tracts and cortical regions. Furthermore, contemporary models offering biophysical interpretations of the dMRI-derived measurements are illustrated to infer the underlying microstructural changes. Collectively, this review summarizes findings that contribute to charting spatiotemporally heterogeneous gray and white matter structural development, offering MRI-based biomarkers of typical brain development and setting the stage for understanding aberrant brain development in neurodevelopmental disorders. Copyright © 2018 Elsevier Inc. All rights reserved.

Phase imaging in brain using SWIFT

NASA Astrophysics Data System (ADS)

Lehto, Lauri Juhani; Garwood, Michael; Gröhn, Olli; Corum, Curtis Andrew

2015-03-01

The majority of MRI phase imaging is based on gradient recalled echo (GRE) sequences. This work studies phase contrast behavior due to small off-resonance frequency offsets in brain using SWIFT, a FID-based sequence with nearly zero acquisition delay. 1D simulations and a phantom study were conducted to describe the behavior of phase accumulation in SWIFT. Imaging experiments of known brain phase contrast properties were conducted in a perfused rat brain comparing GRE and SWIFT. Additionally, a human brain sample was imaged. It is demonstrated how SWIFT phase is orientation dependent and correlates well with GRE, linking SWIFT phase to similar off-resonance sources as GRE. The acquisition time is shown to be analogous to TE for phase accumulation time. Using experiments with and without a magnetization transfer preparation, the likely effect of myelin water pool contribution is seen as a phase increase for all acquisition times. Due to the phase accumulation during acquisition, SWIFT phase contrast can be sensitized to small frequency differences between white and gray matter using low acquisition bandwidths.

On-resonance Variable Delay Multi Pulse Scheme for Imaging of Fast-exchanging Protons and semi-solid Macromolecules

PubMed Central

Xu, Jiadi; Chan, Kannie W.Y.; Xu, Xiang; Yadav, Nibhay; Liu, Guanshu; van Zijl, Peter C. M.

2016-01-01

Purpose To develop an on-resonance variable delay multi-pulse (VDMP) scheme to image magnetization transfer contrast (MTC) as well as the chemical exchange saturation transfer (CEST) contrast of total fast-exchanging protons (TFP) with exchange rate above about 1 kHz. Methods A train of high power binomial pulses was applied at the water resonance. The inter-pulse delay, called mixing time, was varied to observe its effect on the water signal reduction, allowing separation and quantification of MTC and CEST contributions due to their different proton transfer rates. The fast-exchanging protons in CEST and MTC are labeled together with the short T2 components in MTC and separated out using a variable mixing time. Results Phantom studies of selected metabolite solutions (glucose, glutamate, creatine, myo-inositol), bovine serum albumin (BSA) and hair conditioner show the capability of on-resonance VDMP to separate out exchangeable protons with exchange rates above 1 kHz. Quantitative MTC and TFP maps were acquired on healthy mouse brains using this method showing strong gray/white matter contrast for the slowly transferring MTC protons while the TFP map was more uniform across the brain but somewhat higher in gray matter. Conclusions The new method provides a simple way of imaging fast-exchanging protons, as well as MTC components with a slow transfer rate. PMID:26900759

Interpretation of magnetization transfer from inhomogeneously broadened lines (ihMT) in tissues as a dipolar order effect within motion restricted molecules

NASA Astrophysics Data System (ADS)

Varma, G.; Girard, O. M.; Prevost, V. H.; Grant, A. K.; Duhamel, G.; Alsop, D. C.

2015-11-01

Comparison of off-resonance saturation with single and dual frequency irradiation indicates a contribution of inhomogeneously broadened lines to magnetization transfer in tissues. This inhomogeneous magnetization transfer (ihMT) phenomenon can be exploited to produce images that highlight tissues containing myelin, in vivo. Here, a model for ihMT is described that includes dipolar order effects from magnetization associated with motion-restricted macromolecules. In this model, equal irradiation at positive and negative frequency offsets eliminates dipolar order and achieves greater saturation than irradiation at a single offset frequency using the same power. Fitting of mouse and human volunteer brain data at different irradiation powers and offset frequencies was performed to assess the relevance of the model and approximate tissue parameters. A key parameter in determining ihMT signal was found to be the relaxation time T1D associated with the dipolar order reservoir and the fraction f of the semi-solid, bound magnetization that possessed a nonzero T1D. Indeed, better fits of myelinated tissue were achieved when assuming f ≠ 1. From such fits, estimated T1Ds of mice in the white matter, (34 ± 14)ms, were much longer than in muscle, T1D = (1 ± 1)ms and the average f from white matter volunteer data was 2.2 times greater than that in grey matter. The combination of f and longer T1Ds was primarily responsible for the much higher ihMT in myelinated tissues, and provided explanation for the species variation. This dipolar order ihMT model should help guide future research, pulse sequence optimization, and clinical applications.

Targeted drug delivery to the brain using magnetic nanoparticles.

PubMed

Thomsen, Louiza Bohn; Thomsen, Maj Schneider; Moos, Torben

2015-01-01

Brain capillary endothelial cells denote the blood-brain barrier (BBB), and conjugation of nanoparticles with antibodies that target molecules expressed by these endothelial cells may facilitate their uptake and transport into the brain. Magnetic nanoparticles can be encapsulated in liposomes and carry large molecules with therapeutic potential, for example, siRNA, cDNA and polypeptides. An additional approach to enhance the transport of magnetic nanoparticles across the BBB is the application of extracranially applied magnetic force. Stepwise targeting of magnetic nanoparticles to brain capillary endothelial cells followed by transport through the BBB using magnetic force may prove a novel mechanism for targeted therapy of macromolecules to the brain.

Delay Discounting and Frontostriatal Fiber Tracts: A Combined DTI and MTR Study on Impulsive Choices in Healthy Young Adults

PubMed Central

Peper, Jiska S.; Mandl, René C.W.; Braams, Barbara R.; de Water, Erik; Heijboer, Annemieke C.; Koolschijn, P. Cédric M.P.; Crone, Eveline A.

2013-01-01

Delay discounting, a measure of impulsive choice, has been associated with decreased control of the prefrontal cortex over striatum responses. The anatomical connectivity between both brain regions in delaying gratification remains unknown. Here, we investigate whether the quality of frontostriatal (FS) white matter tracts can predict individual differences in delay-discounting behavior. We use tract-based diffusion tensor imaging and magnetization transfer imaging to measure the microstructural properties of FS fiber tracts in 40 healthy young adults (from 18 to 25 years). We additionally explored whether internal sex hormone levels affect the integrity of FS tracts, based on the hypothesis that sex hormones modulate axonal density within prefrontal dopaminergic circuits. We calculated fractional anisotropy (FA), mean diffusivity (MD), longitudinal diffusivity, radial diffusivity (RD), and magnetization transfer ratio (MTR), a putative measure of myelination, for the FS tract. Results showed that lower integrity within the FS tract (higher MD and RD and lower FA), predicts faster discounting in both sexes. MTR was unrelated to delay-discounting performance. In addition, testosterone levels in males were associated with a lower integrity (higher RD) within the FS tract. Our study provides support for the hypothesis that enhanced structural integrity of white matter fiber bundles between prefrontal and striatal brain areas is associated with better impulse control. PMID:22693341

Networks of myelin covariance

PubMed Central

Slater, David; Ruef, Anne; Sanabria‐Diaz, Gretel; Preisig, Martin; Kherif, Ferath; Draganski, Bogdan; Lutti, Antoine

2017-01-01

Abstract Networks of anatomical covariance have been widely used to study connectivity patterns in both normal and pathological brains based on the concurrent changes of morphometric measures (i.e., cortical thickness) between brain structures across subjects (Evans, 2013). However, the existence of networks of microstructural changes within brain tissue has been largely unexplored so far. In this article, we studied in vivo the concurrent myelination processes among brain anatomical structures that gathered together emerge to form nonrandom networks. We name these “networks of myelin covariance” (Myelin‐Nets). The Myelin‐Nets were built from quantitative Magnetization Transfer data—an in‐vivo magnetic resonance imaging (MRI) marker of myelin content. The synchronicity of the variations in myelin content between anatomical regions was measured by computing the Pearson's correlation coefficient. We were especially interested in elucidating the effect of age on the topological organization of the Myelin‐Nets. We therefore selected two age groups: Young‐Age (20–31 years old) and Old‐Age (60–71 years old) and a pool of participants from 48 to 87 years old for a Myelin‐Nets aging trajectory study. We found that the topological organization of the Myelin‐Nets is strongly shaped by aging processes. The global myelin correlation strength, between homologous regions and locally in different brain lobes, showed a significant dependence on age. Interestingly, we also showed that the aging process modulates the resilience of the Myelin‐Nets to damage of principal network structures. In summary, this work sheds light on the organizational principles driving myelination and myelin degeneration in brain gray matter and how such patterns are modulated by aging. PMID:29271053

Dexmedetomidine Disrupts the Local and Global Efficiencies of Large-scale Brain Networks.

PubMed

Hashmi, Javeria A; Loggia, Marco L; Khan, Sheraz; Gao, Lei; Kim, Jieun; Napadow, Vitaly; Brown, Emery N; Akeju, Oluwaseun

2017-03-01

A clear understanding of the neural basis of consciousness is fundamental to research in clinical and basic neuroscience disciplines and anesthesia. Recently, decreased efficiency of information integration was suggested as a core network feature of propofol-induced unconsciousness. However, it is unclear whether this finding can be generalized to dexmedetomidine, which has a different molecular target. Dexmedetomidine was administered as a 1-μg/kg bolus over 10 min, followed by a 0.7-μg · kg · h infusion to healthy human volunteers (age range, 18 to 36 yr; n = 15). Resting-state functional magnetic resonance imaging data were acquired during baseline, dexmedetomidine-induced altered arousal, and recovery states. Zero-lag correlations between resting-state functional magnetic resonance imaging signals extracted from 131 brain parcellations were used to construct weighted brain networks. Network efficiency, degree distribution, and node strength were computed using graph analysis. Parcellated brain regions were also mapped to known resting-state networks to study functional connectivity changes. Dexmedetomidine significantly reduced the local and global efficiencies of graph theory-derived networks. Dexmedetomidine also reduced the average brain connectivity strength without impairing the degree distribution. Functional connectivity within and between all resting-state networks was modulated by dexmedetomidine. Dexmedetomidine is associated with a significant drop in the capacity for efficient information transmission at both the local and global levels. These changes result from reductions in the strength of connectivity and also manifest as reduced within and between resting-state network connectivity. These findings strengthen the hypothesis that conscious processing relies on an efficient system of information transfer in the brain.

Assessment of MRI Parameters as Imaging Biomarkers for Radiation Necrosis in the Rat Brain

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

Wang Silun; Tryggestad, Erik; Zhou Tingting

Purpose: Radiation necrosis is a major complication of radiation therapy. We explore the features of radiation-induced brain necrosis in the rat, using multiple MRI approaches, including T{sub 1}, T{sub 2}, apparent diffusion constant (ADC), cerebral blood flow (CBF), magnetization transfer ratio (MTR), and amide proton transfer (APT) of endogenous mobile proteins and peptides. Methods and Materials: Adult rats (Fischer 344; n = 15) were irradiated with a single, well-collimated X-ray beam (40 Gy; 10 Multiplication-Sign 10 mm{sup 2}) in the left brain hemisphere. MRI was acquired on a 4.7-T animal scanner at {approx}25 weeks' postradiation. The MRI signals of necroticmore » cores and perinecrotic regions were assessed with a one-way analysis of variance. Histological evaluation was accomplished with hematoxylin and eosin staining. Results: ADC and CBF MRI could separate perinecrotic and contralateral normal brain tissue (p < 0.01 and < 0.05, respectively), whereas T{sub 1}, T{sub 2}, MTR, and APT could not. MRI signal intensities were significantly lower in the necrotic core than in normal brain for CBF (p < 0.001) and APT (p < 0.01) and insignificantly higher or lower for T{sub 1}, T{sub 2}, MTR, and ADC. Histological results demonstrated coagulative necrosis within the necrotic core and reactive astrogliosis and vascular damage within the perinecrotic region. Conclusion: ADC and CBF are promising imaging biomarkers for identifying perinecrotic regions, whereas CBF and APT are promising for identifying necrotic cores.« less

Assessment of MRI parameters as imaging biomarkers for radiation necrosis in the rat brain.

PubMed

Wang, Silun; Tryggestad, Erik; Zhou, Tingting; Armour, Michael; Wen, Zhibo; Fu, De-Xue; Ford, Eric; van Zijl, Peter C M; Zhou, Jinyuan

2012-07-01

Radiation necrosis is a major complication of radiation therapy. We explore the features of radiation-induced brain necrosis in the rat, using multiple MRI approaches, including T(1), T(2), apparent diffusion constant (ADC), cerebral blood flow (CBF), magnetization transfer ratio (MTR), and amide proton transfer (APT) of endogenous mobile proteins and peptides. Adult rats (Fischer 344; n = 15) were irradiated with a single, well-collimated X-ray beam (40 Gy; 10 × 10 mm(2)) in the left brain hemisphere. MRI was acquired on a 4.7-T animal scanner at ~25 weeks' postradiation. The MRI signals of necrotic cores and perinecrotic regions were assessed with a one-way analysis of variance. Histological evaluation was accomplished with hematoxylin and eosin staining. ADC and CBF MRI could separate perinecrotic and contralateral normal brain tissue (p < 0.01 and < 0.05, respectively), whereas T(1), T(2), MTR, and APT could not. MRI signal intensities were significantly lower in the necrotic core than in normal brain for CBF (p < 0.001) and APT (p < 0.01) and insignificantly higher or lower for T(1), T(2), MTR, and ADC. Histological results demonstrated coagulative necrosis within the necrotic core and reactive astrogliosis and vascular damage within the perinecrotic region. ADC and CBF are promising imaging biomarkers for identifying perinecrotic regions, whereas CBF and APT are promising for identifying necrotic cores. Copyright © 2012 Elsevier Inc. All rights reserved.

Networks of myelin covariance.

PubMed

Melie-Garcia, Lester; Slater, David; Ruef, Anne; Sanabria-Diaz, Gretel; Preisig, Martin; Kherif, Ferath; Draganski, Bogdan; Lutti, Antoine

2018-04-01

Networks of anatomical covariance have been widely used to study connectivity patterns in both normal and pathological brains based on the concurrent changes of morphometric measures (i.e., cortical thickness) between brain structures across subjects (Evans, ). However, the existence of networks of microstructural changes within brain tissue has been largely unexplored so far. In this article, we studied in vivo the concurrent myelination processes among brain anatomical structures that gathered together emerge to form nonrandom networks. We name these "networks of myelin covariance" (Myelin-Nets). The Myelin-Nets were built from quantitative Magnetization Transfer data-an in-vivo magnetic resonance imaging (MRI) marker of myelin content. The synchronicity of the variations in myelin content between anatomical regions was measured by computing the Pearson's correlation coefficient. We were especially interested in elucidating the effect of age on the topological organization of the Myelin-Nets. We therefore selected two age groups: Young-Age (20-31 years old) and Old-Age (60-71 years old) and a pool of participants from 48 to 87 years old for a Myelin-Nets aging trajectory study. We found that the topological organization of the Myelin-Nets is strongly shaped by aging processes. The global myelin correlation strength, between homologous regions and locally in different brain lobes, showed a significant dependence on age. Interestingly, we also showed that the aging process modulates the resilience of the Myelin-Nets to damage of principal network structures. In summary, this work sheds light on the organizational principles driving myelination and myelin degeneration in brain gray matter and how such patterns are modulated by aging. © 2017 The Authors Human Brain Mapping Published by Wiley Periodicals, Inc.

Non-invasive brain stimulation can induce paradoxical facilitation. Are these neuroenhancements transferable and meaningful to security services?

PubMed Central

Levasseur-Moreau, Jean; Brunelin, Jerome; Fecteau, Shirley

2013-01-01

For ages, we have been looking for ways to enhance our physical and cognitive capacities in order to augment our security. One potential way to enhance our capacities may be to externally stimulate the brain. Methods of non-invasive brain stimulation (NIBS), such as repetitive transcranial magnetic stimulation (rTMS) and transcranial electrical stimulation (tES), have been recently developed to modulate brain activity. Both techniques are relatively safe and can transiently modify motor and cognitive functions outlasting the stimulation period. The purpose of this paper is to review data suggesting that NIBS can enhance motor and cognitive performance in healthy volunteers. We frame these findings in the context of whether they may serve security purposes. Specifically, we review studies reporting that NIBS induces paradoxical facilitation in motor (precision, speed, strength, acceleration endurance, and execution of daily motor task) and cognitive functions (attention, impulsive behavior, risk-taking, working memory, planning, and deceptive capacities). Although transferability and meaningfulness of these NIBS-induced paradoxical facilitations into real-life situations are not clear yet, NIBS may contribute at improving training of motor and cognitive functions relevant for military, civil, and forensic security services. This is an enthusiastic perspective that also calls for fair and open debates on the ethics of using NIBS in healthy individuals to enhance normal functions. PMID:23966923

Pulse Coupled Neural Networks for the Segmentation of Magnetic Resonance Brain Images.

DTIC Science & Technology

1996-12-01

PULSE COUPLED NEURAL NETWORKS FOR THE SEGMENTATION OF MAGNETIC RESONANCE BRAIN IMAGES THESIS Shane Lee Abrahamson First Lieutenant, USAF AFIT/GCS/ENG...COUPLED NEURAL NETWORKS FOR THE SEGMENTATION OF MAGNETIC RESONANCE BRAIN IMAGES THESIS Shane Lee Abrahamson First Lieutenant, USAF AFIT/GCS/ENG/96D-01...research develops an automated method for segmenting Magnetic Resonance (MR) brain images based on Pulse Coupled Neural Networks (PCNN). MR brain image

Assessing perioperative complications associated with use of intraoperative magnetic resonance imaging during glioma surgery - a single centre experience with 516 cases.

PubMed

Ahmadi, Rezvan; Campos, Benito; Haux, Daniel; Rieke, Jörn; Beigel, Bernhard; Unterberg, Andreas

2016-08-01

Intraoperative magnetic resonance imaging (io-MRI) improves the extent of glioma resection. Due to the magnetic field, patients have to be covered with sterile drape and are then transferred into an io-MRI chamber, where ferromagnetic anaesthesia monitors and machines must be kept at distance and can only be applied with limitations. Despite the development of specific paramagnetic equipment for io-MRI use, this method is suspected to carry a higher risk for anaesthesiological and surgical complications. Particularly, serial draping and un-draping cycles as well as the extended surgery duration might increase the risk of perioperative infection. Given the importance of io-MRI for glioma surgery, the question regarding io-MRI safety needs to be answered. We prospectively evaluate the perioperative anaesthesiological and surgical complications for 516 cases of brain tumour surgery involving io-MRI (MRI cohort). As a control group, we evaluate a cohort of 610 cases of brain tumour surgery, performed without io-MRI (control group). The io-MRI procedure (including draping/undraping, transfer to and from the MRI cabinet and io-MRI scan) significantly extended surgery, defined as "skin to skin" time, by 57 min (SD = 16 min) (p ≤ 0.01). Still, we show low and comparable rates of surgical complications in the MRI cohort and the control group. Postoperative haemorrhage (3.7% versus 3.0% in MRI cohort versus control group; p = 0.49) and infections (2.2% versus 1.8% in MRI cohort versus control group; p = 0.69) were not significantly different between both groups. No anaesthesiological disturbances were reported. Despite prolonged surgery and serial draping and un-draping cycles, io-MRI was not linked to higher rates of infections and postoperative haemorrhage in this study.

Comparison of pulsed three-dimensional CEST acquisition schemes at 7 tesla: steady state versus pseudosteady state.

PubMed

Khlebnikov, Vitaliy; Geades, Nicolas; Klomp, Dennis W J; Hoogduin, Hans; Gowland, Penny; Mougin, Olivier

2017-06-01

To compare two pulsed, volumetric chemical exchange saturation transfer (CEST) acquisition schemes: steady state (SS) and pseudosteady state (PS) for the same brain coverage, spatial/spectral resolution and scan time. Both schemes were optimized for maximum sensitivity to amide proton transfer (APT) and nuclear Overhauser enhancement (NOE) effects through Bloch-McConnell simulations, and compared in terms of sensitivity to APT and NOE effects, and to transmit field inhomogeneity. Five consented healthy volunteers were scanned on a 7 Tesla Philips MR-system using the optimized protocols at three nominal B 1 amplitudes: 1 μT, 2 μT, and 3 μT. Region of interest based analysis revealed that PS is more sensitive (P < 0.05) to APT and NOE effects compared with SS at low B 1 amplitudes (0.7-1.0 μT). Also, both sequences have similar dependence on the transmit field inhomogeneity. For the optimum CEST presaturation parameters (1 μT and 2 μT for APT and NOE, respectively), NOE is less sensitive to the inhomogeneity effects (15% signal to noise ratio [SNR] change for a B 1 dropout of 40%) compared with APT (35% SNR change for a B 1 dropout of 40%). For the same brain coverage, spatial/spectral resolution and scan time, at low power levels PS is more sensitive to the slow chemical exchange-mediated processes compared with SS. Magn Reson Med 77:2280-2287, 2017. © 2016 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. © 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine.

Magnetic to magnetic and kinetic to magnetic energy transfers at the top of the Earth's core

NASA Astrophysics Data System (ADS)

Huguet, Ludovic; Amit, Hagay; Alboussière, Thierry

2016-11-01

We develop the theory for the magnetic to magnetic and kinetic to magnetic energy transfer between different spherical harmonic degrees due to the interaction of fluid flow and radial magnetic field at the top of the Earth's core. We show that non-zero secular variation of the total magnetic energy could be significant and may provide evidence for the existence of stretching secular variation, which suggests the existence of radial motions at the top of the Earth's core-whole core convection or MAC waves. However, the uncertainties of the small scales of the geomagnetic field prevent a definite conclusion. Combining core field and flow models we calculate the detailed magnetic to magnetic and kinetic to magnetic energy transfer matrices. The magnetic to magnetic energy transfer shows a complex behaviour with local and non-local transfers. The spectra of magnetic to magnetic energy transfers show clear maxima and minima, suggesting an energy cascade. The kinetic to magnetic energy transfers, which are much weaker due to the weak poloidal flow, are either local or non-local between degree one and higher degrees. The patterns observed in the matrices resemble energy transfer patterns that are typically found in 3-D MHD numerical simulations.

Characterization of Cerebral White Matter Properties Using Quantitative Magnetic Resonance Imaging Stains

PubMed Central

Hurley, Samuel A.; Samsonov, Alexey A.; Adluru, Nagesh; Hosseinbor, Ameer Pasha; Mossahebi, Pouria; Tromp, Do P.M.; Zakszewski, Elizabeth; Field, Aaron S.

2011-01-01

Abstract The image contrast in magnetic resonance imaging (MRI) is highly sensitive to several mechanisms that are modulated by the properties of the tissue environment. The degree and type of contrast weighting may be viewed as image filters that accentuate specific tissue properties. Maps of quantitative measures of these mechanisms, akin to microstructural/environmental-specific tissue stains, may be generated to characterize the MRI and physiological properties of biological tissues. In this article, three quantitative MRI (qMRI) methods for characterizing white matter (WM) microstructural properties are reviewed. All of these measures measure complementary aspects of how water interacts with the tissue environment. Diffusion MRI, including diffusion tensor imaging, characterizes the diffusion of water in the tissues and is sensitive to the microstructural density, spacing, and orientational organization of tissue membranes, including myelin. Magnetization transfer imaging characterizes the amount and degree of magnetization exchange between free water and macromolecules like proteins found in the myelin bilayers. Relaxometry measures the MRI relaxation constants T1 and T2, which in WM have a component associated with the water trapped in the myelin bilayers. The conduction of signals between distant brain regions occurs primarily through myelinated WM tracts; thus, these methods are potential indicators of pathology and structural connectivity in the brain. This article provides an overview of the qMRI stain mechanisms, acquisition and analysis strategies, and applications for these qMRI stains. PMID:22432902

Boolean and brain-inspired computing using spin-transfer torque devices

NASA Astrophysics Data System (ADS)

Fan, Deliang

Several completely new approaches (such as spintronic, carbon nanotube, graphene, TFETs, etc.) to information processing and data storage technologies are emerging to address the time frame beyond current Complementary Metal-Oxide-Semiconductor (CMOS) roadmap. The high speed magnetization switching of a nano-magnet due to current induced spin-transfer torque (STT) have been demonstrated in recent experiments. Such STT devices can be explored in compact, low power memory and logic design. In order to truly leverage STT devices based computing, researchers require a re-think of circuit, architecture, and computing model, since the STT devices are unlikely to be drop-in replacements for CMOS. The potential of STT devices based computing will be best realized by considering new computing models that are inherently suited to the characteristics of STT devices, and new applications that are enabled by their unique capabilities, thereby attaining performance that CMOS cannot achieve. The goal of this research is to conduct synergistic exploration in architecture, circuit and device levels for Boolean and brain-inspired computing using nanoscale STT devices. Specifically, we first show that the non-volatile STT devices can be used in designing configurable Boolean logic blocks. We propose a spin-memristor threshold logic (SMTL) gate design, where memristive cross-bar array is used to perform current mode summation of binary inputs and the low power current mode spintronic threshold device carries out the energy efficient threshold operation. Next, for brain-inspired computing, we have exploited different spin-transfer torque device structures that can implement the hard-limiting and soft-limiting artificial neuron transfer functions respectively. We apply such STT based neuron (or 'spin-neuron') in various neural network architectures, such as hierarchical temporal memory and feed-forward neural network, for performing "human-like" cognitive computing, which show more than two orders of lower energy consumption compared to state of the art CMOS implementation. Finally, we show the dynamics of injection locked Spin Hall Effect Spin-Torque Oscillator (SHE-STO) cluster can be exploited as a robust multi-dimensional distance metric for associative computing, image/ video analysis, etc. Our simulation results show that the proposed system architecture with injection locked SHE-STOs and the associated CMOS interface circuits can be suitable for robust and energy efficient associative computing and pattern matching.

Computational analysis of transcranial magnetic stimulation in the presence of deep brain stimulation probes

NASA Astrophysics Data System (ADS)

Syeda, F.; Holloway, K.; El-Gendy, A. A.; Hadimani, R. L.

2017-05-01

Transcranial Magnetic Stimulation is an emerging non-invasive treatment for depression, Parkinson's disease, and a variety of other neurological disorders. Many Parkinson's patients receive the treatment known as Deep Brain Stimulation, but often require additional therapy for speech and swallowing impairment. Transcranial Magnetic Stimulation has been explored as a possible treatment by stimulating the mouth motor area of the brain. We have calculated induced electric field, magnetic field, and temperature distributions in the brain using finite element analysis and anatomically realistic heterogeneous head models fitted with Deep Brain Stimulation leads. A Figure of 8 coil, current of 5000 A, and frequency of 2.5 kHz are used as simulation parameters. Results suggest that Deep Brain Stimulation leads cause surrounding tissues to experience slightly increased E-field (Δ Emax =30 V/m), but not exceeding the nominal values induced in brain tissue by Transcranial Magnetic Stimulation without leads (215 V/m). The maximum temperature in the brain tissues surrounding leads did not change significantly from the normal human body temperature of 37 °C. Therefore, we ascertain that Transcranial Magnetic Stimulation in the mouth motor area may stimulate brain tissue surrounding Deep Brain Stimulation leads, but will not cause tissue damage.

Real-time fMRI neurofeedback in adolescents with attention deficit hyperactivity disorder.

PubMed

Alegria, Analucia A; Wulff, Melanie; Brinson, Helen; Barker, Gareth J; Norman, Luke J; Brandeis, Daniel; Stahl, Daniel; David, Anthony S; Taylor, Eric; Giampietro, Vincent; Rubia, Katya

2017-06-01

Attention Deficit Hyperactivity Disorder (ADHD) is associated with poor self-control, underpinned by inferior fronto-striatal deficits. Real-time functional magnetic resonance neurofeedback (rtfMRI-NF) allows participants to gain self-control over dysregulated brain regions. Despite evidence for beneficial effects of electrophysiological-NF on ADHD symptoms, no study has applied the spatially superior rtfMRI-NF neurotherapy to ADHD. A randomized controlled trial tested the efficacy of rtfMRI-NF of right inferior prefrontal cortex (rIFG), a key region that is compromised in ADHD and upregulated with psychostimulants, on improvement of ADHD symptoms, cognition, and inhibitory fMRI activation. To control for region-specificity, an active control group received rtfMRI-NF of the left parahippocampal gyrus (lPHG). Thirty-one ADHD boys were randomly allocated and had to learn to upregulate their target brain region in an average of 11 rtfMRI-NF runs over 2 weeks. Feedback was provided through a video-clip of a rocket that had to be moved up into space. A transfer session without feedback tested learning retention as a proximal measure of transfer to everyday life. Both NF groups showed significant linear activation increases with increasing number of runs in their respective target regions and significant reduction in ADHD symptoms after neurotherapy and at 11-month follow-up. Only the group targeting rIFG, however, showed a transfer effect, which correlated with ADHD symptom reductions, improved at trend level in sustained attention, and showed increased IFG activation during an inhibitory fMRI task. This proof-of-concept study demonstrates for the first time feasibility, safety, and shorter- and longer-term efficacy of rtfMRI-NF of rIFG in adolescents with ADHD. Hum Brain Mapp 38:3190-3209, 2017. © 2017 The Authors Human Brain Mapping Published by Wiley Periodicals, Inc. © 2017 The Authors Human Brain Mapping Published by Wiley Periodicals, Inc.

Application of State-Space Smoothing to fMRI Data for Calculation of Lagged Transinformation between Human Brain Activations

NASA Astrophysics Data System (ADS)

Watanabe, Jobu

2009-09-01

Mutual information can be given a directional sense by introducing a time lag in one of the variables. In an author's previous study, to investigate the network dynamics of human brain regions, lagged transinformation (LTI) was introduced using time delayed mutual information. The LTI makes it possible to quantify the time course of dynamic information transfer between regions in the temporal domain. The LTI was applied to functional magnetic resonance imaging (fMRI) data involved in neural processing of the transformation and comparison from three-dimensional (3D) visual information to a two-dimensional (2D) location to calculate directed information flows between the activated brain regions. In the present study, for more precise estimation of LTI, Kalman filter smoothing was applied to the same fMRI data. Because the smoothing method exploits the full length of the time series data for the estimation, its application increases the precision. Large information flows were found from the bilateral prefrontal cortices to the parietal cortices. The results suggest that information of the 3D images stored as working memory was retrieved and transferred from the prefrontal cortices to the parietal cortices for comparison with information of the 2D images.

A digital 3D atlas of the marmoset brain based on multi-modal MRI.

PubMed

Liu, Cirong; Ye, Frank Q; Yen, Cecil Chern-Chyi; Newman, John D; Glen, Daniel; Leopold, David A; Silva, Afonso C

2018-04-01

The common marmoset (Callithrix jacchus) is a New-World monkey of growing interest in neuroscience. Magnetic resonance imaging (MRI) is an essential tool to unveil the anatomical and functional organization of the marmoset brain. To facilitate identification of regions of interest, it is desirable to register MR images to an atlas of the brain. However, currently available atlases of the marmoset brain are mainly based on 2D histological data, which are difficult to apply to 3D imaging techniques. Here, we constructed a 3D digital atlas based on high-resolution ex-vivo MRI images, including magnetization transfer ratio (a T1-like contrast), T2w images, and multi-shell diffusion MRI. Based on the multi-modal MRI images, we manually delineated 54 cortical areas and 16 subcortical regions on one hemisphere of the brain (the core version). The 54 cortical areas were merged into 13 larger cortical regions according to their locations to yield a coarse version of the atlas, and also parcellated into 106 sub-regions using a connectivity-based parcellation method to produce a refined atlas. Finally, we compared the new atlas set with existing histology atlases and demonstrated its applications in connectome studies, and in resting state and stimulus-based fMRI. The atlas set has been integrated into the widely-distributed neuroimaging data analysis software AFNI and SUMA, providing a readily usable multi-modal template space with multi-level anatomical labels (including labels from the Paxinos atlas) that can facilitate various neuroimaging studies of marmosets. Published by Elsevier Inc.

The pros and cons of intraoperative CT scan in evaluation of deep brain stimulation lead implantation: A retrospective study

PubMed Central

Servello, Domenico; Zekaj, Edvin; Saleh, Christian; Pacchetti, Claudio; Porta, Mauro

2016-01-01

Background: Deep brain stimulation (DBS) is an established therapy for movement disorders, such as Parkinson's disease (PD), dystonia, and tremor. The efficacy of DBS depends on the correct lead positioning. The commonly adopted postoperative radiological evaluation is performed with computed tomography (CT) scan and/or magnetic resonance imaging (MRI). Methods: We conducted a retrospective study on 202 patients who underwent DBS from January 2009 to October 2013. DBS indications were PD, progressive supranuclear palsy, tremor, dystonia, Tourette syndrome, obsessive compulsive disorder, depression, and Huntington's disease. Preoperatively, all patients underwent brain MRI and brain CT scan with the stereotactic frame positioned. The lead location was confirmed intraoperatively with CT. The CT images were subsequently transferred to the Stealth Station Medtronic and merged with the preoperative planning. On the first or second day after, implantation we performed a brain MRI to confirm the correct position of the lead. Results: In 14 patients, leads were in suboptimal position after intraoperative CT scan positioning. The cases with alteration in the Z-axis were corrected immediately under fluoroscopic guidance. In all the 14 patients, an immediate repositioning was done. Conclusions: Based on our data, intraoperative CT scan is fast, safe, and a useful tool in the evaluation of the position of the implanted lead. It also reduces the patient's discomfort derived from the transfer of the patient from the operating room to the radiological department. However, intraoperative CT should not be considered as a substitute for postoperative MRI. PMID:27583182

High-resolution maps of magnetization transfer with inherent correction for RF inhomogeneity and T1 relaxation obtained from 3D FLASH MRI.

PubMed

Helms, Gunther; Dathe, Henning; Kallenberg, Kai; Dechent, Peter

2008-12-01

An empirical equation for the magnetization transfer (MT) FLASH signal is derived by analogy to dual-excitation FLASH, introducing a novel semiquantitative parameter for MT, the percentage saturation imposed by one MT pulse during TR. This parameter is obtained by a linear transformation of the inverse signal, using two reference experiments of proton density and T(1) weighting. The influence of sequence parameters on the MT saturation was studied. An 8.5-min protocol for brain imaging at 3 T was based on nonselective sagittal 3D-FLASH at 1.25 mm isotropic resolution using partial acquisition techniques (TR/TE/alpha = 25ms/4.9ms/5 degrees or 11ms/4.9ms/15 degrees for the T(1) reference). A 12.8 ms Gaussian MT pulse was applied 2.2 kHz off-resonance with 540 degrees flip angle. The MT saturation maps showed an excellent contrast in the brain due to clearly separated distributions for white and gray matter and cerebrospinal fluid. Within the limits of the approximation (excitation <15 degrees , TR/T(1) less sign 1) the MT term depends mainly on TR, the energy and offset of the MT pulse, but hardly on excitation and T(1) relaxation. It is inherently compensated for inhomogeneities of receive and transmit RF fields. The MT saturation appeared to be a sensitive parameter to depict MS lesions and alterations of normal-appearing white matter. (c) 2008 Wiley-Liss, Inc.

Imaging outcome measures for progressive multiple sclerosis trials

PubMed Central

Moccia, Marcello; de Stefano, Nicola; Barkhof, Frederik

2017-01-01

Imaging markers that are reliable, reproducible and sensitive to neurodegenerative changes in progressive multiple sclerosis (MS) can enhance the development of new medications with a neuroprotective mode-of-action. Accordingly, in recent years, a considerable number of imaging biomarkers have been included in phase 2 and 3 clinical trials in primary and secondary progressive MS. Brain lesion count and volume are markers of inflammation and demyelination and are important outcomes even in progressive MS trials. Brain and, more recently, spinal cord atrophy are gaining relevance, considering their strong association with disability accrual; ongoing improvements in analysis methods will enhance their applicability in clinical trials, especially for cord atrophy. Advanced magnetic resonance imaging (MRI) techniques (e.g. magnetization transfer ratio (MTR), diffusion tensor imaging (DTI), spectroscopy) have been included in few trials so far and hold promise for the future, as they can reflect specific pathological changes targeted by neuroprotective treatments. Position emission tomography (PET) and optical coherence tomography have yet to be included. Applications, limitations and future perspectives of these techniques in clinical trials in progressive MS are discussed, with emphasis on measurement sensitivity, reliability and sample size calculation. PMID:29041865

Maintenance of Voluntary Self-regulation Learned through Real-Time fMRI Neurofeedback

PubMed Central

Robineau, Fabien; Meskaldji, Djalel E.; Koush, Yury; Rieger, Sebastian W.; Mermoud, Christophe; Morgenthaler, Stephan; Van De Ville, Dimitri; Vuilleumier, Patrik; Scharnowski, Frank

2017-01-01

Neurofeedback based on real-time functional magnetic resonance imaging (fMRI) is an emerging technique that allows for learning voluntary control over brain activity. Such brain training has been shown to cause specific behavioral or cognitive enhancements, and even therapeutic effects in neurological and psychiatric patient populations. However, for clinical applications it is important to know if learned self-regulation can be maintained over longer periods of time and whether it transfers to situations without neurofeedback. Here, we present preliminary results from five healthy participants who successfully learned to control their visual cortex activity and who we re-scanned 6 and 14 months after the initial neurofeedback training to perform learned self-regulation. We found that participants achieved levels of self-regulation that were similar to those achieved at the end of the successful initial training, and this without further neurofeedback information. Our results demonstrate that learned self-regulation can be maintained over longer periods of time and causes lasting transfer effects. They thus support the notion that neurofeedback is a promising therapeutic approach whose effects can last far beyond the actual training period. PMID:28386224

Whole Brain Magnetic Resonance Spectroscopic Determinants of Functional Outcomes in Pediatric Moderate/Severe Traumatic Brain Injury.

PubMed

Babikian, Talin; Alger, Jeffry R; Ellis-Blied, Monica U; Giza, Christopher C; Dennis, Emily; Olsen, Alexander; Mink, Richard; Babbitt, Christopher; Johnson, Jeff; Thompson, Paul M; Asarnow, Robert F

2018-05-18

Diffuse axonal injury contributes to the long-term functional morbidity observed after pediatric moderate/severe traumatic brain injury (msTBI). Whole-brain proton magnetic resonance echo-planar spectroscopic imaging was used to measure the neurometabolite levels in the brain to delineate the course of disruption/repair during the first year post-msTBI. The association between metabolite biomarkers and functional measures (cognitive functioning and corpus callosum [CC] function assessed by interhemispheric transfer time [IHTT] using an event related potential paradigm) was also explored. Pediatric patients with msTBI underwent assessments at two times (post-acutely at a mean of three months post-injury, n = 31, and chronically at a mean of 16 months post-injury, n = 24). Healthy controls also underwent two evaluations, approximately 12 months apart. Post-acutely, in patients with msTBI, there were elevations in choline (Cho; marker for inflammation and/or altered membrane metabolism) in all four brain lobes and the CC and decreases in N-acetylaspartate (NAA; marker for neuronal and axonal integrity) in the CC compared with controls, all of which normalized by the chronic time point. Subgroups of TBI showed variable patterns chronically. Patients with slow IHTT had lower lobar Cho chronically than those with normal IHTT; they also did not show normalization in CC NAA whereas those with normal IHTT showed significantly higher levels of CC NAA relative to controls. In the normal IHTT group only, chronic CC Cho and NAA together explained 70% of the variance in long-term cognitive functioning. MR based whole brain metabolic evaluations show different patterns of neurochemistry after msTBI in two subgroups with different outcomes. There is a dynamic relationship between prolonged inflammatory responses to brain damage, reparative processes/remyelination, and subsequent neurobehavioral outcomes. Multimodal studies allow us to test hypotheses about degenerative and reparative processes in patient groups that have divergent functional outcome, with the ultimate goal of developing targeted therapeutic agents.

Intensity ratio to improve black hole assessment in multiple sclerosis.

PubMed

Adusumilli, Gautam; Trinkaus, Kathryn; Sun, Peng; Lancia, Samantha; Viox, Jeffrey D; Wen, Jie; Naismith, Robert T; Cross, Anne H

2018-01-01

Improved imaging methods are critical to assess neurodegeneration and remyelination in multiple sclerosis. Chronic hypointensities observed on T1-weighted brain MRI, "persistent black holes," reflect severe focal tissue damage. Present measures consist of determining persistent black holes numbers and volumes, but do not quantitate severity of individual lesions. Develop a method to differentiate black and gray holes and estimate the severity of individual multiple sclerosis lesions using standard magnetic resonance imaging. 38 multiple sclerosis patients contributed images. Intensities of lesions on T1-weighted scans were assessed relative to cerebrospinal fluid intensity using commercial software. Magnetization transfer imaging, diffusion tensor imaging and clinical testing were performed to assess associations with T1w intensity-based measures. Intensity-based assessments of T1w hypointensities were reproducible and achieved > 90% concordance with expert rater determinations of "black" and "gray" holes. Intensity ratio values correlated with magnetization transfer ratios (R = 0.473) and diffusion tensor imaging metrics (R values ranging from 0.283 to -0.531) that have been associated with demyelination and axon loss. Intensity ratio values incorporated into T1w hypointensity volumes correlated with clinical measures of cognition. This method of determining the degree of hypointensity within multiple sclerosis lesions can add information to conventional imaging. Copyright © 2017 Elsevier B.V. All rights reserved.

Applying Amide Proton Transfer MR Imaging to Hybrid Brain PET/MR: Concordance with Gadolinium Enhancement and Added Value to [18F]FDG PET.

PubMed

Sun, Hongzan; Xin, Jun; Zhou, Jinyuan; Lu, Zaiming; Guo, Qiyong

2018-06-01

The purpose of this study is to evaluate the diagnostic concordance and metric correlations of amide proton transfer (APT) imaging with gadolinium-enhanced magnetic resonance imaging (MRI) and 2-deoxy-2-[ 18 F-]fluoro-D-glucose ([ 18 F]FDG) positron emission tomography (PET), using hybrid brain PET/MRI. Twenty-one subjects underwent brain gadolinium-enhanced [ 18 F]FDG PET/MRI prospectively. Imaging accuracy was compared between unenhanced MRI, MRI with enhancement, APT-weighted (APTW) images, and PET based on six diagnostic criteria. Among tumors, the McNemar test was further used for concordance assessment between gadolinium-enhanced imaging, APT imaging, and [ 18 F]FDG PET. As well, the relation of metrics between APT imaging and PET was analyzed by the Pearson correlation analysis. APT imaging and gadolinium-enhanced MRI showed superior and similar diagnostic accuracy. APTW signal intensity and gadolinium enhancement were concordant in 19 tumors (100 %), while high [ 18 F]FDG avidity was shown in only 12 (63.2 %). For the metrics from APT imaging and PET, there was significant correlation for 13 hypermetabolic tumors (P < 0.05) and no correlation for the remaining six [ 18 F]FDG-avid tumors. APT imaging can be used to increase diagnostic accuracy with no need to administer gadolinium chelates. APT imaging may provide an added value to [ 18 F]FDG PET in the evaluation of tumor metabolic activity during brain PET/MR studies.

The Combined Quantification and Interpretation of Multiple Quantitative Magnetic Resonance Imaging Metrics Enlightens Longitudinal Changes Compatible with Brain Repair in Relapsing-Remitting Multiple Sclerosis Patients.

PubMed

Bonnier, Guillaume; Maréchal, Benedicte; Fartaria, Mário João; Falkowskiy, Pavel; Marques, José P; Simioni, Samanta; Schluep, Myriam; Du Pasquier, Renaud; Thiran, Jean-Philippe; Krueger, Gunnar; Granziera, Cristina

2017-01-01

Quantitative and semi-quantitative MRI (qMRI) metrics provide complementary specificity and differential sensitivity to pathological brain changes compatible with brain inflammation, degeneration, and repair. Moreover, advanced magnetic resonance imaging (MRI) metrics with overlapping elements amplify the true tissue-related information and limit measurement noise. In this work, we combined multiple advanced MRI parameters to assess focal and diffuse brain changes over 2 years in a group of early-stage relapsing-remitting MS patients. Thirty relapsing-remitting MS patients with less than 5 years disease duration and nine healthy subjects underwent 3T MRI at baseline and after 2 years including T1, T2, T2* relaxometry, and magnetization transfer imaging. To assess longitudinal changes in normal-appearing (NA) tissue and lesions, we used analyses of variance and Bonferroni correction for multiple comparisons. Multivariate linear regression was used to assess the correlation between clinical outcome and multiparametric MRI changes in lesions and NA tissue. In patients, we measured a significant longitudinal decrease of mean T2 relaxation times in NA white matter ( p  = 0.005) and a decrease of T1 relaxation times in the pallidum ( p  < 0.05), which are compatible with edema reabsorption and/or iron deposition. No longitudinal changes in qMRI metrics were observed in controls. In MS lesions, we measured a decrease in T1 relaxation time ( p -value < 2.2e-16) and a significant increase in MTR ( p -value < 1e-6), suggesting repair mechanisms, such as remyelination, increased axonal density, and/or a gliosis. Last, the evolution of advanced MRI metrics-and not changes in lesions or brain volume-were correlated to motor and cognitive tests scores evolution (Adj- R 2  > 0.4, p  < 0.05). In summary, the combination of multiple advanced MRI provided evidence of changes compatible with focal and diffuse brain repair at early MS stages as suggested by histopathological studies.

A new strategy for in vivo spectral editing. Application to GABA editing using selective homonuclear polarization transfer spectroscopy

NASA Astrophysics Data System (ADS)

Shen, Jun; Yang, Jehoon; Choi, In-Young; Li, Shizhe Steve; Chen, Zhengguang

2004-10-01

A novel single-shot in vivo spectral editing method is proposed in which the signal to be detected, is regenerated anew from the thermal equilibrium magnetization of a source to which it is J-coupled. The thermal equilibrium magnetization of the signal to be detected together with those of overlapping signals are suppressed by single-shot gradient dephasing prior to the signal regeneration process. Application of this new strategy to in vivo GABA editing using selective homonuclear polarization transfer allows complete suppression of overlapping creatine and glutathione while detecting the GABA-4 methylene resonance at 3.02 ppm with an editing yield similar to that of conventional editing methods. The NAA methyl group at 2.02 ppm was simultaneously detected and can be used as an internal navigator echo for correcting the zero order phase and frequency shifts and as an internal reference for concentration. This new method has been demonstrated for robust in vivo GABA editing in the rat brain and for study of GABA synthesis after acute vigabatrin administration.

Matrix-algebra-based calculations of the time evolution of the binary spin-bath model for magnetization transfer.

PubMed

Müller, Dirk K; Pampel, André; Möller, Harald E

2013-05-01

Quantification of magnetization-transfer (MT) experiments are typically based on the assumption of the binary spin-bath model. This model allows for the extraction of up to six parameters (relative pool sizes, relaxation times, and exchange rate constants) for the characterization of macromolecules, which are coupled via exchange processes to the water in tissues. Here, an approach is presented for estimating MT parameters acquired with arbitrary saturation schemes and imaging pulse sequences. It uses matrix algebra to solve the Bloch-McConnell equations without unwarranted simplifications, such as assuming steady-state conditions for pulsed saturation schemes or neglecting imaging pulses. The algorithm achieves sufficient efficiency for voxel-by-voxel MT parameter estimations by using a polynomial interpolation technique. Simulations, as well as experiments in agar gels with continuous-wave and pulsed MT preparation, were performed for validation and for assessing approximations in previous modeling approaches. In vivo experiments in the normal human brain yielded results that were consistent with published data. Copyright © 2013 Elsevier Inc. All rights reserved.

Spontaneous brain activity predicts learning ability of foreign sounds.

PubMed

Ventura-Campos, Noelia; Sanjuán, Ana; González, Julio; Palomar-García, María-Ángeles; Rodríguez-Pujadas, Aina; Sebastián-Gallés, Núria; Deco, Gustavo; Ávila, César

2013-05-29

Can learning capacity of the human brain be predicted from initial spontaneous functional connectivity (FC) between brain areas involved in a task? We combined task-related functional magnetic resonance imaging (fMRI) and resting-state fMRI (rs-fMRI) before and after training with a Hindi dental-retroflex nonnative contrast. Previous fMRI results were replicated, demonstrating that this learning recruited the left insula/frontal operculum and the left superior parietal lobe, among other areas of the brain. Crucially, resting-state FC (rs-FC) between these two areas at pretraining predicted individual differences in learning outcomes after distributed (Experiment 1) and intensive training (Experiment 2). Furthermore, this rs-FC was reduced at posttraining, a change that may also account for learning. Finally, resting-state network analyses showed that the mechanism underlying this reduction of rs-FC was mainly a transfer in intrinsic activity of the left frontal operculum/anterior insula from the left frontoparietal network to the salience network. Thus, rs-FC may contribute to predict learning ability and to understand how learning modifies the functioning of the brain. The discovery of this correspondence between initial spontaneous brain activity in task-related areas and posttraining performance opens new avenues to find predictors of learning capacities in the brain using task-related fMRI and rs-fMRI combined.

Comprehensive cellular‐resolution atlas of the adult human brain

PubMed Central

Royall, Joshua J.; Sunkin, Susan M.; Ng, Lydia; Facer, Benjamin A.C.; Lesnar, Phil; Guillozet‐Bongaarts, Angie; McMurray, Bergen; Szafer, Aaron; Dolbeare, Tim A.; Stevens, Allison; Tirrell, Lee; Benner, Thomas; Caldejon, Shiella; Dalley, Rachel A.; Dee, Nick; Lau, Christopher; Nyhus, Julie; Reding, Melissa; Riley, Zackery L.; Sandman, David; Shen, Elaine; van der Kouwe, Andre; Varjabedian, Ani; Write, Michelle; Zollei, Lilla; Dang, Chinh; Knowles, James A.; Koch, Christof; Phillips, John W.; Sestan, Nenad; Wohnoutka, Paul; Zielke, H. Ronald; Hohmann, John G.; Jones, Allan R.; Bernard, Amy; Hawrylycz, Michael J.; Hof, Patrick R.; Fischl, Bruce

2016-01-01

ABSTRACT Detailed anatomical understanding of the human brain is essential for unraveling its functional architecture, yet current reference atlases have major limitations such as lack of whole‐brain coverage, relatively low image resolution, and sparse structural annotation. We present the first digital human brain atlas to incorporate neuroimaging, high‐resolution histology, and chemoarchitecture across a complete adult female brain, consisting of magnetic resonance imaging (MRI), diffusion‐weighted imaging (DWI), and 1,356 large‐format cellular resolution (1 µm/pixel) Nissl and immunohistochemistry anatomical plates. The atlas is comprehensively annotated for 862 structures, including 117 white matter tracts and several novel cyto‐ and chemoarchitecturally defined structures, and these annotations were transferred onto the matching MRI dataset. Neocortical delineations were done for sulci, gyri, and modified Brodmann areas to link macroscopic anatomical and microscopic cytoarchitectural parcellations. Correlated neuroimaging and histological structural delineation allowed fine feature identification in MRI data and subsequent structural identification in MRI data from other brains. This interactive online digital atlas is integrated with existing Allen Institute for Brain Science gene expression atlases and is publicly accessible as a resource for the neuroscience community. J. Comp. Neurol. 524:3127–3481, 2016. © 2016 The Authors The Journal of Comparative Neurology Published by Wiley Periodicals, Inc. PMID:27418273

Dynamics of paramagnetic agents by off-resonance rotating frame technique in the presence of magnetization transfer effect

NASA Astrophysics Data System (ADS)

Zhang, Huiming; Xie, Yang

2007-02-01

The simple method for measuring the rotational correlation time of paramagnetic ion chelates via off-resonance rotating frame technique is challenged in vivo by the magnetization transfer effect. A theoretical model for the spin relaxation of water protons in the presence of paramagnetic ion chelates and magnetization transfer effect is described. This model considers the competitive relaxations of water protons by the paramagnetic relaxation pathway and the magnetization transfer pathway. The influence of magnetization transfer on the total residual z-magnetization has been quantitatively evaluated in the context of the magnetization map and various difference magnetization profiles for the macromolecule conjugated Gd-DTPA in cross-linked protein gels. The numerical simulations and experimental validations confirm that the rotational correlation time for the paramagnetic ion chelates can be measured even in the presence of strong magnetization transfer. This spin relaxation model also provides novel approaches to enhance the detection sensitivity for paramagnetic labeling by suppressing the spin relaxations caused by the magnetization transfer. The inclusion of the magnetization transfer effect allows us to use the magnetization map as a simulation tool to design efficient paramagnetic labeling targeting at specific tissues, to design experiments running at low RF power depositions, and to optimize the sensitivity for detecting paramagnetic labeling. Thus, the presented method will be a very useful tool for the in vivo applications such as molecular imaging via paramagnetic labeling.

Energy transfers in large-scale and small-scale dynamos

NASA Astrophysics Data System (ADS)

Samtaney, Ravi; Kumar, Rohit; Verma, Mahendra

2015-11-01

We present the energy transfers, mainly energy fluxes and shell-to-shell energy transfers in small-scale dynamo (SSD) and large-scale dynamo (LSD) using numerical simulations of MHD turbulence for Pm = 20 (SSD) and for Pm = 0.2 on 10243 grid. For SSD, we demonstrate that the magnetic energy growth is caused by nonlocal energy transfers from the large-scale or forcing-scale velocity field to small-scale magnetic field. The peak of these energy transfers move towards lower wavenumbers as dynamo evolves, which is the reason for the growth of the magnetic fields at the large scales. The energy transfers U2U (velocity to velocity) and B2B (magnetic to magnetic) are forward and local. For LSD, we show that the magnetic energy growth takes place via energy transfers from large-scale velocity field to large-scale magnetic field. We observe forward U2U and B2B energy flux, similar to SSD.

Transfer of motor learning engages specific neural substrates during motor memory consolidation dependent on the practice structure.

PubMed

Kantak, Shailesh S; Sullivan, Katherine J; Fisher, Beth E; Knowlton, Barbara J; Winstein, Carolee J

2011-01-01

The authors investigated how brain activity during motor-memory consolidation contributes to transfer of learning to novel versions of a motor skill following distinct practice structures. They used 1 Hz repetitive Transcranial Magnetic Stimulation (rTMS) immediately after constant or variable practice of an arm movement skill to interfere with primary motor cortex (M1) or dorsolateral prefrontal cortex (DLPFC). The effect of interference was assessed through skill performance on two transfer targets: one within and one outside the range of practiced movement parameters for the variable practice group. For the control (no rTMS) group, variable practice benefited delayed transfer performance more than constant practice. The rTMS effect on delayed transfer performance differed for the two transfer targets. For the within-range target, rTMS interference had no significant affect on the delayed transfer after either practice structure. However, for the outside-range target, rTMS interference to DLPFC but not M1 attenuated delayed transfer benefit following variable practice. Additionally, for the outside-range target, rTMS interference to M1 but not DLPFC attenuated delayed transfer following constant practice. This suggests that variable practice may promote reliance on DLPFC for memory consolidation associated with outside-range transfer of learning, whereas constant practice may promote reliance on M1 for consolidation and long-term transfer.

Transfer learning improves supervised image segmentation across imaging protocols.

PubMed

van Opbroek, Annegreet; Ikram, M Arfan; Vernooij, Meike W; de Bruijne, Marleen

2015-05-01

The variation between images obtained with different scanners or different imaging protocols presents a major challenge in automatic segmentation of biomedical images. This variation especially hampers the application of otherwise successful supervised-learning techniques which, in order to perform well, often require a large amount of labeled training data that is exactly representative of the target data. We therefore propose to use transfer learning for image segmentation. Transfer-learning techniques can cope with differences in distributions between training and target data, and therefore may improve performance over supervised learning for segmentation across scanners and scan protocols. We present four transfer classifiers that can train a classification scheme with only a small amount of representative training data, in addition to a larger amount of other training data with slightly different characteristics. The performance of the four transfer classifiers was compared to that of standard supervised classification on two magnetic resonance imaging brain-segmentation tasks with multi-site data: white matter, gray matter, and cerebrospinal fluid segmentation; and white-matter-/MS-lesion segmentation. The experiments showed that when there is only a small amount of representative training data available, transfer learning can greatly outperform common supervised-learning approaches, minimizing classification errors by up to 60%.

Deep-brain magnetic stimulation promotes adult hippocampal neurogenesis and alleviates stress-related behaviors in mouse models for neuropsychiatric disorders

PubMed Central

2014-01-01

Background Repetitive Transcranial Magnetic Stimulation (rTMS)/ Deep-brain Magnetic Stimulation (DMS) is an effective therapy for various neuropsychiatric disorders including major depression disorder. The molecular and cellular mechanisms underlying the impacts of rTMS/DMS on the brain are not yet fully understood. Results Here we studied the effects of deep-brain magnetic stimulation to brain on the molecular and cellular level. We examined the adult hippocampal neurogenesis and hippocampal synaptic plasticity of rodent under stress conditions with deep-brain magnetic stimulation treatment. We found that DMS promotes adult hippocampal neurogenesis significantly and facilitates the development of adult new-born neurons. Remarkably, DMS exerts anti-depression effects in the learned helplessness mouse model and rescues hippocampal long-term plasticity impaired by restraint stress in rats. Moreover, DMS alleviates the stress response in a mouse model for Rett syndrome and prolongs the life span of these animals dramatically. Conclusions Deep-brain magnetic stimulation greatly facilitates adult hippocampal neurogenesis and maturation, also alleviates depression and stress-related responses in animal models. PMID:24512669

Neurofeedback with fMRI: A critical systematic review.

PubMed

Thibault, Robert T; MacPherson, Amanda; Lifshitz, Michael; Roth, Raquel R; Raz, Amir

2018-05-15

Neurofeedback relying on functional magnetic resonance imaging (fMRI-nf) heralds new prospects for self-regulating brain and behavior. Here we provide the first comprehensive review of the fMRI-nf literature and the first systematic database of fMRI-nf findings. We synthesize information from 99 fMRI-nf experiments-the bulk of currently available data. The vast majority of fMRI-nf findings suggest that self-regulation of specific brain signatures seems viable; however, replication of concomitant behavioral outcomes remains sparse. To disentangle placebo influences and establish the specific effects of neurofeedback, we highlight the need for double-blind placebo-controlled studies alongside rigorous and standardized statistical analyses. Before fMRI-nf can join the clinical armamentarium, research must first confirm the sustainability, transferability, and feasibility of fMRI-nf in patients as well as in healthy individuals. Whereas modulating specific brain activity promises to mold cognition, emotion, thought, and action, reducing complex mental health issues to circumscribed brain regions may represent a tenuous goal. We can certainly change brain activity with fMRI-nf. However, it remains unclear whether such changes translate into meaningful behavioral improvements in the clinical domain. Copyright © 2017 Elsevier Inc. All rights reserved.

In vivo correlation between axon diameter and conduction velocity in the human brain.

PubMed

Horowitz, Assaf; Barazany, Daniel; Tavor, Ido; Bernstein, Moran; Yovel, Galit; Assaf, Yaniv

2015-01-01

The understanding of the relationship between structure and function has always characterized biology in general and neurobiology in particular. One such fundamental relationship is that between axon diameter and the axon's conduction velocity (ACV). Measurement of these neuronal properties, however, requires invasive procedures that preclude direct elucidation of this relationship in vivo. Here we demonstrate that diffusion-based MRI is sensitive to the fine microstructural elements of brain wiring and can be used to quantify axon diameter in vivo. Moreover, we demonstrate the in vivo correlation between the diameter of an axon and its conduction velocity in the human brain. Using AxCaliber, a novel magnetic resonance imaging technique that enables us to estimate in vivo axon diameter distribution (ADD) and by measuring the interhemispheric transfer time (IHTT) by electroencephalography, we found significant linear correlation, across a cohort of subjects, between brain microstructure morphology (ADD) and its physiology (ACV) in the tactile and visual sensory domains. The ability to make a quantitative assessment of a fundamental physiological property in the human brain from in vivo measurements of ADD may shed new light on neurological processes occurring in neuroplasticity as well as in neurological disorders and neurodegenerative diseases.

Minocycline Effects on Intracerebral Hemorrhage-Induced Iron Overload in Aged Rats: Brain Iron Quantification With Magnetic Resonance Imaging.

PubMed

Cao, Shenglong; Hua, Ya; Keep, Richard F; Chaudhary, Neeraj; Xi, Guohua

2018-04-01

Brain iron overload is a key factor causing brain injury after intracerebral hemorrhage (ICH). This study quantified brain iron levels after ICH with magnetic resonance imaging R2* mapping. The effect of minocycline on iron overload and ICH-induced brain injury in aged rats was also determined. Aged (18 months old) male Fischer 344 rats had an intracerebral injection of autologous blood or saline, and brain iron levels were measured by magnetic resonance imaging R2* mapping. Some ICH rats were treated with minocycline or vehicle. The rats were euthanized at days 7 and 28 after ICH, and brains were used for immunohistochemistry and Western blot analyses. Magnetic resonance imaging (T2-weighted, T2* gradient-echo, and R2* mapping) sequences were performed at different time points. ICH-induced brain iron overload in the perihematomal area could be quantified by R2* mapping. Minocycline treatment reduced brain iron accumulation, T2* lesion volume, iron-handling protein upregulation, neuronal cell death, and neurological deficits ( P <0.05). Magnetic resonance imaging R2* mapping is a reliable and noninvasive method, which can quantitatively measure brain iron levels after ICH. Minocycline reduced ICH-related perihematomal iron accumulation and brain injury in aged rats. © 2018 American Heart Association, Inc.

Magnetic Enhancement of Stem Cell-Targeted Delivery into the Brain Following MR-Guided Focused Ultrasound for Opening the Blood-Brain Barrier.

PubMed

Shen, Wei-Bin; Anastasiadis, Pavlos; Nguyen, Ben; Yarnell, Deborah; Yarowsky, Paul J; Frenkel, Victor; Fishman, Paul S

2017-07-01

Focused ultrasound (FUS)-mediated blood-brain barrier disruption (BBBD) can enable even large therapeutics such as stem cells to enter the brain from the bloodstream. However, the efficiency is relatively low. Our previous study showed that human neural progenitor cells (hNPCs) loaded with superparamagnetic iron oxide nanoparticles (SPIONs) in culture were attracted by an external magnetic field. In vivo, enhanced brain retention was observed near a magnet mounted on the skull in a rat model of traumatic brain injury, where BBBD also occurs. The goal of the current study was to determine whether magnetic attraction of SPION-loaded hNPCs would also enhance their retention in the brain after FUS-mediated BBBD. A small animal magnetic resonance imaging (MRI)-guided FUS system operating at 1.5 MHz was used to treat rats (∼120 g) without tissue damage or hemorrhage. Evidence of successful BBBD was validated with both radiologic enhancement of gadolinium on postsonication TI MRI and whole brain section visualization of Evans blue dye. The procedure was then combined with the application of a powerful magnet to the head directly after intravenous injection of the hNPCs. Validation of cells within the brain was performed by staining with Perls' Prussian blue for iron and by immunohistochemistry with a human-specific antigen. By injecting equal numbers of iron oxide (SPIONs) and noniron oxide nanoparticles-loaded hNPCs, each labeled with a different fluorophore, we found significantly greater numbers of SPIONs-loaded cells retained in the brain at the site of BBBD as compared to noniron loaded cells. This result was most pronounced in regions of the brain closest to the skull (dorsal cortex) in proximity to the magnet surface. A more powerful magnet and a Halbach magnetic array resulted in more effective retention of SPION-labeled cells in even deeper brain regions such as the striatum and ventral cortex. There, up to 90% of hNPCs observed contained SPIONs compared to 60% to 70% with the less powerful magnet. Fewer cells were observed at 24 h posttreatment compared to 2 h (primarily in the dorsal cortex). These results demonstrate that magnetic attraction can substantially enhance the retention of stem cells after FUS-mediated BBBD. This procedure could provide a safer and less invasive approach for delivering stem cells to the brain, compared to direct intracranial injections, substantially reducing the risk of bleeding and infection.

Study of intracranial pressure in human brain during transcranial magnetic stimulation.

PubMed

Honrath, Marc; Sabouni, Abas

2015-01-01

This paper presents the results of cranial force in human brain due to electromagnetic pulse during transcranial magnetic stimulation. To model the force in a realistic brain, we used three dimensional magnetic resonance image of the 26 years old female subject. Simulation results show that during TMS procedure, there is a small force generated within the cranial tissue layers along with a torque value in different layers of brain tissues. The force depends on the magnitude of the magnetic field generated by the TMS coil.

Whole-Brain In-vivo Measurements of the Axonal G-Ratio in a Group of 37 Healthy Volunteers

PubMed Central

Mohammadi, Siawoosh; Carey, Daniel; Dick, Fred; Diedrichsen, Joern; Sereno, Martin I.; Reisert, Marco; Callaghan, Martina F.; Weiskopf, Nikolaus

2015-01-01

The g-ratio, quantifying the ratio between the inner and outer diameters of a fiber, is an important microstructural characteristic of fiber pathways and is functionally related to conduction velocity. We introduce a novel method for estimating the MR g-ratio non-invasively across the whole brain using high-fidelity magnetization transfer (MT) imaging and single-shell diffusion MRI. These methods enabled us to map the MR g-ratio in vivo across the brain's prominent fiber pathways in a group of 37 healthy volunteers and to estimate the inter-subject variability. Effective correction of susceptibility-related distortion artifacts was essential before combining the MT and diffusion data, in order to reduce partial volume and edge artifacts. The MR g-ratio is in good qualitative agreement with histological findings despite the different resolution and spatial coverage of MRI and histology. The MR g-ratio holds promise as an important non-invasive biomarker due to its microstructural and functional relevance in neurodegeneration. PMID:26640427

Rapid reduction of acute subdural hematoma and redistribution of hematoma: case report.

PubMed

Watanabe, Arata; Omata, Tomohiro; Kinouchi, Hiroyuki

2010-01-01

An 88-year-old woman presented with acute subdural hematoma (ASDH) which showed rapid resolution on computed tomography (CT) and magnetic resonance (MR) imaging. She was transferred to our hospital after falling out of bed. On admission, she was comatose with Japan Coma Scale score of 200 and Glasgow Coma Scale score of E1V1M2. Brain CT showed a thick left frontotemporal ASDH. Conservative treatment consisted of 200 ml of glycerol administered intravenously twice a day, and maintenance in the approximately 20 degree head-up position to reduce intracranial pressure. Three days later, her consciousness recovered to Japan Coma Scale score of 30 and Glasgow Coma Scale score of E2V4M5. CT showed obvious reduction of the hematoma without brain or scalp swelling. Spinal MR imaging detected no redistribution of hematoma to the spine. The present case illustrates that rapid spontaneous reduction of ASDH may occur by redistribution of hematoma, mainly to the supratentorial subdural space because of brain atrophy.

Glioma Selectivity of Magnetically Targeted Nanoparticles: A Role of Abnormal Tumor Hydrodynamics

PubMed Central

Chertok, Beata; David, Allan E.; Huang, Yongzhuo; Yang, Victor C.

2007-01-01

Magnetic targeting is a promising strategy for achieving localized drug delivery. Application of this strategy to treat brain tumors, however, is complicated by their deep intracranial location, since magnetic field density cannot be focused at a distance from an externally applied magnet. This study intended to examine whether, with magnetic targeting, pathological alteration in brain tumor flow dynamics could be of value in discriminating the diseased site from healthy brain. To address this question, the capture of magnetic nanoparticles was first assessed in vitro using a simple flow system under theoretically estimated glioma and normal brain flow conditions. Secondly, accumulation of nanoparticles via magnetic targeting was evaluated in vivo using 9L-glioma bearing rats. In vitro results that predicted a 7.6-fold increase in nanoparticle capture at glioma-versus contralateral brain-relevant flow rates were relatively consistent with the 9.6-fold glioma selectivity of nanoparticle accumulation over the contralateral brain observed in vivo. Based on these finding, the in vitro ratio of nanoparticle capture can be viewed as a plausible indicator of in vivo glioma selectivity. Overall, it can be concluded that the decreased blood flow rate in glioma, reflecting tumor vascular abnormalities, is an important contributor to glioma-selective nanoparticle accumulation with magnetic targeting. PMID:17628157

Glioma selectivity of magnetically targeted nanoparticles: a role of abnormal tumor hydrodynamics.

PubMed

Chertok, Beata; David, Allan E; Huang, Yongzhuo; Yang, Victor C

2007-10-08

Magnetic targeting is a promising strategy for achieving localized drug delivery. Application of this strategy to treat brain tumors, however, is complicated by their deep intracranial location, since magnetic field density cannot be focused at a distance from an externally applied magnet. This study intended to examine whether, with magnetic targeting, pathological alteration in brain tumor flow dynamics could be of value in discriminating the diseased site from healthy brain. To address this question, the capture of magnetic nanoparticles was first assessed in vitro using a simple flow system under theoretically estimated glioma and normal brain flow conditions. Secondly, accumulation of nanoparticles via magnetic targeting was evaluated in vivo using 9L-glioma bearing rats. In vitro results that predicted a 7.6-fold increase in nanoparticle capture at glioma- versus contralateral brain-relevant flow rates were relatively consistent with the 9.6-fold glioma selectivity of nanoparticle accumulation over the contralateral brain observed in vivo. Based on these finding, the in vitro ratio of nanoparticle capture can be viewed as a plausible indicator of in vivo glioma selectivity. Overall, it can be concluded that the decreased blood flow rate in glioma, reflecting tumor vascular abnormalities, is an important contributor to glioma-selective nanoparticle accumulation with magnetic targeting.

Amide proton transfer imaging of brain tumors using a self-corrected 3D fast spin-echo dixon method: Comparison With separate B0 correction.

PubMed

Togao, Osamu; Keupp, Jochen; Hiwatashi, Akio; Yamashita, Koji; Kikuchi, Kazufumi; Yoneyama, Masami; Honda, Hiroshi

2017-06-01

To assess the quantitative performance of three-dimensional (3D) fast spin-echo (FSE) Dixon amide proton transfer (APT) imaging of brain tumors compared with B 0 correction with separate mapping methods. Twenty-two patients with brain tumors (54.2 ± 18.7 years old, 12 males and 10 females) were scanned at 3 Tesla (T). Z-spectra were obtained at seven different frequency offsets at ±3.1 ppm, ± 3.5 ppm, ± 3.9 ppm, and -1560 ppm. The scan was repeated three times at +3.5 ppm with echo shifts for Dixon B 0 mapping. The APT image corrected by a three-point Dixon-type B 0 map from the same scan (3D-Dixon) or a separate B 0 map (2D-separate and 3D-separate), and an uncorrected APT image (3D-uncorrected) were generated. We compared the APT-weighted signals within a tumor obtained with each 3D method with those obtained with 2D-separate as a reference standard. Excellent agreements and correlations with the 2D-separate were obtained by the 3D-Dixon method for both mean (ICC = 0.964, r = 0.93, P < 0.0001) and 90th-percentile (ICC = 0.972, r = 0.95, P < 0.0001) APT-weighted signals. These agreements and correlations for 3D-Dixon were better than those obtained by the 3D-uncorrected and 3D-separate methods. The 3D FSE Dixon APT method with intrinsic B 0 correction offers a quantitative performance that is similar to that of established two-dimensional (2D) methods. Magn Reson Med 77:2272-2279, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

Increased tissue damage and lesion volumes in African Americans with multiple sclerosis.

PubMed

Weinstock-Guttman, B; Ramanathan, M; Hashmi, K; Abdelrahman, N; Hojnacki, D; Dwyer, M G; Hussein, S; Bergsland, N; Munschauer, F E; Zivadinov, R

2010-02-16

African American (AA) patients with multiple sclerosis (MS) have more rapid disease progression and poorer responses to disease-modifying therapies than white American (WA) patients with MS. To investigate brain MRI characteristics in AA compared to WA in a cohort of consecutive patients with MS. We studied 567 patients with MS (age: 45.1 +/- SD 9.8 years, disease duration: 13.4 +/- 8.6 years), comprised of 488 WA and 79 AA. All patients obtained clinical and quantitative MRI evaluation. The majority of patients, 96% of AA and 94% of WA, were on disease-modifying therapies. The MRI measures included T1-, T2-, and gadolinium contrast-enhancing (CE) lesion volumes (LV) and CE number, global and tissue-specific brain atrophy, and magnetization transfer ratio (MTR) in lesions and normal-appearing gray matter (NAGM) and white matter (NAWM). The associations between race and clinical and MRI measurements were assessed in regression analysis. The MTR values in lesions and in NAGM and NAWM were significantly lower in AA compared to WA. The AA group had 31% greater T2-LV and 101% greater T1-LV compared to WA. The MS Severity Score for AA (mean +/- SD = 4.3 +/- 2.9) was greater than for WA (3.8 +/- 2.5), despite a shorter disease duration in AA, indicating more aggressive clinical disease. African American patients showed increased tissue damage, as measured by magnetization transfer ratio, and presented higher lesion volumes compared to white Americans. The greater tissue damage and faster lesion volume accumulation may explain the rapid clinical progression in African American patients.

Nonhelical inverse transfer of a decaying turbulent magnetic field.

PubMed

Brandenburg, Axel; Kahniashvili, Tina; Tevzadze, Alexander G

2015-02-20

In the presence of magnetic helicity, inverse transfer from small to large scales is well known in magnetohydrodynamic (MHD) turbulence and has applications in astrophysics, cosmology, and fusion plasmas. Using high resolution direct numerical simulations of magnetically dominated self-similarly decaying MHD turbulence, we report a similar inverse transfer even in the absence of magnetic helicity. We compute for the first time spectral energy transfer rates to show that this inverse transfer is about half as strong as with helicity, but in both cases the magnetic gain at large scales results from velocity at similar scales interacting with smaller-scale magnetic fields. This suggests that both inverse transfers are a consequence of universal mechanisms for magnetically dominated turbulence. Possible explanations include inverse cascading of the mean squared vector potential associated with local near two dimensionality and the shallower k^{2} subinertial range spectrum of kinetic energy forcing the magnetic field with a k^{4} subinertial range to attain larger-scale coherence. The inertial range shows a clear k^{-2} spectrum and is the first example of fully isotropic magnetically dominated MHD turbulence exhibiting weak turbulence scaling.

Evaluation method for in situ electric field in standardized human brain for different transcranial magnetic stimulation coils

NASA Astrophysics Data System (ADS)

Iwahashi, Masahiro; Gomez-Tames, Jose; Laakso, Ilkka; Hirata, Akimasa

2017-03-01

This study proposes a method to evaluate the electric field induced in the brain by transcranial magnetic stimulation (TMS) to realize focal stimulation in the target area considering the inter-subject difference of the brain anatomy. The TMS is a non-invasive technique used for treatment/diagnosis, and it works by inducing an electric field in a specific area of the brain via a coil-induced magnetic field. Recent studies that report on the electric field distribution in the brain induced by TMS coils have been limited to simplified human brain models or a small number of detailed human brain models. Until now, no method has been developed that appropriately evaluates the coil performance for a group of subjects. In this study, we first compare the magnetic field and the magnetic vector potential distributions to determine if they can be used as predictors of the TMS focality derived from the electric field distribution. Next, the hotspots of the electric field on the brain surface of ten subjects using six coils are compared. Further, decisive physical factors affecting the focality of the induced electric field by different coils are discussed by registering the computed electric field in a standard brain space for the first time, so as to evaluate coil characteristics for a large population of subjects. The computational results suggest that the induced electric field in the target area cannot be generalized without considering the morphological variability of the human brain. Moreover, there was no remarkable difference between the various coils, although focality could be improved to a certain extent by modifying the coil design (e.g., coil radius). Finally, the focality estimated by the electric field was more correlated with the magnetic vector potential than the magnetic field in a homogeneous sphere.

Evaluation method for in situ electric field in standardized human brain for different transcranial magnetic stimulation coils.

PubMed

Iwahashi, Masahiro; Gomez-Tames, Jose; Laakso, Ilkka; Hirata, Akimasa

2017-03-21

This study proposes a method to evaluate the electric field induced in the brain by transcranial magnetic stimulation (TMS) to realize focal stimulation in the target area considering the inter-subject difference of the brain anatomy. The TMS is a non-invasive technique used for treatment/diagnosis, and it works by inducing an electric field in a specific area of the brain via a coil-induced magnetic field. Recent studies that report on the electric field distribution in the brain induced by TMS coils have been limited to simplified human brain models or a small number of detailed human brain models. Until now, no method has been developed that appropriately evaluates the coil performance for a group of subjects. In this study, we first compare the magnetic field and the magnetic vector potential distributions to determine if they can be used as predictors of the TMS focality derived from the electric field distribution. Next, the hotspots of the electric field on the brain surface of ten subjects using six coils are compared. Further, decisive physical factors affecting the focality of the induced electric field by different coils are discussed by registering the computed electric field in a standard brain space for the first time, so as to evaluate coil characteristics for a large population of subjects. The computational results suggest that the induced electric field in the target area cannot be generalized without considering the morphological variability of the human brain. Moreover, there was no remarkable difference between the various coils, although focality could be improved to a certain extent by modifying the coil design (e.g., coil radius). Finally, the focality estimated by the electric field was more correlated with the magnetic vector potential than the magnetic field in a homogeneous sphere.

Dissociations between behavioural and functional magnetic resonance imaging-based evaluations of cognitive function after brain injury

PubMed Central

Bardin, Jonathan C.; Fins, Joseph J.; Katz, Douglas I.; Hersh, Jennifer; Heier, Linda A.; Tabelow, Karsten; Dyke, Jonathan P.; Ballon, Douglas J.; Schiff, Nicholas D.

2011-01-01

Functional neuroimaging methods hold promise for the identification of cognitive function and communication capacity in some severely brain-injured patients who may not retain sufficient motor function to demonstrate their abilities. We studied seven severely brain-injured patients and a control group of 14 subjects using a novel hierarchical functional magnetic resonance imaging assessment utilizing mental imagery responses. Whereas the control group showed consistent and accurate (for communication) blood-oxygen-level-dependent responses without exception, the brain-injured subjects showed a wide variation in the correlation of blood-oxygen-level-dependent responses and overt behavioural responses. Specifically, the brain-injured subjects dissociated bedside and functional magnetic resonance imaging-based command following and communication capabilities. These observations reveal significant challenges in developing validated functional magnetic resonance imaging-based methods for clinical use and raise interesting questions about underlying brain function assayed using these methods in brain-injured subjects. PMID:21354974

Real‐time fMRI neurofeedback in adolescents with attention deficit hyperactivity disorder

PubMed Central

Alegria, Analucia A.; Wulff, Melanie; Brinson, Helen; Barker, Gareth J.; Norman, Luke J.; Brandeis, Daniel; Stahl, Daniel; David, Anthony S.; Taylor, Eric; Giampietro, Vincent

2017-01-01

Abstract Attention Deficit Hyperactivity Disorder (ADHD) is associated with poor self‐control, underpinned by inferior fronto‐striatal deficits. Real‐time functional magnetic resonance neurofeedback (rtfMRI‐NF) allows participants to gain self‐control over dysregulated brain regions. Despite evidence for beneficial effects of electrophysiological‐NF on ADHD symptoms, no study has applied the spatially superior rtfMRI‐NF neurotherapy to ADHD. A randomized controlled trial tested the efficacy of rtfMRI‐NF of right inferior prefrontal cortex (rIFG), a key region that is compromised in ADHD and upregulated with psychostimulants, on improvement of ADHD symptoms, cognition, and inhibitory fMRI activation. To control for region‐specificity, an active control group received rtfMRI‐NF of the left parahippocampal gyrus (lPHG). Thirty‐one ADHD boys were randomly allocated and had to learn to upregulate their target brain region in an average of 11 rtfMRI‐NF runs over 2 weeks. Feedback was provided through a video‐clip of a rocket that had to be moved up into space. A transfer session without feedback tested learning retention as a proximal measure of transfer to everyday life. Both NF groups showed significant linear activation increases with increasing number of runs in their respective target regions and significant reduction in ADHD symptoms after neurotherapy and at 11‐month follow‐up. Only the group targeting rIFG, however, showed a transfer effect, which correlated with ADHD symptom reductions, improved at trend level in sustained attention, and showed increased IFG activation during an inhibitory fMRI task. This proof‐of‐concept study demonstrates for the first time feasibility, safety, and shorter‐ and longer‐term efficacy of rtfMRI‐NF of rIFG in adolescents with ADHD. Hum Brain Mapp 38:3190–3209, 2017. © 2017 The Authors Human Brain Mapping Published by Wiley Periodicals, Inc. PMID:28342214

Night-Migratory Songbirds Possess a Magnetic Compass in Both Eyes

PubMed Central

Lefeldt, Nele; Prior, Helmut; Mouritsen, Henrik

2012-01-01

Previous studies on European robins, Erithacus rubecula, and Australian silvereyes, Zosterops lateralis, had suggested that magnetic compass information is being processed only in the right eye and left brain hemisphere of migratory birds. However, recently it was demonstrated that both garden warblers, Sylvia borin, and European robins have a magnetic compass in both eyes. These results raise the question if the strong lateralization effect observed in earlier experiments might have arisen from artifacts or from differences in experimental conditions rather than reflecting a true all-or-none lateralization of the magnetic compass in European robins. Here we show that (1) European robins having only their left eye open can orient in their seasonally appropriate direction both during autumn and spring, i.e. there are no strong lateralization differences between the outward journey and the way home, that (2) their directional choices are based on the standard inclination compass as they are turned 180° when the inclination is reversed, and that (3) the capability to use the magnetic compass does not depend on monocular learning or intraocular transfer as it is already present in the first tests of the birds with only one eye open. PMID:22984416

Development and Technology Transfer of the Syncro Blue Tube (Gabriel) Magnetically Guided Feeding Tube

DTIC Science & Technology

2017-06-01

other documentation. TITLE: Development and Technology Transfer of the Syncro Blue Tube (Gabriel) Magnetically Guided Feeding Tube REPORT DOCUMENTATION...TITLE AND SUBTITLE Development and Technology Transfer of the Syncro Blue Tube (Gabriel) Magnetically Guided Feeding Tube 5a. CONTRACT NUMBER W81XWH-09-2...Technical Abstract: Further Development and Technology Transfer of the Syncro BLUETUBE™ (Gabriel) Magnetically Guided Feeding Tube. New Primary

Transferring cognitive tasks between brain imaging modalities: implications for task design and results interpretation in FMRI studies.

PubMed

Warbrick, Tracy; Reske, Martina; Shah, N Jon

2014-09-22

As cognitive neuroscience methods develop, established experimental tasks are used with emerging brain imaging modalities. Here transferring a paradigm (the visual oddball task) with a long history of behavioral and electroencephalography (EEG) experiments to a functional magnetic resonance imaging (fMRI) experiment is considered. The aims of this paper are to briefly describe fMRI and when its use is appropriate in cognitive neuroscience; illustrate how task design can influence the results of an fMRI experiment, particularly when that task is borrowed from another imaging modality; explain the practical aspects of performing an fMRI experiment. It is demonstrated that manipulating the task demands in the visual oddball task results in different patterns of blood oxygen level dependent (BOLD) activation. The nature of the fMRI BOLD measure means that many brain regions are found to be active in a particular task. Determining the functions of these areas of activation is very much dependent on task design and analysis. The complex nature of many fMRI tasks means that the details of the task and its requirements need careful consideration when interpreting data. The data show that this is particularly important in those tasks relying on a motor response as well as cognitive elements and that covert and overt responses should be considered where possible. Furthermore, the data show that transferring an EEG paradigm to an fMRI experiment needs careful consideration and it cannot be assumed that the same paradigm will work equally well across imaging modalities. It is therefore recommended that the design of an fMRI study is pilot tested behaviorally to establish the effects of interest and then pilot tested in the fMRI environment to ensure appropriate design, implementation and analysis for the effects of interest.

Quantitative description of proton exchange processes between water and endogenous and exogenous agents for WEX, CEST, and APT experiments.

PubMed

Zhou, Jinyuan; Wilson, David A; Sun, Phillip Zhe; Klaus, Judith A; Van Zijl, Peter C M

2004-05-01

The proton exchange processes between water and solutes containing exchangeable protons have recently become of interest for monitoring pH effects, detecting cellular mobile proteins and peptides, and enhancing the detection sensitivity of various low-concentration endogenous and exogenous species. In this work, the analytic expressions for water exchange (WEX) filter spectroscopy, chemical exchange-dependent saturation transfer (CEST), and amide proton transfer (APT) experiments are derived by the use of Bloch equations with exchange terms. The effects of the initial states for the system, the difference between a steady state and a saturation state, and the relative contributions of the forward and backward exchange processes are discussed. The theory, in combination with numerical calculations, provides a useful tool for designing experimental schemes and assessing magnetization transfer (MT) processes between water protons and solvent-exchangeable protons. As an example, the case of endogenous amide proton exchange in the rat brain at 4.7 T is analyzed in detail. Copyright 2004 Wiley-Liss, Inc.

Bilateral transfer phenomenon: A functional magnetic resonance imaging pilot study of healthy subjects.

PubMed

Uggetti, Carla; Ausenda, Carlo D; Squarza, Silvia; Cadioli, Marcello; Grimoldi, Ludovico; Cerri, Cesare; Cariati, Maurizio

2016-08-01

The bilateral transfer of a motor skill is a physiological phenomenon: the development of a motor skill with one hand can trigger the development of the same ability of the other hand. The purpose of this study was to verify whether bilateral transfer is associated with a specific brain activation pattern using functional magnetic resonance imaging (fMRI). The motor task was implemented as the execution of the Nine Hole Peg Test. Fifteen healthy subjects (10 right-handers and five left-handers) underwent two identical fMRI runs performing the motor task with the non-dominant hand. Between the first and the second run, each subject was intensively trained for five minutes to perform the same motor task with the dominant hand. Comparing the two functional scans across the pool of subjects, a change of the motor activation pattern was observed. In particular, we observed, in the second run, a change in the activation pattern both in the cerebellum and in the cerebral cortex. We found activations in cortical areas involved in somatosensory integration, areas involved in procedural memory. Our study shows, in a small group of healthy subjects, the modification of the fMRI activation pathway of a motor task performed by the non-dominant hand after intensive exercise performing the same task with the dominant hand. © The Author(s) 2016.

A 3D MRI-based atlas of a lizard brain.

PubMed

Hoops, Daniel; Desfilis, Ester; Ullmann, Jeremy F P; Janke, Andrew L; Stait-Gardner, Timothy; Devenyi, Gabriel A; Price, William S; Medina, Loreta; Whiting, Martin J; Keogh, J Scott

2018-06-22

Magnetic resonance imaging (MRI) is an established technique for neuroanatomical analysis, being particularly useful in the medical sciences. However, the application of MRI to evolutionary neuroscience is still in its infancy. Few magnetic resonance brain atlases exist outside the standard model organisms in neuroscience and no magnetic resonance atlas has been produced for any reptile brain. A detailed understanding of reptilian brain anatomy is necessary to elucidate the evolutionary origin of enigmatic brain structures such as the cerebral cortex. Here, we present a magnetic resonance atlas for the brain of a representative squamate reptile, the Australian tawny dragon (Agamidae: Ctenophorus decresii), which has been the object of numerous ecological and behavioral studies. We used a high-field 11.74T magnet, a paramagnetic contrasting-enhancing agent and minimum-deformation modeling of the brains of thirteen adult male individuals. From this, we created a high-resolution three-dimensional model of a lizard brain . The 3D-MRI model can be freely downloaded and allows a better comprehension of brain areas, nuclei, and fiber tracts, facilitating comparison with other species and setting the basis for future comparative evolution imaging studies. The MRI model of a tawny dragon brain (Ctenophorus decresii) can be viewed online and downloaded using the Wiley Biolucida Server at wiley.biolucida.net. This article is protected by copyright. All rights reserved. © 2018 Wiley Periodicals, Inc.

Abnormal Magnetic Field Effects on Electrogenerated Chemiluminescence

NASA Astrophysics Data System (ADS)

Pan, Haiping; Shen, Yan; Wang, Hongfeng; He, Lei; Hu, Bin

2015-03-01

We report abnormal magnetic field effects on electrogenerated chemiluminescence (MFEECL) based on triplet emission from the Ru(bpy)3Cl2-TPrA electrochemical system: the appearance of MFEECL after magnetic field ceases. In early studies the normal MFEECL have been observed from electrochemical systems during the application of magnetic field. Here, the abnormal MFEECL suggest that the activated charge-transfer [Ru(bpy)33+ … TPrA•] complexes may become magnetized in magnetic field and experience a long magnetic relaxation after removing magnetic field. Our analysis indicates that the magnetic relaxation can gradually increase the density of charge-transfer complexes within reaction region due to decayed magnetic interactions, leading to a positive component in the abnormal MFEECL. On the other hand, the magnetic relaxation facilitates an inverse conversion from triplets to singlets within charge-transfer complexes. The inverse triplet --> singlet conversion reduces the density of triplet light-emitting states through charge-transfer complexes and gives rise to a negative component in the abnormal MFEECL. The combination of positive and negative components can essentially lead to a non-monotonic profile in the abnormal MFEECL after ceasing magnetic field. Nevertheless, our experimental studies may reveal un-usual magnetic behaviors with long magnetic relaxation from the activated charge-transfer [Ru(bpy)33+ … TPrA•] complexes in solution at room temperature.

Modulation of spin transfer torque amplitude in double barrier magnetic tunnel junctions

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

Clément, P.-Y.; Baraduc, C., E-mail: claire.baraduc@cea.fr; Chshiev, M.

2015-09-07

Magnetization switching induced by spin transfer torque is used to write magnetic memories (Magnetic Random Access Memory, MRAM) but can be detrimental to the reading process. It would be quite convenient therefore to modulate the efficiency of spin transfer torque. A solution is adding an extra degree of freedom by using double barrier magnetic tunnel junctions with two spin-polarizers, with controllable relative magnetic alignment. We demonstrate, for these structures, that the amplitude of in-plane spin transfer torque on the middle free layer can be efficiently tuned via the magnetic configuration of the electrodes. Using the proposed design could thus pavemore » the way towards more reliable read/write schemes for MRAM. Moreover, our results suggest an intriguing effect associated with the out-of-plane (field-like) spin transfer torque, which has to be further investigated.« less

Analysis of SAR distribution in human head of antenna used in wireless power transform based on magnetic resonance.

PubMed

Gong, Feixiang; Wei, Zhiqiang; Cong, Yanping; Chi, Haokun; Yin, Bo; Sun, Mingui

2017-07-20

In this paper, a novel wireless power transfer antenna system was designed for human head implantable devices. The antenna system used the structure of three plates and four coils and operated at low frequencies to transfer power via near field. In order to verify the electromagnetic radiation safety on the human head, the electromagnetic intensity and specific absorption rate (SAR) were studied by finite-difference-time-domain (FDTD) method. A three-layer model of human head including skin, bone and brain tissues was constructed. The transmitting and receiving antenna were set outside and inside the model. The local and average SAR were simulated at the resonance frequency of 18.67 MHz in two situations, in one scenario both transmitting and receiving coil worked, while in the other scenario only the transmitting coil worked. The results showed that the maximum of 10 g SAR average value of human thoracic were 0.142 W/kg and 0.148 W/kg, respectively, both were lower than the international safety standards for human body of the ICNIRP and FCC, which verified the safety of the human body in wireless power transmission based on magnetic coupling resonance.

Magnetic resonance imaging of blood-brain barrier permeability in ischemic stroke using diffusion-weighted arterial spin labeling in rats.

PubMed

Tiwari, Yash V; Lu, Jianfei; Shen, Qiang; Cerqueira, Bianca; Duong, Timothy Q

2017-08-01

Diffusion-weighted arterial spin labeling magnetic resonance imaging has recently been proposed to quantify the rate of water exchange (K w ) across the blood-brain barrier in humans. This study aimed to evaluate the blood-brain barrier disruption in transient (60 min) ischemic stroke using K w magnetic resonance imaging with cross-validation by dynamic contrast-enhanced magnetic resonance imaging and Evans blue histology in the same rats. The major findings were: (i) at 90 min after stroke (30 min after reperfusion), group K w magnetic resonance imaging data showed no significant blood-brain barrier permeability changes, although a few animals showed slightly abnormal K w . Dynamic contrast-enhanced magnetic resonance imaging confirmed this finding in the same animals. (ii) At two days after stroke, K w magnetic resonance imaging revealed significant blood-brain barrier disruption. Regions with abnormal K w showed substantial overlap with regions of hyperintense T 2 (vasogenic edema) and hyperperfusion. Dynamic contrast-enhanced magnetic resonance imaging and Evans blue histology confirmed these findings in the same animals. The K w values in the normal contralesional hemisphere and the ipsilesional ischemic core two days after stroke were: 363 ± 17 and 261 ± 18 min -1 , respectively (P < 0.05, n = 9). K w magnetic resonance imaging is sensitive to blood-brain barrier permeability changes in stroke, consistent with dynamic contrast-enhanced magnetic resonance imaging and Evans blue extravasation. K w magnetic resonance imaging offers advantages over existing techniques because contrast agent is not needed and repeated measurements can be made for longitudinal monitoring or averaging.

The Importance of Neurogenic Inflammation in Blast-Induced Neurotrauma

DTIC Science & Technology

2013-01-01

mild/moderate BINT are imaged by magnetic resonance imaging ( MRI ) to visualize potential macrophage infiltration; blood-brain barrier (BBB) disturbance...TERMS blast, traumatic brain injury, brain, inflammation, magnetic resonance imaging , mice 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF...monitoring the success of therapeutic interventions. In this annual report we have utilized current live imaging methods (i.e. magnetic resonance

Magnetic resonance-guided motorized transcranial ultrasound system for blood-brain barrier permeabilization along arbitrary trajectories in rodents.

PubMed

Magnin, Rémi; Rabusseau, Fabien; Salabartan, Frédéric; Mériaux, Sébastien; Aubry, Jean-François; Le Bihan, Denis; Dumont, Erik; Larrat, Benoit

2015-01-01

Focused ultrasound combined with microbubble injection is capable of locally and transiently enhancing the permeability of the blood-brain barrier (BBB). Magnetic resonance imaging (MRI) guidance enables to plan, monitor, and characterize the BBB disruption. Being able to precisely and remotely control the permeabilization location is of great interest to perform reproducible drug delivery protocols. In this study, we developed an MR-guided motorized focused ultrasound (FUS) system allowing the transducer displacement within preclinical MRI scanners, coupled with real-time transfer and reconstruction of MRI images, to help ultrasound guidance. Capabilities of this new device to deliver large molecules to the brain on either single locations or along arbitrary trajectories were characterized in vivo on healthy rats and mice using 1.5 MHz ultrasound sonications combined with microbubble injection. The efficacy of BBB permeabilization was assessed by injecting a gadolinium-based MR contrast agent that does not cross the intact BBB. The compact motorized FUS system developed in this work fits into the 9-cm inner diameter of the gradient insert installed on our 7-T preclinical MRI scanners. MR images acquired after contrast agent injection confirmed that this device can be used to enhance BBB permeability along remotely controlled spatial trajectories of the FUS beam in both rats and mice. The two-axis motor stage enables reaching any region of interest in the rodent brain. The positioning error when targeting the same anatomical location on different animals was estimated to be smaller than 0.5 mm. Finally, this device was demonstrated to be useful for testing BBB opening at various acoustic pressures (0.2, 0.4, 0.7, and 0.9 MPa) in the same animal and during one single ultrasound session. Our system offers the unique possibility to move the transducer within a high magnetic field preclinical MRI scanner, thus enabling the delivery of large molecules to virtually any rodent brain area in a non-invasive manner. It results in time-saving and reproducibility and could be used to either deliver drugs over large parts of the brain or test different acoustic conditions on the same animal during the same session, therefore reducing physiological variability.

Quantitative Study of Longitudinal Relaxation (T 1) Contrast Mechanisms in Brain MRI

NASA Astrophysics Data System (ADS)

Jiang, Xu

Longitudinal relaxation (T1) contrast in MRI is important for studying brain morphology and is widely used in clinical applications. Although MRI only detects signals from water hydrogen ( 1H) protons (WPs), T1 contrast is known to be influenced by other species of 1H protons, including those in macromolecules (MPs), such as lipids and proteins, through magnetization transfer (MT) between WPs and MPs. This complicates the use and quantification of T1 contrast for studying the underlying tissue composition and the physiology of the brain. MT contributes to T1 contrast to an extent that is generally dependent on MT kinetics, as well as the concentration and NMR spectral properties of MPs. However, the MP spectral properties and MT kinetics are both difficult to measure directly, as the signal from MPs is generally invisible to MRI. Therefore, to investigate MT kinetics and further quantify T1 contrast, we first developed a reliable way to indirectly measure the MP fraction and their exchange rate with WPs, with minimal dependence on the spectral properties of MPs. For this purpose, we used brief, highpower radiofrequency (RF) NMR excitation pulses to almost completely saturate the magnetization of MPs. Based on this, both MT kinetics and the contribution of MPs to T1 contrast through MT were studied. The thus obtained knowledge allowed us to subsequently infer the spectral properties of MPs by applying low-power, frequencyselective off-resonance RF pulses and measuring the offset-frequency dependent effect of MPs on the WP MRI signal. A two-pool exchange model was used in both cases to account for direct effects of the RF pulse on WP magnetization. Consistent with earlier works using MRI at low-field and post-mortem analysis of brain tissue, our novel measurement approach found that MPs constitute an up to 27% fraction of the total 1H protons in human brain white matter, and their spectrum follows a super-Lorentzian line with a T2 of 9.6+/-0.6 mus and a resonance frequency centered at -2.58+/-0.05 ppm, at 7 T. T1 contrast was found to be dominated by MP fraction, with iron only modestly contributing even in the iron-rich regions of brain.

Chemical-exchange-sensitive MRI of amide, amine and NOE at 9.4 T versus 15.2 T.

PubMed

Chung, Julius Juhyun; Choi, Wonmin; Jin, Tao; Lee, Jung Hee; Kim, Seong-Gi

2017-09-01

Chemical exchange (CE)-sensitive MRI benefits greatly from stronger magnetic fields; however, field effects on CE-sensitive imaging have not yet been studied well in vivo. We have compared CE-sensitive Z-spectra and maps obtained at the fields of 9.4 T and 15.2 T in phantoms and rats with off-resonance chemical-exchange-sensitive spin lock (CESL), which is similar to conventional chemical exchange saturation transfer. At higher fields, the background peak at water resonance has less spread and the exchange rate relative to chemical shift decreases, thus CESL intensity is dependent on B 0 . For the in vivo amide and nuclear Overhauser enhancement (NOE) composite resonances of rat brains, intensities were similar for both magnetic fields, but effective amide proton transfer and NOE values obtained with three-point quantification or a curve fitting method were larger at 15.2 T due to the reduced spread of attenuation at the direct water resonance. When using intermediate exchange-sensitive irradiation parameters, the amine proton signal was 65% higher at 15.2 T than at 9.4 T due to a reduced ratio of exchange rate to chemical shift. In summary, increasing magnetic field provides enhancements to CE-sensitive signals in the intermediate exchange regime and reduces contamination from background signals in the slow exchange regime. Consequently, ultrahigh magnetic field is advantageous for CE-sensitive MRI, especially for amine and hydroxyl protons. Copyright © 2017 John Wiley & Sons, Ltd.

Anatomical Brain Magnetic Resonance Imaging of Typically Developing Children and Adolescents

ERIC Educational Resources Information Center

Giedd, Jay N.; Lalonde, Francois M.; Celano, Mark J.; White, Samantha L.; Wallace, Gregory L.; Lee, Nancy R.; Lenroot, Rhoshel K.

2009-01-01

Methodological issues relevant to magnetic resonance imaging studies of brain anatomy are discussed along with the findings on the neuroanatomic changes during childhood and adolescence. The development of the brain is also discussed.

Quantitative MRI reveals the elderly ischemic brain is susceptible to increased early blood–brain barrier permeability following tissue plasminogen activator related to claudin 5 and occludin disassembly

PubMed Central

Kaur, Jaspreet; Tuor, Ursula I; Zhao, Zonghang; Barber, Philip A

2011-01-01

Great uncertainty exists as to whether aging enhances the detrimental effects of tissue plasminogen activator (tPA) on vascular integrity of the ischemic brain. We hypothesized that tPA treatment would augment ischemic injury by causing increased blood–brain barrier (BBB) breakdown as determined by quantitative serial T1 and T2 magnetic resonance imaging (MRI), and the transfer constant for gadolinium-diethylenetriamine penta-acetic acid (Gd-DTPA) from blood to brain in aged (18 to 20 months) compared with young (3 to 4 months) Wistar rats after middle cerebral artery occlusion, mediated through the acute disassembly of claudin 5 and occludin. Increased T2 values over the first hour of postreperfusion were independently augmented following treatment with tPA (P<0.001) and aging (P<0.01), supporting a synergistic effect of tPA on the aged ischemic brain. Blood–brain barrier permeability for Gd-DTPA (KGd) was substantial following reperfusion in all animal groups and was exacerbated by tPA treatment in the elderly rat (P<0.001). The frequency of hematoma formation was proportionately increased in the elderly ischemic brain (P<0.05). Both tPA and age independently increased claudin 5 and occludin phosphorylation during ischemia. Early BBB permeability detected by quantitative MRI following ischemic stroke is enhanced by increased age and tPA and is related to claudin 5 and occludin phosphorylation. PMID:21610723

Bat head contains soft magnetic particles: evidence from magnetism.

PubMed

Tian, Lanxiang; Lin, Wei; Zhang, Shuyi; Pan, Yongxin

2010-10-01

Recent behavioral observations have indicated that bats can sense the Earth's magnetic field. To unravel the magnetoreception mechanism, the present study has utilized magnetic measurements on three migratory species (Miniopterus fuliginosus, Chaerephon plicata, and Nyctalus plancyi) and three non-migratory species (Hipposideros armiger, Myotis ricketti, and Rhinolophus ferrumequinum). Room temperature isothermal remanent magnetization acquisition and alternating-field demagnetization showed that the bats' heads contain soft magnetic particles. Statistical analyses indicated that the saturation isothermal remanent magnetization of brains (SIRM(1T_brain)) of migratory species is higher than those of non-migratory species. Furthermore, the SIRM(1T_brain) of migratory bats is greater than their SIRM(1T_skull). Low-temperature magnetic measurements suggested that the magnetic particles are likely magnetite (Fe3O4). This new evidence supports the assumption that some bats use magnetite particles for sensing and orientation in the Earth's magnetic field.

Brain glutamine synthesis requires neuronal-born aspartate as amino donor for glial glutamate formation.

PubMed

Pardo, Beatriz; Rodrigues, Tiago B; Contreras, Laura; Garzón, Miguel; Llorente-Folch, Irene; Kobayashi, Keiko; Saheki, Takeyori; Cerdan, Sebastian; Satrústegui, Jorgina

2011-01-01

The glutamate-glutamine cycle faces a drain of glutamate by oxidation, which is balanced by the anaplerotic synthesis of glutamate and glutamine in astrocytes. De novo synthesis of glutamate by astrocytes requires an amino group whose origin is unknown. The deficiency in Aralar/AGC1, the main mitochondrial carrier for aspartate-glutamate expressed in brain, results in a drastic fall in brain glutamine production but a modest decrease in brain glutamate levels, which is not due to decreases in neuronal or synaptosomal glutamate content. In vivo (13)C nuclear magnetic resonance labeling with (13)C(2)acetate or (1-(13)C) glucose showed that the drop in brain glutamine is due to a failure in glial glutamate synthesis. Aralar deficiency induces a decrease in aspartate content, an increase in lactate production, and lactate-to-pyruvate ratio in cultured neurons but not in cultured astrocytes, indicating that Aralar is only functional in neurons. We find that aspartate, but not other amino acids, increases glutamate synthesis in both control and aralar-deficient astrocytes, mainly by serving as amino donor. These findings suggest the existence of a neuron-to-astrocyte aspartate transcellular pathway required for astrocyte glutamate synthesis and subsequent glutamine formation. This pathway may provide a mechanism to transfer neuronal-born redox equivalents to mitochondria in astrocytes.

Effects of training strategies implemented in a complex videogame on functional connectivity of attentional networks.

PubMed

Voss, Michelle W; Prakash, Ruchika Shaurya; Erickson, Kirk I; Boot, Walter R; Basak, Chandramallika; Neider, Mark B; Simons, Daniel J; Fabiani, Monica; Gratton, Gabriele; Kramer, Arthur F

2012-01-02

We used the Space Fortress videogame, originally developed by cognitive psychologists to study skill acquisition, as a platform to examine learning-induced plasticity of interacting brain networks. Novice videogame players learned Space Fortress using one of two training strategies: (a) focus on all aspects of the game during learning (fixed priority), or (b) focus on improving separate game components in the context of the whole game (variable priority). Participants were scanned during game play using functional magnetic resonance imaging (fMRI), both before and after 20 h of training. As expected, variable priority training enhanced learning, particularly for individuals who initially performed poorly. Functional connectivity analysis revealed changes in brain network interaction reflective of more flexible skill learning and retrieval with variable priority training, compared to procedural learning and skill implementation with fixed priority training. These results provide the first evidence for differences in the interaction of large-scale brain networks when learning with different training strategies. Our approach and findings also provide a foundation for exploring the brain plasticity involved in transfer of trained abilities to novel real-world tasks such as driving, sport, or neurorehabilitation. Copyright © 2011 Elsevier Inc. All rights reserved.

Adaptive Plasticity in the Healthy Language Network: Implications for Language Recovery after Stroke

PubMed Central

2016-01-01

Across the last three decades, the application of noninvasive brain stimulation (NIBS) has substantially increased the current knowledge of the brain's potential to undergo rapid short-term reorganization on the systems level. A large number of studies applied transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS) in the healthy brain to probe the functional relevance and interaction of specific areas for different cognitive processes. NIBS is also increasingly being used to induce adaptive plasticity in motor and cognitive networks and shape cognitive functions. Recently, NIBS has been combined with electrophysiological techniques to modulate neural oscillations of specific cortical networks. In this review, we will discuss recent advances in the use of NIBS to modulate neural activity and effective connectivity in the healthy language network, with a special focus on the combination of NIBS and neuroimaging or electrophysiological approaches. Moreover, we outline how these results can be transferred to the lesioned brain to unravel the dynamics of reorganization processes in poststroke aphasia. We conclude with a critical discussion on the potential of NIBS to facilitate language recovery after stroke and propose a phase-specific model for the application of NIBS in language rehabilitation. PMID:27830094

Polyethyleneimine-modified iron oxide nanoparticles for brain tumor drug delivery using magnetic targeting and intra-carotid administration

PubMed Central

Chertok, Beata; David, Allan E.; Yang, Victor C.

2010-01-01

This study aimed to examine the applicability of polyethyleneimine (PEI)-modified magnetic nanoparticles (GPEI) as a potential vascular drug/gene carrier to brain tumors. In vitro, GPEI exhibited high cell association and low cell toxicity – properties which are highly desirable for intracellular drug/gene delivery. In addition, a high saturation magnetization of 93 emu/g Fe was expected to facilitate magnetic targeting of GPEI to brain tumor lesions. However, following intravenous administration, GPEI could not be magnetically accumulated in tumors of rats harboring orthotopic 9L-gliosarcomas due to its poor pharmacokinetic properties, reflected by a negligibly low plasma AUC of 12 ± 3 μg Fe/ml*min. To improve “passive” GPEI presentation to brain tumor vasculature for subsequent “active” magnetic capture, we examined the intra-carotid route as an alternative for nanoparticle administration. Intra-carotid administration in conjunction with magnetic targeting resulted in 30-fold (p = 0.002) increase in tumor entrapment of GPEI compared to that seen with intravenous administration. In addition, magnetic accumulation of cationic GPEI (ζ-potential = + 37.2 mV) in tumor lesions was 5.2-fold higher (p = 0.004) than that achieved with slightly anionic G100 (ζ-potential = −12 mV) following intra-carotid administration, while no significant accumulation difference was detected between the two types of nanoparticles in the contra-lateral brain (p = 0.187). These promising results warrant further investigation of GPEI as a potential cell-permeable, magnetically-responsive platform for brain tumor delivery of drugs and genes. PMID:20494439

Polyethyleneimine-modified iron oxide nanoparticles for brain tumor drug delivery using magnetic targeting and intra-carotid administration.

PubMed

Chertok, Beata; David, Allan E; Yang, Victor C

2010-08-01

This study aimed to examine the applicability of polyethyleneimine (PEI)-modified magnetic nanoparticles (GPEI) as a potential vascular drug/gene carrier to brain tumors. In vitro, GPEI exhibited high cell association and low cell toxicity--properties which are highly desirable for intracellular drug/gene delivery. In addition, a high saturation magnetization of 93 emu/g Fe was expected to facilitate magnetic targeting of GPEI to brain tumor lesions. However, following intravenous administration, GPEI could not be magnetically accumulated in tumors of rats harboring orthotopic 9L-gliosarcomas due to its poor pharmacokinetic properties, reflected by a negligibly low plasma AUC of 12 +/- 3 microg Fe/ml min. To improve "passive" GPEI presentation to brain tumor vasculature for subsequent "active" magnetic capture, we examined the intra-carotid route as an alternative for nanoparticle administration. Intra-carotid administration in conjunction with magnetic targeting resulted in 30-fold (p=0.002) increase in tumor entrapment of GPEI compared to that seen with intravenous administration. In addition, magnetic accumulation of cationic GPEI (zeta-potential = + 37.2 mV) in tumor lesions was 5.2-fold higher (p=0.004) than that achieved with slightly anionic G100 (zeta-potential= -12 mV) following intra-carotid administration, while no significant accumulation difference was detected between the two types of nanoparticles in the contra-lateral brain (p=0.187). These promising results warrant further investigation of GPEI as a potential cell-permeable, magnetically-responsive platform for brain tumor delivery of drugs and genes. 2010 Elsevier Ltd. All rights reserved.

Magnetic-field-induced DNA strand breaks in brain cells of the rat.

PubMed Central

Lai, Henry; Singh, Narendra P

2004-01-01

In previous research, we found that rats acutely (2 hr) exposed to a 60-Hz sinusoidal magnetic field at intensities of 0.1-0.5 millitesla (mT) showed increases in DNA single- and double-strand breaks in their brain cells. Further research showed that these effects could be blocked by pretreating the rats with the free radical scavengers melatonin and N-tert-butyl-alpha-phenylnitrone, suggesting the involvement of free radicals. In the present study, effects of magnetic field exposure on brain cell DNA in the rat were further investigated. Exposure to a 60-Hz magnetic field at 0.01 mT for 24 hr caused a significant increase in DNA single- and double-strand breaks. Prolonging the exposure to 48 hr caused a larger increase. This indicates that the effect is cumulative. In addition, treatment with Trolox (a vitamin E analog) or 7-nitroindazole (a nitric oxide synthase inhibitor) blocked magnetic-field-induced DNA strand breaks. These data further support a role of free radicals on the effects of magnetic fields. Treatment with the iron chelator deferiprone also blocked the effects of magnetic fields on brain cell DNA, suggesting the involvement of iron. Acute magnetic field exposure increased apoptosis and necrosis of brain cells in the rat. We hypothesize that exposure to a 60-Hz magnetic field initiates an iron-mediated process (e.g., the Fenton reaction) that increases free radical formation in brain cells, leading to DNA strand breaks and cell death. This hypothesis could have an important implication for the possible health effects associated with exposure to extremely low-frequency magnetic fields in the public and occupational environments. PMID:15121512

Imaging of cerebral blood flow in patients with severe traumatic brain injury in the neurointensive care.

PubMed

Rostami, Elham; Engquist, Henrik; Enblad, Per

2014-01-01

Ischemia is a common and deleterious secondary injury following traumatic brain injury (TBI). A great challenge for the treatment of TBI patients in the neurointensive care unit (NICU) is to detect early signs of ischemia in order to prevent further advancement and deterioration of the brain tissue. Today, several imaging techniques are available to monitor cerebral blood flow (CBF) in the injured brain such as positron emission tomography (PET), single-photon emission computed tomography, xenon computed tomography (Xenon-CT), perfusion-weighted magnetic resonance imaging (MRI), and CT perfusion scan. An ideal imaging technique would enable continuous non-invasive measurement of blood flow and metabolism across the whole brain. Unfortunately, no current imaging method meets all these criteria. These techniques offer snapshots of the CBF. MRI may also provide some information about the metabolic state of the brain. PET provides images with high resolution and quantitative measurements of CBF and metabolism; however, it is a complex and costly method limited to few TBI centers. All of these methods except mobile Xenon-CT require transfer of TBI patients to the radiological department. Mobile Xenon-CT emerges as a feasible technique to monitor CBF in the NICU, with lower risk of adverse effects. Promising results have been demonstrated with Xenon-CT in predicting outcome in TBI patients. This review covers available imaging methods used to monitor CBF in patients with severe TBI.

Imaging of Cerebral Blood Flow in Patients with Severe Traumatic Brain Injury in the Neurointensive Care

PubMed Central

Rostami, Elham; Engquist, Henrik; Enblad, Per

2014-01-01

Ischemia is a common and deleterious secondary injury following traumatic brain injury (TBI). A great challenge for the treatment of TBI patients in the neurointensive care unit (NICU) is to detect early signs of ischemia in order to prevent further advancement and deterioration of the brain tissue. Today, several imaging techniques are available to monitor cerebral blood flow (CBF) in the injured brain such as positron emission tomography (PET), single-photon emission computed tomography, xenon computed tomography (Xenon-CT), perfusion-weighted magnetic resonance imaging (MRI), and CT perfusion scan. An ideal imaging technique would enable continuous non-invasive measurement of blood flow and metabolism across the whole brain. Unfortunately, no current imaging method meets all these criteria. These techniques offer snapshots of the CBF. MRI may also provide some information about the metabolic state of the brain. PET provides images with high resolution and quantitative measurements of CBF and metabolism; however, it is a complex and costly method limited to few TBI centers. All of these methods except mobile Xenon-CT require transfer of TBI patients to the radiological department. Mobile Xenon-CT emerges as a feasible technique to monitor CBF in the NICU, with lower risk of adverse effects. Promising results have been demonstrated with Xenon-CT in predicting outcome in TBI patients. This review covers available imaging methods used to monitor CBF in patients with severe TBI. PMID:25071702

MRI measurement of angiogenesis and the therapeutic effect of acute marrow stromal cell administration on traumatic brain injury.

PubMed

Li, Lian; Chopp, Michael; Ding, Guang Liang; Qu, Chang Sheng; Li, Qing Jiang; Lu, Mei; Wang, Shiyang; Nejad-Davarani, Siamak P; Mahmood, Asim; Jiang, Quan

2012-11-01

Using magnetic resonance imaging (MRI), the present study was undertaken to investigate the therapeutic effect of acute administration of human bone marrow stromal cells (hMSCs) on traumatic brain injury (TBI) and to measure the temporal profile of angiogenesis after the injury with or without cell intervention. Male Wistar rats (300 to 350 g, n=18) subjected to controlled cortical impact TBI were intravenously injected with 1 mL of saline (n=9) or hMSCs in suspension (n=9, 3 × 10(6) hMSCs) 6 hours after TBI. In-vivo MRI acquisitions of T2-weighted imaging, cerebral blood flow (CBF), three-dimensional (3D) gradient echo imaging, and blood-to-brain transfer constant (Ki) of contrast agent were performed on all animals 2 days after injury and weekly for 6 weeks. Sensorimotor function and spatial learning were evaluated. Volumetric changes in the trauma-induced brain lesion and the lateral ventricles were tracked and quantified using T2 maps, and hemodynamic alteration and blood-brain barrier permeability were monitored by CBF and Ki, respectively. Our data show that transplantation of hMSCs 6 hours after TBI leads to reduced cerebral atrophy, early and enhanced cerebral tissue perfusion and improved functional outcome compared with controls. The hMSC treatment increases angiogenesis in the injured brain, which may promote neurologic recovery after TBI.

Brain high-energy phosphates and creatine kinase synthesis rate under graded isoflurane anesthesia: An in vivo (31) P magnetization transfer study at 11.7 tesla.

PubMed

Bresnen, Andrew; Duong, Timothy Q

2015-02-01

The creatine kinase rate of metabolic adenosine triphosphate (ATP) synthesis is an important metabolic parameter but is challenging to measure in vivo due to limited signal-to-noise ratio and long measurement time. This study reports the implementation of an accelerated (31) P Four Angle Saturation Transfer (FAST) method to measure the forward creatine kinase (CK) rate of ATP synthesis. Along with a high-field scanner (11.7 Tesla) and a small sensitive surface coil, the forward CK rate in the rat brain was measured in ∼5 min. Under 1.2% isoflurane, the forward CK rate constant and metabolic flux were, respectively, kf , CK =0.26 ± 0.02 s(-1) and Ff,CK =70.8 ± 4.6 μmol/g/min. As a demonstration of utility and sensitivity, measurements were made under graded isoflurane. Under 2.0% isoflurane, kf , CK =0.16 ± 0.02 s(-1) and Ff,CK =410.0 ± 4.2 μmol/g/min, corresponding to a 38% and 42% reduction, respectively, relative to 1.2% isoflurane. By contrast, the ATP and phosphocreatine concentrations were unaltered. This study demonstrated the (31) P FAST measurement of creatine kinase rate of ATP synthesis in rat brain with reasonable temporal resolution. Different isoflurane levels commonly used in animal models significantly alter the CK reaction rate but not ATP and phosphocreatine concentrations. © 2014 Wiley Periodicals, Inc.

Integrating magnetic resonance imaging postprocessing results into neuronavigation for electrode implantation and resection of subtle focal cortical dysplasia in previously cryptogenic epilepsy.

PubMed

Wellmer, Jörg; Parpaley, Yaroslav; von Lehe, Marec; Huppertz, Hans-Jürgen

2010-01-01

Focal cortical dysplasias (FCDs) are highly epileptogenic lesions. Surgical removal is frequently the best treatment option for pharmacoresistant epilepsy. However, subtle FCDs may remain undetected even after high-resolution magnetic resonance imaging (MRI). Morphometric MRI analysis, which compares the individual brain with a normal database, can facilitate the detection of FCDs. We describe how the results of normal database-based MRI postprocessing can be used to guide stereotactic electrode implantation and subsequent resection of lesions that are suspected to be FCDs. A presurgical evaluation was conducted on a 19-year-old woman with pharmacoresistant hypermotor seizures. Conventional high-resolution MRI was classified as negative for epileptogenic lesions. However, morphometric analysis of the spatially normalized MRI revealed abnormal gyration and blurring of the gray-white matter junction, which was suggestive of a small and deeply seated FCD in the left frontal lobe. The brain region highlighted by morphometric analysis was marked as a region of interest, transferred back to the original dimension of the individual MRI, and imported into a neuronavigation system. This allowed the region of interest-targeted stereotactic implantation of 2 depth electrodes, by which seizure onset was confirmed in the lesion. The electrodes also guided the final resection, which rendered the patient seizure-free. The lesion was histologically classified as FCD Palmini and Lüders IIB. Transferring normal database-based MRI postprocessing results into a neuronavigation system is a new and worthwhile extension of multimodal neuronavigation. The combination of resulting regions of interest with functional and anatomic data may facilitate planning of electrode implantation for invasive electroencephalographic recordings and the final resection of small or deeply seated FCDs.

Diagnosing Autism Spectrum Disorder through Brain Functional Magnetic Resonance Imaging

DTIC Science & Technology

2016-03-01

Diagnosing Autism Spectrum Disorder through Brain Functional Magnetic Resonance Imaging THESIS MARCH 2016 Kyle A. Palko, Second Lieutenant, USAF AFIT...declared a work of the U.S. Government and is not subject to copyright protection in the United States. AFIT-ENC-MS-16-M-123 DIAGNOSING AUTISM SPECTRUM...PUBLIC RELEASE; DISTRIBUTION UNLIMITED. AFIT-ENC-MS-16-M-123 DIAGNOSING AUTISM SPECTRUM DISORDER THROUGH BRAIN FUNCTIONAL MAGNETIC RESONANCE IMAGING Kyle

Resting state fMRI: A review on methods in resting state connectivity analysis and resting state networks.

PubMed

Smitha, K A; Akhil Raja, K; Arun, K M; Rajesh, P G; Thomas, Bejoy; Kapilamoorthy, T R; Kesavadas, Chandrasekharan

2017-08-01

The inquisitiveness about what happens in the brain has been there since the beginning of humankind. Functional magnetic resonance imaging is a prominent tool which helps in the non-invasive examination, localisation as well as lateralisation of brain functions such as language, memory, etc. In recent years, there is an apparent shift in the focus of neuroscience research to studies dealing with a brain at 'resting state'. Here the spotlight is on the intrinsic activity within the brain, in the absence of any sensory or cognitive stimulus. The analyses of functional brain connectivity in the state of rest have revealed different resting state networks, which depict specific functions and varied spatial topology. However, different statistical methods have been introduced to study resting state functional magnetic resonance imaging connectivity, yet producing consistent results. In this article, we introduce the concept of resting state functional magnetic resonance imaging in detail, then discuss three most widely used methods for analysis, describe a few of the resting state networks featuring the brain regions, associated cognitive functions and clinical applications of resting state functional magnetic resonance imaging. This review aims to highlight the utility and importance of studying resting state functional magnetic resonance imaging connectivity, underlining its complementary nature to the task-based functional magnetic resonance imaging.

TOPPE: A framework for rapid prototyping of MR pulse sequences.

PubMed

Nielsen, Jon-Fredrik; Noll, Douglas C

2018-06-01

To introduce a framework for rapid prototyping of MR pulse sequences. We propose a simple file format, called "TOPPE", for specifying all details of an MR imaging experiment, such as gradient and radiofrequency waveforms and the complete scan loop. In addition, we provide a TOPPE file "interpreter" for GE scanners, which is a binary executable that loads TOPPE files and executes the sequence on the scanner. We also provide MATLAB scripts for reading and writing TOPPE files and previewing the sequence prior to hardware execution. With this setup, the task of the pulse sequence programmer is reduced to creating TOPPE files, eliminating the need for hardware-specific programming. No sequence-specific compilation is necessary; the interpreter only needs to be compiled once (for every scanner software upgrade). We demonstrate TOPPE in three different applications: k-space mapping, non-Cartesian PRESTO whole-brain dynamic imaging, and myelin mapping in the brain using inhomogeneous magnetization transfer. We successfully implemented and executed the three example sequences. By simply changing the various TOPPE sequence files, a single binary executable (interpreter) was used to execute several different sequences. The TOPPE file format is a complete specification of an MR imaging experiment, based on arbitrary sequences of a (typically small) number of unique modules. Along with the GE interpreter, TOPPE comprises a modular and flexible platform for rapid prototyping of new pulse sequences. Magn Reson Med 79:3128-3134, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

Magnetization reversal in ferromagnetic thin films induced by spin-orbit interaction with Slonczewski-like spin transfer torque

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

Li, Jia, E-mail: lijia@wipm.ac.cn

2014-10-07

We theoretically investigate the dynamics of magnetization in ferromagnetic thin films induced by spin-orbit interaction with Slonczewski-like spin transfer torque. We reproduce the experimental results of perpendicular magnetic anisotropy films by micromagnetic simulation. Due to the spin-orbit interaction, the magnetization can be switched by changing the direction of the current with the assistant of magnetic field. By increasing the current amplitude, wider range of switching events can be achieved. Time evolution of magnetization has provided us a clear view of the process, and explained the role of minimum external field. Slonczewski-like spin transfer torque modifies the magnetization when current ismore » present. The magnitude of the minimum external field is determined by the strength of the Slonczewski-like spin transfer torque. The investigations may provide potential applications in magnetic memories.« less

Brain pathology after mild traumatic brain injury: an exploratory study by repeated magnetic resonance examination.

PubMed

Lannsjö, Marianne; Raininko, Raili; Bustamante, Mariana; von Seth, Charlotta; Borg, Jörgen

2013-09-01

To explore brain pathology after mild traumatic brain injury by repeated magnetic resonance examination. A prospective follow-up study. Nineteen patients with mild traumatic brain injury presenting with Glasgow Coma Scale (GCS) 14-15. The patients were examined on day 2 or 3 and 3-7 months after the injury. The magnetic resonance protocol comprised conventional T1- and T2-weighted sequences including fluid attenuated inversion recovery (FLAIR), two susceptibility-weighted sequences to reveal haemorrhages, and diffusion-weighted sequences. Computer-aided volume comparison was performed. Clinical outcome was assessed by the Rivermead Post-Concussion Symptoms Questionnaire (RPQ), Hospital Anxiety and Depression Scale (HADS) and Glasgow Outcome Scale Extended (GOSE). At follow-up, 7 patients (37%) reported ≥  3 symptoms in RPQ, 5 reported some anxiety and 1 reported mild depression. Fifteen patients reported upper level of good recovery and 4 patients lower level of good recovery (GOSE 8 and 7, respectively). Magnetic resonance pathology was found in 1 patient at the first examination, but 4 patients (21%) showed volume loss at the second examination, at which 3 of them reported < 3 symptoms and 1 ≥ 3 symptoms, all exhibiting GOSE scores of 8. Loss of brain volume, demonstrated by computer-aided magnetic resonance imaging volumetry, may be a feasible marker of brain pathology after mild traumatic brain injury.

Tissue Characterization with Quantitative High-Resolution Magic Angle Spinning Chemical Exchange Saturation Transfer Z-Spectroscopy.

PubMed

Zhou, Iris Yuwen; Fuss, Taylor L; Igarashi, Takahiro; Jiang, Weiping; Zhou, Xin; Cheng, Leo L; Sun, Phillip Zhe

2016-11-01

Chemical exchange saturation transfer (CEST) provides sensitive magnetic resonance (MR) contrast for probing dilute compounds via exchangeable protons, serving as an emerging molecular imaging methodology. CEST Z-spectrum is often acquired by sweeping radiofrequency saturation around bulk water resonance, offset by offset, to detect CEST effects at characteristic chemical shift offsets, which requires prolonged acquisition time. Herein, combining high-resolution magic angle spinning (HRMAS) with concurrent application of gradient and rf saturation to achieve fast Z-spectral acquisition, we demonstrated the feasibility of fast quantitative HRMAS CEST Z-spectroscopy. The concept was validated with phantoms, which showed excellent agreement with results obtained from conventional HRMAS MR spectroscopy (MRS). We further utilized the HRMAS Z-spectroscopy for fast ex vivo quantification of ischemic injury with rodent brain tissues after ischemic stroke. This method allows rapid and quantitative CEST characterization of biological tissues and shows potential for a host of biomedical applications.

Neural field theory of perceptual echo and implications for estimating brain connectivity

NASA Astrophysics Data System (ADS)

Robinson, P. A.; Pagès, J. C.; Gabay, N. C.; Babaie, T.; Mukta, K. N.

2018-04-01

Neural field theory is used to predict and analyze the phenomenon of perceptual echo in which random input stimuli at one location are correlated with electroencephalographic responses at other locations. It is shown that this echo correlation (EC) yields an estimate of the transfer function from the stimulated point to other locations. Modal analysis then explains the observed spatiotemporal structure of visually driven EC and the dominance of the alpha frequency; two eigenmodes of similar amplitude dominate the response, leading to temporal beating and a line of low correlation that runs from the crown of the head toward the ears. These effects result from mode splitting and symmetry breaking caused by interhemispheric coupling and cortical folding. It is shown how eigenmodes obtained from functional magnetic resonance imaging experiments can be combined with temporal dynamics from EC or other evoked responses to estimate the spatiotemporal transfer function between any two points and hence their effective connectivity.

A prototype MR insertable brain PET using tileable GAPD arrays.

PubMed

Hong, Key Jo; Choi, Yong; Jung, Jin Ho; Kang, Jihoon; Hu, Wei; Lim, Hyun Keong; Huh, Yoonsuk; Kim, Sangsu; Jung, Ji Woong; Kim, Kyu Bom; Song, Myung Sung; Park, Hyun-Wook

2013-04-01

The aim of this study was to develop a prototype magnetic resonance (MR)-compatible positron emission tomography (PET) that can be inserted into a MR imager and that allows simultaneous PET and MR imaging of the human brain. This paper reports the initial results of the authors' prototype brain PET system operating within a 3-T magnetic resonance imaging (MRI) system using newly developed Geiger-mode avalanche photodiode (GAPD)-based PET detectors, long flexible flat cables, position decoder circuit with high multiplexing ratio, and digital signal processing with field programmable gate array-based analog to digital converter boards. A brain PET with 72 detector modules arranged in a ring was constructed and mounted in a 3-T MRI. Each PET module was composed of cerium-doped lutetium yttrium orthosilicate (LYSO) crystals coupled to a tileable GAPD. The GAPD output charge signals were transferred to preamplifiers using 3 m long flat cables. The LYSO and GAPD were located inside the MR bore and all electronics were positioned outside the MR bore. The PET detector performance was investigated both outside and inside the MRI, and MR image quality was evaluated with and without the PET system. The performance of the PET detector when operated inside the MRI during MR image acquisition showed no significant change in energy resolution and count rates, except for a slight degradation in timing resolution with an increase from 4.2 to 4.6 ns. Simultaneous PET/MR images of a hot-rod and Hoffman brain phantom were acquired in a 3-T MRI. Rods down to a diameter of 3.5 mm were resolved in the hot-rod PET image. The activity distribution patterns between the white and gray matter in the Hoffman brain phantom were well imaged. The hot-rod and Hoffman brain phantoms on the simultaneously acquired MR images obtained with standard sequences were observed without any noticeable artifacts, although MR image quality requires some improvement. These results demonstrate that the simultaneous acquisition of PET and MR images is feasible using the MR insertable PET developed in this study.

Transcranial magnetic stimulation of mouse brain using high-resolution anatomical models

NASA Astrophysics Data System (ADS)

Crowther, L. J.; Hadimani, R. L.; Kanthasamy, A. G.; Jiles, D. C.

2014-05-01

Transcranial magnetic stimulation (TMS) offers the possibility of non-invasive treatment of brain disorders in humans. Studies on animals can allow rapid progress of the research including exploring a variety of different treatment conditions. Numerical calculations using animal models are needed to help design suitable TMS coils for use in animal experiments, in particular, to estimate the electric field induced in animal brains. In this paper, we have implemented a high-resolution anatomical MRI-derived mouse model consisting of 50 tissue types to accurately calculate induced electric field in the mouse brain. Magnetic field measurements have been performed on the surface of the coil and compared with the calculations in order to validate the calculated magnetic and induced electric fields in the brain. Results show how the induced electric field is distributed in a mouse brain and allow investigation of how this could be improved for TMS studies using mice. The findings have important implications in further preclinical development of TMS for treatment of human diseases.

Registration of 3D fetal neurosonography and MRI☆

PubMed Central

Kuklisova-Murgasova, Maria; Cifor, Amalia; Napolitano, Raffaele; Papageorghiou, Aris; Quaghebeur, Gerardine; Rutherford, Mary A.; Hajnal, Joseph V.; Noble, J. Alison; Schnabel, Julia A.

2013-01-01

We propose a method for registration of 3D fetal brain ultrasound with a reconstructed magnetic resonance fetal brain volume. This method, for the first time, allows the alignment of models of the fetal brain built from magnetic resonance images with 3D fetal brain ultrasound, opening possibilities to develop new, prior information based image analysis methods for 3D fetal neurosonography. The reconstructed magnetic resonance volume is first segmented using a probabilistic atlas and a pseudo ultrasound image volume is simulated from the segmentation. This pseudo ultrasound image is then affinely aligned with clinical ultrasound fetal brain volumes using a robust block-matching approach that can deal with intensity artefacts and missing features in the ultrasound images. A qualitative and quantitative evaluation demonstrates good performance of the method for our application, in comparison with other tested approaches. The intensity average of 27 ultrasound images co-aligned with the pseudo ultrasound template shows good correlation with anatomy of the fetal brain as seen in the reconstructed magnetic resonance image. PMID:23969169

Noninvasive amide proton transfer magnetic resonance imaging in evaluating the grading and cellularity of gliomas.

PubMed

Bai, Yan; Lin, Yusong; Zhang, Wei; Kong, Lingfei; Wang, Lifu; Zuo, Panli; Vallines, Ignacio; Schmitt, Benjamin; Tian, Jie; Song, Xiaolei; Zhou, Jinyuan; Wang, Meiyun

2017-01-24

Using noninvasive magnetic resonance imaging techniques to accurately evaluate the grading and cellularity of gliomas is beneficial for improving the patient outcomes. Amide proton transfer imaging is a noninvasive molecular magnetic resonance imaging technique based on chemical exchange saturation transfer mechanism that detects endogenous mobile proteins and peptides in biological tissues. Between August 2012 and November 2015, a total number of 44 patients with pathologically proven gliomas were included in this study. We compared the capability of amide proton transfer magnetic resonance imaging with that of noninvasive diffusion-weighted imaging and noninvasive 3-dimensional pseudo-continuous arterial spin imaging in evaluating the grading and cellularity of gliomas. Our results reveal that amide proton transfer magnetic resonance imaging is a superior imaging technique to diffusion-weighted imaging and 3-dimensional pseudo-continuous arterial spin imaging in the grading of gliomas. In addition, our results showed that the Ki-67 index correlated better with the amide proton transfer-weighted signal intensity than with the apparent diffusion coefficient value or the cerebral blood flow value in the gliomas. Amide proton transfer magnetic resonance imaging is a promising method for predicting the grading and cellularity of gliomas.

Z-spectrum appearance and interpretation in the presence of fat: Influence of acquisition parameters.

PubMed

Zhang, Shu; Keupp, Jochen; Wang, Xinzeng; Dimitrov, Ivan; Madhuranthakam, Ananth J; Lenkinski, Robert E; Vinogradov, Elena

2018-05-01

Chemical exchange saturation transfer (CEST) MRI is increasingly evolving from brain to body applications. One of the known problems in the body imaging is the presence of strong lipid signals. Although their influence on the CEST effect is acknowledged, there was no study that focuses on the interplay among echo time, fat fraction, and Z-spectrum. This study strives to address these points, with the emphasis on the application in the breast. Z-spectra were simulated in phase and out of phase of the main fat peak at -3.4 ppm, with the fat fraction varying from 0 to 100%. The magnetization transfer ratio asymmetry in two ranges, centering at the exchanging pool and at 3.5 ppm approximately opposite the nonexchanging fat pool, were calculated and were plotted against fat fraction. The results were verified in phantoms and in vivo. The results demonstrate the combined influence of fat fraction and echo time on the Z-spectrum for gradient echo based CEST acquisitions. The influence is straightforward in the in-phase images, but it is more complicated in the out-of-phase images, potentially leading to erroneous CEST contrast. This study provides a basis for understanding the origin and appearance of lipid artifacts in CEST imaging, and lays the foundation for their efficient removal. Magn Reson Med 79:2731-2737, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

Magnetic targeting of nanoparticles across the intact blood–brain barrier

PubMed Central

Kong, Seong Deok; Lee, Jisook; Ramachandran, Srinivasan; Eliceiri, Brian P.; Shubayev, Veronica I.; Lal, Ratnesh; Jin, Sungho

2015-01-01

Delivery of therapeutic or diagnostic agents across an intact blood–brain barrier (BBB) remains a major challenge. Here we demonstrate in a mouse model that magnetic nanoparticles (MNPs) can cross the normal BBB when subjected to an external magnetic field. Following a systemic administration, an applied external magnetic field mediates the ability of MNPs to permeate the BBB and accumulate in a perivascular zone of the brain parenchyma. Direct tracking and localization inside endothelial cells and in the perivascular extracellular matrix in vivo was established using fluorescent MNPs. These MNPs were inert and associated with low toxicity, using a non-invasive reporter for astrogliosis, biochemical and histological studies. Atomic force microscopy demonstrated that MNPs were internalized by endothelial cells, suggesting that trans-cellular trafficking may be a mechanism for the MNP crossing of the BBB observed. The silica-coated magnetic nanocapsules (SiMNCs) allow on-demand drug release via remote radio frequency (RF) magnetic field. Together, these results establish an effective strategy for regulating the biodistribution of MNPs in the brain through the application of an external magnetic field. PMID:23063548

Interleukin-1β transfer across the blood–brain barrier in the ovine fetus

PubMed Central

Sadowska, Grazyna B; Chen, Xiaodi; Zhang, Jiyong; Lim, Yow-Pin; Cummings, Erin E; Makeyev, Oleksandr; Besio, Walter G; Gaitanis, John; Padbury, James F; Banks, William A; Stonestreet, Barbara S

2015-01-01

Pro-inflammatory cytokines contribute to hypoxic–ischemic brain injury. Blood–brain barrier (BBB) dysfunction represents an important component of hypoxic–ischemic brain injury in the fetus. Hypoxic–ischemic injury could accentuate systemic cytokine transfer across the fetal BBB. There has been considerable conjecture suggesting that systemic cytokines could cross the BBB during the perinatal period. Nonetheless, evidence to support this contention is sparse. We hypothesized that ischemia–reperfusion increases the transfer of systemic interleukin-1β (IL-1β) across the BBB in the fetus. Ovine fetuses at 127 days of gestation were studied 4 hours after 30 minutes of bilateral carotid artery occlusion and compared with a nonischemic group. Recombinant ovine IL-1β protein was expressed from an IL-1β pGEX-2 T vector in E. coli BL-21 cells and purified. The BBB function was quantified in 12 brain regions using a blood-to-brain transfer constant with intravenous 125I-radiolabeled IL-1β (125I-IL-1β). Interleukin-1β crossed the intact BBB in nonischemic fetuses. Blood-to-brain transport of 125I-IL-1β was higher (P<0.05) across brain regions in fetuses exposed to ischemia–reperfusion than nonischemic fetuses. We conclude that systemic IL-1β crosses the intact fetal BBB, and that ischemia–reperfusion increases transfer of this cytokine across the fetal BBB. Therefore, altered BBB function after hypoxia–ischemia facilitates entry of systemic cytokines into the brain of the fetus. PMID:26082012

Interleukin-1β transfer across the blood-brain barrier in the ovine fetus.

PubMed

Sadowska, Grazyna B; Chen, Xiaodi; Zhang, Jiyong; Lim, Yow-Pin; Cummings, Erin E; Makeyev, Oleksandr; Besio, Walter G; Gaitanis, John; Padbury, James F; Banks, William A; Stonestreet, Barbara S

2015-09-01

Pro-inflammatory cytokines contribute to hypoxic-ischemic brain injury. Blood-brain barrier (BBB) dysfunction represents an important component of hypoxic-ischemic brain injury in the fetus. Hypoxic-ischemic injury could accentuate systemic cytokine transfer across the fetal BBB. There has been considerable conjecture suggesting that systemic cytokines could cross the BBB during the perinatal period. Nonetheless, evidence to support this contention is sparse. We hypothesized that ischemia-reperfusion increases the transfer of systemic interleukin-1β (IL-1β) across the BBB in the fetus. Ovine fetuses at 127 days of gestation were studied 4 hours after 30 minutes of bilateral carotid artery occlusion and compared with a nonischemic group. Recombinant ovine IL-1β protein was expressed from an IL-1β pGEX-2 T vector in E. coli BL-21 cells and purified. The BBB function was quantified in 12 brain regions using a blood-to-brain transfer constant with intravenous (125)I-radiolabeled IL-1β ((125)I-IL-1β). Interleukin-1β crossed the intact BBB in nonischemic fetuses. Blood-to-brain transport of (125)I-IL-1β was higher (P<0.05) across brain regions in fetuses exposed to ischemia-reperfusion than nonischemic fetuses. We conclude that systemic IL-1β crosses the intact fetal BBB, and that ischemia-reperfusion increases transfer of this cytokine across the fetal BBB. Therefore, altered BBB function after hypoxia-ischemia facilitates entry of systemic cytokines into the brain of the fetus.

A Novel Magnetic Actuation Scheme to Disaggregate Nanoparticles and Enhance Passage across the Blood–Brain Barrier

PubMed Central

Le, Tuan-Anh; Amin, Faiz Ul; Kim, Myeong Ok

2017-01-01

The blood–brain barrier (BBB) hinders drug delivery to the brain. Despite various efforts to develop preprogramed actuation schemes for magnetic drug delivery, the unmodeled aggregation phenomenon limits drug delivery performance. This paper proposes a novel scheme with an aggregation model for a feed-forward magnetic actuation design. A simulation platform for aggregated particle delivery is developed and an actuation scheme is proposed to deliver aggregated magnetic nanoparticles (MNPs) using a discontinuous asymmetrical magnetic actuation. The experimental results with a Y-shaped channel indicated the success of the proposed scheme in steering and disaggregation. The delivery performance of the developed scheme was examined using a realistic, three-dimensional (3D) vessel simulation. Furthermore, the proposed scheme enhanced the transport and uptake of MNPs across the BBB in mice. The scheme presented here facilitates the passage of particles across the BBB to the brain using an electromagnetic actuation scheme. PMID:29271927

A Novel Magnetic Actuation Scheme to Disaggregate Nanoparticles and Enhance Passage across the Blood-Brain Barrier.

PubMed

Hoshiar, Ali Kafash; Le, Tuan-Anh; Amin, Faiz Ul; Kim, Myeong Ok; Yoon, Jungwon

2017-12-22

The blood-brain barrier (BBB) hinders drug delivery to the brain. Despite various efforts to develop preprogramed actuation schemes for magnetic drug delivery, the unmodeled aggregation phenomenon limits drug delivery performance. This paper proposes a novel scheme with an aggregation model for a feed-forward magnetic actuation design. A simulation platform for aggregated particle delivery is developed and an actuation scheme is proposed to deliver aggregated magnetic nanoparticles (MNPs) using a discontinuous asymmetrical magnetic actuation. The experimental results with a Y-shaped channel indicated the success of the proposed scheme in steering and disaggregation. The delivery performance of the developed scheme was examined using a realistic, three-dimensional (3D) vessel simulation. Furthermore, the proposed scheme enhanced the transport and uptake of MNPs across the BBB in mice. The scheme presented here facilitates the passage of particles across the BBB to the brain using an electromagnetic actuation scheme.

On the inverse transfer of (non-)helical magnetic energy in a decaying magnetohydrodynamic turbulence

NASA Astrophysics Data System (ADS)

Park, Kiwan

2017-12-01

In our conventional understanding, large-scale magnetic fields are thought to originate from an inverse cascade in the presence of magnetic helicity, differential rotation or a magneto-rotational instability. However, as recent simulations have given strong indications that an inverse cascade (transfer) may occur even in the absence of magnetic helicity, the physical origin of this inverse cascade is still not fully understood. We here present two simulations of freely decaying helical and non-helical magnetohydrodynamic (MHD) turbulence. We verified the inverse transfer of helical and non-helical magnetic fields in both cases, but we found the underlying physical principles to be fundamentally different. In the former case, the helical magnetic component leads to an inverse cascade of magnetic energy. We derived a semi-analytic formula for the evolution of large-scale magnetic field using α coefficient and compared it with the simulation data. But in the latter case, the α effect, including other conventional dynamo theories, is not suitable to describe the inverse transfer of non-helical magnetic energy. To obtain a better understanding of the physics at work here, we introduced a 'field structure model' based on the magnetic induction equation in the presence of inhomogeneities. This model illustrates how the curl of the electromotive force leads to the build up of a large-scale magnetic field without the requirement of magnetic helicity. And we applied a quasi-normal approximation to the inverse transfer of magnetic energy.

Experimental study on heat transfer enhancement of laminar ferrofluid flow in horizontal tube partially filled porous media under fixed parallel magnet bars

NASA Astrophysics Data System (ADS)

Sheikhnejad, Yahya; Hosseini, Reza; Saffar Avval, Majid

2017-02-01

In this study, steady state laminar ferroconvection through circular horizontal tube partially filled with porous media under constant heat flux is experimentally investigated. Transverse magnetic fields were applied on ferrofluid flow by two fixed parallel magnet bar positioned on a certain distance from beginning of the test section. The results show promising notable enhancement in heat transfer as a consequence of partially filled porous media and magnetic field, up to 2.2 and 1.4 fold enhancement were observed in heat transfer coefficient respectively. It was found that presence of both porous media and magnetic field simultaneously can highly improve heat transfer up to 2.4 fold. Porous media of course plays a major role in this configuration. Virtually, application of Magnetic field and porous media also insert higher pressure loss along the pipe which again porous media contribution is higher that magnetic field.

Modulation and detection of single neuron activity using spin transfer nano-oscillators

NASA Astrophysics Data System (ADS)

Algarin, Jose Miguel; Ramaswamy, Bharath; Venuti, Lucy; Swierzbinski, Matthew; Villar, Pablo; Chen, Yu-Jin; Krivorotov, Ilya; Weinberg, Irving N.; Herberholz, Jens; Araneda, Ricardo; Shapiro, Benjamin; Waks, Edo

2017-09-01

The brain is a complex network of interconnected circuits that exchange electrical signals with each other. These electrical signals provide insight on how neural circuits code information, and give rise to sensations, thoughts, emotions and actions. Currents methods to detect and modulate these electrical signals use implanted electrodes or optical fields with light sensitive dyes in the brain. These techniques require complex surgeries or suffer low resolution. In this talk we explore a new method to both image and stimulate single neurons using spintronics. We propose using a Spin Transfer Nano-Oscillators (STNOs) as a nanoscale sensor that converts neuronal action potentials to microwave field oscillations that can be detected wirelessly by magnetic induction. We will describe our recent proof-of-concept demonstration of both detection and wireless modulation of neuronal activity using STNOs. For detection we use electrodes to connect a STNO to a lateral giant crayfish neuron. When we stimulate the neuron, the STNO responds to the neuronal activity with a corresponding microwave signal. For modulation, we stimulate the STNOs wirelessly using an inductively coupled solenoid. The STNO rectifies the induced microwave signal to produce a direct voltage. This direct voltage from the STNO, when applied in the vicinity of a mammalian neuron, changes the frequency of electrical signals produced by the neuron.

The Correlation Between a Short-term Conventional Electroencephalography in the First Day of Life and Brain Magnetic Resonance Imaging in Newborns Undergoing Hypothermia for Hypoxic-Ischemic Encephalopathy.

PubMed

Obeid, Rawad; Sogawa, Yoshimi; Gedela, Satyanarayana; Naik, Monica; Lee, Vince; Telesco, Richard; Wisnowski, Jessica; Magill, Christine; Painter, Michael J; Panigrahy, Ashok

2017-02-01

Electroencephalograph recorded in the first day of life in newborns treated with hypothermia for hypoxic-ischemic encephalopathy could be utilized as a predictive tool for the severity of brain injury on magnetic resonance imaging and mortality. We analyzed newborns who were admitted for therapeutic hypothermia due to hypoxic-ischemic encephalopathy. All enrolled infants underwent encephalography within the first 24 hours of life and underwent brain magnetic resonance imaging after rewarming. All encephalographs were independently reviewed for background amplitude, continuity, and variability. Brain injury determined by magnetic resonance imaging was scored using methods described by Bonifacio et al. Forty-one newborns were included in the study. Each encephalograph variable correlated significantly with the severity of injury on brain magnetic resonance imaging (P < 0.001 for each). The overall encephalograph severity estimated as mild, moderate, and severe also correlated with injury (P < 0.001). Each encephalograph variable correlated with mortality (P < 0.001 for each) and also the overall encephalograph severity (P < 0.001). Severity of electrographic findings on encephalograph in the first day of life during therapeutic hypothermia for hypoxic-ischemic encephalopathy correlated with the extent of injury on brain magnetic resonance imaging. This information may be useful for families and aid guide clinical decision making. Copyright © 2017 Elsevier Inc. All rights reserved.

Amplitude-integrated EEG in newborns with critical congenital heart disease predicts preoperative brain magnetic resonance imaging findings.

PubMed

Mulkey, Sarah B; Yap, Vivien L; Bai, Shasha; Ramakrishnaiah, Raghu H; Glasier, Charles M; Bornemeier, Renee A; Schmitz, Michael L; Bhutta, Adnan T

2015-06-01

The study aims are to evaluate cerebral background patterns using amplitude-integrated electroencephalography in newborns with critical congenital heart disease, determine if amplitude-integrated electroencephalography is predictive of preoperative brain injury, and assess the incidence of preoperative seizures. We hypothesize that amplitude-integrated electroencephalography will show abnormal background patterns in the early preoperative period in infants with congenital heart disease that have preoperative brain injury on magnetic resonance imaging. Twenty-four newborns with congenital heart disease requiring surgery at younger than 30 days of age were prospectively enrolled within the first 3 days of age at a tertiary care pediatric hospital. Infants had amplitude-integrated electroencephalography for 24 hours beginning close to birth and preoperative brain magnetic resonance imaging. The amplitude-integrated electroencephalographies were read to determine if the background pattern was normal, mildly abnormal, or severely abnormal. The presence of seizures and sleep-wake cycling were noted. The preoperative brain magnetic resonance imaging scans were used for brain injury and brain atrophy assessment. Fifteen of 24 infants had abnormal amplitude-integrated electroencephalography at 0.71 (0-2) (mean [range]) days of age. In five infants, the background pattern was severely abnormal. (burst suppression and/or continuous low voltage). Of the 15 infants with abnormal amplitude-integrated electroencephalography, 9 (60%) had brain injury. One infant with brain injury had a seizure on amplitude-integrated electroencephalography. A severely abnormal background pattern on amplitude-integrated electroencephalography was associated with brain atrophy (P = 0.03) and absent sleep-wake cycling (P = 0.022). Background cerebral activity is abnormal on amplitude-integrated electroencephalography following birth in newborns with congenital heart disease who have findings of brain injury and/or brain atrophy on preoperative brain magnetic resonance imaging. Copyright © 2015 Elsevier Inc. All rights reserved.

Amplification of large scale magnetic fields in a decaying MHD system

NASA Astrophysics Data System (ADS)

Park, Kiwan

2017-10-01

Dynamo theory explains the amplification of magnetic fields in the conducting fluids (plasmas) driven by the continuous external energy. It is known that the nonhelical continuous kinetic or magnetic energy amplifies the small scale magnetic field; and the helical energy, the instability, or the shear with rotation effect amplifies the large scale magnetic field. However, recently it was reported that the decaying magnetic energy independent of helicity or instability could generate the large scale magnetic field. This phenomenon may look somewhat contradictory to the conventional dynamo theory. But it gives us some clues to the fundamental mechanism of energy transfer in the magnetized conducting fluids. It also implies that an ephemeral astrophysical event emitting the magnetic and kinetic energy can be a direct cause of the large scale magnetic field observed in space. As of now the exact physical mechanism is not yet understood in spite of several numerical results. The plasma motion coupled with a nearly conserved vector potential in the magnetohydrodynamic (MHD) system may transfer magnetic energy to the large scale. Also the intrinsic property of the scaling invariant MHD equation may decide the direction of energy transfer. In this paper we present the simulation results of inversely transferred helical and nonhelical energy in a decaying MHD system. We introduce a field structure model based on the MHD equation to show that the transfer of magnetic energy is essentially bidirectional depending on the plasma motion and initial energy distribution. And then we derive α coefficient algebraically in line with the field structure model to explain how the large scale magnetic field is induced by the helical energy in the system regardless of an external forcing source. And for the algebraic analysis of nonhelical magnetic energy, we use the eddy damped quasinormalized Markovian approximation to show the inverse transfer of magnetic energy.

Perceptual learning modifies the functional specializations of visual cortical areas.

PubMed

Chen, Nihong; Cai, Peng; Zhou, Tiangang; Thompson, Benjamin; Fang, Fang

2016-05-17

Training can improve performance of perceptual tasks. This phenomenon, known as perceptual learning, is strongest for the trained task and stimulus, leading to a widely accepted assumption that the associated neuronal plasticity is restricted to brain circuits that mediate performance of the trained task. Nevertheless, learning does transfer to other tasks and stimuli, implying the presence of more widespread plasticity. Here, we trained human subjects to discriminate the direction of coherent motion stimuli. The behavioral learning effect substantially transferred to noisy motion stimuli. We used transcranial magnetic stimulation (TMS) and functional magnetic resonance imaging (fMRI) to investigate the neural mechanisms underlying the transfer of learning. The TMS experiment revealed dissociable, causal contributions of V3A (one of the visual areas in the extrastriate visual cortex) and MT+ (middle temporal/medial superior temporal cortex) to coherent and noisy motion processing. Surprisingly, the contribution of MT+ to noisy motion processing was replaced by V3A after perceptual training. The fMRI experiment complemented and corroborated the TMS finding. Multivariate pattern analysis showed that, before training, among visual cortical areas, coherent and noisy motion was decoded most accurately in V3A and MT+, respectively. After training, both kinds of motion were decoded most accurately in V3A. Our findings demonstrate that the effects of perceptual learning extend far beyond the retuning of specific neural populations for the trained stimuli. Learning could dramatically modify the inherent functional specializations of visual cortical areas and dynamically reweight their contributions to perceptual decisions based on their representational qualities. These neural changes might serve as the neural substrate for the transfer of perceptual learning.

Integrating some mind and brain views of transference: the phenomena.

PubMed

Levin, F M

1997-01-01

Because understanding the underpinnings of transferential learning allows the analyst to more effectively exploit transference in the clinical situation, as well as to advance psychoanalytic theory, the functions and mechanisms of transference phenomena in learning are subjected to an interdisciplinary analysis. Through transference the brain creates hierarchical databases that make emotional sense of the world, especially the world of human relationships. Transference plays a role in defense and resistance clinically; less explored but equally important is the adaptive potential of transference and its effect on an individual's readiness for structural change through the activation of working memory. Most investigators within psychoanalysis have not considered the importance of similarity judgments and memory priming, especially as these help to explain why transference and its proper handling are effective in treatment. Yet there are complex relationships among transference, similarity judgment, and memory priming that tie together psychoanalysis, cognitive psychology, and neurophysiology. Evidence increasingly suggests a relationship between transference and the transfer of knowledge between various content domains (databases) of mind and brain, which is essential to cognitive and emotional learning. There are indications as well that transference decisively facilitates learning readiness ("windows") in general by means of two of its components: free association and spontaneous (self-initiated) activity. The important question of which mind/brain mechanisms motivate transference is not yet understood comprehensively. However, Vygotsky's work on the zone of proximal development (ZPD), M.Stern's teleonomic theory, schema theory, and neural network theory offer further insights into what motivates transference.

Enhancement in heat transfer of a ferrofluid in a differentially heated square cavity through the use of permanent magnets

NASA Astrophysics Data System (ADS)

Joubert, J. C.; Sharifpur, M.; Solomon, A. Brusly; Meyer, J. P.

2017-12-01

The natural convection heat transfer of a magnetic nanofluid in a differentially heated cavity is investigated with and without an applied external magnetic field. The effects of volume fraction, magnetic field configuration, and magnetic field strength are investigated. Spherical Fe2O3 nanoparticles with a diameter of 15-20 nm are used in the nanofluids. Volume fractions ranging between 0.05% and 0.3% are tested for the case with no magnetic field, while only a volume fraction of 0.1% was tested in an externally applied magnetic field. The experiments were conducted for a range of Rayleigh numbers in 1.7 × 108 < Ra < 4.2 × 108. The viscosity of the nanofluid was determined experimentally. An empirical correlation for the viscosity was determined, and the stability of various nanofluids was investigated. Using heat transfer data obtained from the cavity, the average heat transfer coefficient and average Nusselt number for the nanofluids are determined. It was found that a volume fraction of 0.1% showed a maximum increase of 5.63% to the Nu at the maximum Ra. For the magnetic field study, it was found that the best-performing magnetic field enhanced the heat transfer behaviour by an additional 2.81% in Nu at Ra = 3.8 × 108.

A quantitative study of ramped radio frequency, magnetization transfer, and slab thickness in three-dimensional time-of-flight magnetic resonance angiography in a patient population.

PubMed

Goodrich, K C; Blatter, D D; Parker, D L; Du, Y P; Meyer, K J; Bernstein, M A

1996-06-01

The authors compare the effectiveness of various magnetic resonance (MR) angiography acquisition strategies in enhancing the visibility of small intracranial vessels. Blood vessel contrast-to-noise ratio (CNR) in time-of-flight MR angiography was studied as a function of vessel size and several selectable imaging parameters. Contrast-to-noise measurements were made on 257 vessel segments ranging in size from 0.3 mm to 4.2 mm in patients who recently had undergone intraarterial cerebral angiography. Imaging parameters studied included magnetization transfer, spatially variable radio frequency (RF) pulse profile (ramped RF), and imaging slab thickness. The combination of thin slabs (16 slices/slab), ramped RF, and magnetization transfer resulted in the highest CNR for all but the smallest vessel sizes. The smallest vessels (< 0.5 mm) had the highest CNR, using the thick slab (64 slices/slab) with ramped RF and magnetization transfer. Magnetization transfer always improved vessel CNR, but the improvement diminished as the slab thickness was reduced. The CNR increased with a decrease in slab thickness for all but the smallest vessel sizes. Overall, the results provide a quantitative demonstration that inflow enhancement of blood is reduced for small vessels. Thus, whereas magnetization transfer is important at all vessel sizes, it becomes the primary factor in improving the visibility of the smallest vessels.

[Phosphorus magnetic resonance spectroscopy: Brain pathologies applications].

PubMed

Menuel, C; Guillevin, R; Costalat, R; Perrin, M; Sahli-Amor, M; Martin-Duverneuil, N; Chiras, J

2010-05-01

Until recent years, brain applications of (31)P magnetic resonance spectroscopy were poor. Arising of clinical high field strength magnets (three Tesla) as well as dedicated brain coils (eg: bird cage), using specific and useful sequences providing appropriate spatial localisation and signal to noise ratio brought highlights on multinuclear spectroscopy. Better understanding of brain metabolism emphasizes the role of phosphoenergetic compounds and its potential issues in tumoral, metabolic and degenerative diseases. In the present paper, we report 1 year of experience and preliminary results for 40 patients as well as review of the literature. By successive in vivo determination and quantitation of numerous metabolites it allows, multinuclear spectroscopy may provide additional information to biomathematical models of brain metabolism. Copyright 2009. Published by Elsevier Masson SAS.

Dual-Targeting Lactoferrin-Conjugated Polymerized Magnetic Polydiacetylene-Assembled Nanocarriers with Self-Responsive Fluorescence/Magnetic Resonance Imaging for In Vivo Brain Tumor Therapy.

PubMed

Fang, Jen-Hung; Chiu, Tsung-Lang; Huang, Wei-Chen; Lai, Yen-Ho; Hu, Shang-Hsiu; Chen, You-Yin; Chen, San-Yuan

2016-03-01

Maintaining a high concentration of therapeutic agents in the brain is difficult due to the restrictions of the blood-brain barrier (BBB) and rapid removal from blood circulation. To enable controlled drug release and enhance the blood-brain barrier (BBB)-crossing efficiency for brain tumor therapy, a new dual-targeting magnetic polydiacetylene nanocarriers (PDNCs) delivery system modified with lactoferrin (Lf) is developed. The PDNCs are synthesized using the ultraviolet (UV) cross-linkable 10,12-pentacosadiynoic acid (PCDA) monomers through spontaneous assembling onto the surface of superparamagnetic iron oxide (SPIO) nanoparticles to form micelles-polymerized structures. The results demonstrate that PDNCs will reduce the drug leakage and further control the drug release, and display self-responsive fluorescence upon intracellular uptake for cell trafficking and imaging-guided tumor treatment. The magnetic Lf-modified PDNCs with magnetic resonance imaging (MRI) and dual-targeting ability can enhance the transportation of the PDNCs across the BBB for tracking and targeting gliomas. An enhanced therapeutic efficiency can be obtained using Lf-Cur (Curcumin)-PDNCs by improving the retention time of the encapsulated Cur and producing fourfold higher Cur amounts in the brain compared to free Cur. Animal studies also confirm that Lf targeting and controlled release act synergistically to significantly suppress tumors in orthotopic brain-bearing rats. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Brain Lesions

MedlinePlus

... seen on a brain-imaging test, such as magnetic resonance imaging (MRI) or computerized tomography (CT). On ... A cohort study. PLOS One. 2013;8:e71467. Magnetic resonance imaging (MRI). National Multiple Sclerosis Society. http:// ...

Help With Depression

MedlinePlus

... techniques that focus on neuromodulation, which incorporates electrical, magnetic or other forms of energy to stimulate brain ... electroconvulsive therapy (ECT), vagus-nerve stimulation (VNS), transcranial magnetic stimulation (TMS) and the experimental deep-brain stimulation ( ...

Significant Artifact Reduction at 1.5T and 3T MRI by the Use of a Cochlear Implant with Removable Magnet: An Experimental Human Cadaver Study

PubMed Central

Wagner, Franca; Wimmer, Wilhelm; Leidolt, Lars; Vischer, Mattheus; Weder, Stefan; Wiest, Roland; Mantokoudis, Georgios; Caversaccio, Marco D.

2015-01-01

Objective Cochlear implants (CIs) are standard treatment for postlingually deafened individuals and prelingually deafened children. This human cadaver study evaluated diagnostic usefulness, image quality and artifacts in 1.5T and 3T magnetic resonance (MR) brain scans after CI with a removable magnet. Methods Three criteria (diagnostic usefulness, image quality, artifacts) were assessed at 1.5T and 3T in five cadaver heads with CI. The brain magnetic resonance scans were performed with and without the magnet in situ. The criteria were analyzed by two blinded neuroradiologists, with focus on image distortion and limitation of the diagnostic value of the acquired MR images. Results MR images with the magnet in situ were all compromised by artifacts caused by the CI. After removal of the magnet, MR scans showed an unequivocal artifact reduction with significant improvement of the image quality and diagnostic usefulness, both at 1.5T and 3T. Visibility of the brain stem, cerebellopontine angle, and parieto-occipital lobe ipsilateral to the CI increased significantly after magnet removal. Conclusions The results indicate the possible advantages for 1.5T and 3T MR scanning of the brain in CI carriers with removable magnets. Our findings support use of CIs with removable magnets, especially in patients with chronic intracranial pathologies. PMID:26200775

Significant Artifact Reduction at 1.5T and 3T MRI by the Use of a Cochlear Implant with Removable Magnet: An Experimental Human Cadaver Study.

PubMed

Wagner, Franca; Wimmer, Wilhelm; Leidolt, Lars; Vischer, Mattheus; Weder, Stefan; Wiest, Roland; Mantokoudis, Georgios; Caversaccio, Marco D

2015-01-01

Cochlear implants (CIs) are standard treatment for postlingually deafened individuals and prelingually deafened children. This human cadaver study evaluated diagnostic usefulness, image quality and artifacts in 1.5T and 3T magnetic resonance (MR) brain scans after CI with a removable magnet. Three criteria (diagnostic usefulness, image quality, artifacts) were assessed at 1.5T and 3T in five cadaver heads with CI. The brain magnetic resonance scans were performed with and without the magnet in situ. The criteria were analyzed by two blinded neuroradiologists, with focus on image distortion and limitation of the diagnostic value of the acquired MR images. MR images with the magnet in situ were all compromised by artifacts caused by the CI. After removal of the magnet, MR scans showed an unequivocal artifact reduction with significant improvement of the image quality and diagnostic usefulness, both at 1.5T and 3T. Visibility of the brain stem, cerebellopontine angle, and parieto-occipital lobe ipsilateral to the CI increased significantly after magnet removal. The results indicate the possible advantages for 1.5T and 3T MR scanning of the brain in CI carriers with removable magnets. Our findings support use of CIs with removable magnets, especially in patients with chronic intracranial pathologies.

Heat Transfer Affected by Transverse Magnetic Field using 3D Modeling of Arc Plasma

NASA Astrophysics Data System (ADS)

Maeda, Yoshifumi; Tanaka, Tatsuro; Yamamoto, Shinji; Iwao, Toru

2016-10-01

Gas shielded metal arc welding is used to join the various metal because this is the high quality joining technology. Thus, this welding is used for a welding of large buildings such as bridges and LNG tanks. However, the welding defect caused by the heat transfer decrement may occur with increasing the wind velocity. This is because that the convection loss increases because the arc deflects to leeward side with increasing the wind velocity. In order to prevent from the arc deflection, it is used that the transverse magnetic field is applied to the arc. However, the arc deflection occurs with increasing the transverse magnetic field excessively. The energy balance of the arc is changed with increasing the convection loss caused by the arc deflection, and the heat transfer to the anode decreases. Therefore, the analysis including the arc and anode is necessary to elucidate the heat transfer to the anode. In this paper, the heat transfer affected by the transverse magnetic field using 3D modeling of the arc plasma is elucidated. The heat transfer to the anode is calculated by using the EMTF(electromagnetic thermal fluid) simulation with increasing the transverse magnetic field. As a result, the heat transfer decreased with increasing the transverse magnetic field.

Extending brain-training to the affective domain: increasing cognitive and affective executive control through emotional working memory training.

PubMed

Schweizer, Susanne; Hampshire, Adam; Dalgleish, Tim

2011-01-01

So-called 'brain-training' programs are a huge commercial success. However, empirical evidence regarding their effectiveness and generalizability remains equivocal. This study investigated whether brain-training (working memory [WM] training) improves cognitive functions beyond the training task (transfer effects), especially regarding the control of emotional material since it constitutes much of the information we process daily. Forty-five participants received WM training using either emotional or neutral material, or an undemanding control task. WM training, regardless of training material, led to transfer gains on another WM task and in fluid intelligence. However, only brain-training with emotional material yielded transferable gains to improved control over affective information on an emotional Stroop task. The data support the reality of transferable benefits of demanding WM training and suggest that transferable gains across to affective contexts require training with material congruent to those contexts. These findings constitute preliminary evidence that intensive cognitively demanding brain-training can improve not only our abstract problem-solving capacity, but also ameliorate cognitive control processes (e.g. decision-making) in our daily emotive environments.

Inter-Slice Blood Flow and Magnetization Transfer Effects as A New Simultaneous Imaging Strategy.

PubMed

Han, Paul Kyu; Barker, Jeffrey W; Kim, Ki Hwan; Choi, Seung Hong; Bae, Kyongtae Ty; Park, Sung-Hong

2015-01-01

The recent blood flow and magnetization transfer (MT) technique termed alternate ascending/descending directional navigation (ALADDIN) achieves the contrast using interslice blood flow and MT effects with no separate preparation RF pulse, thereby potentially overcoming limitations of conventional methods. In this study, we examined the signal characteristics of ALADDIN as a simultaneous blood flow and MT imaging strategy, by comparing it with pseudo-continuous ASL (pCASL) and conventional MT asymmetry (MTA) methods, all of which had the same bSSFP readout. Bloch-equation simulations and experiments showed ALADDIN perfusion signals increased with flip angle, whereas MTA signals peaked at flip angle around 45°-60°. ALADDIN provided signals comparable to those of pCASL and conventional MTA methods emulating the first, second, and third prior slices of ALADDIN under the same scan conditions, suggesting ALADDIN signals to be superposition of signals from multiple labeling planes. The quantitative cerebral blood flow signals from a modified continuous ASL model overestimated the perfusion signals compared to those measured with a pulsed ASL method. Simultaneous mapping of blood flow, MTA, and MT ratio in the whole brain is feasible with ALADDIN within a clinically reasonable time, which can potentially help diagnosis of various diseases.

[Magnetic Resonance Imaging Conversion Predictors of Clinically Isolated Syndrome to Multiple Sclerosis].

PubMed

Peixoto, Sara; Abreu, Pedro

2016-11-01

Clinically isolated syndrome may be the first manifestation of multiple sclerosis, a chronic demyelinating disease of the central nervous system, and it is defined by a single clinical episode suggestive of demyelination. However, patients with this syndrome, even with long term follow up, may not develop new symptoms or demyelinating lesions that fulfils multiple sclerosis diagnostic criteria. We reviewed, in clinically isolated syndrome, what are the best magnetic resonance imaging findings that may predict its conversion to multiple sclerosis. A search was made in the PubMed database for papers published between January 2010 and June 2015 using the following terms: 'clinically isolated syndrome', 'cis', 'multiple sclerosis', 'magnetic resonance imaging', 'magnetic resonance' and 'mri'. In this review, the following conventional magnetic resonance imaging abnormalities found in literature were included: lesion load, lesion location, Barkhof's criteria and brain atrophy related features. The non conventional magnetic resonance imaging techniques studied were double inversion recovery, magnetization transfer imaging, spectroscopy and diffusion tensor imaging. The number and location of demyelinating lesions have a clear role in predicting clinically isolated syndrome conversion to multiple sclerosis. On the other hand, more data are needed to confirm the ability to predict this disease development of non conventional techniques and remaining neuroimaging abnormalities. In forthcoming years, in addition to the established predictive value of the above mentioned neuroimaging abnormalities, different clinically isolated syndrome neuroradiological findings may be considered in multiple sclerosis diagnostic criteria and/or change its treatment recommendations.

Brain lesions in septic shock: a magnetic resonance imaging study.

PubMed

Sharshar, Tarek; Carlier, Robert; Bernard, Francis; Guidoux, Céline; Brouland, Jean-Philippe; Nardi, Olivier; de la Grandmaison, Geoffroy Lorin; Aboab, Jérôme; Gray, Françoise; Menon, David; Annane, Djillali

2007-05-01

Understanding of sepsis-induced brain dysfunction remains poor, and relies mainly on data from animals or post-mortem studies in patients. The current study provided findings from magnetic resonance imaging of the brain in septic shock. Nine patients with septic shock and brain dysfunction [7 women, median age 63 years (interquartile range 61-79 years), SAPS II: 48 (44-56), SOFA: 8 (6-10)] underwent brain magnetic resonance imaging including gradient echo T1-weighted, fluid-attenuated inversion recovery (FLAIR), T2-weighted and diffusion isotropic images, and mapping of apparent diffusion coefficient. Brain imaging was normal in two patients, showed multiple ischaemic strokes in two patients, and in the remaining patients showed white matter lesions at the level of the centrum semiovale, predominating around Virchow-Robin spaces, ranging from small multiple areas to diffuse lesions, and characterised by hyperintensity on FLAIR images. The main lesions were also characterised by reduced signal on diffusion isotropic images and increased apparent diffusion coefficient. The lesions of the white matter worsened with increasing duration of shock and were correlated with Glasgow Outcome Score. This preliminary study showed that sepsis-induced brain lesions can be documented by magnetic resonance imaging. These lesions predominated in the white matter, suggesting increased blood-brain barrier permeability, and were associated with poor outcome.

An investigation into the induced electric fields from transcranial magnetic stimulation

NASA Astrophysics Data System (ADS)

Hadimani, Ravi; Lee, Erik; Duffy, Walter; Waris, Mohammed; Siddiqui, Waquar; Islam, Faisal; Rajamani, Mahesh; Nathan, Ryan; Jiles, David; David C Jiles Team; Walter Duffy Collaboration

Transcranial magnetic stimulation (TMS) is a promising tool for noninvasive brain stimulation that has been approved by the FDA for the treatment of major depressive disorder. To stimulate the brain, TMS uses large, transient pulses of magnetic field to induce an electric field in the head. This transient magnetic field is large enough to cause the depolarization of cortical neurons and initiate a synaptic signal transmission. For this study, 50 unique head models were created from MRI images. Previous simulation studies have primarily used a single head model, and thus give a limited image of the induced electric field from TMS. This study uses finite element analysis simulations on 50 unique, heterogeneous head models to better investigate the relationship between TMS and the electric field induced in brain tissues. Results showed a significant variation in the strength of the induced electric field in the brain, which can be reasonably predicted by the distance from the TMS coil to the stimulated brain. Further, it was seen that some models had high electric field intensities in over five times as much brain volume as other models.

Dynamic Multi-Coil Shimming of the Human Brain at 7 Tesla

PubMed Central

Juchem, Christoph; Nixon, Terence W.; McIntyre, Scott; Boer, Vincent O.; Rothman, Douglas L.; de Graaf, Robin A.

2011-01-01

High quality magnetic field homogenization of the human brain (i.e. shimming) for MR imaging and spectroscopy is a demanding task. The susceptibility differences between air and tissue are a longstanding problem as they induce complex field distortions in the prefrontal cortex and the temporal lobes. To date, the theoretical gains of high field MR have only been realized partially in the human brain due to limited magnetic field homogeneity. A novel shimming technique for the human brain is presented that is based on the combination of non-orthogonal basis fields from 48 individual, circular coils. Custom-built amplifier electronics enabled the dynamic application of the multi-coil shim fields in a slice-specific fashion. Dynamic multi-coil (DMC) shimming is shown to eliminate most of the magnetic field inhomogeneity apparent in the human brain at 7 Tesla and provided improved performance compared to state-of-the-art dynamic shim updating with zero through third order spherical harmonic functions. The novel technique paves the way for high field MR applications of the human brain for which excellent magnetic field homogeneity is a prerequisite. PMID:21824794

Chemical-exchange-saturation-transfer magnetic resonance imaging to map gamma-aminobutyric acid, glutamate, myoinositol, glycine, and asparagine: Phantom experiments

NASA Astrophysics Data System (ADS)

Oh, Jang-Hoon; Kim, Hyug-Gi; Woo, Dong-Cheol; Jeong, Ha-Kyu; Lee, Soo Yeol; Jahng, Geon-Ho

2017-03-01

The physical and technical development of chemical-exchange-saturation-transfer (CEST) magnetic resonance imaging (MRI) using clinical 3 T MRI was explored with the goal of mapping asparagine (Asn), gamma-aminobutyric acid (GABA), glutamate (Glu), glycine (Gly), and myoinositol (MI), which exist in the brain. Phantoms with nine different conditions at concentrations of 10, 30, and 50 mM and pH values of 5.6, 6.2, and 7.4 were prepared for the five target molecules to evaluate the dependence of the CEST effect in the concentration, the pH, and the amplitude of the applied radiofrequency field B1. CEST images in the offset frequency range of ±6 parts per million (ppm) were acquired using a pulsed radio-frequency saturation scheme with a clinical 3 T MRI system. A voxel-based main magnetic field B0 inhomogeneity correction, where B0 is the center frequency offset at zero ppm, was performed by using the spline interpolation method to fit the full Z-spectrum to estimate the center frequency. A voxel-based CEST asymmetry map was calculated to evaluate amide (-NH), amine (-NH2), and hydroxyl (-OH) groups for the five target molecules. The CEST effect for Glu, GABA, and Gly clearly increased with increasing concentrations. The CEST effect for MI was minimal, with no noticeable differences at different concentrations. The CEST effect for Glu and Gly increased with increasing acidity. The highest CEST asymmetry for GABA was observed at pH 6.2. The CEST effect for Glu, GABA, and Gly increased with increasing B1 amplitude. For all target molecules, the CEST effect for the human 3 T MRI system increased with increasing concentration and B1 amplitude, but varied with pH, depending on the characteristics of the molecules. The CEST effect for MI may be not suitable with clinical MRI systems. These results show that CEST imaging in the brain with the amine protons by using 3 T MRI is possible for several neuronal diseases.

A Wireless Intracranial Brain Deformation Sensing System for Blast-Induced Traumatic Brain Injury

PubMed Central

Song, S.; Race, N. S.; Kim, A.; Zhang, T.; Shi, R.; Ziaie, B.

2015-01-01

Blast-induced traumatic brain injury (bTBI) has been linked to a multitude of delayed-onset neurodegenerative and neuropsychiatric disorders, but complete understanding of their pathogenesis remains elusive. To develop mechanistic relationships between bTBI and post-blast neurological sequelae, it is imperative to characterize the initiating traumatic mechanical events leading to eventual alterations of cell, tissue, and organ structure and function. This paper presents a wireless sensing system capable of monitoring the intracranial brain deformation in real-time during the event of a bTBI. The system consists of an implantable soft magnet and an external head-mounted magnetic sensor that is able to measure the field in three dimensions. The change in the relative position of the soft magnet WITH respect to the external sensor as the result of the blast wave induces changes in the magnetic field. The magnetic field data in turn is used to extract the temporal and spatial motion of the brain under the blast wave in real-time. The system has temporal and spatial resolutions of 5 μs and 10 μm. Following the characterization and validation of the sensor system, we measured brain deformations in a live rodent during a bTBI. PMID:26586273

Connectomic Insights into Topologically Centralized Network Edges and Relevant Motifs in the Human Brain

PubMed Central

Xia, Mingrui; Lin, Qixiang; Bi, Yanchao; He, Yong

2016-01-01

White matter (WM) tracts serve as important material substrates for information transfer across brain regions. However, the topological roles of WM tracts in global brain communications and their underlying microstructural basis remain poorly understood. Here, we employed diffusion magnetic resonance imaging and graph-theoretical approaches to identify the pivotal WM connections in human whole-brain networks and further investigated their wiring substrates (including WM microstructural organization and physical consumption) and topological contributions to the brain's network backbone. We found that the pivotal WM connections with highly topological-edge centrality were primarily distributed in several long-range cortico-cortical connections (including the corpus callosum, cingulum and inferior fronto-occipital fasciculus) and some projection tracts linking subcortical regions. These pivotal WM connections exhibited high levels of microstructural organization indicated by diffusion measures (the fractional anisotropy, the mean diffusivity and the axial diffusivity) and greater physical consumption indicated by streamline lengths, and contributed significantly to the brain's hubs and the rich-club structure. Network motif analysis further revealed their heavy participations in the organization of communication blocks, especially in routes involving inter-hemispheric heterotopic and extremely remote intra-hemispheric systems. Computational simulation models indicated the sharp decrease of global network integrity when attacking these highly centralized edges. Together, our results demonstrated high building-cost consumption and substantial communication capacity contributions for pivotal WM connections, which deepens our understanding of the topological mechanisms that govern the organization of human connectomes. PMID:27148015

Connectomic Insights into Topologically Centralized Network Edges and Relevant Motifs in the Human Brain.

PubMed

Xia, Mingrui; Lin, Qixiang; Bi, Yanchao; He, Yong

2016-01-01

White matter (WM) tracts serve as important material substrates for information transfer across brain regions. However, the topological roles of WM tracts in global brain communications and their underlying microstructural basis remain poorly understood. Here, we employed diffusion magnetic resonance imaging and graph-theoretical approaches to identify the pivotal WM connections in human whole-brain networks and further investigated their wiring substrates (including WM microstructural organization and physical consumption) and topological contributions to the brain's network backbone. We found that the pivotal WM connections with highly topological-edge centrality were primarily distributed in several long-range cortico-cortical connections (including the corpus callosum, cingulum and inferior fronto-occipital fasciculus) and some projection tracts linking subcortical regions. These pivotal WM connections exhibited high levels of microstructural organization indicated by diffusion measures (the fractional anisotropy, the mean diffusivity and the axial diffusivity) and greater physical consumption indicated by streamline lengths, and contributed significantly to the brain's hubs and the rich-club structure. Network motif analysis further revealed their heavy participations in the organization of communication blocks, especially in routes involving inter-hemispheric heterotopic and extremely remote intra-hemispheric systems. Computational simulation models indicated the sharp decrease of global network integrity when attacking these highly centralized edges. Together, our results demonstrated high building-cost consumption and substantial communication capacity contributions for pivotal WM connections, which deepens our understanding of the topological mechanisms that govern the organization of human connectomes.

SU-E-T-549: Modeling Relative Biological Effectiveness of Protons for Radiation Induced Brain Necrosis

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

Mirkovic, D; Peeler, C; Grosshans, D

Purpose: To develop a model of the relative biological effectiveness (RBE) of protons as a function of dose and linear energy transfer (LET) for induction of brain necrosis using clinical data. Methods: In this study, treatment planning information was exported from a clinical treatment planning system (TPS) and used to construct a detailed Monte Carlo model of the patient and the beam delivery system. The physical proton dose and LET were computed in each voxel of the patient volume using Monte Carlo particle transport. A follow-up magnetic resonance imaging (MRI) study registered to the treatment planning CT was used tomore » determine the region of the necrosis in the brain volume. Both, the whole brain and the necrosis volumes were segmented from the computed tomography (CT) dataset using the contours drawn by a physician and the corresponding voxels were binned with respect to dose and LET. The brain necrosis probability was computed as a function of dose and LET by dividing the total volume of all necrosis voxels with a given dose and LET with the corresponding total brain volume resulting in a set of NTCP-like curves (probability as a function of dose parameterized by LET). Results: The resulting model shows dependence on both dose and LET indicating the weakness of the constant RBE model for describing the brain toxicity. To the best of our knowledge the constant RBE model is currently used in all clinical applications which may Result in increased rate of brain toxicities in patients treated with protons. Conclusion: Further studies are needed to develop more accurate brain toxicity models for patients treated with protons and other heavy ions.« less

Magnetic resonance spectroscopy of the human brain

NASA Astrophysics Data System (ADS)

Strózik-Kotlorz, D.

2014-01-01

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

Screening and Monitoring Response to Treatment Using Subsecond Molecular Imaging and Hyperpolarized Contrast Agents

DTIC Science & Technology

2013-05-01

Magnetization transfer MRI in multiple sclerosis . J Neuroimaging. 2007;17 Suppl 1:S22–S26. 82. Filippi M, Rocca MA. Magnetization transfer magnetic resonance... multiple sclerosis . Neuroimaging Clin N Am. 2009;19(1):27–36. 84. Lundbom N. Determination of magnetization transfer contrast in tissue: an MR... multiple RF coils intended for optimal direct and indirect detection of hyperpolarized contrast agents in vivo. 4.b. Y1Q3-Y1Q4. Low field MRI: pre

ROLE FOR THE MAGNETIC FIELD IN THE RADIATION-INDUCED EFFLUX OF CALCIUM IONS FROM BRAIN TISSUE 'IN VITRO'

EPA Science Inventory

Two independent laboratories have demonstrated that specific frequencies of electromagnetic radiation can cause a change in the efflux of calcium ions from brain tissue in vitro. Under a static magnetic field intensity of 38 microTesla (microT) due to the earth's magnetic field, ...

Evidence for Coherent Transfer of para-Hydrogen-Induced Polarization at Low Magnetic Fields.

PubMed

Kiryutin, Alexey S; Yurkovskaya, Alexandra V; Kaptein, Robert; Vieth, Hans-Martin; Ivanov, Konstantin L

2013-08-01

We have investigated the mechanism of para-hydrogen-induced polarization (PHIP) transfer from the original strongly aligned protons to other nuclei at low external magnetic fields. Although it is known that PHIP is efficiently transferred at low fields, the nature of the transfer mechanism, that is, coherent spin mixing or cross-relaxation, is not well established. Polarization transfer kinetics for individual protons of styrene was, for the first time, measured and modeled theoretically. Pronounced oscillations were observed indicating a coherent transfer mechanism. Spin coherences were excited by passing through an avoided level crossing of the nuclear spin energy levels. Transfer at avoided level crossings is selective with respect to spin order. Our work provides evidence that the coherent PHIP transfer mechanism is dominant at low magnetic fields.

White matter hyperintensities and normal-appearing white matter integrity in the aging brain.

PubMed

Maniega, Susana Muñoz; Valdés Hernández, Maria C; Clayden, Jonathan D; Royle, Natalie A; Murray, Catherine; Morris, Zoe; Aribisala, Benjamin S; Gow, Alan J; Starr, John M; Bastin, Mark E; Deary, Ian J; Wardlaw, Joanna M

2015-02-01

White matter hyperintensities (WMH) of presumed vascular origin are a common finding in brain magnetic resonance imaging of older individuals and contribute to cognitive and functional decline. It is unknown how WMH form, although white matter degeneration is characterized pathologically by demyelination, axonal loss, and rarefaction, often attributed to ischemia. Changes within normal-appearing white matter (NAWM) in subjects with WMH have also been reported but have not yet been fully characterized. Here, we describe the in vivo imaging signatures of both NAWM and WMH in a large group of community-dwelling older people of similar age using biomarkers derived from magnetic resonance imaging that collectively reflect white matter integrity, myelination, and brain water content. Fractional anisotropy (FA) and magnetization transfer ratio (MTR) were significantly lower, whereas mean diffusivity (MD) and longitudinal relaxation time (T1) were significantly higher, in WMH than NAWM (p < 0.0001), with MD providing the largest difference between NAWM and WMH. Receiver operating characteristic analysis on each biomarker showed that MD differentiated best between NAWM and WMH, identifying 94.6% of the lesions using a threshold of 0.747 × 10(-9) m(2)s(-1) (area under curve, 0.982; 95% CI, 0.975-0.989). Furthermore, the level of deterioration of NAWM was strongly associated with the severity of WMH, with MD and T1 increasing and FA and MTR decreasing in NAWM with increasing WMH score, a relationship that was sustained regardless of distance from the WMH. These multimodal imaging data indicate that WMH have reduced structural integrity compared with surrounding NAWM, and MD provides the best discriminator between the 2 tissue classes even within the mild range of WMH severity, whereas FA, MTR, and T1 only start reflecting significant changes in tissue microstructure as WMH become more severe. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

Non-caloric sweetener provides magnetic resonance imaging contrast for cancer detection.

PubMed

Bagga, Puneet; Haris, Mohammad; D'Aquilla, Kevin; Wilson, Neil E; Marincola, Francesco M; Schnall, Mitchell D; Hariharan, Hari; Reddy, Ravinder

2017-05-30

Image contrast enhanced by exogenous contrast agents plays a crucial role in the early detection, characterization, and determination of the precise location of cancers. Here, we investigate the feasibility of using a non-nutritive sweetener, sucralose (commercial name, Splenda), as magnetic resonance imaging (MRI) contrast agent for cancer studies. High-resolution nuclear-magnetic-resonance spectroscopy and MR studies on sucralose solution phantom were performed to detect the chemical exchange saturation transfer (CEST) property of sucralose hydroxyl protons with bulk water (sucCEST). For the animal experiments, female Fisher rats (F344/NCR) were used to generate 9L-gliosarcoma model. MRI with CEST experiments were performed on anesthetized rats at 9.4 T MR scanner. Following the baseline CEST scans, sucralose solution was intravenously administered in control and tumor bearing rats. CEST acquisitions were continued during and following the administration of sucralose. Following the sucCEST, Gadolinium-diethylenetriamine pentaacetic acid was injected to perform Gd-enhanced imaging for visualizing the tumor. The sucCEST contrast in vitro was found to correlate positively with the sucralose concentration and negatively with the pH, indicating the potential of this technique in cancer imaging. In a control animal, the CEST contrast from the brain was found to be unaffected following the administration of sucralose, demonstrating its blood-brain barrier impermeability. In a 9L glioma model, enhanced localized sucCEST contrast in the tumor region was detected while the unaffected brain region showed unaltered CEST effect implying the specificity of sucralose toward the tumorous tissue. The CEST asymmetry plots acquired from the tumor region before and after the sucralose infusion showed elevation of asymmetry at 1 ppm, pointing towards the role of sucralose in increased contrast. We show the feasibility of using sucralose and sucCEST in study of preclinical models of cancer. This study paves the way for the potential development of sucralose and other sucrose derivatives as contrast agents for clinical MRI applications.

MRI Evaluation and Safety in the Developing Brain

PubMed Central

Tocchio, Shannon; Kline-Fath, Beth; Kanal, Emanuel; Schmithorst, Vincent J.; Panigrahy, Ashok

2015-01-01

Magnetic resonance imaging (MRI) evaluation of the developing brain has dramatically increased over the last decade. Faster acquisitions and the development of advanced MRI sequences such as magnetic resonance spectroscopy (MRS), diffusion tensor imaging (DTI), perfusion imaging, functional MR imaging (fMRI), and susceptibility weighted imaging (SWI), as well as the use of higher magnetic field strengths has made MRI an invaluable tool for detailed evaluation of the developing brain. This article will provide an overview of the use and challenges associated with 1.5T and 3T static magnetic fields for evaluation of the developing brain. This review will also summarize the advantages, clinical challenges and safety concerns specifically related to MRI in the fetus and newborn, including the implications of increased magnetic field strength, logistics related to transporting and monitoring of neonates during scanning, sedation considerations and a discussion of current technologies such as MRI-conditional neonatal incubators and dedicated small-foot print neonatal intensive care unit (NICU) scanners. PMID:25743582

MRI evaluation and safety in the developing brain.

PubMed

Tocchio, Shannon; Kline-Fath, Beth; Kanal, Emanuel; Schmithorst, Vincent J; Panigrahy, Ashok

2015-03-01

Magnetic resonance imaging (MRI) evaluation of the developing brain has dramatically increased over the last decade. Faster acquisitions and the development of advanced MRI sequences, such as magnetic resonance spectroscopy (MRS), diffusion tensor imaging (DTI), perfusion imaging, functional MR imaging (fMRI), and susceptibility-weighted imaging (SWI), as well as the use of higher magnetic field strengths has made MRI an invaluable tool for detailed evaluation of the developing brain. This article will provide an overview of the use and challenges associated with 1.5-T and 3-T static magnetic fields for evaluation of the developing brain. This review will also summarize the advantages, clinical challenges, and safety concerns specifically related to MRI in the fetus and newborn, including the implications of increased magnetic field strength, logistics related to transporting and monitoring of neonates during scanning, and sedation considerations, and a discussion of current technologies such as MRI conditional neonatal incubators and dedicated small-foot print neonatal intensive care unit (NICU) scanners. Copyright © 2015 Elsevier Inc. All rights reserved.

Auditory evoked field measurement using magneto-impedance sensors

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

Wang, K., E-mail: o-kabou@echo.nuee.nagoya-u.ac.jp; Tajima, S.; Song, D.

The magnetic field of the human brain is extremely weak, and it is mostly measured and monitored in the magnetoencephalography method using superconducting quantum interference devices. In this study, in order to measure the weak magnetic field of the brain, we constructed a Magneto-Impedance sensor (MI sensor) system that can cancel out the background noise without any magnetic shield. Based on our previous studies of brain wave measurements, we used two MI sensors in this system for monitoring both cerebral hemispheres. In this study, we recorded and compared the auditory evoked field signals of the subject, including the N100 (ormore » N1) and the P300 (or P3) brain waves. The results suggest that the MI sensor can be applied to brain activity measurement.« less

N-Acetylaspartate reductions in brain injury: impact on post-injury neuroenergetics, lipid synthesis, and protein acetylation

PubMed Central

Moffett, John R.; Arun, Peethambaran; Ariyannur, Prasanth S.; Namboodiri, Aryan M. A.

2013-01-01

N-Acetylaspartate (NAA) is employed as a non-invasive marker for neuronal health using proton magnetic resonance spectroscopy (MRS). This utility is afforded by the fact that NAA is one of the most concentrated brain metabolites and that it produces the largest peak in MRS scans of the healthy human brain. NAA levels in the brain are reduced proportionately to the degree of tissue damage after traumatic brain injury (TBI) and the reductions parallel the reductions in ATP levels. Because NAA is the most concentrated acetylated metabolite in the brain, we have hypothesized that NAA acts in part as an extensive reservoir of acetate for acetyl coenzyme A synthesis. Therefore, the loss of NAA after TBI impairs acetyl coenzyme A dependent functions including energy derivation, lipid synthesis, and protein acetylation reactions in distinct ways in different cell populations. The enzymes involved in synthesizing and metabolizing NAA are predominantly expressed in neurons and oligodendrocytes, respectively, and therefore some proportion of NAA must be transferred between cell types before the acetate can be liberated, converted to acetyl coenzyme A and utilized. Studies have indicated that glucose metabolism in neurons is reduced, but that acetate metabolism in astrocytes is increased following TBI, possibly reflecting an increased role for non-glucose energy sources in response to injury. NAA can provide additional acetate for intercellular metabolite trafficking to maintain acetyl CoA levels after injury. Here we explore changes in NAA, acetate, and acetyl coenzyme A metabolism in response to brain injury. PMID:24421768

Cortical brain connectivity evaluated by graph theory in dementia: a correlation study between functional and structural data.

PubMed

Vecchio, Fabrizio; Miraglia, Francesca; Curcio, Giuseppe; Altavilla, Riccardo; Scrascia, Federica; Giambattistelli, Federica; Quattrocchi, Carlo Cosimo; Bramanti, Placido; Vernieri, Fabrizio; Rossini, Paolo Maria

2015-01-01

A relatively new approach to brain function in neuroscience is the "functional connectivity", namely the synchrony in time of activity in anatomically-distinct but functionally-collaborating brain regions. On the other hand, diffusion tensor imaging (DTI) is a recently developed magnetic resonance imaging (MRI)-based technique with the capability to detect brain structural connection with fractional anisotropy (FA) identification. FA decrease has been observed in the corpus callosum of subjects with Alzheimer's disease (AD) and mild cognitive impairment (MCI, an AD prodromal stage). Corpus callosum splenium DTI abnormalities are thought to be associated with functional disconnections among cortical areas. This study aimed to investigate possible correlations between structural damage, measured by MRI-DTI, and functional abnormalities of brain integration, measured by characteristic path length detected in resting state EEG source activity (40 participants: 9 healthy controls, 10 MCI, 10 mild AD, 11 moderate AD). For each subject, undirected and weighted brain network was built to evaluate graph core measures. eLORETA lagged linear connectivity values were used as weight of the edges of the network. Results showed that callosal FA reduction is associated to a loss of brain interhemispheric functional connectivity characterized by increased delta and decreased alpha path length. These findings suggest that "global" (average network shortest path length representing an index of how efficient is the information transfer between two parts of the network) functional measure can reflect the reduction of fiber connecting the two hemispheres as revealed by DTI analysis and also anticipate in time this structural loss.

Amide proton transfer imaging of adult diffuse gliomas: correlation with histopathological grades.

PubMed

Togao, Osamu; Yoshiura, Takashi; Keupp, Jochen; Hiwatashi, Akio; Yamashita, Koji; Kikuchi, Kazufumi; Suzuki, Yuriko; Suzuki, Satoshi O; Iwaki, Toru; Hata, Nobuhiro; Mizoguchi, Masahiro; Yoshimoto, Koji; Sagiyama, Koji; Takahashi, Masaya; Honda, Hiroshi

2014-03-01

Amide proton transfer (APT) imaging is a novel molecular MRI technique to detect endogenous mobile proteins and peptides through chemical exchange saturation transfer. We prospectively assessed the usefulness of APT imaging in predicting the histological grade of adult diffuse gliomas. Thirty-six consecutive patients with histopathologically proven diffuse glioma (48.1 ± 14.7 y old, 16 males and 20 females) were included in the study. APT MRI was conducted on a 3T clinical scanner and was obtained with 2 s saturation at 25 saturation frequency offsets ω = -6 to +6 ppm (step 0.5 ppm). δB0 maps were acquired separately for a point-by-point δB0 correction. APT signal intensity (SI) was defined as magnetization transfer asymmetry at 3.5 ppm: magnetization transfer ratio (MTR)asym = (S[-3.5 ppm] - S[+3.5 ppm])/S0. Regions of interest were carefully placed by 2 neuroradiologists in solid parts within brain tumors. The APT SI was compared with World Health Organization grade, Ki-67 labeling index (LI), and cell density. The mean APT SI values were 2.1 ± 0.4% in grade II gliomas (n = 8), 3.2 ± 0.9% in grade III gliomas (n = 10), and 4.1 ± 1.0% in grade IV gliomas (n = 18). Significant differences in APT intensity were observed between grades II and III (P < .05) and grades III and IV (P < .05), as well as between grades II and IV (P < .001). There were positive correlations between APT SI and Ki-67 LI (P = .01, R = 0.43) and between APT SI and cell density (P < .05, R = 0.38). The gliomas with microscopic necrosis showed higher APT SI than those without necrosis (P < .001). APT imaging can predict the histopathological grades of adult diffuse gliomas.

Language Development and Brain Magnetic Resonance Imaging Characteristics in Preschool Children with Cerebral Palsy

ERIC Educational Resources Information Center

Choi, Ja Young; Choi, Yoon Seong; Park, Eun Sook

2017-01-01

Purpose: The purpose of this study was to investigate characteristics of language development in relation to brain magnetic resonance imaging (MRI) characteristics and the other contributing factors to language development in children with cerebral palsy (CP). Method: The study included 172 children with CP who underwent brain MRI and language…

Transfer Rate Edited experiment for the selective detection of Chemical Exchange via Saturation Transfer (TRE-CEST).

PubMed

Friedman, Joshua I; Xia, Ding; Regatte, Ravinder R; Jerschow, Alexej

2015-07-01

Chemical Exchange Saturation Transfer (CEST) magnetic resonance experiments have become valuable tools in magnetic resonance for the detection of low concentration solutes with far greater sensitivity than direct detection methods. Accurate measures of rates of chemical exchange provided by CEST are of particular interest to biomedical imaging communities where variations in chemical exchange can be related to subtle variations in biomarker concentration, temperature and pH within tissues using MRI. Despite their name, however, traditional CEST methods are not truly selective for chemical exchange and instead detect all forms of magnetization transfer including through-space NOE. This ambiguity crowds CEST spectra and greatly complicates subsequent data analysis. We have developed a Transfer Rate Edited CEST experiment (TRE-CEST) that uses two different types of solute labeling in order to selectively amplify signals of rapidly exchanging proton species while simultaneously suppressing 'slower' NOE-dominated magnetization transfer processes. This approach is demonstrated in the context of both NMR and MRI, where it is used to detect the labile amide protons of proteins undergoing chemical exchange (at rates⩾30s(-1)) while simultaneously eliminating signals originating from slower (∼5s(-1)) NOE-mediated magnetization transfer processes. TRE-CEST greatly expands the utility of CEST experiments in complex systems, and in-vivo, in particular, where it is expected to improve the quantification of chemical exchange and magnetization transfer rates while enabling new forms of imaging contrast. Copyright © 2015 Elsevier Inc. All rights reserved.

Transfer Rate Edited experiment for the selective detection of Chemical Exchange via Saturation Transfer (TRE-CEST)

NASA Astrophysics Data System (ADS)

Friedman, Joshua I.; Xia, Ding; Regatte, Ravinder R.; Jerschow, Alexej

2015-07-01

Chemical Exchange Saturation Transfer (CEST) magnetic resonance experiments have become valuable tools in magnetic resonance for the detection of low concentration solutes with far greater sensitivity than direct detection methods. Accurate measures of rates of chemical exchange provided by CEST are of particular interest to biomedical imaging communities where variations in chemical exchange can be related to subtle variations in biomarker concentration, temperature and pH within tissues using MRI. Despite their name, however, traditional CEST methods are not truly selective for chemical exchange and instead detect all forms of magnetization transfer including through-space NOE. This ambiguity crowds CEST spectra and greatly complicates subsequent data analysis. We have developed a Transfer Rate Edited CEST experiment (TRE-CEST) that uses two different types of solute labeling in order to selectively amplify signals of rapidly exchanging proton species while simultaneously suppressing 'slower' NOE-dominated magnetization transfer processes. This approach is demonstrated in the context of both NMR and MRI, where it is used to detect the labile amide protons of proteins undergoing chemical exchange (at rates ⩾ 30 s-1) while simultaneously eliminating signals originating from slower (∼5 s-1) NOE-mediated magnetization transfer processes. TRE-CEST greatly expands the utility of CEST experiments in complex systems, and in-vivo, in particular, where it is expected to improve the quantification of chemical exchange and magnetization transfer rates while enabling new forms of imaging contrast.

Comparison of Coil Designs for Transcranial Magnetic Stimulation on Mice

NASA Astrophysics Data System (ADS)

Rastogi, Priyam; Hadimani, Ravi; Jiles, David

2015-03-01

Transcranial magnetic stimulation (TMS) is a non-invasive treatment for neurological disorders using time varying magnetic field. The electric field generated by the time varying magnetic field is used to depolarize the brain neurons which can lead to measurable effects. TMS provides a surgical free method for the treatment of neurological brain disorders like depression, post-traumatic stress disorder, traumatic brain injury and Parkinson's disease. Before using TMS on human subjects, it is appropriate that its effects are verified on animals such as mice. The magnetic field intensity and stimulated region of the brain can be controlled by the shape, position and current in the coils. There are few reports on the designs of the coils for mice. In this paper, different types of coils are developed and compared using an anatomically realistic mouse model derived from MRI images. Parameters such as focality, depth of the stimulation, electric field strength on the scalp and in the deep brain regions, are taken into account. These parameters will help researchers to determine the most suitable coil design according to their need. This should result in improvements in treatment of specific disorders. Carver Charitable Trust.

Effect of high-frequency repetitive transcranial magnetic stimulation on chronic central pain after mild traumatic brain injury: A pilot study.

PubMed

Choi, Gyu-Sik; Kwak, Sang Gyu; Lee, Han Do; Chang, Min Cheol

2018-02-28

Central pain can occur following traumatic brain injury, leading to poor functional recovery, limitation of activities of daily living, and decreased quality of life. The aim of this study was to determine whether high-frequency (10 Hz) repetitive transcranial magnetic stimulation, applied over the primary motor cortex of the affected hemisphere, can be used to manage chronic central pain after mild traumatic brain injury. Prospective randomized feasibility study. Twelve patients with mild traumatic brain injury and chronic central pain were randomly assigned to transcranial magnetic stimulation (high-frequency stimulation, 10 sessions) or sham groups. Diffuse tensor tractography revealed partially injured spinothalamocortical tracts in all recruited patients. A numerical rating scale (NRS) was used to evaluate pain intensity during pre-treatment and immediately after the 5th transcranial magnetic stimulation session (post1), 10th transcranial magnetic stimulation session (post2), and 1 (post3), 2 (post4), and 4 weeks (post 5) after finishing treatment. Physical and mental health status were evaluated using the Short Form 36 Health Survey (SF-36), including physical and mental component scores (PCS, MCS). The NRS score of the repetitive transcranial magnetic stimulation group was significantly lower than the sham group score at all clinical evaluation time-points during and after transcranial magnetic stimulation sessions. The transcranial magnetic stimulation group's SF-36 PCS score was significantly higher at post2, post3, post4, and post5 compared with the sham group. High-frequency transcranial magnetic stimulation may be used to manage chronic central pain and improve quality of life in patients with mild traumatic brain injury. However, this is a pilot study and further research is needed.

Functional Magnetic Resonance Imaging and Spectroscopic Imaging of the Brain: Application of fMRI and fMRS to Reading Disabilities and Education.

ERIC Educational Resources Information Center

Richards, Todd L.

2001-01-01

This tutorial/review covers functional brain-imaging methods and results used to study language and reading disabilities. Although the emphasis is on magnetic resonance imaging and functional magnetic resonance spectroscopy, other imaging techniques are also discussed including positron emission tomography, electroencephalography,…

Transcranial magnetic stimulation assisted by neuronavigation of magnetic resonance images

NASA Astrophysics Data System (ADS)

Viesca, N. Angeline; Alcauter, S. Sarael; Barrios, A. Fernando; González, O. Jorge J.; Márquez, F. Jorge A.

2012-10-01

Technological advance has improved the way scientists and doctors can learn about the brain and treat different disorders. A non-invasive method used for this is Transcranial Magnetic Stimulation (TMS) based on neuron excitation by electromagnetic induction. Combining this method with functional Magnetic Resonance Images (fMRI), it is intended to improve the localization technique of cortical brain structures by designing an extracranial localization system, based on Alcauter et al. work.

Quantitative susceptibility mapping (QSM) as a means to measure brain iron? A post mortem validation study

PubMed Central

Langkammer, Christian; Schweser, Ferdinand; Krebs, Nikolaus; Deistung, Andreas; Goessler, Walter; Scheurer, Eva; Sommer, Karsten; Reishofer, Gernot; Yen, Kathrin; Fazekas, Franz; Ropele, Stefan; Reichenbach, Jürgen R.

2012-01-01

Quantitative susceptibility mapping (QSM) is a novel technique which allows determining the bulk magnetic susceptibility distribution of tissue in vivo from gradient echo magnetic resonance phase images. It is commonly assumed that paramagnetic iron is the predominant source of susceptibility variations in gray matter as many studies have reported a reasonable correlation of magnetic susceptibility with brain iron concentrations in vivo. Instead of performing direct comparisons, however, all these studies used the putative iron concentrations reported in the hallmark study by Hallgren and Sourander (1958) for their analysis. Consequently, the extent to which QSM can serve to reliably assess brain iron levels is not yet fully clear. To provide such information we investigated the relation between bulk tissue magnetic susceptibility and brain iron concentration in unfixed (in situ) post mortem brains of 13 subjects using MRI and inductively coupled plasma mass spectrometry. A strong linear correlation between chemically determined iron concentration and bulk magnetic susceptibility was found in gray matter structures (r = 0.84, p < 0.001), whereas the correlation coefficient was much lower in white matter (r = 0.27, p < 0.001). The slope of the overall linear correlation was consistent with theoretical considerations of the magnetism of ferritin supporting that most of the iron in the brain is bound to ferritin proteins. In conclusion, iron is the dominant source of magnetic susceptibility in deep gray matter and can be assessed with QSM. In white matter regions the estimation of iron concentrations by QSM is less accurate and more complex because the counteracting contribution from diamagnetic myelinated neuronal fibers confounds the interpretation. PMID:22634862

Passage of Magnetic Tat-Conjugated Fe3O4@SiO2 Nanoparticles Across In Vitro Blood-Brain Barrier

NASA Astrophysics Data System (ADS)

Zhao, Xueqin; Shang, Ting; Zhang, Xiaodan; Ye, Ting; Wang, Dajin; Rei, Lei

2016-10-01

Delivery of diagnostic or therapeutic agents across the blood-brain barrier (BBB) remains a major challenge of brain disease treatment. Magnetic nanoparticles are actively being developed as drug carriers due to magnetic targeting and subsequently reduced off-target effects. In this paper, we developed a magnetic SiO2@Fe3O4 nanoparticle-based carrier bound to cell-penetrating peptide Tat (SiO2@Fe3O4 -Tat) and studied its fates in accessing BBB. SiO2@Fe3O4-Tat nanoparticles (NPs) exhibited suitable magnetism and good biocompatibility. NPs adding to the apical chamber of in vitro BBB model were found in the U251 glioma cells co-cultured at the bottom of the Transwell, indicating that particles passed through the barrier and taken up by glioma cells. Moreover, the synergistic effects of Tat and magnetic field could promote the efficient cellular internalization and the permeability across the barrier. Besides, functionalization with Tat peptide allowed particles to locate into the nucleus of U251 cells than the non-conjugated NPs. These results suggest that SiO2@Fe3O4-Tat NPs could penetrate the BBB through the transcytosis of brain endothelial cells and magnetically mediated dragging. Therefore, SiO2@Fe3O4-Tat NPs could be exploited as a potential drug delivery system for chemotherapy and gene therapy of brain disease.

Studying the Transfer of Magnetic Helicity in Solar Active Regions with the Connectivity-based Helicity Flux Density Method

NASA Astrophysics Data System (ADS)

Dalmasse, K.; Pariat, É.; Valori, G.; Jing, J.; Démoulin, P.

2018-01-01

In the solar corona, magnetic helicity slowly and continuously accumulates in response to plasma flows tangential to the photosphere and magnetic flux emergence through it. Analyzing this transfer of magnetic helicity is key for identifying its role in the dynamics of active regions (ARs). The connectivity-based helicity flux density method was recently developed for studying the 2D and 3D transfer of magnetic helicity in ARs. The method takes into account the 3D nature of magnetic helicity by explicitly using knowledge of the magnetic field connectivity, which allows it to faithfully track the photospheric flux of magnetic helicity. Because the magnetic field is not measured in the solar corona, modeled 3D solutions obtained from force-free magnetic field extrapolations must be used to derive the magnetic connectivity. Different extrapolation methods can lead to markedly different 3D magnetic field connectivities, thus questioning the reliability of the connectivity-based approach in observational applications. We address these concerns by applying this method to the isolated and internally complex AR 11158 with different magnetic field extrapolation models. We show that the connectivity-based calculations are robust to different extrapolation methods, in particular with regard to identifying regions of opposite magnetic helicity flux. We conclude that the connectivity-based approach can be reliably used in observational analyses and is a promising tool for studying the transfer of magnetic helicity in ARs and relating it to their flaring activity.

Technical and experimental features of Magnetic Resonance Spectroscopy of brain glycogen metabolism.

PubMed

Soares, Ana Francisca; Gruetter, Rolf; Lei, Hongxia

2017-07-15

In the brain, glycogen is a source of glucose not only in emergency situations but also during normal brain activity. Altered brain glycogen metabolism is associated with energetic dysregulation in pathological conditions, such as diabetes or epilepsy. Both in humans and animals, brain glycogen levels have been assessed non-invasively by Carbon-13 Magnetic Resonance Spectroscopy ( 13 C-MRS) in vivo. With this approach, glycogen synthesis and degradation may be followed in real time, thereby providing valuable insights into brain glycogen dynamics. However, compared to the liver and muscle, where glycogen is abundant, the sensitivity for detection of brain glycogen by 13 C-MRS is inherently low. In this review we focus on strategies used to optimize the sensitivity for 13 C-MRS detection of glycogen. Namely, we explore several technical perspectives, such as magnetic field strength, field homogeneity, coil design, decoupling, and localization methods. Furthermore, we also address basic principles underlying the use of 13 C-labeled precursors to enhance the detectable glycogen signal, emphasizing specific experimental aspects relevant for obtaining kinetic information on brain glycogen. Copyright © 2016 Elsevier Inc. All rights reserved.

Unusual negative permeability of single magnetic nanowire excited by the spin transfer torque effect

NASA Astrophysics Data System (ADS)

Han, Mangui; Zhou, Wu

2018-07-01

Due to the effect of spin transfer torque, negative imaginary parts of permeability (μ″ < 0) are reported in a ferromagnetic nanowire. It is found that negative μ″ values are resulted from the interaction of spin polarized conduction electrons with the spatially non-uniform distributed magnetic moments at both ends of nanowires. The results are well explained from the effect of spin transfer torque on the precession of magnetization under the excitation of both the pulsed magnetic field and static electric field.

Toward Distinguishing Recurrent Tumor From Radiation Necrosis: DWI and MTC in a Gamma Knife–Irradiated Mouse Glioma Model

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

Perez-Torres, Carlos J.; Engelbach, John A.; Cates, Jeremy

Purpose: Accurate noninvasive diagnosis is vital for effective treatment planning. Presently, standard anatomical magnetic resonance imaging (MRI) is incapable of differentiating recurring tumor from delayed radiation injury, as both lesions are hyperintense in both postcontrast T1- and T2-weighted images. Further studies are therefore necessary to identify an MRI paradigm that can differentially diagnose these pathologies. Mouse glioma and radiation injury models provide a powerful platform for this purpose. Methods and Materials: Two MRI contrasts that are widely used in the clinic were chosen for application to a glioma/radiation-injury model: diffusion weighted imaging, from which the apparent diffusion coefficient (ADC) ismore » obtained, and magnetization transfer contrast, from which the magnetization transfer ratio (MTR) is obtained. These metrics were evaluated longitudinally, first in each lesion type alone–glioma versus irradiation – and then in a combined irradiated glioma model. Results: MTR was found to be consistently decreased in all lesions compared to nonlesion brain tissue (contralateral hemisphere), with limited specificity between lesion types. In contrast, ADC, though less sensitive to the presence of pathology, was increased in radiation injury and decreased in tumors. In the irradiated glioma model, ADC also increased immediately after irradiation, but decreased as the tumor regrew. Conclusions: ADC is a better metric than MTR for differentiating glioma from radiation injury. However, MTR was more sensitive to both tumor and radiation injury than ADC, suggesting a possible role in detecting lesions that do not enhance strongly on T1-weighted images.« less

Quantitative MRI in hypomyelinating disorders: Correlation with motor handicap.

PubMed

Steenweg, Marjan E; Wolf, Nicole I; van Wieringen, Wessel N; Barkhof, Frederik; van der Knaap, Marjo S; Pouwels, Petra J W

2016-08-23

To assess the correlation of tissue parameters estimated by quantitative magnetic resonance (MR) techniques and motor handicap in patients with hypomyelination. Twenty-eight patients with different causes of hypomyelination (12 males, 16 females; mean age 10 years) and 61 controls (33 males, 28 females; mean age 8 years) were prospectively investigated. We quantified T2 relaxation time, magnetization transfer ratio, fractional anisotropy, mean, axial, and radial diffusivities, and brain metabolites. We performed measurements in the splenium, parietal deep white matter, and corticospinal tracts in the centrum semiovale. We further analyzed diffusion measures using tract-based spatial statistics. We estimated severity of motor handicap by the gross motor function classification system. We evaluated correlation of handicap with MR measures by linear regression analyses. Fractional anisotropy, magnetization transfer ratio, choline, and N-acetylaspartate/creatine ratio were lower and diffusivities, T2 values, and inositol were higher in patients than in controls. Tract-based spatial statistics showed that these changes were widespread for fractional anisotropy (96% of the white matter skeleton), radial (93%) and mean (84%) diffusivity, and less so for axial diffusivity (20%). Correlation with handicap yielded radial diffusivity and N-acetylaspartate/creatine ratio as strongest independent explanatory variables. Gross motor function classification system grades are in part explained by MR measures. They indicate that mainly lack of myelin and, to a lesser degree, loss of axonal integrity codetermine the degree of motor handicap in patients with hypomyelinating disorders. These MR measures can be used to evaluate strategies that are aimed at promotion of myelination. © 2016 American Academy of Neurology.

Proton Magnetic Resonance Spectroscopy and MRI Reveal No Evidence for Brain Mitochondrial Dysfunction in Children with Autism Spectrum Disorder

ERIC Educational Resources Information Center

Corrigan, Neva M.; Shaw, Dennis. W. W.; Richards, Todd L.; Estes, Annette M.; Friedman, Seth D.; Petropoulos, Helen; Artru, Alan A.; Dager, Stephen R.

2012-01-01

Brain mitochondrial dysfunction has been proposed as an etiologic factor in autism spectrum disorder (ASD). Proton magnetic resonance spectroscopic imaging ([superscript 1]HMRS) and MRI were used to assess for evidence of brain mitochondrial dysfunction in longitudinal samples of children with ASD or developmental delay (DD), and cross-sectionally…

A Method for Whole Brain Ex Vivo Magnetic Resonance Imaging with Minimal Susceptibility Artifacts

PubMed Central

Shatil, Anwar S.; Matsuda, Kant M.; Figley, Chase R.

2016-01-01

Magnetic resonance imaging (MRI) is a non-destructive technique that is capable of localizing pathologies and assessing other anatomical features (e.g., tissue volume, microstructure, and white matter connectivity) in postmortem, ex vivo human brains. However, when brains are removed from the skull and cerebrospinal fluid (i.e., their normal in vivo magnetic environment), air bubbles and air–tissue interfaces typically cause magnetic susceptibility artifacts that severely degrade the quality of ex vivo MRI data. In this report, we describe a relatively simple and cost-effective experimental setup for acquiring artifact-free ex vivo brain images using a clinical MRI system with standard hardware. In particular, we outline the necessary steps, from collecting an ex vivo human brain to the MRI scanner setup, and have also described changing the formalin (as might be necessary in longitudinal postmortem studies). Finally, we share some representative ex vivo MRI images that have been acquired using the proposed setup in order to demonstrate the efficacy of this approach. We hope that this protocol will provide both clinicians and researchers with a straight-forward and cost-effective solution for acquiring ex vivo MRI data from whole postmortem human brains. PMID:27965620

Fine-tuning convolutional deep features for MRI based brain tumor classification

NASA Astrophysics Data System (ADS)

Ahmed, Kaoutar B.; Hall, Lawrence O.; Goldgof, Dmitry B.; Liu, Renhao; Gatenby, Robert A.

2017-03-01

Prediction of survival time from brain tumor magnetic resonance images (MRI) is not commonly performed and would ordinarily be a time consuming process. However, current cross-sectional imaging techniques, particularly MRI, can be used to generate many features that may provide information on the patient's prognosis, including survival. This information can potentially be used to identify individuals who would benefit from more aggressive therapy. Rather than using pre-defined and hand-engineered features as with current radiomics methods, we investigated the use of deep features extracted from pre-trained convolutional neural networks (CNNs) in predicting survival time. We also provide evidence for the power of domain specific fine-tuning in improving the performance of a pre-trained CNN's, even though our data set is small. We fine-tuned a CNN initially trained on a large natural image recognition dataset (Imagenet ILSVRC) and transferred the learned feature representations to the survival time prediction task, obtaining over 81% accuracy in a leave one out cross validation.

Susceptibility Tensor Imaging (STI) of the Brain

PubMed Central

Li, Wei; Liu, Chunlei; Duong, Timothy Q.; van Zijl, Peter C.M.; Li, Xu

2016-01-01

Susceptibility tensor imaging (STI) is a recently developed MRI technique that allows quantitative determination of orientation-independent magnetic susceptibility parameters from the dependence of gradient echo signal phase on the orientation of biological tissues with respect to the main magnetic field. By modeling the magnetic susceptibility of each voxel as a symmetric rank-2 tensor, individual magnetic susceptibility tensor elements as well as the mean magnetic susceptibility (MMS) and magnetic susceptibility anisotropy (MSA) can be determined for brain tissues that would still show orientation dependence after conventional scalar-based quantitative susceptibility mapping (QSM) to remove such dependence. Similar to diffusion tensor imaging (DTI), STI allows mapping of brain white matter fiber orientations and reconstruction of 3D white matter pathways using the principal eigenvectors of the susceptibility tensor. In contrast to diffusion anisotropy, the main determinant factor of susceptibility anisotropy in brain white matter is myelin. Another unique feature of susceptibility anisotropy of white matter is its sensitivity to gadolinium-based contrast agents. Mechanistically, MRI-observed susceptibility anisotropy is mainly attributed to the highly ordered lipid molecules in myelin sheath. STI provides a consistent interpretation of the dependence of phase and susceptibility on orientation at multiple scales. This article reviews the key experimental findings and physical theories that led to the development of STI, its practical implementations, and its applications for brain research. PMID:27120169

Transcranial magnetic stimulation: Improved coil design for deep brain investigation

NASA Astrophysics Data System (ADS)

Crowther, L. J.; Marketos, P.; Williams, P. I.; Melikhov, Y.; Jiles, D. C.; Starzewski, J. H.

2011-04-01

This paper reports on a design for a coil for transcranial magnetic stimulation. The design shows potential for improving the penetration depth of the magnetic field, allowing stimulation of subcortical structures within the brain. The magnetic and induced electric fields in the human head have been calculated with finite element electromagnetic modeling software and compared with empirical measurements. Results show that the coil design used gives improved penetration depth, but also indicates the likelihood of stimulation of additional tissue resulting from the spatial distribution of the magnetic field.

Estimation of the EEG power spectrum using MRI T(2) relaxation time in traumatic brain injury.

PubMed

Thatcher, R W; Biver, C; Gomez, J F; North, D; Curtin, R; Walker, R A; Salazar, A

2001-09-01

To study the relationship between magnetic resonance imaging (MRI) T(2) relaxation time and the power spectrum of the electroencephalogram (EEG) in long-term follow up of traumatic brain injury. Nineteen channel quantitative electroencephalograms or qEEG, tests of cognitive function and quantitative MRI T(2) relaxation times (qMRI) were measured in 18 mild to severe closed head injured outpatients 2 months to 4.6 years after injury and 11 normal controls. MRI T(2) and the Laplacian of T(2) were then correlated with the power spectrum of the scalp electrical potentials and current source densities of the qEEG. qEEG and qMRI T(2) were related by a frequency tuning with maxima in the alpha (8-12Hz) and the lower EEG frequencies (0.5-5Hz), which varied as a function of spatial location. The Laplacian of T(2) acted like a spatial-temporal "lens" by increasing the spatial-temporal resolution of correlation between 3-dimensional T(2) and the ear referenced alert but resting spontaneous qEEG. The severity of traumatic brain injury can be modeled by a linear transfer function that relates the molecular qMRI to qEEG resonant frequencies.

Memory in multiple sclerosis is linked to glutamate concentration in grey matter regions

PubMed Central

Muhlert, Nils; Atzori, Matteo; De Vita, Enrico; Thomas, David L; Samson, Rebecca S; Wheeler-Kingshott, Claudia A M; Geurts, Jeroen J G; Miller, David H; Thompson, Alan J; Ciccarelli, Olga

2014-01-01

Objective Glutamate is the principal excitatory neurotransmitter and is involved in normal brain function. Cognitive impairment is common in multiple sclerosis (MS), and understanding its mechanisms is crucial for developing effective treatments. We used structural and metabolic brain imaging to test two hypotheses: (i) glutamate levels in grey matter regions are abnormal in MS, and (ii) patients show a relationship between glutamate concentration and memory performance. Methods Eighteen patients with relapsing-remitting MS and 17 healthy controls were cognitively assessed and underwent 1H-magnetic resonance spectroscopy at 3 T to assess glutamate levels in the hippocampus, thalamus, cingulate and parietal cortices. Regression models investigated the association between glutamate concentration and memory performance independently of magnetisation transfer ratio values and grey matter lesions withint he same regions, and whole-brain grey matter volume. Results Patients had worse visual and verbal memory than controls. A positive relationship between glutamate levels in the hippocampal, thalamic and cingulate regions and visuospatial memory was detected in patients, but not in healthy controls. Conclusions The relationship between memory and glutamate concentration, which is unique to MS patients, suggests the reliance of memory on glutamatergic systems in MS. PMID:24431465

Multi circular-cavity surface coil for magnetic resonance imaging of monkey's brain at 4 Tesla

NASA Astrophysics Data System (ADS)

Osorio, A. I.; Solis-Najera, S. E.; Vázquez, F.; Wang, R. L.; Tomasi, D.; Rodriguez, A. O.

2014-11-01

Animal models in medical research has been used to study humans diseases for several decades. The use of different imaging techniques together with different animal models offers a great advantage due to the possibility to study some human pathologies without the necessity of chirurgical intervention. The employ of magnetic resonance imaging for the acquisition of anatomical and functional images is an excellent tool because its noninvasive nature. Dedicated coils to perform magnetic resonance imaging experiments are obligatory due to the improvement on the signal-to-noise ratio and reduced specific absorption ratio. A specifically designed surface coil for magnetic resonance imaging of monkey's brain is proposed based on the multi circular-slot coil. Numerical simulations of the magnetic and electric fields were also performed using the Finite Integration Method to solve Maxwell's equations for this particular coil design and, to study the behavior of various vector magnetic field configurations and specific absorption ratio. Monkey's brain images were then acquired with a research-dedicated magnetic resonance imaging system at 4T, to evaluate the anatomical images with conventional imaging sequences. This coil showed good quality images of a monkey's brain and full compatibility with standard pulse sequences implemented in research-dedicated imager.

Expansion of brain T cells in homeostatic conditions in lymphopenic Rag2(-/-) mice.

PubMed

Song, Chang; Nicholson, James D; Clark, Sarah M; Li, Xin; Keegan, Achsah D; Tonelli, Leonardo H

2016-10-01

The concept of the brain as an immune privileged organ is rapidly evolving in light of new findings outlining the sophisticated relationship between the central nervous and the immune systems. The role of T cells in brain development and function, as well as modulation of behavior has been demonstrated by an increasing number of studies. Moreover, recent studies have redefined the existence of a brain lymphatic system and the presence of T cells in specific brain structures, such as the meninges and choroid plexus. Nevertheless, much information is needed to further the understanding of brain T cells and their relationship with the central nervous system under non-inflammatory conditions. In the present study we employed the Rag2(-/-) mouse model of lymphocyte deficiency and reconstitution by adoptive transfer to study the temporal and anatomical expansion of T cells in the brain under homeostatic conditions. Lymphopenic Rag2(-/-) mice were reconstituted with 10 million lymphoid cells and studied at one, two and four weeks after transfer. Moreover, lymphoid cells and purified CD4(+) and CD8(+) T cells from transgenic GFP expressing mice were used to define the neuroanatomical localization of transferred cells. T cell numbers were very low in the brain of reconstituted mice up to one week after transfer and significantly increased by 2weeks, reaching wild type values at 4weeks after transfer. CD4(+) T cells were the most abundant lymphocyte subtype found in the brain followed by CD8(+) T cells and lastly B cells. Furthermore, proliferation studies showed that CD4(+) T cells expand more rapidly than CD8(+) T cells. Lymphoid cells localize abundantly in meningeal structures, choroid plexus, and circumventricular organs. Lymphocytes were also found in vascular and perivascular spaces and in the brain parenchyma across several regions of the brain, in particular in structures rich in white matter content. These results provide proof of concept that the brain meningeal system, as well as vascular and perivascular spaces, are homing sites of lymphocytes and suggest the possibility of a brain specific T cell subtype. Published by Elsevier Inc.

Combined magnetic nanoparticle-based microRNA and hyperthermia therapy to enhance apoptosis in brain cancer cells.

PubMed

Yin, Perry T; Shah, Birju P; Lee, Ki-Bum

2014-10-29

A novel therapy is demonstrated utilizing magnetic nanoparticles for the dual purpose of delivering microRNA and inducing magnetic hyperthermia. In particular, the combination of lethal-7a microRNA (let-7a), which targets a number of the survival pathways that typically limit the effectiveness of hyperthermia, with magnetic hyperthermia greatly enhances apoptosis in brain cancer cells. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Heat transfer enhancement of Fe3O4 ferrofluids in the presence of magnetic field

NASA Astrophysics Data System (ADS)

Fadaei, Farzad; Shahrokhi, Mohammad; Molaei Dehkordi, Asghar; Abbasi, Zeinab

2017-05-01

In this article, three-dimensional (3D) forced-convection heat transfer of magnetic nanofluids in a pipe subject to constant wall heat flux in the presence of single or double permanent magnet(s) or current-carrying wire has been investigated and compared. In this regard, laminar fluid flow and equilibrium magnetization for the ferrofluid were considered. In addition, variations of magnetic field in different media were taken into account and the assumption of having a linear relationship of magnetization with applied magnetic field intensity was also relaxed. Effects of magnetic field intensity, nanoparticle volume fraction, Reynolds number value, and the type of magnetic field source (i.e., a permanent magnet or current-carrying wire) on the forced-convection heat transfer of magnetic nanofluids were carefully investigated. It was found that by applying the magnetic field, the fluid mixing could be intensified that leads to an increase in the Nusselt number value along the pipe length. Moreover, the obtained simulation results indicate that applying the magnetic field induced by two permanent magnets with a magnetization of 3×105 (A/m) (for each one), the fully developed Nusselt number value can be increased by 196%.

Ex-vivo quantitative susceptibility mapping of human brain hemispheres

PubMed Central

Kotrotsou, Aikaterini; Tamhane, Ashish A.; Dawe, Robert J.; Kapasi, Alifiya; Leurgans, Sue E.; Schneider, Julie A.; Bennett, David A.; Arfanakis, Konstantinos

2017-01-01

Ex-vivo brain quantitative susceptibility mapping (QSM) allows investigation of brain characteristics at essentially the same point in time as histopathologic examination, and therefore has the potential to become an important tool for determining the role of QSM as a diagnostic and monitoring tool of age-related neuropathologies. In order to be able to translate the ex-vivo QSM findings to in-vivo, it is crucial to understand the effects of death and chemical fixation on brain magnetic susceptibility measurements collected ex-vivo. Thus, the objective of this work was twofold: a) to assess the behavior of magnetic susceptibility in both gray and white matter of human brain hemispheres as a function of time postmortem, and b) to establish the relationship between in-vivo and ex-vivo gray matter susceptibility measurements on the same hemispheres. Five brain hemispheres from community-dwelling older adults were imaged ex-vivo with QSM on a weekly basis for six weeks postmortem, and the longitudinal behavior of ex-vivo magnetic susceptibility in both gray and white matter was assessed. The relationship between in-vivo and ex-vivo gray matter susceptibility measurements was investigated using QSM data from eleven older adults imaged both antemortem and postmortem. No systematic change in ex-vivo magnetic susceptibility of gray or white matter was observed over time postmortem. Additionally, it was demonstrated that, gray matter magnetic susceptibility measured ex-vivo may be well modeled as a linear function of susceptibility measured in-vivo. In conclusion, magnetic susceptibility in gray and white matter measured ex-vivo with QSM does not systematically change in the first six weeks after death. This information is important for future cross-sectional ex-vivo QSM studies of hemispheres imaged at different postmortem intervals. Furthermore, the linear relationship between in-vivo and ex-vivo gray matter magnetic susceptibility suggests that ex-vivo QSM captures information linked to antemortem gray matter magnetic susceptibility, which is important for translation of ex-vivo QSM findings to in-vivo. PMID:29261693

Advanced neuroimaging techniques for the term newborn with encephalopathy.

PubMed

Chau, Vann; Poskitt, Kenneth John; Miller, Steven Paul

2009-03-01

Neonatal encephalopathy is associated with a high risk of morbidity and mortality in the neonatal period and of long-term neurodevelopmental disability in survivors. Advanced magnetic resonance techniques now play a major role in the clinical care of newborns with encephalopathy and in research addressing this important condition. From conventional magnetic resonance imaging, typical patterns of injury have been defined in neonatal encephalopathy. When applied in contemporary cohorts of newborns with encephalopathy, the patterns of brain injury on magnetic resonance imaging distinguish risk factors, clinical presentation, and risk of abnormal outcome. Advanced magnetic resonance techniques such as magnetic resonance spectroscopy, diffusion-weighted imaging, and diffusion tensor imaging provide novel perspectives on neonatal brain metabolism, microstructure, and connectivity. With the application of these imaging tools, it is increasingly apparent that brain injury commonly occurs at or near the time of birth and evolves over the first weeks of life. These observations have complemented findings from trials of emerging strategies of brain protection, such as hypothermia. Application of these advanced magnetic resonance techniques may enable the earliest possible identification of newborns at risk of neurodevelopmental impairment, thereby ensuring appropriate follow-up with rehabilitation and psychoeducational resources.

Magnetic field transfer device and method

DOEpatents

Wipf, S.L.

1990-02-13

A magnetic field transfer device includes a pair of oppositely wound inner coils which each include at least one winding around an inner coil axis, and an outer coil which includes at least one winding around an outer coil axis. The windings may be formed of superconductors. The axes of the two inner coils are parallel and laterally spaced from each other so that the inner coils are positioned in side-by-side relation. The outer coil is outwardly positioned from the inner coils and rotatable relative to the inner coils about a rotational axis substantially perpendicular to the inner coil axes to generate a hypothetical surface which substantially encloses the inner coils. The outer coil rotates relative to the inner coils between a first position in which the outer coil axis is substantially parallel to the inner coil axes and the outer coil augments the magnetic field formed in one of the inner coils, and a second position 180[degree] from the first position, in which the augmented magnetic field is transferred into the other inner coil and reoriented 180[degree] from the original magnetic field. The magnetic field transfer device allows a magnetic field to be transferred between volumes with negligible work being required to rotate the outer coil with respect to the inner coils. 16 figs.

Magnetic field transfer device and method

DOEpatents

Wipf, Stefan L.

1990-01-01

A magnetic field transfer device includes a pair of oppositely wound inner coils which each include at least one winding around an inner coil axis, and an outer coil which includes at least one winding around an outer coil axis. The windings may be formed of superconductors. The axes of the two inner coils are parallel and laterally spaced from each other so that the inner coils are positioned in side-by-side relation. The outer coil is outwardly positioned from the inner coils and rotatable relative to the inner coils about a rotational axis substantially perpendicular to the inner coil axes to generate a hypothetical surface which substantially encloses the inner coils. The outer coil rotates relative to the inner coils between a first position in which the outer coil axis is substantially parallel to the inner coil axes and the outer coil augments the magnetic field formed in one of the inner coils, and a second position 180.degree. from the first position, in which the augmented magnetic field is transferred into the other inner coil and reoriented 180.degree. from the original magnetic field. The magnetic field transfer device allows a magnetic field to be transferred between volumes with negligible work being required to rotate the outer coil with respect to the inner coils.

α-synuclein transfer through tunneling nanotubes occurs in SH-SY5Y cells and primary brain pericytes from Parkinson’s disease patients

PubMed Central

Dieriks, Birger Victor; Park, Thomas I-H.; Fourie, Chantelle; Faull, Richard L. M.; Dragunow, Mike; Curtis, Maurice A.

2017-01-01

Parkinson’s disease (PD) is characterized by the presence of inclusions known as Lewy bodies, which mainly consist of α-synuclein (α-syn) aggregates. There is growing evidence that α-syn self-propagates in non-neuronal cells, thereby contributing to the progression and spread of PD pathology in the brain. Tunneling nanotubes (TNTs) are long, thin, F-actin-based membranous channels that connect cells and have been proposed to act as conduits for α-syn transfer between cells. SH-SY5Y cells and primary human brain pericytes, derived from postmortem PD brains, frequently form TNTs that allow α-syn transfer and long-distance electrical coupling between cells. Pericytes in situ contain α-syn precipitates like those seen in neurons. Exchange through TNTs was rapid, but dependent on the size of the protein. Proteins were able to spread throughout a network of cells connected by TNTs. Transfer through TNTs was not restricted to α-syn; fluorescent control proteins and labeled membrane were also exchanged through TNTs. Most importantly the formation of TNTs and transfer continued during mitosis. Together, our results provide a detailed description of TNTs in SH-SY5Y cells and human brain PD pericytes, demonstrating their role in α-syn transfer and further emphasize the importance that non-neuronal cells, such as pericytes play in disease progression. PMID:28230073

Transfer coefficients for L-valine and the rate of incorporation of L-(1-/sup 14/C) valine into proteins in normal adult rat brain

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

Kirikae, M.; Diksic, M.; Yamamoto, Y.L.

1988-08-01

An autoradiographic method for the measurement of the rate of valine incorporation into brain proteins is described. The transfer coefficients for valine into and out of the brain and the rate of valine incorporation into normal rat brain proteins are given. The valine incorporation and the transfer constants of valine between different biological compartments are provided for 14 gray matter and 2 white matter structures of an adult rat brain. The rate of valine incorporation varies between 0.52 +/- 0.19 nmol/g/min in white matter and 1.94 +/- 0.47 in inferior colliculus (gray matter). Generally, the rate of valine incorporation ismore » about three to four times higher in the gray matter than in the white matter structures.« less

Normal feline brain: clinical anatomy using magnetic resonance imaging.

PubMed

Mogicato, G; Conchou, F; Layssol-Lamour, C; Raharison, F; Sautet, J

2012-04-01

The purpose of this study was to provide a clinical anatomy atlas of the feline brain using magnetic resonance imaging (MRI). Brains of twelve normal cats were imaged using a 1.5 T magnetic resonance unit and an inversion/recovery sequence (T1). Fourteen relevant MRI sections were chosen in transverse, dorsal, median and sagittal planes. Anatomic structures were identified and labelled using anatomical texts and Nomina Anatomica Veterinaria, sectioned specimen heads, and previously published articles. The MRI sections were stained according to the major embryological and anatomical subdivisions of the brain. The relevant anatomical structures seen on MRI will assist clinicians to better understand MR images and to relate this neuro-anatomy to clinical signs. © 2011 Blackwell Verlag GmbH.

Bound Pool Fractions Complement Diffusion Measures to Describe White Matter Micro and Macrostructure

PubMed Central

Stikov, Nikola; Perry, Lee M.; Mezer, Aviv; Rykhlevskaia, Elena; Wandell, Brian A.; Pauly, John M.; Dougherty, Robert F.

2010-01-01

Diffusion imaging and bound pool fraction (BPF) mapping are two quantitative magnetic resonance imaging techniques that measure microstructural features of the white matter of the brain. Diffusion imaging provides a quantitative measure of the diffusivity of water in tissue. BPF mapping is a quantitative magnetization transfer (qMT) technique that estimates the proportion of exchanging protons bound to macromolecules, such as those found in myelin, and is thus a more direct measure of myelin content than diffusion. In this work, we combine BPF estimates of macromolecular content with measurements of diffusivity within human white matter tracts. Within the white matter, the correlation between BPFs and diffusivity measures such as fractional anisotropy and radial diffusivity was modest, suggesting that diffusion tensor imaging and bound pool fractions are complementary techniques. We found that several major tracts have high BPF, suggesting a higher density of myelin in these tracts. We interpret these results in the context of a quantitative tissue model. PMID:20828622

Quantitative Assessment of Normal Fetal Brain Myelination Using Fast Macromolecular Proton Fraction Mapping.

PubMed

Yarnykh, V L; Prihod'ko, I Y; Savelov, A A; Korostyshevskaya, A M

2018-05-10

Fast macromolecular proton fraction mapping is a recently emerged MRI method for quantitative myelin imaging. Our aim was to develop a clinically targeted technique for macromolecular proton fraction mapping of the fetal brain and test its capability to characterize normal prenatal myelination. This prospective study included 41 pregnant women (gestational age range, 18-38 weeks) without abnormal findings on fetal brain MR imaging performed for clinical indications. A fast fetal brain macromolecular proton fraction mapping protocol was implemented on a clinical 1.5T MR imaging scanner without software modifications and was performed after a clinical examination with an additional scan time of <5 minutes. 3D macromolecular proton fraction maps were reconstructed from magnetization transfer-weighted, T1-weighted, and proton density-weighted images by the single-point method. Mean macromolecular proton fraction in the brain stem, cerebellum, and thalamus and frontal, temporal, and occipital WM was compared between structures and pregnancy trimesters using analysis of variance. Gestational age dependence of the macromolecular proton fraction was assessed using the Pearson correlation coefficient ( r ). The mean macromolecular proton fraction in the fetal brain structures varied between 2.3% and 4.3%, being 5-fold lower than macromolecular proton fraction in adult WM. The macromolecular proton fraction in the third trimester was higher compared with the second trimester in the brain stem, cerebellum, and thalamus. The highest macromolecular proton fraction was observed in the brain stem, followed by the thalamus, cerebellum, and cerebral WM. The macromolecular proton fraction in the brain stem, cerebellum, and thalamus strongly correlated with gestational age ( r = 0.88, 0.80, and 0.73; P < .001). No significant correlations were found for cerebral WM regions. Myelin is the main factor determining macromolecular proton fraction in brain tissues. Macromolecular proton fraction mapping is sensitive to the earliest stages of the fetal brain myelination and can be implemented in a clinical setting. © 2018 by American Journal of Neuroradiology.

Heat Transfer to Anode of Arc as Function of Transverse Magnetic Field and Lateral Gas Flow Velocity

NASA Astrophysics Data System (ADS)

Zama, Yoshiyuki; Shiino, Toru; Ishii, Yoko; Maeda, Yoshifumi; Yamamoto, Shinji; Iwao, Toru

2016-10-01

Gas tungsten arc welding has useful joining technology because of high-energy and high-current characteristics. It can be flexible from the transverse magnetic field and lateral gas flow velocity. In this case, the weld defect occurs. In this research, the heat transfer to the anode of the arc as a function of the transverse magnetic field and lateral gas flow velocity is elucidated. That magnetic flux density and lateral gas velocity were varied from 0 to 3 mT and 0 to 50?m?s -1, respectively. The axial plasma gas argon flow rates were 3?slm. A transverse magnetic field is applied to the arc using Helmholtz coil. The anode is used by a water-cooled copper plate, and the heat transfer is measured by temperature of cooled water. As a result, the arc is deflected by the Lorentz force and lateral gas convection. Thus, the heat transfer to the anode of the arc decreases with increasing the transverse magnetic field and lateral gas flow velocity. In addition, the heat transfer to the anode changes with different attachments modes. The lateral gas flow causes a convective heat loss from the arc to the chamber walls.

Serotonergic Psychedelics Temporarily Modify Information Transfer in Humans

PubMed Central

Alonso, Joan Francesc; Romero, Sergio; Mañanas, Miquel Àngel

2015-01-01

Background: Psychedelics induce intense modifications in the sensorium, the sense of “self,” and the experience of reality. Despite advances in our understanding of the molecular and cellular level mechanisms of these drugs, knowledge of their actions on global brain dynamics is still incomplete. Recent imaging studies have found changes in functional coupling between frontal and parietal brain structures, suggesting a modification in information flow between brain regions during acute effects. Methods: Here we assessed the psychedelic-induced changes in directionality of information flow during the acute effects of a psychedelic in humans. We measured modifications in connectivity of brain oscillations using transfer entropy, a nonlinear measure of directed functional connectivity based on information theory. Ten healthy male volunteers with prior experience with psychedelics participated in 2 experimental sessions. They received a placebo or a dose of ayahuasca, a psychedelic preparation containing the serotonergic 5-HT2A agonist N,N-dimethyltryptamine. Results: The analysis showed significant changes in the coupling of brain oscillations between anterior and posterior recording sites. Transfer entropy analysis showed that frontal sources decreased their influence over central, parietal, and occipital sites. Conversely, sources in posterior locations increased their influence over signals measured at anterior locations. Exploratory correlations found that anterior-to-posterior transfer entropy decreases were correlated with the intensity of subjective effects, while the imbalance between anterior-to-posterior and posterior-to-anterior transfer entropy correlated with the degree of incapacitation experienced. Conclusions: These results suggest that psychedelics induce a temporary disruption of neural hierarchies by reducing top-down control and increasing bottom-up information transfer in the human brain. PMID:25820842

Brain-Behavior Mechanisms for the Transfer of Neuromuscular Training Adaptions to Simulated Sport: Initial Findings from the Train the Brain Project.

PubMed

Grooms, Dustin R; Kiefer, Adam W; Riley, Michael A; Ellis, Jonathan D; Thomas, Staci; Kitchen, Katie; DiCesare, Christopher; Bonnette, Scott; Gadd, Brooke; Barber Foss, Kim D; Yuan, Weihong; Silva, Paula; Galloway, Ryan; Diekfuss, Jed; Leach, James; Berz, Kate; Myer, Gregory D

2018-03-27

A limiting factor for reducing anterior cruciate ligament (ACL) injury risk is ensuring that the movement adaptions made during the prevention program transfer to sport-specific activity. Virtual reality provides a mechanism to assess transferability and neuroimaging provides a means to assay the neural processes allowing for such skill transfer. To determine the neural mechanisms for injury risk reducing biomechanics transfer to sport after ACL injury prevention training. Cohort study Setting: Research laboratory Participants: Four healthy high school soccer athletes. Participants completed augmented neuromuscular training utilizing real-time visual feedback. An unloaded knee extension task and a loaded leg-press task was completed with neuroimaging before and after training. A virtual reality soccer specific landing task was also competed following training to assess transfer of movement mechanics. Landing mechanics during the virtual reality soccer task and blood oxygen level dependent signal change during neuroimaging. Increased motor planning, sensory and visual region activity during unloaded knee extension and decreased motor cortex activity during loaded leg-press were highly correlated with improvements in landing mechanics (decreased hip adduction and knee rotation). Changes in brain activity may underlie adaptation and transfer of injury risk reducing movement mechanics to sport activity. Clinicians may be able to target these specific brain processes with adjunctive therapy to facilitate intervention improvements transferring to sport.

Mathematical Model of the Processes of Heat and Mass Transfer and Diffusion of the Magnetic Field in an Induction Furnace

NASA Astrophysics Data System (ADS)

Perminov, A. V.; Nikulin, I. L.

2016-03-01

We propose a mathematical model describing the motion of a metal melt in a variable inhomogeneous magnetic field of a short solenoid. In formulating the problem, we made estimates and showed the possibility of splitting the complete magnetohydrodynamical problem into two subproblems: a magnetic field diffusion problem where the distributions of the external and induced magnetic fields and currents are determined, and a heat and mass transfer problem with known distributions of volume sources of heat and forces. The dimensionless form of the heat and mass transfer equation was obtained with the use of averaging and multiscale methods, which permitted writing and solving separately the equations for averaged flows and temperature fields and their oscillations. For the heat and mass transfer problem, the boundary conditions for a real technological facility are discussed. The dimensionless form of the magnetic field diffusion equation is presented, and the experimental computational procedure and results of the numerical simulation of the magnetic field structure in the melt for various magnetic Reynolds numbers are described. The extreme dependence of heat release on the magnetic Reynolds number has been interpreted.

Oscillation characteristics of zero-field spin transfer oscillators with field-like torque

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

Guo, Yuan-Yuan; Xue, Hai-Bin, E-mail: xuehaibin@tyut.edu.cn; Department of Physics and Optoelectronics, Taiyuan University of Technology, Taiyuan 030024

2015-05-15

We theoretically investigate the influence of the field-like spin torque term on the oscillation characteristics of spin transfer oscillators, which are based on MgO magnetic tunnel junctions (MTJs) consisting of a perpendicular magnetized free layer and an in-plane magnetized pinned layer. It is demonstrated that the field-like torque has a strong impact on the steady-state precession current region and the oscillation frequency. In particular, the steady-state precession can occur at zero applied magnetic field when the ratio between the field-like torque and the spin transfer torque takes up a negative value. In addition, the dependence of the oscillation properties onmore » the junction sizes has also been analyzed. The results indicate that this compact structure of spin transfer oscillator without the applied magnetic field is practicable under certain conditions, and it may be a promising configuration for the new generation of on-chip oscillators.« less

Transferring and generalizing deep-learning-based neural encoding models across subjects.

PubMed

Wen, Haiguang; Shi, Junxing; Chen, Wei; Liu, Zhongming

2018-08-01

Recent studies have shown the value of using deep learning models for mapping and characterizing how the brain represents and organizes information for natural vision. However, modeling the relationship between deep learning models and the brain (or encoding models), requires measuring cortical responses to large and diverse sets of natural visual stimuli from single subjects. This requirement limits prior studies to few subjects, making it difficult to generalize findings across subjects or for a population. In this study, we developed new methods to transfer and generalize encoding models across subjects. To train encoding models specific to a target subject, the models trained for other subjects were used as the prior models and were refined efficiently using Bayesian inference with a limited amount of data from the target subject. To train encoding models for a population, the models were progressively trained and updated with incremental data from different subjects. For the proof of principle, we applied these methods to functional magnetic resonance imaging (fMRI) data from three subjects watching tens of hours of naturalistic videos, while a deep residual neural network driven by image recognition was used to model visual cortical processing. Results demonstrate that the methods developed herein provide an efficient and effective strategy to establish both subject-specific and population-wide predictive models of cortical representations of high-dimensional and hierarchical visual features. Copyright © 2018 Elsevier Inc. All rights reserved.

[Possibilities of magnetic-laser therapy in comprehensive treatment of patients with brain concussion in acute period].

PubMed

Zubkova, O V; Samosiuk, I Z; Polishchuk, O V; Shul'ga, N M; Samosiuk, N I

2012-01-01

The efficacy of magnetic-laser therapy used according to the method developed by us was studied in patients having the brain concussion (BC) in an acute period. The study was based on the dynamics of values of the evoked vestibular potentials and the disease clinical course. It was shown that following the magnetic-laser therapy in combination with traditional pharmacotherapy in BC acute period, the statistically significant positive changes were registered in the quantitative characteristics of the evoked vestibular brain potentials that correlated with the dynamics of the disease clinical course. The data obtained substantiate the possibility of using the magnetic-laser therapy in patients with a mild craniocereblal injury in an acute period.

The Relationship of Three-Dimensional Human Skull Motion to Brain Tissue Deformation in Magnetic Resonance Elastography Studies

PubMed Central

Badachhape, Andrew A.; Okamoto, Ruth J.; Durham, Ramona S.; Efron, Brent D.; Nadell, Sam J.; Johnson, Curtis L.; Bayly, Philip V.

2017-01-01

In traumatic brain injury (TBI), membranes such as the dura mater, arachnoid mater, and pia mater play a vital role in transmitting motion from the skull to brain tissue. Magnetic resonance elastography (MRE) is an imaging technique developed for noninvasive estimation of soft tissue material parameters. In MRE, dynamic deformation of brain tissue is induced by skull vibrations during magnetic resonance imaging (MRI); however, skull motion and its mode of transmission to the brain remain largely uncharacterized. In this study, displacements of points in the skull, reconstructed using data from an array of MRI-safe accelerometers, were compared to displacements of neighboring material points in brain tissue, estimated from MRE measurements. Comparison of the relative amplitudes, directions, and temporal phases of harmonic motion in the skulls and brains of six human subjects shows that the skull–brain interface significantly attenuates and delays transmission of motion from skull to brain. In contrast, in a cylindrical gelatin “phantom,” displacements of the rigid case (reconstructed from accelerometer data) were transmitted to the gelatin inside (estimated from MRE data) with little attenuation or phase lag. This quantitative characterization of the skull–brain interface will be valuable in the parameterization and validation of computer models of TBI. PMID:28267188

The Relationship of Three-Dimensional Human Skull Motion to Brain Tissue Deformation in Magnetic Resonance Elastography Studies.

PubMed

Badachhape, Andrew A; Okamoto, Ruth J; Durham, Ramona S; Efron, Brent D; Nadell, Sam J; Johnson, Curtis L; Bayly, Philip V

2017-05-01

In traumatic brain injury (TBI), membranes such as the dura mater, arachnoid mater, and pia mater play a vital role in transmitting motion from the skull to brain tissue. Magnetic resonance elastography (MRE) is an imaging technique developed for noninvasive estimation of soft tissue material parameters. In MRE, dynamic deformation of brain tissue is induced by skull vibrations during magnetic resonance imaging (MRI); however, skull motion and its mode of transmission to the brain remain largely uncharacterized. In this study, displacements of points in the skull, reconstructed using data from an array of MRI-safe accelerometers, were compared to displacements of neighboring material points in brain tissue, estimated from MRE measurements. Comparison of the relative amplitudes, directions, and temporal phases of harmonic motion in the skulls and brains of six human subjects shows that the skull-brain interface significantly attenuates and delays transmission of motion from skull to brain. In contrast, in a cylindrical gelatin "phantom," displacements of the rigid case (reconstructed from accelerometer data) were transmitted to the gelatin inside (estimated from MRE data) with little attenuation or phase lag. This quantitative characterization of the skull-brain interface will be valuable in the parameterization and validation of computer models of TBI.

Diffusion weighted magnetic resonance imaging and its recent trend—a survey

PubMed Central

Chilla, Geetha Soujanya; Tan, Cher Heng

2015-01-01

Since its inception in 1985, diffusion weighted magnetic resonance imaging has been evolving and is becoming instrumental in diagnosis and investigation of tissue functions in various organs including brain, cartilage, and liver. Even though brain related pathology and/or investigation remains as the main application, diffusion weighted magnetic resonance imaging (DWI) is becoming a standard in oncology and in several other applications. This review article provides a brief introduction of diffusion weighted magnetic resonance imaging, challenges involved and recent advancements. PMID:26029644

Magnetic bead-quantum dot assay for detection of a biomarker for traumatic brain injury

NASA Astrophysics Data System (ADS)

Kim, Chloe; Searson, Peter C.

2015-10-01

Current diagnostic methods for traumatic brain injury (TBI), which accounts for 15% of all emergency room visits, are limited to neuroimaging modalities. The challenges of accurate diagnosis and monitoring of TBI have created the need for a simple and sensitive blood test to detect brain-specific biomarkers. Here we report on an assay for detection of S100B, a putative biomarker for TBI, using antibody-conjugated magnetic beads for capture of the protein, and antibody-conjugated quantum dots for optical detection. From Western Blot, we show efficient antigen capture and concentration by the magnetic beads. Using magnetic bead capture and quantum dot detection in serum samples, we show a wide detection range and detection limit below the clinical cut-off level.Current diagnostic methods for traumatic brain injury (TBI), which accounts for 15% of all emergency room visits, are limited to neuroimaging modalities. The challenges of accurate diagnosis and monitoring of TBI have created the need for a simple and sensitive blood test to detect brain-specific biomarkers. Here we report on an assay for detection of S100B, a putative biomarker for TBI, using antibody-conjugated magnetic beads for capture of the protein, and antibody-conjugated quantum dots for optical detection. From Western Blot, we show efficient antigen capture and concentration by the magnetic beads. Using magnetic bead capture and quantum dot detection in serum samples, we show a wide detection range and detection limit below the clinical cut-off level. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr05608j

Low-frequency transcranial magnetic stimulation is beneficial for enhancing synaptic plasticity in the aging brain.

PubMed

Zhang, Zhan-Chi; Luan, Feng; Xie, Chun-Yan; Geng, Dan-Dan; Wang, Yan-Yong; Ma, Jun

2015-06-01

In the aging brain, cognitive function gradually declines and causes a progressive reduction in the structural and functional plasticity of the hippocampus. Transcranial magnetic stimulation is an emerging and novel neurological and psychiatric tool used to investigate the neurobiology of cognitive function. Recent studies have demonstrated that low-frequency transcranial magnetic stimulation (≤1 Hz) ameliorates synaptic plasticity and spatial cognitive deficits in learning-impaired mice. However, the mechanisms by which this treatment improves these deficits during normal aging are still unknown. Therefore, the current study investigated the effects of transcranial magnetic stimulation on the brain-derived neurotrophic factor signal pathway, synaptic protein markers, and spatial memory behavior in the hippocampus of normal aged mice. The study also investigated the downstream regulator, Fyn kinase, and the downstream effectors, synaptophysin and growth-associated protein 43 (both synaptic markers), to determine the possible mechanisms by which transcranial magnetic stimulation regulates cognitive capacity. Transcranial magnetic stimulation with low intensity (110% average resting motor threshold intensity, 1 Hz) increased mRNA and protein levels of brain-derived neurotrophic factor, tropomyosin receptor kinase B, and Fyn in the hippocampus of aged mice. The treatment also upregulated the mRNA and protein expression of synaptophysin and growth-associated protein 43 in the hippocampus of these mice. In conclusion, brain-derived neurotrophic factor signaling may play an important role in sustaining and regulating structural synaptic plasticity induced by transcranial magnetic stimulation in the hippocampus of aging mice, and Fyn may be critical during this regulation. These responses may change the structural plasticity of the aging hippocampus, thereby improving cognitive function.

Magnetic resonance imaging of the kinked fetal brain stem: a sign of severe dysgenesis.

PubMed

Stroustrup Smith, Annemarie; Levine, Deborah; Barnes, Patrick D; Robertson, Richard L

2005-12-01

Magnetic resonance imaging (MRI) allows visualization of the fetal brain stem in a manner not previously possible. A "kinked" brain stem is a sign of severe neurodysgenesis. The purpose of this series was to describe cases of a kinked brain stem detected on prenatal MRI and to discuss the possible genetic and syndromic etiologies. Seven cases of a kinked brain stem on fetal MRI (gestational age range, 18-34 weeks) were reviewed and correlated with other clinical, genetic, imaging, and autopsy findings. In all cases, there was associated cerebellar hypogenesis. Additional findings were ventriculomegaly (4 cases), cerebral hypogenesis (3 cases), microcephaly (4 cases), schizencephaly (1 case), cephalocele (1 case), hypogenesis of the corpus callosum (1 case), and hydrocephalus (1 case). In 2 cases, prenatal sonography misidentified the kinked brain stem as the cerebellum. A kinked brain stem is an indicator of severe neurodysgenesis arising early in gestation. Magnetic resonance imaging provides the necessary resolution to detect this sign and delineate any associated anomalies in utero to assist with further genetic evaluation, management, and counseling.

Coupling of transient near infrared photonic with magnetic nanoparticle for potential dissipation-free biomedical application in brain

PubMed Central

Sagar, Vidya; Atluri, V. S. R.; Tomitaka, A.; Shah, P.; Nagasetti, A.; Pilakka-Kanthikeel, S.; El-Hage, N.; McGoron, A.; Takemura, Y.; Nair, M.

2016-01-01

Combined treatment strategies based on magnetic nanoparticles (MNPs) with near infrared ray (NIR) biophotonic possess tremendous potential for non-invasive therapeutic approach. Nonetheless, investigations in this direction have been limited to peripheral body region and little is known about the potential biomedical application of this approach for brain. Here we report that transient NIR exposure is dissipation-free and has no adverse effect on the viability and plasticity of major brain cells in the presence or absence superparamagnetic nanoparticles. The 808 nm NIR laser module with thermocouple was employed for functional studies upon NIR exposure to brain cells. Magnetic nanoparticles were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), dynamic laser scattering (DLS), and vibrating sample magnetometer (VSM). Brain cells viability and plasticity were analyzed using electric cell-substrate impedance sensing system, cytotoxicity evaluation, and confocal microscopy. When efficacious non-invasive photobiomodulation and neuro-therapeutical targeting and monitoring to brain remain a formidable task, the discovery of this dissipation-free, transient NIR photonic approach for brain cells possesses remarkable potential to add new dimension. PMID:27465276

Coupling of transient near infrared photonic with magnetic nanoparticle for potential dissipation-free biomedical application in brain.

PubMed

Sagar, Vidya; Atluri, V S R; Tomitaka, A; Shah, P; Nagasetti, A; Pilakka-Kanthikeel, S; El-Hage, N; McGoron, A; Takemura, Y; Nair, M

2016-07-28

Combined treatment strategies based on magnetic nanoparticles (MNPs) with near infrared ray (NIR) biophotonic possess tremendous potential for non-invasive therapeutic approach. Nonetheless, investigations in this direction have been limited to peripheral body region and little is known about the potential biomedical application of this approach for brain. Here we report that transient NIR exposure is dissipation-free and has no adverse effect on the viability and plasticity of major brain cells in the presence or absence superparamagnetic nanoparticles. The 808 nm NIR laser module with thermocouple was employed for functional studies upon NIR exposure to brain cells. Magnetic nanoparticles were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), dynamic laser scattering (DLS), and vibrating sample magnetometer (VSM). Brain cells viability and plasticity were analyzed using electric cell-substrate impedance sensing system, cytotoxicity evaluation, and confocal microscopy. When efficacious non-invasive photobiomodulation and neuro-therapeutical targeting and monitoring to brain remain a formidable task, the discovery of this dissipation-free, transient NIR photonic approach for brain cells possesses remarkable potential to add new dimension.

Coupling of transient near infrared photonic with magnetic nanoparticle for potential dissipation-free biomedical application in brain

NASA Astrophysics Data System (ADS)

Sagar, Vidya; Atluri, V. S. R.; Tomitaka, A.; Shah, P.; Nagasetti, A.; Pilakka-Kanthikeel, S.; El-Hage, N.; McGoron, A.; Takemura, Y.; Nair, M.

2016-07-01

Combined treatment strategies based on magnetic nanoparticles (MNPs) with near infrared ray (NIR) biophotonic possess tremendous potential for non-invasive therapeutic approach. Nonetheless, investigations in this direction have been limited to peripheral body region and little is known about the potential biomedical application of this approach for brain. Here we report that transient NIR exposure is dissipation-free and has no adverse effect on the viability and plasticity of major brain cells in the presence or absence superparamagnetic nanoparticles. The 808 nm NIR laser module with thermocouple was employed for functional studies upon NIR exposure to brain cells. Magnetic nanoparticles were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), dynamic laser scattering (DLS), and vibrating sample magnetometer (VSM). Brain cells viability and plasticity were analyzed using electric cell-substrate impedance sensing system, cytotoxicity evaluation, and confocal microscopy. When efficacious non-invasive photobiomodulation and neuro-therapeutical targeting and monitoring to brain remain a formidable task, the discovery of this dissipation-free, transient NIR photonic approach for brain cells possesses remarkable potential to add new dimension.

Measuring iron in the brain using quantitative susceptibility mapping and X-ray fluorescence imaging

PubMed Central

Zheng, Weili; Nichol, Helen; Liu, Saifeng; Cheng, Yu-Chung N.; Haacke, E. Mark

2013-01-01

Measuring iron content in the brain has important implications for a number of neurodegenerative diseases. Quantitative susceptibility mapping (QSM), derived from magnetic resonance images, has been used to measure total iron content in vivo and in post mortem brain. In this paper, we show how magnetic susceptibility from QSM correlates with total iron content measured by X-ray fluorescence (XRF) imaging and by inductively coupled plasma mass spectrometry (ICPMS). The relationship between susceptibility and ferritin iron was estimated at 1.10 ± 0.08 ppb susceptibility per μg iron/g wet tissue, similar to that of iron in fixed (frozen/thawed) cadaveric brain and previously published data from unfixed brains. We conclude that magnetic susceptibility can provide a direct and reliable quantitative measurement of iron content and that it can be used clinically at least in regions with high iron content. PMID:23591072

Item-specific and generalization effects on brain activation when learning Chinese characters

PubMed Central

Deng, Yuan; Booth, James R.; Chou, Tai-Li; Ding, Guo-Sheng; Peng, Dan-Ling

2009-01-01

Neural changes related to learning of the meaning of Chinese characters in English speakers were examined using functional magnetic resonance imaging (fMRI). We examined item specific learning effects for trained characters, but also the generalization of semantic knowledge to novel transfer characters that shared a semantic radical (part of a character that gives a clue to word meaning, e.g. water for lake) with trained characters. Behavioral results show that acquired semantic knowledge improves performance for both trained and transfer characters. Neuroimaging results show that the left fusiform gyrus plays a central role in the visual processing of orthographic information in characters. The left superior parietal cortex seems to play a crucial role in learning the visual–spatial aspects of the characters because it shows learning related decreases for trained characters, is correlated with behavioral improvement from early to late in learning for the trained characters, and is correlated with better long-term retention for the transfer characters. The inferior frontal gyrus seems to be associated with the efficiency of retrieving and manipulating semantic representations because there are learning related decreases for trained characters and this decrease is correlated with greater behavioral improvement from early to late in learning. PMID:18514678

Functional relevance of interindividual differences in temporal lobe callosal pathways: a DTI tractography study.

PubMed

Westerhausen, René; Grüner, Renate; Specht, Karsten; Hugdahl, Kenneth

2009-06-01

The midsagittal corpus callosum is topographically organized, that is, with regard to their cortical origin several subtracts can be distinguished within the corpus callosum that belong to specific functional brain networks. Recent diffusion tensor tractography studies have also revealed remarkable interindividual differences in the size and exact localization of these tracts. To examine the functional relevance of interindividual variability in callosal tracts, 17 right-handed male participants underwent structural and diffusion tensor magnetic resonance imaging. Probabilistic tractography was carried out to identify the callosal subregions that interconnect left and right temporal lobe auditory processing areas, and the midsagittal size of this tract was seen as indicator of the (anatomical) strength of this connection. Auditory information transfer was assessed applying an auditory speech perception task with dichotic presentations of consonant-vowel syllables (e.g., /ba-ga/). The frequency of correct left ear reports in this task served as a functional measure of interhemispheric transfer. Statistical analysis showed that a stronger anatomical connection between the superior temporal lobe areas supports a better information transfer. This specific structure-function association in the auditory modality supports the general notion that interindividual differences in callosal topography possess functional relevance.

Functional Magnetic Resonance Imaging

ERIC Educational Resources Information Center

Voos, Avery; Pelphrey, Kevin

2013-01-01

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

Magnetic Silica-Supported Ruthenium Nanoparticles: An Efficient Catalyst for Transfer Hydrogenation of Carbonyl Compounds

EPA Science Inventory

One-pot synthesis of ruthenium nanoparticles on magnetic silica is described which involve the in situ generation of magnetic silica (Fe3O4@ SiO2) and ruthenium nano particles immobilization; the hydration of nitriles and transfer hydrogenation of carbonyl compounds occurs in hi...

Simultaneous pH-sensitive and oxygen-sensitive MRI of human gliomas at 3 T using multi-echo amine proton chemical exchange saturation transfer spin-and-gradient echo echo-planar imaging (CEST-SAGE-EPI).

PubMed

Harris, Robert J; Yao, Jingwen; Chakhoyan, Ararat; Raymond, Catalina; Leu, Kevin; Liau, Linda M; Nghiemphu, Phioanh L; Lai, Albert; Salamon, Noriko; Pope, Whitney B; Cloughesy, Timothy F; Ellingson, Benjamin M

2018-04-06

To introduce a new pH-sensitive and oxygen-sensitive MRI technique using amine proton CEST echo spin-and-gradient echo (SAGE) EPI (CEST-SAGE-EPI). pH-weighting was obtained using CEST estimations of magnetization transfer ratio asymmetry (MTR asym ) at 3 ppm, and oxygen-weighting was obtained using R2' measurements. Glutamine concentration, pH, and relaxation rates were varied in phantoms to validate simulations and estimate relaxation rates. The values of MTR asym and R2' in normal-appearing white matter, T 2 hyperintensity, contrast enhancement, and macroscopic necrosis were measured in 47 gliomas. Simulation and phantom results confirmed an increase in MTR asym with decreasing pH. The CEST-SAGE-EPI estimates of R 2 , R2*, and R2' varied linearly with gadolinium diethylenetriamine penta-acetic acid concentration (R 2  = 6.2 mM -1 ·sec -1 and R2* = 6.9 mM -1 ·sec -1 ). The CEST-SAGE-EPI and Carr-Purcell-Meiboom-Gill estimates of R 2 (R 2  = 0.9943) and multi-echo gradient-echo estimates of R2* (R 2  = 0.9727) were highly correlated. T 2 lesions had lower R2' and higher MTR asym compared with normal-appearing white matter, suggesting lower hypoxia and high acidity, whereas contrast-enhancement tumor regions had elevated R2' and MTR asym , indicating high hypoxia and acidity. The CEST-SAGE-EPI technique provides simultaneous pH-sensitive and oxygen-sensitive image contrasts for evaluation of the brain tumor microenvironment. Advantages include fast whole-brain acquisition, in-line B 0 correction, and simultaneous estimation of CEST effects, R 2 , R2*, and R2' at 3 T. © 2018 International Society for Magnetic Resonance in Medicine.

Transcranial magnetic stimulation-induced global propagation of transient phase resetting associated with directional information flow.

PubMed

Kawasaki, Masahiro; Uno, Yutaka; Mori, Jumpei; Kobata, Kenji; Kitajo, Keiichi

2014-01-01

Electroencephalogram (EEG) phase synchronization analyses can reveal large-scale communication between distant brain areas. However, it is not possible to identify the directional information flow between distant areas using conventional phase synchronization analyses. In the present study, we applied transcranial magnetic stimulation (TMS) to the occipital area in subjects who were resting with their eyes closed, and analyzed the spatial propagation of transient TMS-induced phase resetting by using the transfer entropy (TE), to quantify the causal and directional flow of information. The time-frequency EEG analysis indicated that the theta (5 Hz) phase locking factor (PLF) reached its highest value at the distant area (the motor area in this study), with a time lag that followed the peak of the transient PLF enhancements of the TMS-targeted area at the TMS onset. Phase-preservation index (PPI) analyses demonstrated significant phase resetting at the TMS-targeted area and distant area. Moreover, the TE from the TMS-targeted area to the distant area increased clearly during the delay that followed TMS onset. Interestingly, the time lags were almost coincident between the PLF and TE results (152 vs. 165 ms), which provides strong evidence that the emergence of the delayed PLF reflects the causal information flow. Such tendencies were observed only in the higher-intensity TMS condition, and not in the lower-intensity or sham TMS conditions. Thus, TMS may manipulate large-scale causal relationships between brain areas in an intensity-dependent manner. We demonstrated that single-pulse TMS modulated global phase dynamics and directional information flow among synchronized brain networks. Therefore, our results suggest that single-pulse TMS can manipulate both incoming and outgoing information in the TMS-targeted area associated with functional changes.

Temperature control at DBS electrodes using a heat sink: experimentally validated FEM model of DBS lead architecture.

PubMed

Elwassif, Maged M; Datta, Abhishek; Rahman, Asif; Bikson, Marom

2012-08-01

There is a growing interest in the use of deep brain stimulation (DBS) for the treatment of medically refractory movement disorders and other neurological and psychiatric conditions. The extent of temperature increases around DBS electrodes during normal operation (joule heating and increased metabolic activity) or coupling with an external source (e.g. magnetic resonance imaging) remains poorly understood and methods to mitigate temperature increases are being actively investigated. We developed a heat transfer finite element method (FEM) simulation of DBS incorporating the realistic architecture of Medtronic 3389 leads. The temperature changes were analyzed considering different electrode configurations, stimulation protocols and tissue properties. The heat-transfer model results were then validated using micro-thermocouple measurements during DBS lead stimulation in a saline bath. FEM results indicate that lead design (materials and geometry) may have a central role in controlling temperature rise by conducting heat. We show how modifying lead design can effectively control temperature increases. The robustness of this heat-sink approach over complimentary heat-mitigation technologies follows from several features: (1) it is insensitive to the mechanisms of heating (e.g. nature of magnetic coupling); (2) it does not interfere with device efficacy; and (3) can be practically implemented in a broad range of implanted devices without modifying the normal device operations or the implant procedure.

Temperature control at DBS electrodes using a heat sink: experimentally validated FEM model of DBS lead architecture

NASA Astrophysics Data System (ADS)

Elwassif, Maged M.; Datta, Abhishek; Rahman, Asif; Bikson, Marom

2012-08-01

There is a growing interest in the use of deep brain stimulation (DBS) for the treatment of medically refractory movement disorders and other neurological and psychiatric conditions. The extent of temperature increases around DBS electrodes during normal operation (joule heating and increased metabolic activity) or coupling with an external source (e.g. magnetic resonance imaging) remains poorly understood and methods to mitigate temperature increases are being actively investigated. We developed a heat transfer finite element method (FEM) simulation of DBS incorporating the realistic architecture of Medtronic 3389 leads. The temperature changes were analyzed considering different electrode configurations, stimulation protocols and tissue properties. The heat-transfer model results were then validated using micro-thermocouple measurements during DBS lead stimulation in a saline bath. FEM results indicate that lead design (materials and geometry) may have a central role in controlling temperature rise by conducting heat. We show how modifying lead design can effectively control temperature increases. The robustness of this heat-sink approach over complimentary heat-mitigation technologies follows from several features: (1) it is insensitive to the mechanisms of heating (e.g. nature of magnetic coupling); (2) it does not interfere with device efficacy; and (3) can be practically implemented in a broad range of implanted devices without modifying the normal device operations or the implant procedure.

Mechanism of orientation of stimulating currents in magnetic brain stimulation (abstract)

NASA Astrophysics Data System (ADS)

Ueno, S.; Matsuda, T.

1991-04-01

We made a functional map of the human motor cortex related to the hand and foot areas by stimulating the human brain with a focused magnetic pulse. We observed that each functional area in the cortex has an optimum direction for which stimulating currents can produce neural excitation. The present report focuses on the mechanism which is responsible for producing this anisotropic response to brain stimulation. We first obtained a functional map of the brain related to the left ADM (abductor digiti minimi muscles). When the stimulating currents were aligned in the direction from the left to the right hemisphere, clear EMG (electromyographic) responses were obtained only from the left ADM to magnetic stimulation of both hemisphere. When the stimulating currents were aligned in the direction from the right to the left hemisphere, clear EMG signals were obtained only from the right ADM to magnetic stimulation of both hemisphere. The functional maps of the brain were sensitive to changes in the direction of the stimulating currents. To explain the phenomena obtained in the experiments, we developed a model of neural excitation elicited by magnetic stimulation. When eddy currents which are induced by pulsed magnetic fields flow in the direction from soma to the distal part of neural fiber, depolarized area in the distal part are excited, and the membrane excitation propagates along the nerve fiber. In contrast, when the induced currents flow in the direction from the distal part to soma, hyperpolarized parts block or inhibit neural excitation even if the depolarized parts near the soma can be excited. The model explains our observation that the orientation of the induced current vectors reflect both the functional and anatomical organization of the neural fibers in the brain.

Occupational exposure to magnetic fields in relation to mortality from brain cancer among electricity generation and transmission workers.

PubMed Central

Harrington, J M; McBride, D I; Sorahan, T; Paddle, G M; van Tongeren, M

1997-01-01

OBJECTIVE: To investigate whether the risks of mortality from brain cancer are related to occupational exposure to magnetic fields. METHODS: A total of 112 cases of primary brain cancer (1972-91) were identified from a cohort of 84,018 male and female employees of the (then) Central Electricity Generating Board and its privatised successor companies. Individual cumulative occupational exposures to magnetic fields were estimated by linking available computerised job history data with magnetic field measurements collected over 675 person-workshifts. Estimated exposure histories of the case workers were compared with those of 654 control workers drawn from the cohort (nested case-control study), by means of conditional logistic regression. RESULTS: For exposure assessments based on arithmetic means, the risk of mortality from brain cancer for subjects with an estimated cumulative exposure to magnetic fields of 5.4-13.4 microT.y v subjects with lower exposures (0.0-5.3 microT.y) was 1.04 (95% confidence interval (95% CI) 0.60 to 1.80). The corresponding relative risk in subjects with higher exposures (> or = 13.5 microT.y) was 0.95 (95% CI 0.54 to 1.69). There was no indication of a positive trend for cumulative exposure and risk of mortality from brain cancer either when the analysis used exposure assessments based on geometric means or when the analysis was restricted to exposures received within five years of the case diagnosis (or corresponding period for controls). CONCLUSIONS: Although the exposure categorisation was based solely on recent observations, the study findings do not support the hypothesis that the risk of brain cancer is associated with occupational exposure to magnetic fields. PMID:9072027

Whole brain myelin mapping using T1- and T2-weighted MR imaging data

PubMed Central

Ganzetti, Marco; Wenderoth, Nicole; Mantini, Dante

2014-01-01

Despite recent advancements in MR imaging, non-invasive mapping of myelin in the brain still remains an open issue. Here we attempted to provide a potential solution. Specifically, we developed a processing workflow based on T1-w and T2-w MR data to generate an optimized myelin enhanced contrast image. The workflow allows whole brain mapping using the T1-w/T2-w technique, which was originally introduced as a non-invasive method for assessing cortical myelin content. The hallmark of our approach is a retrospective calibration algorithm, applied to bias-corrected T1-w and T2-w images, that relies on image intensities outside the brain. This permits standardizing the intensity histogram of the ratio image, thereby allowing for across-subject statistical analyses. Quantitative comparisons of image histograms within and across different datasets confirmed the effectiveness of our normalization procedure. Not only did the calibrated T1-w/T2-w images exhibit a comparable intensity range, but also the shape of the intensity histograms was largely corresponding. We also assessed the reliability and specificity of the ratio image compared to other MR-based techniques, such as magnetization transfer ratio (MTR), fractional anisotropy (FA), and fluid-attenuated inversion recovery (FLAIR). With respect to these other techniques, T1-w/T2-w had consistently high values, as well as low inter-subject variability, in brain structures where myelin is most abundant. Overall, our results suggested that the T1-w/T2-w technique may be a valid tool supporting the non-invasive mapping of myelin in the brain. Therefore, it might find important applications in the study of brain development, aging and disease. PMID:25228871

Cerebral motor function in very premature-at-birth adolescents: a brain stimulation exploration of kangaroo mother care effects.

PubMed

Schneider, Cyril; Charpak, Nathalie; Ruiz-Peláez, Juan G; Tessier, Réjean

2012-10-01

  Given that prematurity has deleterious effects on brain networking development beyond childhood, the study explored whether an early intervention such as Kangaroo Mother Care (KMC) in very preterm preemies could have influenced brain motor function up to adolescence.   Transcranial magnetic stimulation (TMS) was applied over the primary motor cortex (M1) of 39 adolescents born very prematurely (<33 weeks' gestational age, 21 having received KMC after birth, 18 Controls with no KMC) and nine adolescents born at term (>37 weeks' gestational age, >2500 g) to assess the functional integrity of motor circuits in each hemisphere (motor planning) and between hemispheres (callosal function).   All TMS outcomes were similar between KMC and term adolescents, with typical values as in healthy adults, and better than in Controls. KMC adolescents presented faster conduction times revealing more efficient M1 cell synchronization (p < 0.05) and interhemispheric transfer time (p < 0.0001), more frequent inhibitory processes with a better control between hemispheres (p < 0.0001).   The enhanced synchronization, conduction times and connectivity of cerebral motor pathways in the KMC group suggests that the Kangaroo Mother Care positively influenced the premature brain networks and synaptic efficacy up to adolescence. © 2012 The Author(s)/Acta Paediatrica © 2012 Foundation Acta Paediatrica.

Brain functional magnetic resonance imaging response to glucose and fructose infusions in humans

USDA-ARS?s Scientific Manuscript database

Objective: In animals, intracerebroventricular glucose and fructose have opposing effects on appetite and weight regulation. In humans, functional brain magnetic resonance imaging (fMRI) studies during carbohydrate ingestion suggest that glucose may regulate HT signaling but are potentially confoun...

Theory of atomistic simulation of spin-transfer torque in nanomagnets

NASA Astrophysics Data System (ADS)

Tay, Tiamhock; Sham, L. J.

2013-05-01

In spin-transfer torque (STT) for technological applications, the miniaturization of the magnet may reach the stage of requiring a fully quantum-mechanical treatment. We present an STT theory which uses the quantum macrospin ground and excited (magnon) states of the nanomagnet. This allows for energy and angular momentum exchanges between the current electron and the nano-magnet. We develop a method of magnetization dynamics simulation which captures the heating effect on the magnet by the spin-polarized current and the temperature dependence in STT. We also discuss the magnetostatics effect on magnon scattering for ferromagnetic relaxation in a thin film. Our work demonstrates a realistic step towards simulation of quantum spin-transfer torque physics in nanoscale magnets.

Brain-Targeted Delivery of Trans-Activating Transcriptor-Conjugated Magnetic PLGA/Lipid Nanoparticles

PubMed Central

Zhang, Yifang; Sun, Tingting; Zhang, Fang; Wu, Jian; Fu, Yanyan; Du, Yang; Zhang, Lei; Sun, Ying; Liu, YongHai; Ma, Kai; Liu, Hongzhi; Song, Yuanjian

2014-01-01

Magnetic poly (D,L-lactide-co-glycolide) (PLGA)/lipid nanoparticles (MPLs) were fabricated from PLGA, L-α-phosphatidylethanolamine (DOPE), 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-amino (polyethylene glycol) (DSPE-PEG-NH2), and magnetic nanoparticles (NPs), and then conjugated to trans-activating transcriptor (TAT) peptide. The TAT-MPLs were designed to target the brain by magnetic guidance and TAT conjugation. The drugs hesperidin (HES), naringin (NAR), and glutathione (GSH) were encapsulated in MPLs with drug loading capacity (>10%) and drug encapsulation efficiency (>90%). The therapeutic efficacy of the drug-loaded TAT-MPLs in bEnd.3 cells was compared with that of drug-loaded MPLs. The cells accumulated higher levels of TAT-MPLs than MPLs. In addition, the accumulation of QD-loaded fluorescein isothiocyanate (FITC)-labeled TAT-MPLs in bEnd.3 cells was dose and time dependent. Our results show that TAT-conjugated MPLs may function as an effective drug delivery system that crosses the blood brain barrier to the brain. PMID:25187980

Brain-targeted delivery of trans-activating transcriptor-conjugated magnetic PLGA/lipid nanoparticles.

PubMed

Wen, Xiangru; Wang, Kai; Zhao, Ziming; Zhang, Yifang; Sun, Tingting; Zhang, Fang; Wu, Jian; Fu, Yanyan; Du, Yang; Zhang, Lei; Sun, Ying; Liu, YongHai; Ma, Kai; Liu, Hongzhi; Song, Yuanjian

2014-01-01

Magnetic poly (D,L-lactide-co-glycolide) (PLGA)/lipid nanoparticles (MPLs) were fabricated from PLGA, L-α-phosphatidylethanolamine (DOPE), 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-amino (polyethylene glycol) (DSPE-PEG-NH2), and magnetic nanoparticles (NPs), and then conjugated to trans-activating transcriptor (TAT) peptide. The TAT-MPLs were designed to target the brain by magnetic guidance and TAT conjugation. The drugs hesperidin (HES), naringin (NAR), and glutathione (GSH) were encapsulated in MPLs with drug loading capacity (>10%) and drug encapsulation efficiency (>90%). The therapeutic efficacy of the drug-loaded TAT-MPLs in bEnd.3 cells was compared with that of drug-loaded MPLs. The cells accumulated higher levels of TAT-MPLs than MPLs. In addition, the accumulation of QD-loaded fluorescein isothiocyanate (FITC)-labeled TAT-MPLs in bEnd.3 cells was dose and time dependent. Our results show that TAT-conjugated MPLs may function as an effective drug delivery system that crosses the blood brain barrier to the brain.

Noninvasive Brain Stimulation in Pediatric Attention-Deficit Hyperactivity Disorder (ADHD): A Review.

PubMed

Rubio, Belen; Boes, Aaron D; Laganiere, Simon; Rotenberg, Alexander; Jeurissen, Danique; Pascual-Leone, Alvaro

2016-05-01

Attention-deficit hyperactivity disorder (ADHD) is one of the most prevalent neurodevelopmental disorders in the pediatric population. The clinical management of ADHD is currently limited by a lack of reliable diagnostic biomarkers and inadequate therapy for a minority of patients who do not respond to standard pharmacotherapy. There is optimism that noninvasive brain stimulation may help to address these limitations. Transcranial magnetic stimulation and transcranial direct current stimulation are 2 methods of noninvasive brain stimulation that modulate cortical excitability and brain network activity. Transcranial magnetic stimulation can be used diagnostically to probe cortical neurophysiology, whereas daily use of repetitive transcranial magnetic stimulation or transcranial direct current stimulation can induce long-lasting and potentially therapeutic changes in targeted networks. In this review, we highlight research showing the potential diagnostic and therapeutic applications of transcranial magnetic stimulation and transcranial direct current stimulation in pediatric ADHD. We also discuss the safety and ethics of using these tools in the pediatric population. © The Author(s) 2015.

Magnetic Resonance, Functional (fMRI) -- Brain

MedlinePlus

... thought, speech, movement and sensation, which is called brain mapping. help assess the effects of stroke, trauma, or degenerative disease (such as Alzheimer's) on brain function. monitor the growth and function of brain ...

Quantitative analysis of the z-spectrum using a numerically simulated look-up table: Application to the healthy human brain at 7T.

PubMed

Geades, Nicolas; Hunt, Benjamin A E; Shah, Simon M; Peters, Andrew; Mougin, Olivier E; Gowland, Penny A

2017-08-01

To develop a method that fits a multipool model to z-spectra acquired from non-steady state sequences, taking into account the effects of variations in T1 or B1 amplitude and the results estimating the parameters for a four-pool model to describe the z-spectrum from the healthy brain. We compared measured spectra with a look-up table (LUT) of possible spectra and investigated the potential advantages of simultaneously considering spectra acquired at different saturation powers (coupled spectra) to provide sensitivity to a range of different physicochemical phenomena. The LUT method provided reproducible results in healthy controls. The average values of the macromolecular pool sizes measured in white matter (WM) and gray matter (GM) of 10 healthy volunteers were 8.9% ± 0.3% (intersubject standard deviation) and 4.4% ± 0.4%, respectively, whereas the average nuclear Overhauser effect pool sizes in WM and GM were 5% ± 0.1% and 3% ± 0.1%, respectively, and average amide proton transfer pool sizes in WM and GM were 0.21% ± 0.03% and 0.20% ± 0.02%, respectively. The proposed method demonstrated increased robustness when compared with existing methods (such as Lorentzian fitting and asymmetry analysis) while yielding fully quantitative results. The method can be adjusted to measure other parameters relevant to the z-spectrum. Magn Reson Med 78:645-655, 2017. © 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. © 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine.

Transcallosal transfer of information and functional asymmetry of the human brain.

PubMed

Nowicka, Anna; Tacikowski, Pawel

2011-01-01

The corpus callosum is the largest commissure in the brain and acts as a "bridge" of nerve fibres connecting the two cerebral hemispheres. It plays a crucial role in interhemispheric integration and is responsible for normal communication and cooperation between the two hemispheres. Evolutionary pressures guiding brain size are accompanied by reduced interhemispheric and enhanced intrahemispheric connectivity. Some lines of evidence suggest that the speed of transcallosal conduction is limited in large brains (e.g., in humans), thus favouring intrahemispheric processing and brain lateralisation. Patterns of directional symmetry/asymmetry of transcallosal transfer time may be related to the degree of brain lateralisation. Neural network modelling and electrophysiological studies on interhemispheric transmission provide data supporting this supposition.

Electro-mechanical energy conversion system having a permanent magnet machine with stator, resonant transfer link and energy converter controls

DOEpatents

Skeist, S. Merrill; Baker, Richard H.

2006-01-10

An electro-mechanical energy conversion system coupled between an energy source and an energy load comprising an energy converter device including a permanent magnet induction machine coupled between the energy source and the energy load to convert the energy from the energy source and to transfer the converted energy to the energy load and an energy transfer multiplexer to control the flow of power or energy through the permanent magnetic induction machine.

Serotonergic psychedelics temporarily modify information transfer in humans.

PubMed

Alonso, Joan Francesc; Romero, Sergio; Mañanas, Miquel Àngel; Riba, Jordi

2015-03-28

Psychedelics induce intense modifications in the sensorium, the sense of "self," and the experience of reality. Despite advances in our understanding of the molecular and cellular level mechanisms of these drugs, knowledge of their actions on global brain dynamics is still incomplete. Recent imaging studies have found changes in functional coupling between frontal and parietal brain structures, suggesting a modification in information flow between brain regions during acute effects. Here we assessed the psychedelic-induced changes in directionality of information flow during the acute effects of a psychedelic in humans. We measured modifications in connectivity of brain oscillations using transfer entropy, a nonlinear measure of directed functional connectivity based on information theory. Ten healthy male volunteers with prior experience with psychedelics participated in 2 experimental sessions. They received a placebo or a dose of ayahuasca, a psychedelic preparation containing the serotonergic 5-HT2A agonist N,N-dimethyltryptamine. The analysis showed significant changes in the coupling of brain oscillations between anterior and posterior recording sites. Transfer entropy analysis showed that frontal sources decreased their influence over central, parietal, and occipital sites. Conversely, sources in posterior locations increased their influence over signals measured at anterior locations. Exploratory correlations found that anterior-to-posterior transfer entropy decreases were correlated with the intensity of subjective effects, while the imbalance between anterior-to-posterior and posterior-to-anterior transfer entropy correlated with the degree of incapacitation experienced. These results suggest that psychedelics induce a temporary disruption of neural hierarchies by reducing top-down control and increasing bottom-up information transfer in the human brain. © The Author 2015. Published by Oxford University Press on behalf of CINP.

Digital photography and 3D MRI-based multimodal imaging for individualized planning of resective neocortical epilepsy surgery.

PubMed

Wellmer, Jörg; von Oertzen, Joachim; Schaller, Carlo; Urbach, Horst; König, Roy; Widman, Guido; Van Roost, Dirk; Elger, Christian E

2002-12-01

Invasive presurgical work up of pharmacoresistant epilepsies presumes integration of multiple diagnostic modalities into a comprehensive picture of seizure onset and eloquent brain areas. During resection, reliable transfer of evaluation results to the patient's individual anatomy must be made. We investigated the value of digital photography-based grid localization in combination with preoperative three-dimensional (3D) magnetic resonance imaging (MRI) for clinical routine. Digital photographs of the exposed cortex were taken before and after grid placement. Location of electrode contacts on the cortex was identified and schematically indicated on native cortex prints. Accordingly, transfer of contact positions to a 3D MRI brain-surface rendering was carried out manually by using the rendering software. Results of the electrophysiologic evaluation were transferred to either electrode contact reproduction and co-registered with imaging-based techniques such as single-photon emission computed tomography (SPECT), positron emission tomography (PET), and functional MRI (fMRI). Digital photography allows precise and highly realistic documentation of electrode contact positions on the individual neocortical surface. Lesions underneath grids can be highlighted by semitransparent MRI surface rendering, and lobar boundaries can be identified. Because of integrating electrode contact positions into the postprocessed 3D MRI data set, imaging-based techniques can be codisplayed with the results of the electrophysiologic evaluation. Comparison with CT/MRI co-registration showed good accuracy of the method. However, grids not sewn to the dura at implantation can become subject to significant displacement. Digital photography in combination with preimplantation 3D MRI allows the generation of reliable tailored resection plans in neocortical epilepsy surgery. The method enhances surgical safety and confidence.

Cellular transfer of magnetic nanoparticles via cell microvesicles: impact on cell tracking by magnetic resonance imaging.

PubMed

Silva, Amanda K Andriola; Wilhelm, Claire; Kolosnjaj-Tabi, Jelena; Luciani, Nathalie; Gazeau, Florence

2012-05-01

Cell labeling with magnetic nanoparticles can be used to monitor the fate of transplanted cells in vivo by magnetic resonance imaging. However, nanoparticles initially internalized in administered cells might end up in other cells of the host organism. We investigated a mechanism of intercellular cross-transfer of magnetic nanoparticles to different types of recipient cells via cell microvesicles released under cellular stress. Three cell types (mesenchymal stem cells, endothelial cells and macrophages) were labeled with 8-nm iron oxide nanoparticles. Then cells underwent starvation stress, during which they produced microvesicles that were subsequently transferred to unlabeled recipient cells. The analysis of the magnetophoretic mobility of donor cells indicated that magnetic load was partially lost under cell stress. Microvesicles shed by stressed cells participated in the release of magnetic label. Moreover, such microvesicles were uptaken by naïve cells, resulting in cellular redistribution of nanoparticles. Iron load of recipient cells allowed their detection by MRI. Cell microvesicles released under stress may be disseminated throughout the organism, where they can be uptaken by host cells. The transferred cargo may be sufficient to allow MRI detection of these secondarily labeled cells, leading to misinterpretations of the effectiveness of transplanted cells.

Selective transfer of visual working memory training on Chinese character learning.

PubMed

Opitz, Bertram; Schneiders, Julia A; Krick, Christoph M; Mecklinger, Axel

2014-01-01

Previous research has shown a systematic relationship between phonological working memory capacity and second language proficiency for alphabetic languages. However, little is known about the impact of working memory processes on second language learning in a non-alphabetic language such as Mandarin Chinese. Due to the greater complexity of the Chinese writing system we expect that visual working memory rather than phonological working memory exerts a unique influence on learning Chinese characters. This issue was explored in the present experiment by comparing visual working memory training with an active (auditory working memory training) control condition and a passive, no training control condition. Training induced modulations in language-related brain networks were additionally examined using functional magnetic resonance imaging in a pretest-training-posttest design. As revealed by pre- to posttest comparisons and analyses of individual differences in working memory training gains, visual working memory training led to positive transfer effects on visual Chinese vocabulary learning compared to both control conditions. In addition, we found sustained activation after visual working memory training in the (predominantly visual) left infero-temporal cortex that was associated with behavioral transfer. In the control conditions, activation either increased (active control condition) or decreased (passive control condition) without reliable behavioral transfer effects. This suggests that visual working memory training leads to more efficient processing and more refined responses in brain regions involved in visual processing. Furthermore, visual working memory training boosted additional activation in the precuneus, presumably reflecting mental image generation of the learned characters. We, therefore, suggest that the conjoint activity of the mid-fusiform gyrus and the precuneus after visual working memory training reflects an interaction of working memory and imagery processes with complex visual stimuli that fosters the coherent synthesis of a percept from a complex visual input in service of enhanced Chinese character learning. © 2013 Published by Elsevier Ltd.

Brain signal variability as a window into the bidirectionality between music and language processing: moving from a linear to a nonlinear model.

PubMed

Hutka, Stefanie; Bidelman, Gavin M; Moreno, Sylvain

2013-12-30

There is convincing empirical evidence for bidirectional transfer between music and language, such that experience in either domain can improve mental processes required by the other. This music-language relationship has been studied using linear models (e.g., comparing mean neural activity) that conceptualize brain activity as a static entity. The linear approach limits how we can understand the brain's processing of music and language because the brain is a nonlinear system. Furthermore, there is evidence that the networks supporting music and language processing interact in a nonlinear manner. We therefore posit that the neural processing and transfer between the domains of language and music are best viewed through the lens of a nonlinear framework. Nonlinear analysis of neurophysiological activity may yield new insight into the commonalities, differences, and bidirectionality between these two cognitive domains not measurable in the local output of a cortical patch. We thus propose a novel application of brain signal variability (BSV) analysis, based on mutual information and signal entropy, to better understand the bidirectionality of music-to-language transfer in the context of a nonlinear framework. This approach will extend current methods by offering a nuanced, network-level understanding of the brain complexity involved in music-language transfer.

Wireless power transfer magnetic couplers

DOEpatents

Wu, Hunter; Gilchrist, Aaron; Sealy, Kylee

2016-01-19

A magnetic coupler is disclosed for wireless power transfer systems. A ferrimagnetic component is capable of guiding a magnetic field. A wire coil is wrapped around at least a portion of the ferrimagnetic component. A screen is capable of blocking leakage magnetic fields. The screen may be positioned to cover at least one side of the ferrimagnetic component and the coil. A distance across the screen may be at least six times an air gap distance between the ferrimagnetic component and a receiving magnetic coupler.

Three-dimensional functional magnetic resonance imaging of human brain on a clinical 1.5-T scanner.

PubMed Central

van Gelderen, P; Ramsey, N F; Liu, G; Duyn, J H; Frank, J A; Weinberger, D R; Moonen, C T

1995-01-01

Functional magnetic resonance imaging (fMRI) is a tool for mapping brain function that utilizes neuronal activity-induced changes in blood oxygenation. An efficient three-dimensional fMRI method is presented for imaging brain activity on conventional, widely available, 1.5-T scanners, without additional hardware. This approach uses large magnetic susceptibility weighting based on the echo-shifting principle combined with multiple gradient echoes per excitation. Motor stimulation, induced by self-paced finger tapping, reliably produced significant signal increase in the hand region of the contralateral primary motor cortex in every subject tested. Images Fig. 2 Fig. 3 PMID:7624341

Fetal magnetic resonance imaging (MRI): a tool for a better understanding of normal and abnormal brain development.

PubMed

Saleem, Sahar N

2013-07-01

Knowledge of the anatomy of the developing fetal brain is essential to detect abnormalities and understand their pathogenesis. Capability of magnetic resonance imaging (MRI) to visualize the brain in utero and to differentiate between its various tissues makes fetal MRI a potential diagnostic and research tool for the developing brain. This article provides an approach to understand the normal and abnormal brain development through schematic interpretation of fetal brain MR images. MRI is a potential screening tool in the second trimester of pregnancies in fetuses at risk for brain anomalies and helps in describing new brain syndromes with in utero presentation. Accurate interpretation of fetal MRI can provide valuable information that helps genetic counseling, facilitates management decisions, and guides therapy. Fetal MRI can help in better understanding the pathogenesis of fetal brain malformations and can support research that could lead to disease-specific interventions.

Numerical investigation of the heat transfer of a ferrofluid inside a tube in the presence of a non-uniform magnetic field

NASA Astrophysics Data System (ADS)

Hariri, Saman; Mokhtari, Mojtaba; Gerdroodbary, M. Barzegar; Fallah, Keivan

2017-02-01

In this article, a three-dimensional numerical investigation is performed to study the effect of a magnetic field on a ferrofluid inside a tube. This study comprehensively analyzes the influence of a non-uniform magnetic field in the heat transfer of a tube while a ferrofluid (water with 0.86 vol% nanoparticles (Fe3O4) is let flow. The SIMPLEC algorithm is used for obtaining the flow and heat transfer inside the tube. The influence of various parameters, such as concentration of nanoparticles, intensity of the magnetic field, wire distance and Reynolds number, on the heat transfer is investigated. According to the obtained results, the presence of a non-uniform magnetic field significantly increases the Nusselt number (more than 300%) inside the tube. Also, the magnetic field induced by the parallel wire affects the average velocity of the ferrofluid and forms two strong eddies in the tube. Our findings show that the diffusion also raises as the concentration of the nanoparticle is increased.

Heat transfer in turbulent magneto-fluid-mechanic pipe flow

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

Andelman, M.P.

1975-12-01

The ability to predict heat transfer in Magneto-Fluid-Mechanic flow is of importance in light of the development of MHD generators and the proposed development of thermonuclear reactors. In both cases heat transfer from (or to) a conducting fluid in the presence of a magnetic field plays an important part in the overall economics of the system. A semi-empirical analytical method is given for obtaining heat transfer coefficients in turbulent liquid metal pipe flow in the presence of a magnetic field aligned to the flow. The analysis was based on the Lykoudis turbulent transport model with the influence of a longitudinalmore » magnetic field included. The results are shown to be in agreement with available experimental values. Experimental velocity profiles in mercury for pipe flow in a transverse magnetic field were made at a Reynolds number of 315,000; for Hartmann numbers of 0, 92, 184, 369, and 1198; and at orientations of 0 degrees, 45 degrees, and 90 degrees from the magnetic field. These results provide a basis for the determination of the effect of a transverse magnetic field on turbulent diffusivities.« less

Apparent isotropic electrical property for electrical brain stimulation (EBS) using magnetic resonance diffusion weighted imaging (MR-DWI)

NASA Astrophysics Data System (ADS)

Lee, Mun Bae; Kwon, Oh-In

2018-04-01

Electrical brain stimulation (EBS) is an invasive electrotherapy and technique used in brain neurological disorders through direct or indirect stimulation using a small electric current. EBS has relied on computational modeling to achieve optimal stimulation effects and investigate the internal activations. Magnetic resonance diffusion weighted imaging (DWI) is commonly useful for diagnosis and investigation of tissue functions in various organs. The apparent diffusion coefficient (ADC) measures the intensity of water diffusion within biological tissues using DWI. By measuring trace ADC and magnetic flux density induced by the EBS, we propose a method to extract electrical properties including the effective extracellular ion-concentration (EEIC) and the apparent isotropic conductivity without any auxiliary additional current injection. First, the internal current density due to EBS is recovered using the measured one component of magnetic flux density. We update the EEIC by introducing a repetitive scheme called the diffusion weighting J-substitution algorithm using the recovered current density and the trace ADC. To verify the proposed method, we study an anesthetized canine brain to visualize electrical properties including electrical current density, effective extracellular ion-concentration, and effective isotropic conductivity by applying electrical stimulation of the brain.

Magnetic Resonance Elastography Demonstrating Low Brain Stiffness in a Patient with Low-Pressure Hydrocephalus: Case Report.

PubMed

Olivero, William C; Wszalek, Tracey; Wang, Huan; Farahvar, Arash; Rieth, Sandra M; Johnson, Curtis L

2016-01-01

The authors describe the case of a 19-year-old female with shunted aqueductal stenosis who presented with low-pressure hydrocephalus that responded to negative pressure drainage. A magnetic resonance elastography scan performed 3 weeks later demonstrated very low brain tissue stiffness (high brain tissue compliance). An analysis of the importance of this finding in understanding this rare condition is discussed. © 2016 S. Karger AG, Basel.

Reversible lesions in the brain parenchyma in Wilson's disease confirmed by magnetic resonance imaging: earlier administration of chelating therapy can reduce the damage to the brain.

PubMed

Kozić, Duško B; Petrović, Igor; Svetel, Marina; Pekmezović, Tatjana; Ragaji, Aleksandar; Kostić, Vladimir S

2014-11-01

The aim of this study was to evaluate the resolution of brain lesions in patients with Wilson's disease during the long-term chelating therapy using magnetic resonance imaging and a possible significance of the time latency between the initial symptoms of the disease and the introduction of this therapy. Initial magnetic resonance examination was performed in 37 patients with proven neurological form of Wilson's disease with cerebellar, parkinsonian and dystonic presentation. Magnetic resonance reexamination was done 5.7 ± 1.3 years later in 14 patients. Patients were divided into: group A, where chelating therapy was initiated < 24 months from the first symptoms and group B, where the therapy started ≥ 24 months after the initial symptoms. Symmetry of the lesions was seen in 100% of patients. There was a significant difference between groups A and B regarding complete resolution of brain stem and putaminal lesions (P = 0.005 and P = 0.024, respectively). If the correct diagnosis and adequate treatment are not established less than 24 months after onset of the symptoms, irreversible lesions in the brain parenchyma could be expected. Signal abnormalities on magnetic resonance imaging might therefore, at least in the early stages, represent reversible myelinolisis or cytotoxic edema associated with copper toxicity.

Voltage-controlled magnetization switching in MRAMs in conjunction with spin-transfer torque and applied magnetic field

NASA Astrophysics Data System (ADS)

Munira, Kamaram; Pandey, Sumeet C.; Kula, Witold; Sandhu, Gurtej S.

2016-11-01

Voltage-controlled magnetic anisotropy (VCMA) effect has attracted a significant amount of attention in recent years because of its low cell power consumption during the anisotropy modulation of a thin ferromagnetic film. However, the applied voltage or electric field alone is not enough to completely and reliably reverse the magnetization of the free layer of a magnetic random access memory (MRAM) cell from anti-parallel to parallel configuration or vice versa. An additional symmetry-breaking mechanism needs to be employed to ensure the deterministic writing process. Combinations of voltage-controlled magnetic anisotropy together with spin-transfer torque (STT) and with an applied magnetic field (Happ) were evaluated for switching reliability, time taken to switch with low error rate, and energy consumption during the switching process. In order to get a low write error rate in the MRAM cell with VCMA switching mechanism, a spin-transfer torque current or an applied magnetic field comparable to the critical current and field of the free layer is necessary. In the hybrid processes, the VCMA effect lowers the duration during which the higher power hungry secondary mechanism is in place. Therefore, the total energy consumed during the hybrid writing processes, VCMA + STT or VCMA + Happ, is less than the energy consumed during pure spin-transfer torque or applied magnetic field switching.

Brain Training in Children and Adolescents: Is It Scientifically Valid?

PubMed

Rossignoli-Palomeque, Teresa; Perez-Hernandez, Elena; González-Marqués, Javier

2018-01-01

Background: Brain training products are becoming increasingly popular for children and adolescents. Despite the marketing aimed at their use in the general population, these products may provide more benefits for specific neurologically impaired populations. A review of Brain Training (BT) products analyzing their efficacy while considering the methodological limitations of supporting research is required for practical applications. Method: searches were made of the PubMed database (until March 2017) for studies including: (1) empirical data on the use of brain training for children or adolescents and any effects on near transfer (NT) and/or far transfer (FT) and/or neuroplasticity, (2) use of brain training for cognitive training purposes, (3) commercially available training applications, (4) computer-based programs for children developed since the 1990s, and (5) relevant printed and peer-reviewed material. Results: Database searches yielded a total of 16,402 references, of which 70 met the inclusion criteria for the review. We classified programs in terms of neuroplasticity, near and far transfer, and long-term effects and their applied methodology. Regarding efficacy, only 10 studies (14.2%) have been found that support neuroplasticity, and the majority of brain training platforms claimed to be based on such concepts without providing any supporting scientific data. Thirty-six studies (51.4%) have shown far transfer (7 of them are non-independent) and only 11 (15.7%) maintained far transfer at follow-up. Considering the methodology, 40 studies (68.2%) were not randomized and controlled; for those randomized, only 9 studies (12.9%) were double-blind, and only 13 studies (18.6%) included active controls in their trials. Conclusion: Overall, few independent studies have found far transfer and long-term effects. The majority of independent results found only near transfer. There is a lack of double-blind randomized trials which include an active control group as well as a passive control to properly control for contaminant variables. Based on our results, Brain Training Programs as commercially available products are not as effective as first expected or as they promise in their advertisements.

Brain Training in Children and Adolescents: Is It Scientifically Valid?

PubMed Central

Rossignoli-Palomeque, Teresa; Perez-Hernandez, Elena; González-Marqués, Javier

2018-01-01

Background: Brain training products are becoming increasingly popular for children and adolescents. Despite the marketing aimed at their use in the general population, these products may provide more benefits for specific neurologically impaired populations. A review of Brain Training (BT) products analyzing their efficacy while considering the methodological limitations of supporting research is required for practical applications. Method: searches were made of the PubMed database (until March 2017) for studies including: (1) empirical data on the use of brain training for children or adolescents and any effects on near transfer (NT) and/or far transfer (FT) and/or neuroplasticity, (2) use of brain training for cognitive training purposes, (3) commercially available training applications, (4) computer-based programs for children developed since the 1990s, and (5) relevant printed and peer-reviewed material. Results: Database searches yielded a total of 16,402 references, of which 70 met the inclusion criteria for the review. We classified programs in terms of neuroplasticity, near and far transfer, and long-term effects and their applied methodology. Regarding efficacy, only 10 studies (14.2%) have been found that support neuroplasticity, and the majority of brain training platforms claimed to be based on such concepts without providing any supporting scientific data. Thirty-six studies (51.4%) have shown far transfer (7 of them are non-independent) and only 11 (15.7%) maintained far transfer at follow-up. Considering the methodology, 40 studies (68.2%) were not randomized and controlled; for those randomized, only 9 studies (12.9%) were double-blind, and only 13 studies (18.6%) included active controls in their trials. Conclusion: Overall, few independent studies have found far transfer and long-term effects. The majority of independent results found only near transfer. There is a lack of double-blind randomized trials which include an active control group as well as a passive control to properly control for contaminant variables. Based on our results, Brain Training Programs as commercially available products are not as effective as first expected or as they promise in their advertisements. PMID:29780336

Hybrid MR-PET of brain tumours using amino acid PET and chemical exchange saturation transfer MRI.

PubMed

da Silva, N A; Lohmann, P; Fairney, J; Magill, A W; Oros Peusquens, A-M; Choi, C-H; Stirnberg, R; Stoffels, G; Galldiks, N; Golay, X; Langen, K-J; Jon Shah, N

2018-06-01

PET using radiolabelled amino acids has become a promising tool in the diagnostics of gliomas and brain metastasis. Current research is focused on the evaluation of amide proton transfer (APT) chemical exchange saturation transfer (CEST) MR imaging for brain tumour imaging. In this hybrid MR-PET study, brain tumours were compared using 3D data derived from APT-CEST MRI and amino acid PET using O-(2- 18 F-fluoroethyl)-L-tyrosine ( 18 F-FET). Eight patients with gliomas were investigated simultaneously with 18 F-FET PET and APT-CEST MRI using a 3-T MR-BrainPET scanner. CEST imaging was based on a steady-state approach using a B 1 average power of 1μT. B 0 field inhomogeneities were corrected a Prametric images of magnetisation transfer ratio asymmetry (MTR asym ) and differences to the extrapolated semi-solid magnetisation transfer reference method, APT# and nuclear Overhauser effect (NOE#), were calculated. Statistical analysis of the tumour-to-brain ratio of the CEST data was performed against PET data using the non-parametric Wilcoxon test. A tumour-to-brain ratio derived from APT# and 18 F-FET presented no significant differences, and no correlation was found between APT# and 18 F-FET PET data. The distance between local hot spot APT# and 18 F-FET were different (average 20 ± 13 mm, range 4-45 mm). For the first time, CEST images were compared with 18 F-FET in a simultaneous MR-PET measurement. Imaging findings derived from 18 F-FET PET and APT CEST MRI seem to provide different biological information. The validation of these imaging findings by histological confirmation is necessary, ideally using stereotactic biopsy.

Magnetic Resonance Spectroscopy: An Objective Technique for the Quantification of Prostate Cancer Pathologies

DTIC Science & Technology

2007-02-01

5d. PROJECT NUMBER Leo L. Cheng, Ph.D. 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S...Scott RM, Anthony DC, Gonzalez RG, Black PM. Biochemical characterization of pediatric brain tumors by using in vivo and ex vivo magnetic resonance...Biochemical characterization of pediatric brain tumors by using in vivo and ex vivo magnetic resonance spectroscopy. J Neurosurg 2002;96: 1023–1031. 7

Functional Connectivity Magnetic Resonance Imaging Classification of Autism

ERIC Educational Resources Information Center

Anderson, Jeffrey S.; Nielsen, Jared A.; Froehlich, Alyson L.; DuBray, Molly B.; Druzgal, T. Jason; Cariello, Annahir N.; Cooperrider, Jason R.; Zielinski, Brandon A.; Ravichandran, Caitlin; Fletcher, P. Thomas; Alexander, Andrew L.; Bigler, Erin D.; Lange, Nicholas; Lainhart, Janet E.

2011-01-01

Group differences in resting state functional magnetic resonance imaging connectivity between individuals with autism and typically developing controls have been widely replicated for a small number of discrete brain regions, yet the whole-brain distribution of connectivity abnormalities in autism is not well characterized. It is also unclear…

In vivo mapping of current density distribution in brain tissues during deep brain stimulation (DBS)

NASA Astrophysics Data System (ADS)

Sajib, Saurav Z. K.; Oh, Tong In; Kim, Hyung Joong; Kwon, Oh In; Woo, Eung Je

2017-01-01

New methods for in vivo mapping of brain responses during deep brain stimulation (DBS) are indispensable to secure clinical applications. Assessment of current density distribution, induced by internally injected currents, may provide an alternative method for understanding the therapeutic effects of electrical stimulation. The current flow and pathway are affected by internal conductivity, and can be imaged using magnetic resonance-based conductivity imaging methods. Magnetic resonance electrical impedance tomography (MREIT) is an imaging method that can enable highly resolved mapping of electromagnetic tissue properties such as current density and conductivity of living tissues. In the current study, we experimentally imaged current density distribution of in vivo canine brains by applying MREIT to electrical stimulation. The current density maps of three canine brains were calculated from the measured magnetic flux density data. The absolute current density values of brain tissues, including gray matter, white matter, and cerebrospinal fluid were compared to assess the active regions during DBS. The resulting current density in different tissue types may provide useful information about current pathways and volume activation for adjusting surgical planning and understanding the therapeutic effects of DBS.

[Application of anoptomagnetic probe Gd-DO3A-EA-FITC in imaging and analyzing the brain interstitial space].

PubMed

Li, Y Q; Sheng, Y; Liang, L; Zhao, Y; Li, H Y; Bai, N; Wang, T; Yuan, L; Han, H B

2018-04-18

To investigate the application of the optical magnetic bimodal molecular probe Gd-DO3A-ethylthiouret-fluorescein isothiocyanate (Gd -DO3A-EA-FITC) in brain tissue imaging and brain interstitial space (ISS). In the study, 24 male SD rats were randomly divided into 3 groups, including magnetic probe group (n=6), optical probe group (n=6) and optical magnetic bimodal probe group (n=12), then the optical magnetic bimodal probe group was divided equally into magnetic probe subgroup (n=6) and optical probe subgroup (n=6). Referencing the brain stereotaxic atlas, the coronal globus pallidus as center level, the probes including gadolinium-diethylene triamine pentaacetic acid (Gd-DTPA), fluorescein isothiocyanate (FITC) and Gd-DO3A-EA-FITC of 2 μL (10 mmol/L) were injected into the caudate nucleus respectively, magnetic resonance imaging (MRI) was performed in the magnetic probe group and magnetic probe subgroup to image the dynamic diffusion and distribution of the probes in the brain ISS, a self-developed brain ISS image processing system was used to measure the diffusion coefficient, clearance, volume fraction and half-time in these two groups. Laser scanning confocal microscope (LSCM) was performed in vitro in the optical probe group and optical probe subgroup for fluorescence imaging at the time points 2 hours after the injection of the probe, and the distribution in the oblique sagittal slice was compared with the result of the first two groups. For the magnetic probe group and magnetic probe subgroup, there were the same imaging results between the probes of Gd-DTPA and Gd-DO3A-EA-FITC. The diffusion parameters of Gd-DTPA and Gd-DO3A-EA-FITC were as follows: the average diffusion coefficients [(3.31±0.11)×10 -4 mm 2 /s vs. (3.37±0.15)×10 -4 mm 2 /s, t=0.942, P=0.360], the clearance [(3.04±0.37) mmol/L vs. (2.90±0.51) mmol/L, t=0.640, P=0.531], the volume fractions (17.18%±0.14% vs. 17.31%±0.15%, t=1.961, P=0.068), the half-time [(86.58±3.31) min vs. (84.61±2.38) min, t=1.412, P=0.177], the diffusion areas [(23.25±0.68) mm 2 vs. (22.71±1.00) mm 2 , t=1.100, P=0.297]. The statistical analysis of each brain was made by t test, and the diffusion parameters were not statistically significant. Moreover, for the optical probe group and optical probe subgroup, the diffusion area of Gd-DO3A-EA-FITC [(22.61±1.16) mm 2 ] was slightly larger than that of FITC [(22.10±1.29) mm 2 ], the statistical analysis of each brain was made by t test, and the diffusion parameters were not statistically significant (t=0.713, P=0.492). Gd-DO3A-EA-FITC shows the same imaging results as the traditional GD-DTPA, and it can be used in measuring brain ISS.

Brain control and information transfer.

PubMed

Tehovnik, Edward J; Chen, Lewis L

2015-12-01

In this review, we examine the importance of having a body as essential for the brain to transfer information about the outside world to generate appropriate motor responses. We discuss the context-dependent conditioning of the motor control neural circuits and its dependence on the completion of feedback loops, which is in close agreement with the insights of Hebb and colleagues, who have stressed that for learning to occur the body must be intact and able to interact with the outside world. Finally, we apply information theory to data from published studies to evaluate the robustness of the neuronal signals obtained by bypassing the body (as used for brain-machine interfaces) versus via the body to move in the world. We show that recording from a group of neurons that bypasses the body exhibits a vastly degraded level of transfer of information as compared to that of an entire brain using the body to engage in the normal execution of behaviour. We conclude that body sensations provide more than just feedback for movements; they sustain the necessary transfer of information as animals explore their environment, thereby creating associations through learning. This work has implications for the development of brain-machine interfaces used to move external devices.

Topology of magnetic flux ropes and formation of fossil flux transfer events and boundary layer plasmas

NASA Technical Reports Server (NTRS)

Lee, L. C.; Ma, Z. W.; Fu, Z. F.; Otto, A.

1993-01-01

A mechanism for the formation of fossil flux transfer events and the low-level boundary layer within the framework of multiple X-line reconnection is proposed. Attention is given to conditions for which the bulk of magnetic flux in a flux rope of finite extent has a simple magnetic topology, where the four possible connections of magnetic field lines are: IMF to MSP, MSP to IMF, IMF to IMF, and MSP to MSP. For a sufficient relative shift of the X lines, magnetic flux may enter a flux rope from the magnetosphere and exit into the magnetosphere. This process leads to the formation of magnetic flux ropes which contain a considerable amount of magnetosheath plasma on closed magnetospheric field lines. This process is discussed as a possible explanation for the formation of fossil flux transfer events in the magnetosphere and the formation of the low-latitude boundary layer.

Quantized spin-momentum transfer in atom-sized magnetic systems

NASA Astrophysics Data System (ADS)

Loth, Sebastian

2010-03-01

Our ability to quickly access the vast amounts of information linked in the internet is owed to the miniaturization of magnetic data storage. In modern disk drives the tunnel magnetoresistance effect (TMR) serves as sensitive reading mechanism for the nanoscopic magnetic bits [1]. At its core lies the ability to control the flow of electrons with a material's magnetization. The inverse effect, spin transfer torque (STT), allows one to influence a magnetic layer by high current densities of spin-polarized electrons and carries high hopes for applications in non-volatile magnetic memory [2]. We show that equivalent processes are active in quantum spin systems. We use a scanning tunneling microscope (STM) operating at low temperature and high magnetic field to address individual magnetic structures and probe their spin excitations by inelastic electron tunneling [3]. As model system we investigate transition metal atoms adsorbed to a copper nitride layer grown on a Cu crystal. The magnetic atoms on the surface possess well-defined spin states [4]. Transfer of one magnetic atom to the STM tip's apex creates spin-polarization in the probe tip. The combination of functionalized tip and surface adsorbed atom resembles a TMR structure where the magnetic layers now consist of one magnetic atom each. Spin-polarized current emitted from the probe tip not only senses the magnetic orientation of the atomic spin system, it efficiently transfers spin angular momentum and pumps the quantum spin system between the different spin states. This enables further exploration of the microscopic mechanisms for spin-relaxation and stability of quantum spin systems. [4pt] [1] Zhu and Park, Mater. Today 9, 36 (2006).[0pt] [2] Huai, AAPPS Bulletin 18, 33 (2008).[0pt] [3] Heinrich et al., Science 306, 466 (2004).[0pt] [4] Hirjibehedin et al., Science 317, 1199 (2007).

Proteomic analysis of trans-hemispheric motor cortex reorganization following contralateral C7 nerve transfer

PubMed Central

Yuan, Yin; Xu, Xiu-yue; Lao, Jie; Zhao, Xin

2018-01-01

Nerve transfer is the most common treatment for total brachial plexus avulsion injury. After nerve transfer, the movement of the injured limb may be activated by certain movements of the healthy limb at the early stage of recovery, i.e., trans-hemispheric reorganization. Previous studies have focused on functional magnetic resonance imaging and changes in brain-derived neurotrophic factor and growth associated protein 43, but there have been no proteomics studies. In this study, we designed a rat model of total brachial plexus avulsion injury involving contralateral C7 nerve transfer. Isobaric tags for relative and absolute quantitation and western blot assay were then used to screen differentially expressed proteins in bilateral motor cortices. We found that most differentially expressed proteins in both cortices of upper limb were associated with nervous system development and function (including neuron differentiation and development, axonogenesis, and guidance), microtubule and cytoskeleton organization, synapse plasticity, and transmission of nerve impulses. Two key differentially expressed proteins, neurofilament light (NFL) and Thy-1, were identified. In contralateral cortex, the NFL level was upregulated 2 weeks after transfer and downregulated at 1 and 5 months. The Thy-1 level was upregulated from 1 to 5 months. In the affected cortex, the NFL level increased gradually from 1 to 5 months. Western blot results of key differentially expressed proteins were consistent with the proteomic findings. These results indicate that NFL and Thy-1 play an important role in trans-hemispheric organization following total brachial plexus root avulsion and contralateral C7 nerve transfer. PMID:29557385

Contribution of transcranial magnetic stimulation to assessment of brain connectivity and networks.

PubMed

Hallett, Mark; Di Iorio, Riccardo; Rossini, Paolo Maria; Park, Jung E; Chen, Robert; Celnik, Pablo; Strafella, Antonio P; Matsumoto, Hideyuki; Ugawa, Yoshikazu

2017-11-01

The goal of this review is to show how transcranial magnetic stimulation (TMS) techniques can make a contribution to the study of brain networks. Brain networks are fundamental in understanding how the brain operates. Effects on remote areas can be directly observed or identified after a period of stimulation, and each section of this review will discuss one method. EEG analyzed following TMS is called TMS-evoked potentials (TEPs). A conditioning TMS can influence the effect of a test TMS given over the motor cortex. A disynaptic connection can be tested also by assessing the effect of a pre-conditioning stimulus on the conditioning-test pair. Basal ganglia-cortical relationships can be assessed using electrodes placed in the process of deep brain stimulation therapy. Cerebellar-cortical relationships can be determined using TMS over the cerebellum. Remote effects of TMS on the brain can be found as well using neuroimaging, including both positron emission tomography (PET) and functional magnetic resonance imaging (fMRI). The methods complement each other since they give different views of brain networks, and it is often valuable to use more than one technique to achieve converging evidence. The final product of this type of work is to show how information is processed and transmitted in the brain. Published by Elsevier B.V.

Dynamics of magnetization in ferromagnet with spin-transfer torque

NASA Astrophysics Data System (ADS)

Li, Zai-Dong; He, Peng-Bin; Liu, Wu-Ming

2014-11-01

We review our recent works on dynamics of magnetization in ferromagnet with spin-transfer torque. Driven by constant spin-polarized current, the spin-transfer torque counteracts both the precession driven by the effective field and the Gilbert damping term different from the common understanding. When the spin current exceeds the critical value, the conjunctive action of Gilbert damping and spin-transfer torque leads naturally the novel screw-pitch effect characterized by the temporal oscillation of domain wall velocity and width. Driven by space- and time-dependent spin-polarized current and magnetic field, we expatiate the formation of domain wall velocity in ferromagnetic nanowire. We discuss the properties of dynamic magnetic soliton in uniaxial anisotropic ferromagnetic nanowire driven by spin-transfer torque, and analyze the modulation instability and dark soliton on the spin wave background, which shows the characteristic breather behavior of the soliton as it propagates along the ferromagnetic nanowire. With stronger breather character, we get the novel magnetic rogue wave and clarify its formation mechanism. The generation of magnetic rogue wave mainly arises from the accumulation of energy and magnons toward to its central part. We also observe that the spin-polarized current can control the exchange rate of magnons between the envelope soliton and the background, and the critical current condition is obtained analytically. At last, we have theoretically investigated the current-excited and frequency-adjusted ferromagnetic resonance in magnetic trilayers. A particular case of the perpendicular analyzer reveals that the ferromagnetic resonance curves, including the resonant location and the resonant linewidth, can be adjusted by changing the pinned magnetization direction and the direct current. Under the control of the current and external magnetic field, several magnetic states, such as quasi-parallel and quasi-antiparallel stable states, out-of-plane precession, and bistable states can be realized. The precession frequency can be expressed as a function of the current and external magnetic field.

Guidance of Magnetic Nanocontainers for Treating Alzheimer's Disease Using an Electromagnetic, Targeted Drug-Delivery Actuator.

PubMed

Do, Ton Duc; Ul Amin, Faiz; Noh, Yeongil; Kim, Myeong Ok; Yoon, Jungwon

2016-03-01

The "impermeability" of the blood-brain barrier (BBB) has hindered effective treatment of central nervous system (CNS) disorders such as Alzheimer's disease (AD), which is one of the most common neurodegenerative disorders. A drug can be delivered to a targeted disease site effectively by applying a strong electromagnetic force to the conjugate of a drug and magnetic nanocontainers. This study developed a novel nanotechnology-based strategy to deliver therapeutic agents to the brain via the BBB as a possible therapeutic approach for AD. First, a novel approach for an electromagnetic actuator for guiding nanocontainers is introduced. Then, we analyzed the in vivo uptake in mice experimentally to evaluate the capacity of the nanocontainers. In the mouse model, we demonstrated that magnetic particles can cross the normal BBB when subjected to external electromagnetic fields of 28 mT (0.43 T/m) and 79.8 mT (1.39 T/m). Our study also assessed the differential effects of pulsed (0.25, 0.5, and 1 Hz) and constant magnetic fields on the transport of particles across the BBB in mice injected with magnetic nanoparticles (MNPs) via a tail vein. The applied magnetic field was either kept constant or pulsed on and off. Relative to a constant magnetic field, the rate of MNP uptake and transport across the BBB was enhanced significantly by a pulsed magnetic field. Localization inside the brain was established using fluorescent MNPs. These results using 770-nm fluorescent carboxyl magnetic nanocontainers demonstrated the feasibility of the proposed electromagnetic targeted drug delivery actuator. These results establish an effective strategy for regulating the biodistribution of MNPs in the brain through the application of an external electromagnetic field. This might be a valuable targeting system for AD diagnosis and therapy.

Repetitive Transcranial Magnetic Stimulation Activates Specific Regions in Rat Brain

NASA Astrophysics Data System (ADS)

Ji, Ru-Rong; Schlaepfer, Thomas E.; Aizenman, Carlos D.; Epstein, Charles M.; Qiu, Dike; Huang, Justin C.; Rupp, Fabio

1998-12-01

Repetitive transcranial magnetic stimulation (rTMS) is a noninvasive technique to induce electric currents in the brain. Although rTMS is being evaluated as a possible alternative to electroconvulsive therapy for the treatment of refractory depression, little is known about the pattern of activation induced in the brain by rTMS. We have compared immediate early gene expression in rat brain after rTMS and electroconvulsive stimulation, a well-established animal model for electroconvulsive therapy. Our result shows that rTMS applied in conditions effective in animal models of depression induces different patterns of immediate-early gene expression than does electroconvulsive stimulation. In particular, rTMS evokes strong neural responses in the paraventricular nucleus of the thalamus (PVT) and in other regions involved in the regulation of circadian rhythms. The response in PVT is independent of the orientation of the stimulation probe relative to the head. Part of this response is likely because of direct activation, as repetitive magnetic stimulation also activates PVT neurons in brain slices.

Real-time visualization of magnetic flux densities for transcranial magnetic stimulation on commodity and fully immersive VR systems

NASA Astrophysics Data System (ADS)

Kalivarapu, Vijay K.; Serrate, Ciro; Hadimani, Ravi L.

2017-05-01

Transcranial Magnetic Stimulation (TMS) is a non-invasive procedure that uses time varying short pulses of magnetic fields to stimulate nerve cells in the brain. In this method, a magnetic field generator ("TMS coil") produces small electric fields in the region of the brain via electromagnetic induction. This technique can be used to excite or inhibit firing of neurons, which can then be used for treatment of various neurological disorders such as Parkinson's disease, stroke, migraine, and depression. It is however challenging to focus the induced electric field from TMS coils to smaller regions of the brain. Since electric and magnetic fields are governed by laws of electromagnetism, it is possible to numerically simulate and visualize these fields to accurately determine the site of maximum stimulation and also to develop TMS coils that can focus the fields on the targeted regions. However, current software to compute and visualize these fields are not real-time and can work for only one position/orientation of TMS coil, severely limiting their usage. This paper describes the development of an application that computes magnetic flux densities (h-fields) and visualizes their distribution for different TMS coil position/orientations in real-time using GPU shaders. The application is developed for desktop, commodity VR (HTC Vive), and fully immersive VR CAVETM systems, for use by researchers, scientists, and medical professionals to quickly and effectively view the distribution of h-fields from MRI brain scans.

[Influence of low frequency magnetic field used in magnetotherapy on interleukin 6 (IL-6) contents in rat heart and brain].

PubMed

Ciejka, Elżbieta; Skibska, Beata; Gorąca, Anna

2017-06-27

The human population is exposed ever more frequently to magnetic fields (MF). This is due to both technological progress and development of the economy as well as to advances made in medical science. That is why the thorough understanding and systematized knowledge about mechanisms by which MF exerts its effects on living organisms play such an important role. In this context the health of MF-exposed people is the subject of particular concern. The aim of the study was to evaluate the effect of extremely low frequency magnetic field (ELFMF) used in magnetotherapy on the concentration of interleukin 6 (IL-6) in rat heart and brain. The male rats were randomly divided into 3 experimental groups: group I - control, without contact with magnetic field; group II - exposed to bipolar, rectangular magnetic field 40 Hz, induction "peak-to-peak" 7 mT 30 min/day for 2 weeks; and group III - exposed to bipolar, rectangular magnetic field 40 Hz, 7 mT 60 min/day for 2 weeks. Concentration of IL-6 in the heart and brain of animals was measured after MF exposure. Exposure to ELFMF: 40 Hz, induction "peak-to-peak" 7 mT 30 min/day for 2 weeks caused a significant IL-6 increase in rat hearts compared to the control group (p < 0.05) and a non-significant IL-6 decrease in rat brain. The magnetic field applied for 60 min resulted in non-significant IL-6 increase in rat hearts compared to the control group and significant IL-6 decrease in rat brain (p < 0.05). The influence of magnetic field on inflammation in the body varies depending on the MF parameters and the affected tissues or cells. Med Pr 2017;68(4):517-523. This work is available in Open Access model and licensed under a CC BY-NC 3.0 PL license.

Does inhibitory control training transfer?: behavioral and neural effects on an untrained emotion regulation task.

PubMed

Beauchamp, Kathryn G; Kahn, Lauren E; Berkman, Elliot T

2016-09-01

Inhibitory control (IC) is a critical neurocognitive skill for successfully navigating challenges across domains. Several studies have attempted to use training to improve neurocognitive skills such as IC, but few have found that training generalizes to performance on non-trained tasks. We used functional magnetic resonance imaging (fMRI) to investigate the effect of IC training on a related but untrained emotion regulation (ER) task with the goal of clarifying how training alters brain function and why its effects typically do not transfer across tasks. We suggest hypotheses for training-related changes in activation relevant to transfer effects: the strength model and several plausible alternatives (shifting priorities, stimulus-response automaticity, scaffolding). Sixty participants completed three weeks of IC training and underwent fMRI scanning before and after. The training produced pre- to post-training changes in neural activation during the ER task in the absence of behavioral changes. Specifically, individuals in the training group demonstrated reduced activation during ER in the left inferior frontal gyrus and supramarginal gyrus, key regions in the IC neural network. This result is less consistent with the strength model and more consistent with a motivational account. Implications for future work aiming to further pinpoint mechanisms of training transfer are discussed. © The Author (2016). Published by Oxford University Press. For Permissions, please email: journals.permissions@oup.com.

Test-retest assessment of cortical activation induced by repetitive transcranial magnetic stimulation with brain atlas-guided optical topography

NASA Astrophysics Data System (ADS)

Tian, Fenghua; Kozel, F. Andrew; Yennu, Amarnath; Croarkin, Paul E.; McClintock, Shawn M.; Mapes, Kimberly S.; Husain, Mustafa M.; Liu, Hanli

2012-11-01

Repetitive transcranial magnetic stimulation (rTMS) is a technology that stimulates neurons with rapidly changing magnetic pulses with demonstrated therapeutic applications for various neuropsychiatric disorders. Functional near-infrared spectroscopy (fNIRS) is a suitable tool to assess rTMS-evoked brain responses without interference from the magnetic or electric fields generated by the TMS coil. We have previously reported a channel-wise study of combined rTMS/fNIRS on the motor and prefrontal cortices, showing a robust decrease of oxygenated hemoglobin concentration (Δ[HbO2]) at the sites of 1-Hz rTMS and the contralateral brain regions. However, the reliability of this putative clinical tool is unknown. In this study, we develop a rapid optical topography approach to spatially characterize the rTMS-evoked hemodynamic responses on a standard brain atlas. A hemispherical approximation of the brain is employed to convert the three-dimensional topography on the complex brain surface to a two-dimensional topography in the spherical coordinate system. The test-retest reliability of the combined rTMS/fNIRS is assessed using repeated measurements performed two to three days apart. The results demonstrate that the Δ[HbO2] amplitudes have moderate-to-high reliability at the group level; and the spatial patterns of the topographic images have high reproducibility in size and a moderate degree of overlap at the individual level.

Quantitative Susceptibility Mapping of Human Brain Reflects Spatial Variation in Tissue Composition

PubMed Central

Li, Wei; Wu, Bing; Liu, Chunlei

2011-01-01

Image phase from gradient echo MRI provides a unique contrast that reflects brain tissue composition variations, such as iron and myelin distribution. Phase imaging is emerging as a powerful tool for the investigation of functional brain anatomy and disease diagnosis. However, the quantitative value of phase is compromised by its nonlocal and orientation dependent properties. There is an increasing need for reliable quantification of magnetic susceptibility, the intrinsic property of tissue. In this study, we developed a novel and accurate susceptibility mapping method that is also phase-wrap insensitive. The proposed susceptibility mapping method utilized two complementary equations: (1) the Fourier relationship of phase and magnetic susceptibility; and (2) the first-order partial derivative of the first equation in the spatial frequency domain. In numerical simulation, this method reconstructed the susceptibility map almost free of streaking artifact. Further, the iterative implementation of this method allowed for high quality reconstruction of susceptibility maps of human brain in vivo. The reconstructed susceptibility map provided excellent contrast of iron-rich deep nuclei and white matter bundles from surrounding tissues. Further, it also revealed anisotropic magnetic susceptibility in brain white matter. Hence, the proposed susceptibility mapping method may provide a powerful tool for the study of brain physiology and pathophysiology. Further elucidation of anisotropic magnetic susceptibility in vivo may allow us to gain more insight into the white matter microarchitectures. PMID:21224002

Evolution of magnetic flux ropes associated with flux transfer events and interplanetary magnetic clouds

NASA Technical Reports Server (NTRS)

Wei, C. Q.; Lee, L. C.; Wang, S.; Akasofu, S.-I.

1991-01-01

Spacecraft observations suggest that flux transfer events and interplanetary magnetic clouds may be associated with magnetic flux ropes which are magnetic flux tubes containing helical magnetic field lines. In the magnetic flux ropes, the azimuthal magnetic field is superposed on the axial field. The time evolution of a localized magnetic flux rope is studied. A two-dimensional compressible MHD simulation code with a cylindrical symmetry is developed to study the wave modes associated with the evolution of flux ropes. It is found that in the initial phase both the fast magnetosonic wave and the Alfven wave are developed in the flux rope. After this initial phase, the Alfven wave becomes the dominant wave mode for the evolution of the magnetic flux rope and the radial expansion velocity of the flux rope is found to be negligible. Numerical results further show that even for a large initial azimuthal component of the magnetic field, the propagation velocity along the axial direction of the flux rope remains the Alfven velocity. It is also found that the localized magnetic flux rope tends to evolve into two separate magnetic ropes propagating in opposite directions. The simulation results are used to study the evolution of magnetic flux ropes associated with flux transfer events observed at the earth's dayside magnetopause and magnetic clouds in the interplanetary space.

Noninvasive transcranial focused ultrasonic-magnetic stimulation for modulating brain oscillatory activity

NASA Astrophysics Data System (ADS)

Yuan, Yi; Chen, Yudong; Li, Xiaoli

2016-02-01

A novel technique, transcranial focused ultrasonic-magnetic stimulation (tFUMS), has been developed for noninvasive brain modulation in vivo. tFUMS has a higher spatial resolution (<2 mm) and a higher penetration depth than other noninvasive neuromodulation methods. The in vivo animal experimental results show that tFUMS can not only increase the power of local field potentials and the firing rate of the neurons, but also enhance the effect of transcranial focused ultrasound stimulation on the neuromodulation. The results demonstrate that tFUMS can modulate brain oscillatory activities by stimulating brain tissues.

Quantitative magnetic resonance imaging in traumatic brain injury.

PubMed

Bigler, E D

2001-04-01

Quantitative neuroimaging has now become a well-established method for analyzing magnetic resonance imaging in traumatic brain injury (TBI). A general review of studies that have examined quantitative changes following TBI is presented. The consensus of quantitative neuroimaging studies is that most brain structures demonstrate changes in volume or surface area after injury. The patterns of atrophy are consistent with the generalized nature of brain injury and diffuse axonal injury. Various clinical caveats are provided including how quantitative neuroimaging findings can be used clinically and in predicting rehabilitation outcome. The future of quantitative neuroimaging also is discussed.

A radiologic correlation with the basic functional neuroanatomy of the brain.

PubMed

Bilicka, Z; Liska, M; Bluska, P; Bilicky, J

2014-01-01

Primary cortical areas for motor, sensory and sensitive functions are localized in certain areas of the brain cortex. In clinical practice, cross sectional imaging (computer tomography and magnetic resonance) is wildy used for diagnostics purpose, treatment planning and follow up of the patients. Accurate orientation in brain structures is necessary for the evaluation of radiological images. There are numerable landmark signs, which can be used for precise identification of important brain structures. In this review article, the mostly used anatomical landmarks are described and shown on the cross sectional images (magnetic resonance imaging) (Fig. 14, Ref. 25).

Fetal Magnetic Resonance Imaging Findings in Prenatal Zika Virus Infection.

PubMed

Sanín-Blair, José Enrique; Gutiérrez-Márquez, Carolina; Herrera, Diego A; Vossough, Arastoo

2017-01-01

Brain lesions and malformations have been described on ultrasonography of prenatal Zika infection; however, there are scarce reports about fetal magnetic resonance (MR) findings. We report 3 cases of fetuses with confirmed intrauterine Zika virus infection evaluated by ultrasound and fetal MR. Various morphometric measurements were assessed and brain maturation was calculated with the fetal total maturation score. Fetuses with prenatal Zika virus infection showed retardation in brain maturation indexes evaluated by fetal MR. Brain calcifications were demonstrated by neurosonography in all cases, while fetal MR characterized the specific type of cortical development malformation. © 2017 S. Karger AG, Basel.

In vivo detection of brain Krebs cycle intermediate by hyperpolarized magnetic resonance.

PubMed

Mishkovsky, Mor; Comment, Arnaud; Gruetter, Rolf

2012-12-01

The Krebs (or tricarboxylic acid (TCA)) cycle has a central role in the regulation of brain energy regulation and metabolism, yet brain TCA cycle intermediates have never been directly detected in vivo. This study reports the first direct in vivo observation of a TCA cycle intermediate in intact brain, namely, 2-oxoglutarate, a key biomolecule connecting metabolism to neuronal activity. Our observation reveals important information about in vivo biochemical processes hitherto considered undetectable. In particular, it provides direct evidence that transport across the inner mitochondria membrane is rate limiting in the brain. The hyperpolarized magnetic resonance protocol designed for this study opens the way to direct and real-time studies of TCA cycle kinetics.

Molecular orbital (SCF-X-α-SW) theory of Fe2+-Mn3+, Fe3+-Mn2+, and Fe3+-Mn3+ charge transfer and magnetic exchange in oxides and silicates

USGS Publications Warehouse

Sherman, David M.

1990-01-01

Metal-metal charge-transfer and magnetic exchange interactions have important effects on the optical spectra, crystal chemistry, and physics of minerals. Previous molecular orbital calculations have provided insight on the nature of Fe2+-Fe3+ and Fe2+-Ti4+ charge-transfer transitions in oxides and silicates. In this work, spin-unrestricted molecular orbital calculations on (FeMnO10) clusters are used to study the nature of magnetic exchange and electron delocalization (charge transfer) associated with Fe3+-Mn2+, Fe3+-Mn3+, and Fe2+-Mn3+ interactions in oxides and silicates. 

Preliminary experimental investigation of in vivo magnetic manipulation: results and potential application in hyperthermia.

PubMed

Grady, M S; Howard, M A; Molloy, J A; Ritter, R C; Quate, E G; Gillies, G T

1989-01-01

The first in vivo experiments in support of a new technique for delivering stereotaxic hyperthermia have been conducted at the Experimental Surgery Facility of the University of Virginia's Medical Center. We call this technique the "Video Tumor Fighter." In each of twelve trials a single, small permanent magnet or train of small permanent magnets was implanted on the brain surface of adult canine models. In three of the trials, this "seed" (typically 6-mm diameter X 6-mm long) was moved by magnetic manipulation to different locations within the brain. In two other trials, the seed moved along the interface between the brain and the inner vault of the skull. The noncontact magnetic manipulation was accomplished by coupling the permanently magnetized seed to the large dc magnetic field gradient created by a water-cooled coil surrounding the animal's head. The seed's motions were monitored with x-ray fluoroscopy; its rate of movement was found to be approximately 0.8 mm s-1. The forces required to produce these motions were on the order of 0.07 N. We document here the instrumentation used in these trials, describe the experimental procedures employed, and discuss the technical aspects of the results.

Empirical and Theoretical Aspects of Generation and Transfer of Information in a Neuromagnetic Source Network

PubMed Central

Vakorin, Vasily A.; Mišić, Bratislav; Krakovska, Olga; McIntosh, Anthony Randal

2011-01-01

Variability in source dynamics across the sources in an activated network may be indicative of how the information is processed within a network. Information-theoretic tools allow one not only to characterize local brain dynamics but also to describe interactions between distributed brain activity. This study follows such a framework and explores the relations between signal variability and asymmetry in mutual interdependencies in a data-driven pipeline of non-linear analysis of neuromagnetic sources reconstructed from human magnetoencephalographic (MEG) data collected as a reaction to a face recognition task. Asymmetry in non-linear interdependencies in the network was analyzed using transfer entropy, which quantifies predictive information transfer between the sources. Variability of the source activity was estimated using multi-scale entropy, quantifying the rate of which information is generated. The empirical results are supported by an analysis of synthetic data based on the dynamics of coupled systems with time delay in coupling. We found that the amount of information transferred from one source to another was correlated with the difference in variability between the dynamics of these two sources, with the directionality of net information transfer depending on the time scale at which the sample entropy was computed. The results based on synthetic data suggest that both time delay and strength of coupling can contribute to the relations between variability of brain signals and information transfer between them. Our findings support the previous attempts to characterize functional organization of the activated brain, based on a combination of non-linear dynamics and temporal features of brain connectivity, such as time delay. PMID:22131968

Detectability of early brain meningitis with magnetic resonance imaging

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

Runge, V.M.; Wells, J.W.; Williams, N.M.

1995-08-01

The ability of high-field (1.5 T) magnetic resonance imaging (MRI) to detect early brain meningitis was evaluated in a canine model. Contrast dose, timing postinjection, and imaging technique (specifically the use of magnetization transfer) were assessed. Imaging of five canines was performed at 1.5 T 24 hours after injection of Cowans staphylococcus into the cisterna magna. Two control animals also were imaged using the same protocol. Contrast doses of 0.1, 0.3, and 0.8 mmol/kg gadoteridol were compared. Scans were performed at 2, 13, and 22 minutes after an initial injection of 0.1 mmol/kg. Thirty minutes after the initial injection ofmore » contrast, a supplemental dose of 0.2 mmol/kg was given. Scans were then repeated at 2, 12, and 22 minutes after this dose was administered. A second supplemental contrast injection of 0.5 mmol/kg was given at 70 minutes, and immediate postinjection scans with and without MT were acquired. Results. In the animals receiving a cisternal injection of bacteria, the degree of meningeal enhancement was greatest at 0.8 mmol/kg, intermediate at 0.3 mmol/kg, and least at 0.1 mmol/kg. Scans in control studies did not demonstrate abnormal meningeal enhancement. High-contrast dose, MT, and acquisition of immediate postcontrast scans all resulted in statistically significant improvement. On masked film review, abnormal meningeal enhancement was noted in only 2 of 5 experimental dogs at a dose of 0.1 mmol/kg (regardless of the use of MT) compared with all animals at a dose of 0.3 mmol/kg. In 18 of 37 dogs (paired scans with and without MT), when abnormal enhancement was noted, the use of MT improved the visualization of abnormal meningeal enhancement. In early brain meningitis, high-contrast dose (0.3 mmol/kg), MT, and scanning immediately after injection improve detection of abnormal meningeal enhancement, thus facilitating the diagnosis of meningitis. Of these factors, contrast dose is the most important. 14 refs., 9 figs., 2 tabs.« less

New Methods of Low-Field Magnetic Resonance Imaging for Application to Traumatic Brain Injury

DTIC Science & Technology

2016-04-01

the need for high power radio - frequency (RF) to saturate the electron spins. Addition- ally, as EPR frequencies are two orders of magnitude higher...Crozier S. Electromechanical design and construction of a rotating radio - frequency coil system for applications in magnetic resonance. IEEE Trans Biomed...1 Award Number: W81XWH- 11 -2-0076 TITLE: New Methods of Low-Field Magnetic Resonance Imaging for Application to Traumatic Brain Injury PRINCIPAL

Social reinforcement can regulate localized brain activity.

PubMed

Mathiak, Krystyna A; Koush, Yury; Dyck, Miriam; Gaber, Tilman J; Alawi, Eliza; Zepf, Florian D; Zvyagintsev, Mikhail; Mathiak, Klaus

2010-11-01

Social learning is essential for adaptive behavior in humans. Neurofeedback based on functional magnetic resonance imaging (fMRI) trains control over localized brain activity. It can disentangle learning processes at the neural level and thus investigate the mechanisms of operant conditioning with explicit social reinforcers. In a pilot study, a computer-generated face provided a positive feedback (smiling) when activity in the anterior cingulate cortex (ACC) increased and gradually returned to a neutral expression when the activity dropped. One female volunteer without previous experience in fMRI underwent training based on a social reinforcer. Directly before and after the neurofeedback runs, neural responses to a cognitive interference task (Simon task) were recorded. We observed a significant increase in activity within ACC during the neurofeedback blocks, correspondent with the a-priori defined anatomical region of interest. In the course of the neurofeedback training, the subject learned to regulate ACC activity and could maintain the control even without direct feedback. Moreover, ACC was activated significantly stronger during Simon task after the neurofeedback training when compared to before. Localized brain activity can be controlled by social reward. The increased ACC activity transferred to a cognitive task with the potential to reduce cognitive interference. Systematic studies are required to explore long-term effects on social behavior and clinical applications.

Time-efficient high-resolution whole-brain three-dimensional macromolecular proton fraction mapping

PubMed Central

Yarnykh, Vasily L.

2015-01-01

Purpose Macromolecular proton fraction (MPF) mapping is a quantitative MRI method that reconstructs parametric maps of a relative amount of macromolecular protons causing the magnetization transfer (MT) effect and provides a biomarker of myelination in neural tissues. This study aimed to develop a high-resolution whole-brain MPF mapping technique utilizing a minimal possible number of source images for scan time reduction. Methods The described technique is based on replacement of an actually acquired reference image without MT saturation by a synthetic one reconstructed from R1 and proton density maps, thus requiring only three source images. This approach enabled whole-brain three-dimensional MPF mapping with isotropic 1.25×1.25×1.25 mm3 voxel size and scan time of 20 minutes. The synthetic reference method was validated against standard MPF mapping with acquired reference images based on data from 8 healthy subjects. Results Mean MPF values in segmented white and gray matter appeared in close agreement with no significant bias and small within-subject coefficients of variation (<2%). High-resolution MPF maps demonstrated sharp white-gray matter contrast and clear visualization of anatomical details including gray matter structures with high iron content. Conclusions Synthetic reference method improves resolution of MPF mapping and combines accurate MPF measurements with unique neuroanatomical contrast features. PMID:26102097

Prolonged rote learning produces delayed memory facilitation and metabolic changes in the hippocampus of the ageing human brain.

PubMed

Roche, Richard Ap; Mullally, Sinéad L; McNulty, Jonathan P; Hayden, Judy; Brennan, Paul; Doherty, Colin P; Fitzsimons, Mary; McMackin, Deirdre; Prendergast, Julie; Sukumaran, Sunita; Mangaoang, Maeve A; Robertson, Ian H; O'Mara, Shane M

2009-11-20

Repeated rehearsal is one method by which verbal material may be transferred from short- to long-term memory. We hypothesised that extended engagement of memory structures through prolonged rehearsal would result in enhanced efficacy of recall and also of brain structures implicated in new learning. Twenty-four normal participants aged 55-70 (mean = 60.1) engaged in six weeks of rote learning, during which they learned 500 words per week every week (prose, poetry etc.). An extensive battery of memory tests was administered on three occasions, each six weeks apart. In addition, proton magnetic resonance spectroscopy (1H-MRS) was used to measure metabolite levels in seven voxels of interest (VOIs) (including hippocampus) before and after learning. Results indicate a facilitation of new learning that was evident six weeks after rote learning ceased. This facilitation occurred for verbal/episodic material only, and was mirrored by a metabolic change in left posterior hippocampus, specifically an increase in NAA/(Cr+Cho) ratio. Results suggest that repeated activation of memory structures facilitates anamnesis and may promote neuronal plasticity in the ageing brain, and that compliance is a key factor in such facilitation as the effect was confined to those who engaged fully with the training.

Multiprotocol MR image segmentation in multiple sclerosis: experience with over 1000 studies

NASA Astrophysics Data System (ADS)

Udupa, Jayaram K.; Nyul, Laszlo G.; Ge, Yulin; Grossman, Robert I.

2000-06-01

Multiple Sclerosis (MS) is an acquired disease of the central nervous system. Subjective cognitive and ambulatory test scores on a scale called EDSS are currently utilized to assess the disease severity. Various MRI protocols are being investigated to study the disease based on how it manifests itself in the images. In an attempt to eventually replace EDSS by an objective measure to assess the natural course of the disease and its response to therapy, we have developed image segmentation methods based on fuzzy connectedness to quantify various objects in multiprotocol MRI. These include the macroscopic objects such as lesions, the gray matter (GM), white matter (WM), cerebrospinal fluid (CSF), and brain parenchyma as well as the microscopic aspects of the diseased WM. Over 1000 studies have been processed to date. By far the strongest correlations with the clinical measures were demonstrated by the Magnetization Transfer Ratio (MTR) histogram parameters obtained for the various segmented tissue regions emphasizing the importance of considering the microscopic/diffused nature of the disease in the individual tissue regions. Brain parenchymal volume also demonstrated a strong correlation with the clinical measures indicating that brain atrophy is an important indicator of the disease. Fuzzy connectedness is a viable segmentation method for studying MS.

Measurement of Lactate Content and Amide Proton Transfer Values in the Basal Ganglia of a Neonatal Piglet Hypoxic-Ischemic Brain Injury Model Using MRI.

PubMed

Zheng, Y; Wang, X-M

2017-04-01

As amide proton transfer imaging is sensitive to protein content and intracellular pH, it has been widely used in the nervous system, including brain tumors and stroke. This work aimed to measure the lactate content and amide proton transfer values in the basal ganglia of a neonatal piglet hypoxic-ischemic brain injury model by using MR spectroscopy and amide proton transfer imaging. From 58 healthy neonatal piglets (3-5 days after birth; weight, 1-1.5 kg) selected initially, 9 piglets remained in the control group and 43 piglets, in the hypoxic-ischemic brain injury group. Single-section amide proton transfer imaging was performed at the coronal level of the basal ganglia. Amide proton transfer values of the bilateral basal ganglia were measured in all piglets. The ROI of MR spectroscopy imaging was the right basal ganglia, and the postprocessing was completed with LCModel software. After hypoxic-ischemic insult, the amide proton transfer values immediately decreased, and at 0-2 hours, they remained at their lowest level. Thereafter, they gradually increased and finally exceeded those of the control group at 48-72 hours. After hypoxic-ischemic insult, the lactate content increased immediately, was maximal at 2-6 hours, and then gradually decreased to the level of the control group. The amide proton transfer values were negatively correlated with lactate content ( r = -0.79, P < .05). This observation suggests that after hypoxic-ischemic insult, the recovery of pH was faster than that of lactate homeostasis. © 2017 by American Journal of Neuroradiology.

Adoptive transfer of T regulatory cells inhibits lipopolysaccharide-induced inflammation in fetal brain tissue in a late-pregnancy preterm birth mouse model.

PubMed

Wang, Fan; Xiao, Mi; Chen, Ru-Juan; Lin, Xiao-Jie; Siddiq, Muhammad; Liu, Li

2017-02-01

To evaluate the effect of regulatory T cells (Tregs) on the inflammation resulting from lipopolysaccharide (LPS) challenge in prenatal brain tissue, Tregs isolated from pregnant mice were transferred into model mice, and the expression levels of fork head family transcription factor (Foxp3), interleukin-6 (IL-6), CD68 (a marker of microglia), and toll-like receptor 4 (TLR-4) were assessed in the fetal brain tissue. Foxp3, IL-6, and TLR-4 expression were detected by polymerase chain reaction and Western blot; CD68 expression level was detected using immunochemical analysis. Foxp3, IL-6, TLR-4, and CD68 expressions in fetal brain were significantly induced by maternal LPS administration, and the increased expression levels were markedly reduced by adoptive transfer of Tregs. Maternal LPS exposure significantly induced inflammation in perinatal brain tissue, and Tregs negatively regulated this LPS-induced inflammation. © 2016 International Federation for Cell Biology.

Interferometric study on the mass transfer in cryogenic distillation under magnetic field

NASA Astrophysics Data System (ADS)

Bao, S. R.; Zhang, R. P.; Y Rong, Y.; Zhi, X. Q.; Qiu, L. M.

2017-12-01

Cryogenic distillation has long been used for the mass production of industrial gases because of its features of high efficiency, high purity, and capability to produce noble gases. It is of great theoretical and practical significance to explore methods to improve the mass transfer efficiency in cryogenic distillation. The negative correlation between the susceptibility of paramagnetic oxygen and temperature provides a new possibility of comprehensive utilization of boiling point and susceptibility differences in cryogenic distillation. Starting from this concept, we proposed a novel distillation intensifying method by using gradient magnetic field, in which the magnetic forces enhance the transport of the oxygen molecules to the liquid phase in the distillation. In this study, a cryogenic testbed was designed and fabricated to study the diffusion between oxygen and nitrogen under magnetic field. A Mach-Zehnder interferometer was used to visualize the concentration distribution during the diffusion process. The mass transfer characteristics with and without magnetic field, in the chamber filled with the magnetized medium, were systematically studied. The concentration redistribution of oxygen was observed, and the stable stratified diffusion between liquid oxygen and nitrogen was prolonged by the non-uniform magnetic field. The experimental results show that the magnetic field can efficiently influence the mass transfer in cryogenic distillation, which can provide a new mechanism for the optimization of air separation process.

Automatic Semantic Segmentation of Brain Gliomas from MRI Images Using a Deep Cascaded Neural Network.

PubMed

Cui, Shaoguo; Mao, Lei; Jiang, Jingfeng; Liu, Chang; Xiong, Shuyu

2018-01-01

Brain tumors can appear anywhere in the brain and have vastly different sizes and morphology. Additionally, these tumors are often diffused and poorly contrasted. Consequently, the segmentation of brain tumor and intratumor subregions using magnetic resonance imaging (MRI) data with minimal human interventions remains a challenging task. In this paper, we present a novel fully automatic segmentation method from MRI data containing in vivo brain gliomas. This approach can not only localize the entire tumor region but can also accurately segment the intratumor structure. The proposed work was based on a cascaded deep learning convolutional neural network consisting of two subnetworks: (1) a tumor localization network (TLN) and (2) an intratumor classification network (ITCN). The TLN, a fully convolutional network (FCN) in conjunction with the transfer learning technology, was used to first process MRI data. The goal of the first subnetwork was to define the tumor region from an MRI slice. Then, the ITCN was used to label the defined tumor region into multiple subregions. Particularly, ITCN exploited a convolutional neural network (CNN) with deeper architecture and smaller kernel. The proposed approach was validated on multimodal brain tumor segmentation (BRATS 2015) datasets, which contain 220 high-grade glioma (HGG) and 54 low-grade glioma (LGG) cases. Dice similarity coefficient (DSC), positive predictive value (PPV), and sensitivity were used as evaluation metrics. Our experimental results indicated that our method could obtain the promising segmentation results and had a faster segmentation speed. More specifically, the proposed method obtained comparable and overall better DSC values (0.89, 0.77, and 0.80) on the combined (HGG + LGG) testing set, as compared to other methods reported in the literature. Additionally, the proposed approach was able to complete a segmentation task at a rate of 1.54 seconds per slice.

Individual diversity of functional brain network economy.

PubMed

Hahn, Andreas; Kranz, Georg S; Sladky, Ronald; Ganger, Sebastian; Windischberger, Christian; Kasper, Siegfried; Lanzenberger, Rupert

2015-04-01

On average, brain network economy represents a trade-off between communication efficiency, robustness, and connection cost, although an analogous understanding on an individual level is largely missing. Evaluating resting-state networks of 42 healthy participants with seven Tesla functional magnetic resonance imaging and graph theory revealed that not even half of all possible connections were common across subjects. The strongest similarities among individuals were observed for interhemispheric and/or short-range connections, which may relate to the essential feature of the human brain to develop specialized systems within each hemisphere. Despite this marked variability in individual network architecture, all subjects exhibited equal small-world properties. Furthermore, interdependency between four major network economy metrics was observed across healthy individuals. The characteristic path length was associated with the clustering coefficient (peak correlation r=0.93), the response to network attacks (r=-0.97), and the physical connection cost in three-dimensional space (r=-0.62). On the other hand, clustering was negatively related to attack response (r=-0.75) and connection cost (r=-0.59). Finally, increased connection cost was associated with better response to attacks (r=0.65). This indicates that functional brain networks with high global information transfer also exhibit strong network resilience. However, it seems that these advantages come at the cost of decreased local communication efficiency and increased physical connection cost. Except for wiring length, the results were replicated on a subsample at three Tesla (n=20). These findings highlight the finely tuned interrelationships between different parameters of brain network economy. Moreover, the understanding of the individual diversity of functional brain network economy may provide further insights in the vulnerability to mental and neurological disorders.

On judgement of electron transfer between two regions divided by the separatrix of confronting divergent magnetic fields applied to an inductively coupled plasma

NASA Astrophysics Data System (ADS)

Sugawara, Hirotake; Yamamoto, Tappei

2016-09-01

In order to quantitatively evaluate the electron confinement effect of the confronting divergent magnetic fields (CDMFs) applied to an inductively coupled plasma, we analyzed the electron transfer between two regions divided by the separatrix of the CDMFs in Ar at 0.67 Pa at 300 K using a Monte Carlo method. A conventional transfer judgement was simply based on the electron passage across the separatrix from the upstream source region to the downstream diffusion region. An issue was an overestimation of the transfer due to temporary stay of electrons in the downstream region. Electrons may pass the downstream region during their gyration even in case they are effectively bound to the upstream region, where their guiding magnetic flux lines run. More than half of the transfers were temporary ones and such seeming transfers were relevantly excluded from the statistics by introducing a newly chosen criterion based on the passage of electron gyrocenters across the separatrix and collisional events in the downstream region. Simulation results showed a tendency that the ratio of the temporary transfers excluded was higher under stronger magnetic fields because of higher cyclotron frequency. Work supported by JSPS Kakenhi Grant Number 16K05626.

Semiautomated volumetry of the cerebrum, cerebellum-brain stem, and temporal lobe on brain magnetic resonance images.

PubMed

Hayashi, Norio; Sanada, Shigeru; Suzuki, Masayuki; Matsuura, Yukihiro; Kawahara, Kazuhiro; Tsujii, Hideo; Yamamoto, Tomoyuki; Matsui, Osamu

2008-02-01

The aim of this study was to develop an automated method of segmenting the cerebrum, cerebellum-brain stem, and temporal lobe simultaneously on magnetic resonance (MR) images. We obtained T1-weighted MR images from 10 normal subjects and 19 patients with brain atrophy. To perform automated volumetry from MR images, we performed the following three steps: (1) segmentation of the brain region; (2) separation between the cerebrum and the cerebellum-brain stem; and (3) segmentation of the temporal lobe. Evaluation was based on the correctly recognized region (CRR) (i.e., the region recognized by both the automated and manual methods). The mean CRRs of the normal and atrophic brains were 98.2% and 97.9% for the cerebrum, 87.9% and 88.5% for the cerebellum-brain stem, and 76.9% and 85.8% for the temporal lobe, respectively. We introduce an automated volumetric method for the cerebrum, cerebellum-brain stem, and temporal lobe on brain MR images. Our method can be applied to not only the normal brain but also the atrophic brain.

Spin Transfer Torque in Graphene

NASA Astrophysics Data System (ADS)

Lin, Chia-Ching; Chen, Zhihong

2014-03-01

Graphene is an idea channel material for spin transport due to its long spin diffusion length. To develop graphene based spin logic, it is important to demonstrate spin transfer torque in graphene. Here, we report the experimental measurement of spin transfer torque in graphene nonlocal spin valve devices. Assisted by a small external in-plane magnetic field, the magnetization reversal of the receiving magnet is induced by pure spin diffusion currents from the injector magnet. The magnetization switching is reversible between parallel and antiparallel configurations by controlling the polarity of the applied charged currents. Current induced heating and Oersted field from the nonlocal charge flow have also been excluded in this study. Next, we further enhance the spin angular momentum absorption at the interface of the receiving magnet and graphene channel by removing the tunneling barrier in the receiving magnet. The device with a tunneling barrier only at the injector magnet shows a comparable nonlocal spin valve signal but lower electrical noise. Moreover, in the same preset condition, the critical charge current density for spin torque in the single tunneling barrier device shows a substantial reduction if compared to the double tunneling barrier device.

Magnetic resonance elastography of the brain: A comparison between pigs and humans.

PubMed

Weickenmeier, Johannes; Kurt, Mehmet; Ozkaya, Efe; Wintermark, Max; Pauly, Kim Butts; Kuhl, Ellen

2018-01-01

Magnetic resonance elastography holds promise as a non-invasive, easy-to-use, in vivo biomarker for neurodegenerative diseases. Throughout the past decade, pigs have gained increased popularity as large animal models for human neurodegeneration. However, the volume of a pig brain is an order of magnitude smaller than the human brain, its skull is 40% thicker, and its head is about twice as big. This raises the question to which extent established vibration devices, actuation frequencies, and analysis tools for humans translate to large animal studies in pigs. Here we explored the feasibility of using human brain magnetic resonance elastography to characterize the dynamic properties of the porcine brain. In contrast to humans, where vibration devices induce an anterior-posterior displacement recorded in transverse sections, the porcine anatomy requires a dorsal-ventral displacement recorded in coronal sections. Within these settings, we applied a wide range of actuation frequencies, from 40Hz to 90Hz, and recorded the storage and loss moduli for human and porcine brains. Strikingly, we found that optimal actuation frequencies for humans translate one-to-one to pigs and reliably generate shear waves for elastographic post-processing. In a direct comparison, human and porcine storage and loss moduli followed similar trends and increased with increasing frequency. When translating these frequency-dependent storage and loss moduli into the frequency-independent stiffnesses and viscosities of a standard linear solid model, we found human values of μ 1 =1.3kPa, μ 2 =2.1kPa, and η=0.025kPas and porcine values of μ 1 =2.0kPa, μ 2 =4.9kPa, and η=0.046kPas. These results suggest that living human brain is softer and less viscous than dead porcine brain. Our study compares, for the first time, magnetic resonance elastography in human and porcine brains, and paves the way towards systematic interspecies comparison studies and ex vivo validation of magnetic resonance elastography as a whole. Copyright © 2017 Elsevier Ltd. All rights reserved.

Transcranial magnetic stimulation: physics, electrophysiology, and applications.

PubMed

Fatemi-Ardekani, Ali

2008-01-01

Transcranial magnetic stimulation (TMS) is a noninvasive technique used to stimulate the brain. This review will examine the fundamental principles of physics upon which magnetic stimulation is based, the design considerations of the TMS device, and hypotheses about its electrophysiological effects resulting in neuromodulation. TMS is valuable in neurophysiology research and has significant therapeutic potential in clinical neurology and psychiatry. While TMS can modify neuronal currents in the brain, its underlying mechanism remains unknown. Salient applications are included and some suggestions are outlined for future development of magnetic stimulators that could lead to more effective neuronal stimulation and therefore better therapeutic and diagnostic applications.

Brain Morphometry Using Anatomical Magnetic Resonance Imaging

ERIC Educational Resources Information Center

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

2008-01-01

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

Effect of anatomical variability in brain on transcranial magnetic stimulation treatment

NASA Astrophysics Data System (ADS)

Syeda, F.; Magsood, H.; Lee, E. G.; El-Gendy, A. A.; Jiles, D. C.; Hadimani, R. L.

2017-05-01

Transcranial Magnetic Stimulation is a non-invasive clinical therapy used to treat depression and migraine, and shows further promise as treatment for Parkinson's disease, Alzheimer's disease, and other neurological disorders. However, it is yet unclear as to how anatomical differences may affect stimulation from this treatment. We use finite element analysis to model and analyze the results of Transcranial Magnetic Stimulation in various head models. A number of heterogeneous head models have been developed using MRI data of real patients, including healthy individuals as well as patients of Parkinson's disease. Simulations of Transcranial Magnetic Stimulation performed on 22 anatomically different models highlight the differences in induced stimulation. A standard Figure of 8 coil is used with frequency 2.5 kHz, placed 5 mm above the head. We compare cortical stimulation, volume of brain tissue stimulated, specificity, and maximum E-field induced in the brain for models ranging from ages 20 to 60. Results show that stimulation varies drastically between patients of the same age and health status depending upon brain-scalp distance, which is not necessarily a linear progression with age.

Identification of disappearing brain lesions with intraoperative magnetic resonance imaging prevents surgery.

PubMed

Sutherland, Christina S; Kelly, John Jp; Morrish, William; Sutherland, Garnette R

2010-10-01

Typically, neurosurgery is performed several weeks after diagnostic imaging. In the majority of cases, histopathology confirms the diagnosis of neoplasia. In a small number of cases, a different diagnosis is established or histopathology is nondiagnostic. The frequency with which these outcomes occur has not been established. To determine the frequency and outcome of disappearing brain lesions within a group of patients undergoing surgery for suspected brain tumor. Over the past decade, 982 patients were managed in the intraoperative magnetic resonance imaging unit at the University of Calgary, Calgary, Alberta, Canada. These patients have been prospectively evaluated. In 652 patients, a brain tumor was suspected. In 6 of the 652 patients, histopathology indicated a nontumor diagnosis. In 5 patients, intraoperative images, acquired after induction of anesthesia, showed complete or nearly complete resolution of the suspected tumor identified on diagnostic magnetic resonance imaging acquired 6 ± 4 (mean ± SD) weeks previously. Anesthesia was reversed, and the surgical procedure aborted. The lesions have not progressed with 6 ± 2 years of follow-up. Intraoperative magnetic resonance imaging prevented surgery on 5 patients with disappearing lesions.

The influence of a magnetic field on the heat transfer of a magnetic nanofluid in a sinusoidal channel

NASA Astrophysics Data System (ADS)

Valiallah Mousavi, S.; Barzegar Gerdroodbary, M.; Sheikholeslami, Mohsen; Ganji, D. D.

2016-09-01

In this study, two dimensional numerical simulations are performed to investigate the influence of the magnetic field on the nanofluid flow inside a sinusoidal channel. This work reveals the influence of variable magnetic field in the heat transfer of heat exchanger while the mixture is in a single phase. In this heat exchanger, the inner tube is sinusoidal and the outer tube is considered smooth. The magnetic field is applied orthogonal to the axis of the sinusoidal tube. In our study, the ferrofluid (water with 4 vol% nanoparticles (Fe3O4)) flows in a channel with sinusoidal bottom. The finite volume method with the SIMPLEC algorithm is used for handling the pressure-velocity coupling. The numerical results present validated data with experimentally measured data and show good agreement with measurement. The influence of different parameters, like the intensity of magnetic field and Reynolds number, on the heat transfer is investigated. According to the obtained results, the sinusoidal formation of the internal tube significantly increases the Nusselt number inside the channel. Our findings show that the magnetic field increases the probability of eddy formation inside the cavities and consequently enhances the heat transfer (more than 200%) in the vicinity of the magnetic field at low Reynolds number ( Re=50). In addition, the variation of the skin friction shows that the magnetic field increases the skin friction (more than 600%) inside the sinusoidal channel.

Emerging imaging tools for use with traumatic brain injury research.

PubMed

Hunter, Jill V; Wilde, Elisabeth A; Tong, Karen A; Holshouser, Barbara A

2012-03-01

This article identifies emerging neuroimaging measures considered by the inter-agency Pediatric Traumatic Brain Injury (TBI) Neuroimaging Workgroup. This article attempts to address some of the potential uses of more advanced forms of imaging in TBI as well as highlight some of the current considerations and unresolved challenges of using them. We summarize emerging elements likely to gain more widespread use in the coming years, because of 1) their utility in diagnosis, prognosis, and understanding the natural course of degeneration or recovery following TBI, and potential for evaluating treatment strategies; 2) the ability of many centers to acquire these data with scanners and equipment that are readily available in existing clinical and research settings; and 3) advances in software that provide more automated, readily available, and cost-effective analysis methods for large scale data image analysis. These include multi-slice CT, volumetric MRI analysis, susceptibility-weighted imaging (SWI), diffusion tensor imaging (DTI), magnetization transfer imaging (MTI), arterial spin tag labeling (ASL), functional MRI (fMRI), including resting state and connectivity MRI, MR spectroscopy (MRS), and hyperpolarization scanning. However, we also include brief introductions to other specialized forms of advanced imaging that currently do require specialized equipment, for example, single photon emission computed tomography (SPECT), positron emission tomography (PET), encephalography (EEG), and magnetoencephalography (MEG)/magnetic source imaging (MSI). Finally, we identify some of the challenges that users of the emerging imaging CDEs may wish to consider, including quality control, performing multi-site and longitudinal imaging studies, and MR scanning in infants and children.

Comparison of direct 13C and indirect 1H-[13C] MR detection methods for the study of dynamic metabolic turnover in the human brain

NASA Astrophysics Data System (ADS)

Chen, Hao; De Feyter, Henk M.; Brown, Peter B.; Rothman, Douglas L.; Cai, Shuhui; de Graaf, Robin A.

2017-10-01

A wide range of direct 13C and indirect 1H-[13C] MR detection methods exist to probe dynamic metabolic pathways in the human brain. Choosing an optimal detection method is difficult as sequence-specific features regarding spatial localization, broadband decoupling, spectral resolution, power requirements and sensitivity complicate a straightforward comparison. Here we combine density matrix simulations with experimentally determined values for intrinsic 1H and 13C sensitivity, T1 and T2 relaxation and transmit efficiency to allow selection of an optimal 13C MR detection method for a given application and magnetic field. The indirect proton-observed, carbon-edited (POCE) detection method provides the highest accuracy at reasonable RF power deposition both at 4 T and 7 T. The various polarization transfer methods all have comparable performances, but may become infeasible at 7 T due to the high RF power deposition. 2D MR methods have limited value for the metabolites considered (primarily glutamate, glutamine and γ-amino butyric acid (GABA)), but may prove valuable when additional information can be extracted, such as isotopomers or lipid composition. While providing the lowest accuracy, the detection of non-protonated carbons is the simplest to implement with the lowest RF power deposition. The magnetic field homogeneity is one of the most important parameters affecting the detection accuracy for all metabolites and all acquisition methods.

Oxidation of [U-13 C]glucose in the human brain at 7T under steady state conditions.

PubMed

Cheshkov, Sergey; Dimitrov, Ivan E; Jakkamsetti, Vikram; Good, Levi; Kelly, Dorothy; Rajasekaran, Karthik; DeBerardinis, Ralph J; Pascual, Juan M; Sherry, A Dean; Malloy, Craig R

2017-12-01

Disorders of brain energy metabolism and neurotransmitter recycling have been implicated in multiple neurological conditions. 13 C magnetic resonance spectroscopy ( 13 C MRS) during intravenous administration of 13 C-labeled compounds has been used to measure turnover rates of brain metabolites. This approach, however, requires prolonged infusion inside the magnet. Proton decoupling is typically required but may be difficult to implement with standard equipment. We examined an alternative approach to monitor glucose metabolism in the human brain. 13 C-enriched glucose was infused in healthy subjects outside the magnet to a steady-state level of 13 C enrichment. Subsequently, the subjects were scanned at 7T for 60 min without 1 H decoupling. Metabolic modeling was used to calculate anaplerosis. Biomarkers of energy metabolism and anaplerosis were detected. The glutamate C5 doublet provided information about glucose-derived acetyl-coenzyme A flux into the tricarboxylic acid (TCA) cycle via pyruvate dehydrogenase, and the bicarbonate signal reflected overall TCA cycle activity. The glutamate C1/C5 ratio is sensitive to anaplerosis. Brain 13 C MRS at 7T provides information about glucose oxidation and anaplerosis without the need of prolonged 13 C infusions inside the scanner and without technical challenges of 1 H decoupling, making it a feasible approach for clinical research. Magn Reson Med 78:2065-2071, 2017. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

Deep Brain Stimulation using Magnetic Fields

NASA Astrophysics Data System (ADS)

Jiles, David; Williams, Paul; Crowther, Lawrence; Iowa State University Team; Wolfson CentreMagnetics Team

2011-03-01

New applications for transcranial magnetic stimulation are developing rapidly for both diagnostic and therapeutic purposes. Therefore so is the demand for improved performance, particularly in terms of their ability to stimulate deeper regions of the brain and to do so selectively. The coil designs that are used presently are limited in their ability to stimulate the brain at depth and with high spatial focality. Consequently, any improvement in coil performance would have a significant impact in extending the usefulness of TMS in both clinical applications and academic research studies. New and improved coil designs have then been developed, modeled and tested as a result of this work. A large magnetizing coil, 300mm in diameter and compatible with a commercial TMS system has been constructed to determine its feasibility for use as a deep brain stimulator. The results of this work have suggested directions that could be pursued in order to further improve the coil designs.

[Fundamentals and Clinical Applications of Transcranial Magnetic Stimulation in Neuropsychiatry].

PubMed

Malavera, Mayra; Silva, Federico; García, Ronald; Rueda, Ligia; Carrillo, Sandra

2014-03-01

Transcranial Magnetic Stimulation (TMS) is a non-invasive method for stimulation of brain that is based on the ability of a generated magnetic field to penetrate skull and brain meninges, inducing an electric current in the brain tissues that produces neuronal depolarization. TMS can be applied as single pulse of stimulation, pairs of stimuli separated by variable intervals to the same or different brain areas, or as trains of repetitive stimuli at various frequencies. Its mechanism of action is currently unknown. Repetitive TMS can modify the excitability of the cerebral cortex, and has been postulated as a diagnostic and therapeutic tool in the area of neuropsychiatry. The aim of this article is to review the knowledge of the TMS as regards its basic principles, pathophysiological mechanism, and its usefulness in clinical practice. Copyright © 2014 Asociación Colombiana de Psiquiatría. Publicado por Elsevier España. All rights reserved.

Over-hydration detection in brain by magnetic induction spectroscopy

NASA Astrophysics Data System (ADS)

González, César A.; Pérez, María; Hevia, Nidiyare; Arámbula, Fernándo; Flores, Omar; Aguilar, Eliot; Hinojosa, Ivonne; Joskowicz, Leo; Rubinsky, Boris

2010-04-01

Detection and continuous monitoring of edema in the brain in early stages is useful for assessment of medical condition and treatment. We have proposed a solution in which the bulk measurements of the tissue electrical properties to detect edema or in general accumulation of fluids are made through measurement of the magnetic induction phase shift between applied and measured currents at different frequencies (Magnetic Induction Spectroscopy; MIS). Magnetic Resonant Imaging (MRI) has been characterized because its capability to detect different levels of brain tissue hydration by differences in diffusion-weighted (DW) sequences and it's involve apparent diffusion coefficient (ADC). The objective of this study was to explore the viability to use measurements of the bulk tissue electrical properties to detect edema or in general accumulation of fluids by MIS. We have induced a transitory and generalized tissue over-hydration condition in ten volunteers ingesting 1.5 to 2 liters of water in ten minutes. Basal and over-hydration conditions were monitored by MIS and MRI. Changes in the inductive phase shift at certain frequencies were consistent with changes in the brain tissue hydration level observed by DW-ADC. The results suggest that MIS has the potential to detect pathologies associated to changes in the content of fluids in brain tissue such as edema and hematomas.

Structural Image Analysis of the Brain in Neuropsychology Using Magnetic Resonance Imaging (MRI) Techniques.

PubMed

Bigler, Erin D

2015-09-01

Magnetic resonance imaging (MRI) of the brain provides exceptional image quality for visualization and neuroanatomical classification of brain structure. A variety of image analysis techniques provide both qualitative as well as quantitative methods to relate brain structure with neuropsychological outcome and are reviewed herein. Of particular importance are more automated methods that permit analysis of a broad spectrum of anatomical measures including volume, thickness and shape. The challenge for neuropsychology is which metric to use, for which disorder and the timing of when image analysis methods are applied to assess brain structure and pathology. A basic overview is provided as to the anatomical and pathoanatomical relations of different MRI sequences in assessing normal and abnormal findings. Some interpretive guidelines are offered including factors related to similarity and symmetry of typical brain development along with size-normalcy features of brain anatomy related to function. The review concludes with a detailed example of various quantitative techniques applied to analyzing brain structure for neuropsychological outcome studies in traumatic brain injury.

Current driven dynamics of magnetic domain walls in permalloy nanowires

NASA Astrophysics Data System (ADS)

Hayashi, Masamitsu

The significant advances in micro-fabrication techniques opened the door to access interesting properties in solid state physics. With regard to magnetic materials, geometrical confinement of magnetic structures alters the defining parameters that govern magnetism. For example, development of single domain nano-pillars made from magnetic multilayers led to the discovery of electrical current controlled magnetization switching, which revealed the existence of spin transfer torque. Magnetic domain walls (DWs) are boundaries in magnetic materials that divide regions with distinct magnetization directions. DWs play an important role in the magnetization reversal processes of both bulk and thin film magnetic materials. The motion of DW is conventionally controlled by magnetic fields. Recently, it has been proposed that spin polarized current passed across the DW can also control the motion of DWs. Current in most magnetic materials is spin-polarized, due to spin-dependent scattering of the electrons, and thus can deliver spin angular momentum to the DW, providing a "spin transfer" torque on the DW which leads to DW motion. In addition, owing to the development of micro-fabrication techniques, geometrical confinement of magnetic materials enables creation and manipulation of a "single" DW in magnetic nanostructures. New paradigms for DW-based devices are made possible by the direct manipulation of DWs using spin polarized electrical current via spin transfer torque. This dissertation covers research on current induced DW motion in magnetic nanowires. Fascinating effects arising from the interplay between DWs with spin polarized current will be revealed.

Magnetic fields in noninvasive brain stimulation.

PubMed

Vidal-Dourado, Marcos; Conforto, Adriana Bastos; Caboclo, Luis Otávio Sales Ferreira; Scaff, Milberto; Guilhoto, Laura Maria de Figueiredo Ferreira; Yacubian, Elza Márcia Targas

2014-04-01

The idea that magnetic fields could be used therapeutically arose 2000 years ago. These therapeutic possibilities were expanded after the discovery of electromagnetic induction by the Englishman Michael Faraday and the American Joseph Henry. In 1896, Arsène d'Arsonval reported his experience with noninvasive brain magnetic stimulation to the scientific French community. In the second half of the 20th century, changing magnetic fields emerged as a noninvasive tool to study the nervous system and to modulate neural function. In 1985, Barker, Jalinous, and Freeston presented transcranial magnetic stimulation, a relatively focal and painless technique. Transcranial magnetic stimulation has been proposed as a clinical neurophysiology tool and as a potential adjuvant treatment for psychiatric and neurologic conditions. This article aims to contextualize the progress of use of magnetic fields in the history of neuroscience and medical sciences, until 1985.

Advances in magnetic resonance neuroimaging techniques in the evaluation of neonatal encephalopathy.

PubMed

Panigrahy, Ashok; Blüml, Stefan

2007-02-01

Magnetic resonance (MR) imaging has become an essential tool in the evaluation of neonatal encephalopathy. Magnetic resonance-compatible neonatal incubators allow sick neonates to be transported to the MR scanner, and neonatal head coils can improve signal-to-noise ratio, critical for advanced MR imaging techniques. Refinement of conventional imaging techniques include the use of PROPELLER techniques for motion correction. Magnetic resonance spectroscopic imaging and diffusion tensor imaging provide quantitative assessment of both brain development and brain injury in the newborn with respect to metabolite abnormalities and hypoxic-ischemic injury. Knowledge of normal developmental changes in MR spectroscopy metabolite concentration and diffusion tensor metrics is essential to interpret pathological cases. Perfusion MR and functional MR can provide additional physiological information. Both MR spectroscopy and diffusion tensor imaging can provide additional information in the differential of neonatal encephalopathy, including perinatal white matter injury, hypoxic-ischemic brain injury, metabolic disease, infection, and birth injury.

Improved field localization in transcranial magnetic stimulation of the brain with the utilization of a conductive shield plate in the stimulator.

PubMed

Kim, Dong-Hun; Georghiou, George E; Won, Chulho

2006-04-01

In this paper, a carefully designed conductive shield plate is presented, which helps to improve localization of the electric field distribution induced by transcranial magnetic stimulation for neuron stimulation. The shield plate is introduced between a figure-of-eight coil and the head. In order to accurately predict the field distribution inside the brain and to examine the effects of the shield plate, a realistic head model is constructed from magnetic resonance image data with the help of image processing tools and the finite-element method in three dimensions is employed. Finally, to show the improvements obtained, the results are compared with two conventional coil designs. It is found that an incorporation of the shield plate into the coil, effectively improves the induced field localization by more than 50%, and prevents other parts of the brain from exposure to high pulsed magnetic fields.

Developments in deep brain stimulation using time dependent magnetic fields

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

Crowther, L.J.; Nlebedim, I.C.; Jiles, D.C.

2012-03-07

The effect of head model complexity upon the strength of field in different brain regions for transcranial magnetic stimulation (TMS) has been investigated. Experimental measurements were used to verify the validity of magnetic field calculations and induced electric field calculations for three 3D human head models of varying complexity. Results show the inability for simplified head models to accurately determine the site of high fields that lead to neuronal stimulation and highlight the necessity for realistic head modeling for TMS applications.

Developments in deep brain stimulation using time dependent magnetic fields

NASA Astrophysics Data System (ADS)

Crowther, L. J.; Nlebedim, I. C.; Jiles, D. C.

2012-04-01

The effect of head model complexity upon the strength of field in different brain regions for transcranial magnetic stimulation (TMS) has been investigated. Experimental measurements were used to verify the validity of magnetic field calculations and induced electric field calculations for three 3D human head models of varying complexity. Results show the inability for simplified head models to accurately determine the site of high fields that lead to neuronal stimulation and highlight the necessity for realistic head modeling for TMS applications.

Music and the Brain in Childhood Development. Review of Research.

ERIC Educational Resources Information Center

Strickland, Susan J.

2002-01-01

Reviews literature on effects of music on the brain in childhood development. Areas include: (1) early synaptic growth; (2) nature versus nurture; (3) background music; (4) musical practice; (5) music learning and cognitive skills; (6) transfer of music learning; (7) musical instrument practice; (8) children and music; and (9) transfer effects.…

Handedness- and brain size-related efficiency differences in small-world brain networks: a resting-state functional magnetic resonance imaging study.

PubMed

Li, Meiling; Wang, Junping; Liu, Feng; Chen, Heng; Lu, Fengmei; Wu, Guorong; Yu, Chunshui; Chen, Huafu

2015-05-01

The human brain has been described as a complex network, which integrates information with high efficiency. However, the relationships between the efficiency of human brain functional networks and handedness and brain size remain unclear. Twenty-one left-handed and 32 right-handed healthy subjects underwent a resting-state functional magnetic resonance imaging scan. The whole brain functional networks were constructed by thresholding Pearson correlation matrices of 90 cortical and subcortical regions. Graph theory-based methods were employed to further analyze their topological properties. As expected, all participants demonstrated small-world topology, suggesting a highly efficient topological structure. Furthermore, we found that smaller brains showed higher local efficiency, whereas larger brains showed higher global efficiency, reflecting a suitable efficiency balance between local specialization and global integration of brain functional activity. Compared with right-handers, significant alterations in nodal efficiency were revealed in left-handers, involving the anterior and median cingulate gyrus, middle temporal gyrus, angular gyrus, and amygdala. Our findings indicated that the functional network organization in the human brain was associated with handedness and brain size.

Optimal design of implants for magnetically mediated hyperthermia: A wireless power transfer approach

NASA Astrophysics Data System (ADS)

Lang, Hans-Dieter; Sarris, Costas D.

2017-09-01

In magnetically mediated hyperthermia (MMH), an externally applied alternating magnetic field interacts with a mediator (such as a magnetic nanoparticle or an implant) inside the body to heat up the tissue in its proximity. Producing heat via induced currents in this manner is strikingly similar to wireless power transfer (WPT) for implants, where power is transferred from a transmitter outside of the body to an implanted receiver, in most cases via magnetic fields as well. Leveraging this analogy, a systematic method to design MMH implants for optimal heating efficiency is introduced, akin to the design of WPT systems for optimal power transfer efficiency. This paper provides analytical formulas for the achievable heating efficiency bounds as well as the optimal operating frequency and the implant material. Multiphysics simulations validate the approach and further demonstrate that optimization with respect to maximum heating efficiency is accompanied by minimizing heat delivery to healthy tissue. This is a property that is highly desirable when considering MMH as a key component or complementary method of cancer treatment and other applications.

Magnetic resonance imaging of the fetal brain.

PubMed

Tee, L Mf; Kan, E Yl; Cheung, J Cy; Leung, W C

2016-06-01

This review covers the recent literature on fetal brain magnetic resonance imaging, with emphasis on techniques, advances, common indications, and safety. We conducted a search of MEDLINE for articles published after 2010. The search terms used were "(fetal OR foetal OR fetus OR foetus) AND (MR OR MRI OR [magnetic resonance]) AND (brain OR cerebral)". Consensus statements from major authorities were also included. As a result, 44 relevant articles were included and formed the basis of this review. One major challenge is fetal motion that is largely overcome by ultra-fast sequences. Currently, single-shot fast spin-echo T2-weighted imaging remains the mainstay for motion resistance and anatomical delineation. Recently, a snap-shot inversion recovery sequence has enabled robust T1-weighted images to be obtained, which is previously a challenge for standard gradient-echo acquisitions. Fetal diffusion-weighted imaging, diffusion tensor imaging, and magnetic resonance spectroscopy are also being developed. With multiplanar capabilities, superior contrast resolution and field of view, magnetic resonance imaging does not have the limitations of sonography, and can provide additional important information. Common indications include ventriculomegaly, callosum and posterior fossa abnormalities, and twin complications. There are safety concerns about magnetic resonance-induced heating and acoustic damage but current literature showed no conclusive evidence of deleterious fetal effects. The American College of Radiology guideline states that pregnant patients can be accepted to undergo magnetic resonance imaging at any stage of pregnancy if risk-benefit ratio to patients warrants that the study be performed. Magnetic resonance imaging of the fetal brain is a safe and powerful adjunct to sonography in prenatal diagnosis. It can provide additional information that aids clinical management, prognostication, and counselling.

Magnetic field concentration using ferromagnetic material to propel a wireless power transfer based micro-robot

NASA Astrophysics Data System (ADS)

Kim, Dongwook; Park, Bumjin; Park, Jaehyoung; Park, Hyun Ho; Ahn, Seungyoung

2018-05-01

In this paper, we propose a novel coil structure, using a ferromagnetic material which concentrates the magnetic field, as the propulsion system of a wireless power transfer (WPT) based micro-robot. This structure uses an incident magnetic field to induce current during wireless power transfer, to generate a Lorentz force. To prevent net cancelation of the Lorentz force in the load coil, ferrite films were applied to one side of the coil segment. The demonstrated simplicity and effectiveness of the proposed micro-robot showed its suitability for applications. Simulation and experimental results confirmed a velocity of 1.02 mm/s with 6 mW power transfer capacity for the 3 mm sized micro-robot.

Transport characteristics of nanoparticle-based ferrofluids in a gel model of the brain

PubMed Central

Basak, Soubir; Brogan, David; Dietrich, Hans; Ritter, Rogers; Dacey, Ralph G; Biswas, Pratim

2009-01-01

A current advance in nanotechnology is the selective targeting of therapeutics by external magnetic field-guided delivery. This is an important area of research in medicine. The use of magnetic forces results in the formation of agglomerated structures in the field region. The transport characteristics of these agglomerated structures are explored. A nonintrusive method based on in situ light-scattering techniques is used to characterize the velocity of such particles in a magnetic field gradient. A transport model for the chain-like agglomerates is developed based on these experimental observations. The transport characteristics of magnetic nanoparticle drug carriers are then explored in gel-based simulated models of the brain. Results of such measurements demonstrate decreased diffusion of magnetic nanoparticles when placed in a high magnetic field gradient. PMID:19421367

Magnetite pollution nanoparticles in the human brain

NASA Astrophysics Data System (ADS)

Maher, Barbara A.; Ahmed, Imad A. M.; Karloukovski, Vassil; MacLaren, Donald A.; Foulds, Penelope G.; Allsop, David; Mann, David M. A.; Torres-Jardón, Ricardo; Calderon-Garciduenas, Lilian

2016-09-01

Biologically formed nanoparticles of the strongly magnetic mineral, magnetite, were first detected in the human brain over 20 y ago [Kirschvink JL, Kobayashi-Kirschvink A, Woodford BJ (1992) Proc Natl Acad Sci USA 89(16):7683-7687]. Magnetite can have potentially large impacts on the brain due to its unique combination of redox activity, surface charge, and strongly magnetic behavior. We used magnetic analyses and electron microscopy to identify the abundant presence in the brain of magnetite nanoparticles that are consistent with high-temperature formation, suggesting, therefore, an external, not internal, source. Comprising a separate nanoparticle population from the euhedral particles ascribed to endogenous sources, these brain magnetites are often found with other transition metal nanoparticles, and they display rounded crystal morphologies and fused surface textures, reflecting crystallization upon cooling from an initially heated, iron-bearing source material. Such high-temperature magnetite nanospheres are ubiquitous and abundant in airborne particulate matter pollution. They arise as combustion-derived, iron-rich particles, often associated with other transition metal particles, which condense and/or oxidize upon airborne release. Those magnetite pollutant particles which are <˜200 nm in diameter can enter the brain directly via the olfactory bulb. Their presence proves that externally sourced iron-bearing nanoparticles, rather than their soluble compounds, can be transported directly into the brain, where they may pose hazard to human health.

Magnetite pollution nanoparticles in the human brain.

PubMed

Maher, Barbara A; Ahmed, Imad A M; Karloukovski, Vassil; MacLaren, Donald A; Foulds, Penelope G; Allsop, David; Mann, David M A; Torres-Jardón, Ricardo; Calderon-Garciduenas, Lilian

2016-09-27

Biologically formed nanoparticles of the strongly magnetic mineral, magnetite, were first detected in the human brain over 20 y ago [Kirschvink JL, Kobayashi-Kirschvink A, Woodford BJ (1992) Proc Natl Acad Sci USA 89(16):7683-7687]. Magnetite can have potentially large impacts on the brain due to its unique combination of redox activity, surface charge, and strongly magnetic behavior. We used magnetic analyses and electron microscopy to identify the abundant presence in the brain of magnetite nanoparticles that are consistent with high-temperature formation, suggesting, therefore, an external, not internal, source. Comprising a separate nanoparticle population from the euhedral particles ascribed to endogenous sources, these brain magnetites are often found with other transition metal nanoparticles, and they display rounded crystal morphologies and fused surface textures, reflecting crystallization upon cooling from an initially heated, iron-bearing source material. Such high-temperature magnetite nanospheres are ubiquitous and abundant in airborne particulate matter pollution. They arise as combustion-derived, iron-rich particles, often associated with other transition metal particles, which condense and/or oxidize upon airborne release. Those magnetite pollutant particles which are <∼200 nm in diameter can enter the brain directly via the olfactory bulb. Their presence proves that externally sourced iron-bearing nanoparticles, rather than their soluble compounds, can be transported directly into the brain, where they may pose hazard to human health.

Neuroanatomy of the killer whale (Orcinus orca) from magnetic resonance images.

PubMed

Marino, Lori; Sherwood, Chet C; Delman, Bradley N; Tang, Cheuk Y; Naidich, Thomas P; Hof, Patrick R

2004-12-01

This article presents the first series of MRI-based anatomically labeled sectioned images of the brain of the killer whale (Orcinus orca). Magnetic resonance images of the brain of an adult killer whale were acquired in the coronal and axial planes. The gross morphology of the killer whale brain is comparable in some respects to that of other odontocete brains, including the unusual spatial arrangement of midbrain structures. There are also intriguing differences. Cerebral hemispheres appear extremely convoluted and, in contrast to smaller cetacean species, the killer whale brain possesses an exceptional degree of cortical elaboration in the insular cortex, temporal operculum, and the cortical limbic lobe. The functional and evolutionary implications of these features are discussed. (c) 2004 Wiley-Liss, Inc.

Demyelinating and ischemic brain diseases: detection algorithm through regular magnetic resonance images

NASA Astrophysics Data System (ADS)

Castillo, D.; Samaniego, René; Jiménez, Y.; Cuenca, L.; Vivanco, O.; Rodríguez-Álvarez, M. J.

2017-09-01

This work presents the advance to development of an algorithm for automatic detection of demyelinating lesions and cerebral ischemia through magnetic resonance images, which have contributed in paramount importance in the diagnosis of brain diseases. The sequences of images to be used are T1, T2, and FLAIR. Brain demyelination lesions occur due to damage of the myelin layer of nerve fibers; and therefore this deterioration is the cause of serious pathologies such as multiple sclerosis (MS), leukodystrophy, disseminated acute encephalomyelitis. Cerebral or cerebrovascular ischemia is the interruption of the blood supply to the brain, thus interrupting; the flow of oxygen and nutrients needed to maintain the functioning of brain cells. The algorithm allows the differentiation between these lesions.

In vivo detection of brain Krebs cycle intermediate by hyperpolarized magnetic resonance

PubMed Central

Mishkovsky, Mor; Comment, Arnaud; Gruetter, Rolf

2012-01-01

The Krebs (or tricarboxylic acid (TCA)) cycle has a central role in the regulation of brain energy regulation and metabolism, yet brain TCA cycle intermediates have never been directly detected in vivo. This study reports the first direct in vivo observation of a TCA cycle intermediate in intact brain, namely, 2-oxoglutarate, a key biomolecule connecting metabolism to neuronal activity. Our observation reveals important information about in vivo biochemical processes hitherto considered undetectable. In particular, it provides direct evidence that transport across the inner mitochondria membrane is rate limiting in the brain. The hyperpolarized magnetic resonance protocol designed for this study opens the way to direct and real-time studies of TCA cycle kinetics. PMID:22990416

Brain signal variability as a window into the bidirectionality between music and language processing: moving from a linear to a nonlinear model

PubMed Central

Hutka, Stefanie; Bidelman, Gavin M.; Moreno, Sylvain

2013-01-01

There is convincing empirical evidence for bidirectional transfer between music and language, such that experience in either domain can improve mental processes required by the other. This music-language relationship has been studied using linear models (e.g., comparing mean neural activity) that conceptualize brain activity as a static entity. The linear approach limits how we can understand the brain’s processing of music and language because the brain is a nonlinear system. Furthermore, there is evidence that the networks supporting music and language processing interact in a nonlinear manner. We therefore posit that the neural processing and transfer between the domains of language and music are best viewed through the lens of a nonlinear framework. Nonlinear analysis of neurophysiological activity may yield new insight into the commonalities, differences, and bidirectionality between these two cognitive domains not measurable in the local output of a cortical patch. We thus propose a novel application of brain signal variability (BSV) analysis, based on mutual information and signal entropy, to better understand the bidirectionality of music-to-language transfer in the context of a nonlinear framework. This approach will extend current methods by offering a nuanced, network-level understanding of the brain complexity involved in music-language transfer. PMID:24454295

Leukoencephalopathy with brain stem and spinal cord involvement and high lactate: a genetically proven case without elevated white matter lactate.

PubMed

Sharma, Suvasini; Sankhyan, Naveen; Kumar, Atin; Scheper, Gert C; van der Knaap, Marjo S; Gulati, Sheffali

2011-06-01

A 17-year-old Indian boy with gradually progressive ataxia with onset at 12 years of age is described. Magnetic resonance imaging (MRI) of the brain revealed extensive, inhomogeneous signal abnormalities in the cerebral white matter, with involvement of selected tracts in the brain stem and spinal cord. The imaging findings were characteristic of leukoencephalopathy with brain stem and spinal cord involvement and high lactate, a recently described leukodystrophy. Interestingly, magnetic resonance spectroscopy of the abnormal white matter did not reveal elevated lactate. The patient was compound heterozygous for 2 new mutations in DARS2, genetically confirming the diagnosis.

Effect of liver transplantation on brain magnetic resonance imaging pathology in Wilson disease: a case report.

PubMed

Litwin, T; Dzieżyc, K; Poniatowska, R; Członkowska, A

2013-01-01

The authors present a case report of a 28-year-old patient with hepatic, but no neurological, signs of Wilson disease, with pathological changes in both the globi pallidi and caudate found with routine brain magnetic resonance imaging (MRI). The patient was recommended for liver transplantation by hepatologists, and during the two years of observation after liver transplantation, MRI brain abnormalities due to Wilson disease completely regressed. On the basis of this case, the authors present an argument for the prognostic significance of brain MRI in Wilson disease as well as current recommendations concerning liver transplantation in Wilson disease.

Brain palpation from physiological vibrations using MRI.

PubMed

Zorgani, Ali; Souchon, Rémi; Dinh, Au-Hoang; Chapelon, Jean-Yves; Ménager, Jean-Michel; Lounis, Samir; Rouvière, Olivier; Catheline, Stefan

2015-10-20

We present a magnetic resonance elastography approach for tissue characterization that is inspired by seismic noise correlation and time reversal. The idea consists of extracting the elasticity from the natural shear waves in living tissues that are caused by cardiac motion, blood pulsatility, and any muscle activity. In contrast to other magnetic resonance elastography techniques, this noise-based approach is, thus, passive and broadband and does not need any synchronization with sources. The experimental demonstration is conducted in a calibrated phantom and in vivo in the brain of two healthy volunteers. Potential applications of this "brain palpation" approach for characterizing brain anomalies and diseases are foreseen.

Multi-Coil Shimming of the Mouse Brain

PubMed Central

Juchem, Christoph; Brown, Peter B.; Nixon, Terence W.; McIntyre, Scott; Rothman, Douglas L.; de Graaf, Robin A.

2011-01-01

MR imaging and spectroscopy allow the non-invasive measurement of brain function and physiology, but excellent magnetic field homogeneity is required for meaningful results. The homogenization of the magnetic field distribution in the mouse brain (i.e. shimming) is a difficult task due to complex susceptibility-induced field distortions combined with the small size of the object. To date, the achievement of satisfactory whole brain shimming in the mouse remains a major challenge. The magnetic fields generated by a set of 48 circular coils (diameter 13 mm) that were arranged in a cylinder-shaped pattern of 32 mm diameter and driven with individual dynamic current ranges of ±1 A are shown to be capable of substantially reducing the field distortions encountered in the mouse brain at 9.4 Tesla. Static multi-coil shim fields allowed the reduction of the standard deviation of Larmor frequencies by 31% compared to second order spherical harmonics shimming and a 66% narrowing was achieved with the slice-specific application of the multi-coil shimming with a dynamic approach. For gradient echo imaging, multi-coil shimming minimized shim-related signal voids in the brain periphery and allowed overall signal gains of up to 51% compared to spherical harmonics shimming. PMID:21442653

Dynamic Multi-Coil Technique (DYNAMITE) Shimming of the Rat Brain at 11.7 Tesla

PubMed Central

Juchem, Christoph; Herman, Peter; Sanganahalli, Basavaraju G.; Brown, Peter B.; McIntyre, Scott; Nixon, Terence W.; Green, Dan; Hyder, Fahmeed; de Graaf, Robin A.

2014-01-01

The in vivo rat model is a workhorse in neuroscience research, preclinical studies and drug development. A repertoire of MR tools has been developed for its investigation, however, high levels of B0 magnetic field homogeneity are required for meaningful results. The homogenization of magnetic fields in the rat brain, i.e. shimming, is a difficult task due to a multitude of complex, susceptibility-induced field distortions. Conventional shimming with spherical harmonic (SH) functions is capable of compensating shallow field distortions in limited areas, e.g. in the cortex, but performs poorly in difficult-to-shim subcortical structures or for the entire brain. Based on the recently introduced multi-coil approach for magnetic field modeling, the DYNAmic Multi-coIl TEchnique (DYNAMITE) is introduced for magnetic field shimming of the in vivo rat brain and its benefits for gradient-echo echo-planar imaging (EPI) are demonstrated. An integrated multi-coil/radio-frequency (MC/RF) system comprising 48 individual localized DC coils for B0 shimming and a surface transceive RF coil has been developed that allows MR investigations of the anesthetized rat brain in vivo. DYNAMITE shimming with this MC/RF setup is shown to reduce the B0 standard deviation to a third of that achieved with current shim technology employing static first through third order SH shapes. The EPI signal over the rat brain increased by 31% and a 24% gain in usable EPI voxels could be realized. DYNAMITE shimming is expected to critically benefit a wide range of preclinical and neuroscientific MR research. Improved magnetic field homogeneity, along with the achievable large brain coverage of this method will be crucial when signal pathways, cortical circuitry or the brain’s default network are studied. Along with the efficiency gains of MC-based shimming compared to SH approaches demonstrated recently, DYNAMITE shimming has the potential to replace conventional SH shim systems in small bore animal scanners. PMID:24839167

Brain Activation during Semantic Processing in Autism Spectrum Disorders via Functional Magnetic Resonance Imaging

ERIC Educational Resources Information Center

Harris, Gordon J.; Chabris, Christopher F.; Clark, Jill; Urban, Trinity; Aharon, Itzhak; Steele, Shelley; McGrath, Lauren; Condouris, Karen; Tager-Flusberg, Helen

2006-01-01

Language and communication deficits are core features of autism spectrum disorders (ASD), even in high-functioning adults with ASD. This study investigated brain activation patterns using functional magnetic resonance imaging in right-handed adult males with ASD and a control group, matched on age, handedness, and verbal IQ. Semantic processing in…

First in vivo traumatic brain injury imaging via magnetic particle imaging

NASA Astrophysics Data System (ADS)

Orendorff, Ryan; Peck, Austin J.; Zheng, Bo; Shirazi, Shawn N.; Ferguson, R. Matthew; Khandhar, Amit P.; Kemp, Scott J.; Goodwill, Patrick; Krishnan, Kannan M.; Brooks, George A.; Kaufer, Daniela; Conolly, Steven

2017-05-01

Emergency room visits due to traumatic brain injury (TBI) is common, but classifying the severity of the injury remains an open challenge. Some subjective methods such as the Glasgow Coma Scale attempt to classify traumatic brain injuries, as well as some imaging based modalities such as computed tomography and magnetic resonance imaging. However, to date it is still difficult to detect and monitor mild to moderate injuries. In this report, we demonstrate that the magnetic particle imaging (MPI) modality can be applied to imaging TBI events with excellent contrast. MPI can monitor injected iron nanoparticles over long time scales without signal loss, allowing researchers and clinicians to monitor the change in blood pools as the wound heals.

Brain anatomical networks in early human brain development.

PubMed

Fan, Yong; Shi, Feng; Smith, Jeffrey Keith; Lin, Weili; Gilmore, John H; Shen, Dinggang

2011-02-01

Recent neuroimaging studies have demonstrated that human brain networks have economic small-world topology and modular organization, enabling efficient information transfer among brain regions. However, it remains largely unknown how the small-world topology and modular organization of human brain networks emerge and develop. Using longitudinal MRI data of 28 healthy pediatric subjects, collected at their ages of 1 month, 1 year, and 2 years, we analyzed development patterns of brain anatomical networks derived from morphological correlations of brain regional volumes. The results show that the brain network of 1-month-olds has the characteristically economic small-world topology and nonrandom modular organization. The network's cost efficiency increases with the brain development to 1 year and 2 years, so does the modularity, providing supportive evidence for the hypothesis that the small-world topology and the modular organization of brain networks are established during early brain development to support rapid synchronization and information transfer with minimal rewiring cost, as well as to balance between local processing and global integration of information. Copyright © 2010. Published by Elsevier Inc.

Automatic Brain Portion Segmentation From Magnetic Resonance Images of Head Scans Using Gray Scale Transformation and Morphological Operations.

PubMed

Somasundaram, Karuppanagounder; Ezhilarasan, Kamalanathan

2015-01-01

To develop an automatic skull stripping method for magnetic resonance imaging (MRI) of human head scans. The proposed method is based on gray scale transformation and morphological operations. The proposed method has been tested with 20 volumes of normal T1-weighted images taken from Internet Brain Segmentation Repository. Experimental results show that the proposed method gives better results than the popular skull stripping methods Brain Extraction Tool and Brain Surface Extractor. The average value of Jaccard and Dice coefficients are 0.93 and 0.962 respectively. In this article, we have proposed a novel skull stripping method using intensity transformation and morphological operations. This is a low computational complexity method but gives competitive or better results than that of the popular skull stripping methods Brain Surface Extractor and Brain Extraction Tool.

Analysis and experimental study of wireless power transfer with HTS coil and copper coil as the intermediate resonators system

NASA Astrophysics Data System (ADS)

Wang, Xiufang; Nie, Xinyi; Liang, Yilang; Lu, Falong; Yan, Zhongming; Wang, Yu

2017-01-01

Intermediate resonator (repeater) between transmitter and receiver can significantly increase the distance of wireless power transfer (WPT) and the efficiency of wireless power transfer. The wireless power transfer via strongly coupled magnetic resonances with an high temperature superconducting (HTS) coil and copper coil as intermediate resonators was presented in this paper. The electromagnetic experiment system under different conditions with different repeating coils were simulated by finite element software. The spatial distribution patterns of magnetic induction intensity at different distances were plotted. In this paper, we examined transfer characteristics with HTS repeating coil and copper repeating coil at 77 K and 300 K, respectively. Simulation and experimental results show that HTS and copper repeating coil can effectively enhance the space magnetic induction intensity, which has significant effect on improving the transmission efficiency and lengthening transmission distance. We found that the efficiency and the distance of wireless power transfer system with an HTS coil as repeater is much higher by using of copper coil as repeater.

Magnetic resonance imaging using chemical exchange saturation transfer

NASA Astrophysics Data System (ADS)

Park, Jaeseok

2012-10-01

Magnetic resonance imaging (MRI) has been widely used as a valuable diagnostic imaging modality that exploits water content and water relaxation properties to provide both structural and functional information with high resolution. Chemical exchange saturation transfer (CEST) in MRI has been recently introduced as a new mechanism of image contrast, wherein exchangeable protons from mobile proteins and peptides are indirectly detected through saturation transfer and are not observable using conventional MRI. It has been demonstrated that CEST MRI can detect important tissue metabolites and byproducts such as glucose, glycogen, and lactate. Additionally, CEST MRI is sensitive to pH or temperature and can calibrate microenvironment dependent on pH or temperature. In this work, we provide an overview on recent trends in CEST MRI, introducing general principles of CEST mechanism, quantitative description of proton transfer process between water pool and exchangeable solute pool in the presence or absence of conventional magnetization transfer effect, and its applications

Investigating spin-transfer torques induced by thermal gradients in magnetic tunnel junctions by using micro-cavity ferromagnetic resonance

NASA Astrophysics Data System (ADS)

Cansever, H.; Narkowicz, R.; Lenz, K.; Fowley, C.; Ramasubramanian, L.; Yildirim, O.; Niesen, A.; Huebner, T.; Reiss, G.; Lindner, J.; Fassbender, J.; Deac, A. M.

2018-06-01

Similar to electrical currents flowing through magnetic multilayers, thermal gradients applied across the barrier of a magnetic tunnel junction may induce pure spin-currents and generate ‘thermal’ spin-transfer torques large enough to induce magnetization dynamics in the free layer. In this study, we describe a novel experimental approach to observe spin-transfer torques induced by thermal gradients in magnetic multilayers by studying their ferromagnetic resonance response in microwave cavities. Utilizing this approach allows for measuring the magnetization dynamics on micron/nano-sized samples in open-circuit conditions, i.e. without the need of electrical contacts. We performed first experiments on magnetic tunnel junctions patterned into 6  ×  9 µm2 ellipses from Co2FeAl/MgO/CoFeB stacks. We conducted microresonator ferromagnetic resonance (FMR) under focused laser illumination to induce thermal gradients in the layer stack and compared them to measurements in which the sample was globally heated from the backside of the substrate. Moreover, we carried out broadband FMR measurements under global heating conditions on the same extended films the microstructures were later on prepared from. The results clearly demonstrate the effect of thermal spin-torque on the FMR response and thus show that the microresonator approach is well suited to investigate thermal spin-transfer-driven processes for small temperatures gradients, far below the gradients required for magnetic switching.

Glucose-Coated Gold Nanoparticles Transfer across Human Brain Endothelium and Enter Astrocytes In Vitro

PubMed Central

Gromnicova, Radka; Davies, Heather A.; Sreekanthreddy, Peddagangannagari; Romero, Ignacio A.; Lund, Torben; Roitt, Ivan M.; Phillips, James B.; Male, David K.

2013-01-01

The blood-brain barrier prevents the entry of many therapeutic agents into the brain. Various nanocarriers have been developed to help agents to cross this barrier, but they all have limitations, with regard to tissue-selectivity and their ability to cross the endothelium. This study investigated the potential for 4 nm coated gold nanoparticles to act as selective carriers across human brain endothelium and subsequently to enter astrocytes. The transfer rate of glucose-coated gold nanoparticles across primary human brain endothelium was at least three times faster than across non-brain endothelia. Movement of these nanoparticles occurred across the apical and basal plasma membranes via the cytosol with relatively little vesicular or paracellular migration; antibiotics that interfere with vesicular transport did not block migration. The transfer rate was also dependent on the surface coating of the nanoparticle and incubation temperature. Using a novel 3-dimensional co-culture system, which includes primary human astrocytes and a brain endothelial cell line hCMEC/D3, we demonstrated that the glucose-coated nanoparticles traverse the endothelium, move through the extracellular matrix and localize in astrocytes. The movement of the nanoparticles through the matrix was >10 µm/hour and they appeared in the nuclei of the astrocytes in considerable numbers. These nanoparticles have the correct properties for efficient and selective carriers of therapeutic agents across the blood-brain barrier. PMID:24339894

Magnetic nanoparticles stimulation to enhance liquid-liquid two-phase mass transfer under static and rotating magnetic fields

NASA Astrophysics Data System (ADS)

Azimi, Neda; Rahimi, Masoud

2017-01-01

Rotating magnetic field (RMF) was applied on a micromixer to break the laminar flow and induce chaotic flow to enhance mass transfer between two-immiscible organic and aqueous phases. The results of RMF were compared to those of static magnetic field (SMF). For this purpose, experiments were carried out in a T-micromixer at equal volumetric flow rates of organic and aqueous phases. Fe3O4 nanoparticles were synthesized by co-precipitation technique and they were dissolved in organic phase. Results obtained from RMF and SMF were compared in terms of overall volumetric mass transfer coefficient (KLa) and extraction efficiency (E) at various Reynolds numbers. Generally, RMF showed higher effect in mass transfer characteristics enhancement compared with SMF. The influence of rotational speeds of magnets (ω) in RMF was investigated, and measurable enhancements of KLa and E were observed. In RMF, the effect of magnetic field induction (B) was investigated. The results reveal that at constant concentration of nanoparticles, by increasing of B, mass transfer characteristics will be enhanced. The effect of various nanoparticles concentrations (ϕ) within 0.002-0.01 (w/v) on KLa and E at maximum induction of RMF (B=76 mT) was evaluated. Maximum values of KLa (2.1±0.001) and E (0.884±0.001) were achieved for the layout of RMF (B=76 mT), ω=16 rad/s and MNPs concentration of 0.008-0.01 (w/v).

Quantitative analysis of brain magnetic resonance imaging for hepatic encephalopathy

NASA Astrophysics Data System (ADS)

Syh, Hon-Wei; Chu, Wei-Kom; Ong, Chin-Sing

1992-06-01

High intensity lesions around ventricles have recently been observed in T1-weighted brain magnetic resonance images for patients suffering hepatic encephalopathy. The exact etiology that causes magnetic resonance imaging (MRI) gray scale changes has not been totally understood. The objective of our study was to investigate, through quantitative means, (1) the amount of changes to brain white matter due to the disease process, and (2) the extent and distribution of these high intensity lesions, since it is believed that the abnormality may not be entirely limited to the white matter only. Eleven patients with proven haptic encephalopathy and three normal persons without any evidence of liver abnormality constituted our current data base. Trans-axial, sagittal, and coronal brain MRI were obtained on a 1.5 Tesla scanner. All processing was carried out on a microcomputer-based image analysis system in an off-line manner. Histograms were decomposed into regular brain tissues and lesions. Gray scale ranges coded as lesion were then brought back to original images to identify distribution of abnormality. Our results indicated the disease process involved pallidus, mesencephalon, and subthalamic regions.

Imaging of brain metastases.

PubMed

Fink, Kathleen R; Fink, James R

2013-01-01

Imaging plays a key role in the diagnosis of central nervous system (CNS) metastasis. Imaging is used to detect metastases in patients with known malignancies and new neurological signs or symptoms, as well as to screen for CNS involvement in patients with known cancer. Computed tomography (CT) and magnetic resonance imaging (MRI) are the key imaging modalities used in the diagnosis of brain metastases. In difficult cases, such as newly diagnosed solitary enhancing brain lesions in patients without known malignancy, advanced imaging techniques including proton magnetic resonance spectroscopy (MRS), contrast enhanced magnetic resonance perfusion (MRP), diffusion weighted imaging (DWI), and diffusion tensor imaging (DTI) may aid in arriving at the correct diagnosis. This image-rich review discusses the imaging evaluation of patients with suspected intracranial involvement and malignancy, describes typical imaging findings of parenchymal brain metastasis on CT and MRI, and provides clues to specific histological diagnoses such as the presence of hemorrhage. Additionally, the role of advanced imaging techniques is reviewed, specifically in the context of differentiating metastasis from high-grade glioma and other solitary enhancing brain lesions. Extra-axial CNS involvement by metastases, including pachymeningeal and leptomeningeal metastases is also briefly reviewed.

Deep brain transcranial magnetic stimulation using variable "Halo coil" system

NASA Astrophysics Data System (ADS)

Meng, Y.; Hadimani, R. L.; Crowther, L. J.; Xu, Z.; Qu, J.; Jiles, D. C.

2015-05-01

Transcranial Magnetic Stimulation has the potential to treat various neurological disorders non-invasively and safely. The "Halo coil" configuration can stimulate deeper regions of the brain with lower surface to deep-brain field ratio compared to other coil configurations. The existing "Halo coil" configuration is fixed and is limited in varying the site of stimulation in the brain. We have developed a new system based on the current "Halo coil" design along with a graphical user interface system that enables the larger coil to rotate along the transverse plane. The new system can also enable vertical movement of larger coil. Thus, this adjustable "Halo coil" configuration can stimulate different regions of the brain by adjusting the position and orientation of the larger coil on the head. We have calculated magnetic and electric fields inside a MRI-derived heterogeneous head model for various positions and orientations of the coil. We have also investigated the mechanical and thermal stability of the adjustable "Halo coil" configuration for various positions and orientations of the coil to ensure safe operation of the system.

Magnetoencephalography - a noninvasive brain imaging method with 1 ms time resolution

NASA Astrophysics Data System (ADS)

DelGratta, Cosimo; Pizzella, Vittorio; Tecchio, Franca; Luca Romani, Gian

2001-12-01

The basics of magnetoencephalography (MEG), i.e. the measurement and the analysis of the tiny magnetic fields generated outside the scalp by the working human brain, are reviewed. Three main topics are discussed: (1) the relationship between the magnetic field and its generators, including on one hand the neurophysiological basis and the physical theory of magnetic field generation, and on the other hand the techniques for the estimation of the sources from the magnetic field measurements; (2) the instrumental techniques and the laboratory practice of neuromagnetic field measurement and (3) the main applications of MEG in basic neurophysiology as well as in clinical neurology.

Estimation of electrical conductivity distribution within the human head from magnetic flux density measurement.

PubMed

Gao, Nuo; Zhu, S A; He, Bin

2005-06-07

We have developed a new algorithm for magnetic resonance electrical impedance tomography (MREIT), which uses only one component of the magnetic flux density to reconstruct the electrical conductivity distribution within the body. The radial basis function (RBF) network and simplex method are used in the present approach to estimate the conductivity distribution by minimizing the errors between the 'measured' and model-predicted magnetic flux densities. Computer simulations were conducted in a realistic-geometry head model to test the feasibility of the proposed approach. Single-variable and three-variable simulations were performed to estimate the brain-skull conductivity ratio and the conductivity values of the brain, skull and scalp layers. When SNR = 15 for magnetic flux density measurements with the target skull-to-brain conductivity ratio being 1/15, the relative error (RE) between the target and estimated conductivity was 0.0737 +/- 0.0746 in the single-variable simulations. In the three-variable simulations, the RE was 0.1676 +/- 0.0317. Effects of electrode position uncertainty were also assessed by computer simulations. The present promising results suggest the feasibility of estimating important conductivity values within the head from noninvasive magnetic flux density measurements.

Brain and Language.

ERIC Educational Resources Information Center

Damasio, Antonio R., Damasio, Hanna

1992-01-01

Discusses the advances made in understanding the brain structures responsible for language. Presents findings made using magnetic resonance imaging (MRI) and positron emission tomographic (PET) scans to study brain activity. These findings map the structures in the brain that manipulate concepts and those that turn concepts into words. (MCO)

Brain Stimulation in Alzheimer's Disease.

PubMed

Chang, Chun-Hung; Lane, Hsien-Yuan; Lin, Chieh-Hsin

2018-01-01

Brain stimulation techniques can modulate cognitive functions in many neuropsychiatric diseases. Pilot studies have shown promising effects of brain stimulations on Alzheimer's disease (AD). Brain stimulations can be categorized into non-invasive brain stimulation (NIBS) and invasive brain stimulation (IBS). IBS includes deep brain stimulation (DBS), and invasive vagus nerve stimulation (VNS), whereas NIBS includes transcranial magnetic stimulation (TMS), transcranial direct current stimulation (tDCS), transcranial alternating current stimulation (tACS), electroconvulsive treatment (ECT), magnetic seizure therapy (MST), cranial electrostimulation (CES), and non-invasive VNS. We reviewed the cutting-edge research on these brain stimulation techniques and discussed their therapeutic effects on AD. Both IBS and NIBS may have potential to be developed as novel treatments for AD; however, mixed findings may result from different study designs, patients selection, population, or samples sizes. Therefore, the efficacy of NIBS and IBS in AD remains uncertain, and needs to be further investigated. Moreover, more standardized study designs with larger sample sizes and longitudinal follow-up are warranted for establishing a structural guide for future studies and clinical application.

Transfer of Learning Relates to Intrinsic Connectivity between Hippocampus, Ventromedial Prefrontal Cortex, and Large-Scale Networks

PubMed Central

Gerraty, Raphael T.; Davidow, Juliet Y.; Wimmer, G. Elliott; Kahn, Itamar

2014-01-01

An important aspect of adaptive learning is the ability to flexibly use past experiences to guide new decisions. When facing a new decision, some people automatically leverage previously learned associations, while others do not. This variability in transfer of learning across individuals has been demonstrated repeatedly and has important implications for understanding adaptive behavior, yet the source of these individual differences remains poorly understood. In particular, it is unknown why such variability in transfer emerges even among homogeneous groups of young healthy participants who do not vary on other learning-related measures. Here we hypothesized that individual differences in the transfer of learning could be related to relatively stable differences in intrinsic brain connectivity, which could constrain how individuals learn. To test this, we obtained a behavioral measure of memory-based transfer outside of the scanner and on a separate day acquired resting-state functional MRI images in 42 participants. We then analyzed connectivity across independent component analysis-derived brain networks during rest, and tested whether intrinsic connectivity in learning-related networks was associated with transfer. We found that individual differences in transfer were related to intrinsic connectivity between the hippocampus and the ventromedial prefrontal cortex, and between these regions and large-scale functional brain networks. Together, the findings demonstrate a novel role for intrinsic brain dynamics in flexible learning-guided behavior, both within a set of functionally specific regions known to be important for learning, as well as between these regions and the default and frontoparietal networks, which are thought to serve more general cognitive functions. PMID:25143610

MHD Forced Convective Laminar Boundary Layer Flow from a Convectively Heated Moving Vertical Plate with Radiation and Transpiration Effect

PubMed Central

Uddin, Md. Jashim; Khan, Waqar A.; Ismail, A. I. Md.

2013-01-01

A two-dimensional steady forced convective flow of a Newtonian fluid past a convectively heated permeable vertically moving plate in the presence of a variable magnetic field and radiation effect has been investigated numerically. The plate moves either in assisting or opposing direction to the free stream. The plate and free stream velocities are considered to be proportional to whilst the magnetic field and mass transfer velocity are taken to be proportional to where is the distance along the plate from the leading edge of the plate. Instead of using existing similarity transformations, we use a linear group of transformations to transform the governing equations into similarity equations with relevant boundary conditions. Numerical solutions of the similarity equations are presented to show the effects of the controlling parameters on the dimensionless velocity, temperature and concentration profiles as well as on the friction factor, rate of heat and mass transfer. It is found that the rate of heat transfer elevates with the mass transfer velocity, convective heat transfer, Prandtl number, velocity ratio and the magnetic field parameters. It is also found that the rate of mass transfer enhances with the mass transfer velocity, velocity ratio, power law index and the Schmidt number, whilst it suppresses with the magnetic field parameter. Our results are compared with the results existing in the open literature. The comparisons are satisfactory. PMID:23741295

Two-Dimensional Magnetotelluric Modelling of Ore Deposits: Improvements in Model Constraints by Inclusion of Borehole Measurements

NASA Astrophysics Data System (ADS)

Kalscheuer, Thomas; Juhojuntti, Niklas; Vaittinen, Katri

2017-12-01

A combination of magnetotelluric (MT) measurements on the surface and in boreholes (without metal casing) can be expected to enhance resolution and reduce the ambiguity in models of electrical resistivity derived from MT surface measurements alone. In order to quantify potential improvement in inversion models and to aid design of electromagnetic (EM) borehole sensors, we considered two synthetic 2D models containing ore bodies down to 3000 m depth (the first with two dipping conductors in resistive crystalline host rock and the second with three mineralisation zones in a sedimentary succession exhibiting only moderate resistivity contrasts). We computed 2D inversion models from the forward responses based on combinations of surface impedance measurements and borehole measurements such as (1) skin-effect transfer functions relating horizontal magnetic fields at depth to those on the surface, (2) vertical magnetic transfer functions relating vertical magnetic fields at depth to horizontal magnetic fields on the surface and (3) vertical electric transfer functions relating vertical electric fields at depth to horizontal magnetic fields on the surface. Whereas skin-effect transfer functions are sensitive to the resistivity of the background medium and 2D anomalies, the vertical magnetic and electric field transfer functions have the disadvantage that they are comparatively insensitive to the resistivity of the layered background medium. This insensitivity introduces convergence problems in the inversion of data from structures with strong 2D resistivity contrasts. Hence, we adjusted the inversion approach to a three-step procedure, where (1) an initial inversion model is computed from surface impedance measurements, (2) this inversion model from surface impedances is used as the initial model for a joint inversion of surface impedances and skin-effect transfer functions and (3) the joint inversion model derived from the surface impedances and skin-effect transfer functions is used as the initial model for the inversion of the surface impedances, skin-effect transfer functions and vertical magnetic and electric transfer functions. For both synthetic examples, the inversion models resulting from surface and borehole measurements have higher similarity to the true models than models computed exclusively from surface measurements. However, the most prominent improvements were obtained for the first example, in which a deep small-sized ore body is more easily distinguished from a shallow main ore body penetrated by a borehole and the extent of the shadow zone (a conductive artefact) underneath the main conductor is strongly reduced. Formal model error and resolution analysis demonstrated that predominantly the skin-effect transfer functions improve model resolution at depth below the sensors and at distance of ˜ 300-1000 m laterally off a borehole, whereas the vertical electric and magnetic transfer functions improve resolution along the borehole and in its immediate vicinity. Furthermore, we studied the signal levels at depth and provided specifications of borehole magnetic and electric field sensors to be developed in a future project. Our results suggest that three-component SQUID and fluxgate magnetometers should be developed to facilitate borehole MT measurements at signal frequencies above and below 1 Hz, respectively.

Whole-head SQUID system in a superconducting magnetic shield.

PubMed

Ohta, H; Matsui, T; Uchikawa, Y

2004-11-30

We have constructed a mobile whole-head SQUID system in a superconducting magnetic shield - a cylinder of high Tc superconductor BSCCO of 65 cm in diameter and 160 cm in length. We compared the noise spectra of several SQUID sensors of SNS Josephson junctions in the superconducting magnetic shield with those of the same SQUID sensors in a magnetically shielded room of Permalloy. The SQUID sensors in the superconducting magnetic shield are more than 100 times more sensitive than those in a magnetically shielded room of Permalloy below 1 Hz. We tested the whole-head SQUID system in the superconducting magnetic shield observing somatosensory signals evoked by stimulating the median nerve in the right wrist of patients by current pulses. We present data of 64 and 128 traces versus the common time axis for comparison. Most sensory responses of human brains phase out near 250 ms. However monotonic rhythms still remain even at longer latencies than 250 ms. The nodes of these rhythm are very narrow even at these longer latencies just indicating low noise characteristics of the SQUID system at low-frequencies. The current dipoles at the secondary somatosensory area SII are evoked at longer latencies than 250 ms contributing to a higher-level brain function. The SQUID system in a superconducting magnetic shield will also have advantages when it is used as a DC MEG to study very slow activities and function of the brain.

Effects of magnetic fields on improving mass transfer in flue gas desulfurization using a fluidized bed

NASA Astrophysics Data System (ADS)

Zhang, Qi; Gui, Keting; Wang, Xiaobo

2016-02-01

The effects of magnetic fields on improving the mass transfer in flue gas desulfurization using a fluidized bed are investigated in the paper. In this research, the magnetically fluidized bed (MFB) is used as the reactor in which ferromagnetic particles are fluidized with simulated flue gas under the influence of an external magnetic field. Lime slurry is continuously sprayed into the reactor. As a consequence, the desulfurization reaction and the slurry drying process take place simultaneously in the MFB. In this paper, the effects of ferromagnetic particles and external magnetic fields on the desulphurization efficiency are studied and compared with that of quartz particles as the fluidized particles. Experimental results show that the ferromagnetic particles not only act as a platform for lime slurry to precipitate on like quartz particles, but also take part in the desulfurization reaction. The results also show that the specific surface area of ferromagnetic particles after reaction is enlarged as the magnetic intensity increases, and the external magnetic field promotes the oxidation of S(IV), improving the mass transfer between sulphur and its sorbent. Hence, the efficiency of desulphurization under the effects of external magnetic fields is higher than that in general fluidized beds.

Spin-transfer torque switched magnetic tunnel junctions in magnetic random access memory

NASA Astrophysics Data System (ADS)

Sun, Jonathan Z.

2016-10-01

Spin-transfer torque (or spin-torque, or STT) based magnetic tunnel junction (MTJ) is at the heart of a new generation of magnetism-based solid-state memory, the so-called spin-transfer-torque magnetic random access memory, or STT-MRAM. Over the past decades, STT-based switchable magnetic tunnel junction has seen progress on many fronts, including the discovery of (001) MgO as the most favored tunnel barrier, which together with (bcc) Fe or FeCo alloy are yielding best demonstrated tunnel magneto-resistance (TMR); the development of perpendicularly magnetized ultrathin CoFeB-type of thin films sufficient to support high density memories with junction sizes demonstrated down to 11nm in diameter; and record-low spin-torque switching threshold current, giving best reported switching efficiency over 5 kBT/μA. Here we review the basic device properties focusing on the perpendicularly magnetized MTJs, both in terms of switching efficiency as measured by sub-threshold, quasi-static methods, and of switching speed at super-threshold, forced switching. We focus on device behaviors important for memory applications that are rooted in fundamental device physics, which highlights the trade-off of device parameters for best suitable system integration.

Mass Transfer Process by Magneto-convection at a Solid-liquid Interface in a Heterogeneous Vertical Magnetic Field

NASA Astrophysics Data System (ADS)

Sugiyama, Atsushi; Morisaki, Shigeyoshi; Aogaki, Ryoichi

2003-08-01

When an external magnetic field is vertically imposed on a solid-liquid interface, the mass transfer process of a solute dissolving from or depositing on the interface was theoretically examined. In a heterogeneous vertical magnetic field, a material receives a magnetic force in proportion to the product of the magnetic susceptibility, the magnetic flux density B and its gradient (dB/dz). As the reaction proceeds, a diffusion layer of the solute with changing susceptibility is formed at the interface because of the difference of the the magnetic susceptibility on the concentration of the solute. In the case of an unstable condition where the dimensionless number of magneto-convection S takes a positive value, the magnetic force is applied to the layer and induces numerous minute convection cells. The mass transfer of the solute is thus accelerated, so that it is predicted that the mass flux increases with the 1/3rd order of B(dB/dz) and the 4/3rd order of the concentration. The experiment was then performed by measuring the rate of the dissolution of copper sulfate pentahydrate crystal in water.

Magnetic induced heating of nanoparticle solutions

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

Murph, S. Hunyadi; Brown, M.; Coopersmith, K.

2016-12-02

Magnetic induced heating of nanoparticles (NP) provides a useful advantage for many energy transfer applications. This study aims to gain an understanding of the key parameters responsible for maximizing the energy transfer leading to nanoparticle heating through the use of simulations and experimental results. It was found that magnetic field strength, NP concentration, NP composition, and coil size can be controlled to generate accurate temperature profiles in NP aqueous solutions.

Energy transport in cooling device by magnetic fluid

NASA Astrophysics Data System (ADS)

Yamaguchi, Hiroshi; Iwamoto, Yuhiro

2017-06-01

Temperature sensitive magnetic fluid has a great potential with high performance heat transport ability as well as long distance energy (heat) transporting. In the present study experimental set-up was newly designed and constructed in order to measure basic heat transport characteristics under various magnetic field conditions. Angular dependence for the device (heat transfer section) was also taken into consideration for a sake of practical applications. The energy transfer characteristic (heat transport capability) in the magnetically-driven heat transport (cooling) device using the binary TSMF was fully investigated with the set-up. The obtained results indicate that boiling of the organic mixture (before the magnetic fluid itself reaching boiling point) effectively enhances the heat transfer as well as boosting the flow to circulate in the closed loop by itself. A long-distance heat transport of 5 m is experimentally confirmed, transferring the thermal energy of 35.8 W, even when the device (circulation loop) is horizontally placed. The highlighted results reveal that the proposed cooling device is innovative in a sense of transporting substantial amount of thermal energy (heat) as well as a long distance heat transport. The development of the magnetically-driven heat transport device has a great potential to be replaced for the conventional heat pipe in application of thermal engineering.

Nonlinear Magnetic Dynamics and The Switching Phase Diagrams in Spintronic Devices

NASA Astrophysics Data System (ADS)

Yan, Shu

Spin-transfer torque induced magnetic switching, by which the spin-polarized current transfers its magnetic moment to the ferromagnetic layer and changes its magnetization, holds great promise towards faster and smaller magnetic bits in data-storage applications due to the lower power consumption and better scalability. We propose an analytic approach which can be used to calculate the switching phase diagram of a nanomagnetic system in the presence of both magnetic field and spin-transfer torque in an exact fashion. This method is applied to the study of switching conditions for the uniaxial, single domain magnetic layers in different spin-transfer devices. In a spin valve with spin polarization collinear with the easy axis, we get a modified Stoner-Wohlfarth astroid which represents many of the features that have been found in experiment. It also shows a self-crossing boundary and demonstrates a region with three stable equilibria. We demonstrate that the region of stable equilibria with energy near the maximum can be reached only through a narrow bottleneck in the field space, which sets a stringent requirement for magnetic field alignment in the experiments. Switching diagrams are then calculated for the setups with magnetic field not perfectly aligned with the easy axis. In a ferromagnet-heavy-metal bilayer device with strong spin Hall effect, the in plane current becomes spin-polarized and transfers its magnetic moment to the ferromagnetic layer by diffusion. The three-dimensional asymmetric phase diagram is calculated. In the case that the external field is confined in the vertical plane defined by the direction of the current and the easy axis, the spin-transfer torque shifts the conventional in-plane (IP) equilibria within the same plane, and also creates two out-of-plane (OOP) equilibria, one of which can be stable. The threshold switching currents for IP switching and OOP switching are discussed. We also address the magnetic switching processes. Damping switching and precessional switching are two different switching types that are typically considered in recent studies. In the damping mode the switching is slow and heavily depends on the initial deviation, while in the precessional mode the accurate manipulation of the field or current pulse is required. We propose a switching scenario for a fast and reliable switching by taking advantage of the out-of-plane stable equilibrium in the SHE induced magnetic switching. The magnetization is first driven by a pulse of field and current towards the OOP equilibrium without precession. Since it is in the lower half of the unit sphere, no backwards pulse is required for a complete switching. This indicates a potentially feasible method of reliable ultra-fast magnetic control.

Active Magnetic Regenerative Liquefier

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

Barclay, John A.; Oseen-Send, Kathryn; Ferguson, Luke

2016-01-12

This final report for the DOE Project entitled Active Magnetic Regenerative Liquefier (AMRL) funded under Grant DE-FG36-08GO18064 to Heracles Energy Corporation d.b.a. Prometheus Energy (Heracles/Prometheus) describes an active magnetic regenerative refrigerator (AMRR) prototype designed and built during the period from July 2008 through May 2011. The primary goal of this project was to make significant technical advances toward highly efficient liquefaction of hydrogen. Conventional hydrogen liquefiers at any scale have a maximum FOM of ~0.35 due primarily to the intrinsic difficulty of rapid, efficient compression of either hydrogen or helium working gases. Numerical simulation modeling of high performance AMRL designsmore » indicates certain designs have promise to increase thermodynamic efficiency from a FOM of ~0.35 toward ~0.5 to ~0.6. The technical approach was the use of solid magnetic working refrigerants cycled in and out of high magnetic fields to build an efficient active regenerative magnetic refrigeration module providing cooling power for AMRL. A single-stage reciprocating AMRR with a design temperature span from ~290 K to ~120 K was built and tested with dual magnetic regenerators moving in and out of the conductively-cooled superconducting magnet subsystem. The heat transfer fluid (helium) was coupled to the process stream (refrigeration/liquefaction load) via high performance heat exchangers. In order to maximize AMRR efficiency a helium bypass loop with adjustable flow was incorporated in the design because the thermal mass of magnetic refrigerants is higher in low magnetic field than in high magnetic field. Heracles/Prometheus designed experiments to measure AMRR performance under a variety of different operational parameters such as cycle frequency, magnetic field strength, heat transfer fluid flow rate, amount of bypass flow of the heat transfer fluid while measuring work input, temperature span, cooling capability as a function of cold temperature as a function of the amount of bypass flow of the heat transfer fluid. The operational AMRR prototype can be used to answer key questions such as the best recipe for multiple layers of different magnetic refrigerants in one or more integrated regenerators with varying amounts of bypass flow of the heat transfer fluid. Layered regenerators are necessary to span the AMRR range from 290 K to 120K. Our AMRR performance simulation model predicts that ~10-15 % of bypass flow should significantly improve the thermodynamic performance. Initial results obtained with regenerators made of gadolinium spheres were very encouraging; a temperature span of ~ 50 K (between 295K and 245 K) across both regenerators was achieved with zero bypass flow of the heat transfer fluid and with the magnetic field strength of ~4 T.« less

Highly Efficient Wireless Powering for Autonomous Structural Health Monitoring and Test/Evaluation Systems

DTIC Science & Technology

2016-07-27

ADDRESS (ES) U.S. Army Research Office P.O. Box 12211 Research Triangle Park, NC 27709-2211 Wireless Power Transfer , Structural Health Monitoring...efficient strongly coupled magnetic resonant systems, Wireless Power Transfer , (03 2014): 0. doi: 10.1017/wpt.2014.3 TOTAL: 1 Received Paper TOTAL...2016 Received Paper . Miniaturized Strongly Coupled Magnetic Resonant Systems for Wireless Power Transfer , 2016 IEEE Antennas Propagat. Society

Responses to magnetic stimuli recorded in peripheral nerves in the marine nudibranch mollusk Tritonia diomedea.

PubMed

Pavlova, Galina A; Glantz, Raymon M; Dennis Willows, A O

2011-10-01

Prior behavioral and neurophysiological studies provide evidence that the nudibranch mollusk Tritonia orients to the earth's magnetic field. Earlier studies of electrophysiological responses in certain neurons of the brain to changing ambient magnetic fields suggest that although certain identified brain cells fire impulses when the ambient field is changed, these neuron somata and their central dentritic and axonal processes are themselves not primary magnetic receptors. Here, using semi-intact animal preparations from which the brain was removed, we recorded from peripheral nerve trunks. Using techniques to count spikes in individual nerves and separately also to identify, then count individual axonal spikes in extracellular records, we found both excitatory and inhibitory axonal responses elicited by changes in the direction of ambient earth strength magnetic fields. We found responses in nerves from many locations throughout the body and in axons innervating the body wall and rhinophores. Our results indicate that primary receptors for geomagnetism in Tritonia are not focally concentrated in any particular organ, but appear to be widely dispersed in the peripheral body tissues.

MHD boundary layer slip flow and heat transfer of ferrofluid along a stretching cylinder with prescribed heat flux.

PubMed

Qasim, Muhammad; Khan, Zafar Hayat; Khan, Waqar Ahmad; Ali Shah, Inayat

2014-01-01

This study investigates the magnetohydrodynamic (MHD) flow of ferrofluid along a stretching cylinder. The velocity slip and prescribed surface heat flux boundary conditions are employed on the cylinder surface. Water as conventional base fluid containing nanoparticles of magnetite (Fe3O4) is used. Comparison between magnetic (Fe3O4) and non-magnetic (Al2O3) nanoparticles is also made. The governing non-linear partial differential equations are reduced to non-linear ordinary differential equations and then solved numerically using shooting method. Present results are compared with the available data in the limiting cases. The present results are found to be in an excellent agreement. It is observed that with an increase in the magnetic field strength, the percent difference in the heat transfer rate of magnetic nanoparticles with Al2O3 decreases. Surface shear stress and the heat transfer rate at the surface increase as the curvature parameter increases, i.e curvature helps to enhance the heat transfer.

Magnetic metamaterial superlens for increased range wireless power transfer.

PubMed

Lipworth, Guy; Ensworth, Joshua; Seetharam, Kushal; Huang, Da; Lee, Jae Seung; Schmalenberg, Paul; Nomura, Tsuyoshi; Reynolds, Matthew S; Smith, David R; Urzhumov, Yaroslav

2014-01-10

The ability to wirelessly power electrical devices is becoming of greater urgency as a component of energy conservation and sustainability efforts. Due to health and safety concerns, most wireless power transfer (WPT) schemes utilize very low frequency, quasi-static, magnetic fields; power transfer occurs via magneto-inductive (MI) coupling between conducting loops serving as transmitter and receiver. At the "long range" regime - referring to distances larger than the diameter of the largest loop - WPT efficiency in free space falls off as (1/d)(6); power loss quickly approaches 100% and limits practical implementations of WPT to relatively tight distances between power source and device. A "superlens", however, can concentrate the magnetic near fields of a source. Here, we demonstrate the impact of a magnetic metamaterial (MM) superlens on long-range near-field WPT, quantitatively confirming in simulation and measurement at 13-16 MHz the conditions under which the superlens can enhance power transfer efficiency compared to the lens-less free-space system.

Magnetically guided central nervous system delivery and toxicity evaluation of magneto-electric nanocarriers.

PubMed

Kaushik, Ajeet; Jayant, Rahul D; Nikkhah-Moshaie, Roozbeh; Bhardwaj, Vinay; Roy, Upal; Huang, Zaohua; Ruiz, Ariel; Yndart, Adriana; Atluri, Venkata; El-Hage, Nazira; Khalili, Kamel; Nair, Madhavan

2016-05-04

Least component-based delivery of drug-tagged-nanocarriers across blood-brain-barriers (BBB) will allow site-specific and on-demand release of therapeutics to prevent CNS diseases. We developed a non-invasive magnetically guided delivery of magneto-electric nanocarriers (MENCs), ~20 nm, 10 mg/kg, across BBB in C57Bl/J mice. Delivered MENCs were uniformly distributed inside the brain, and were non-toxic to brain and other major organs, such as kidney, lung, liver, and spleen, and did not affect hepatic, kidney and neurobehavioral functioning.

BDNF Val66Met polymorphism is associated with abnormal interhemispheric transfer of a newly acquired motor skill.

PubMed

Morin-Moncet, Olivier; Beaumont, Vincent; de Beaumont, Louis; Lepage, Jean-Francois; Théoret, Hugo

2014-05-01

Recent data suggest that the Val66Met polymorphism of the brain-derived neurotrophic factor (BDNF) gene can alter cortical plasticity within the motor cortex of carriers, which exhibits abnormally low rates of cortical reorganization after repetitive motor tasks. To verify whether long-term retention of a motor skill is also modulated by the presence of the polymorphism, 20 participants (10 Val66Val, 10 Val66Met) were tested twice at a 1-wk interval. During each visit, excitability of the motor cortex was measured by transcranial magnetic stimulations (TMS) before and after performance of a procedural motor learning task (serial reaction time task) designed to study sequence-specific learning of the right hand and sequence-specific transfer from the right to the left hand. Behavioral results showed a motor learning effect that persisted for at least a week and task-related increases in corticospinal excitability identical for both sessions and without distinction for genetic group. Sequence-specific transfer of the motor skill from the right hand to the left hand was greater in session 2 than in session 1 only in the Val66Met genetic group. Further analysis revealed that the sequence-specific transfer occurred equally at both sessions in the Val66Val genotype group. In the Val66Met genotype group, sequence-specific transfer did not occur at session 1 but did at session 2. These data suggest a limited impact of Val66Met polymorphism on the learning and retention of a complex motor skill and its associated changes in corticospinal excitability over time, and a possible modulation of the interhemispheric transfer of procedural learning. Copyright © 2014 the American Physiological Society.

Neuromodulation for mood and memory: from the engineering bench to the patient bedside

PubMed Central

Deng, Zhi-De; McClintock, Shawn M.; Oey, Nicodemus E.; Luber, Bruce; Lisanby, Sarah H.

2014-01-01

Brain stimulation, in the form of electroconvulsive therapy (ECT), has long been a gold standard treatment for depression, but today, the field of neuromodulation is rapidly changing with the advent of newer and more precise tools to alter neuroplasticity and to treat brain-based disorders. Now there are new means to induce focal seizures, as with magnetic seizure therapy (MST), or modifications to ECT. There are also surgical approaches to target brain circuits via implanted stimulators placed in the brain or on cranial nerves. Finally, there are noninvasive subconvulsive approaches for the transcranial application of either electric or magnetic fields. Collectively, these tools have transformed the face of neurotherapeutics and informed our understanding of the brain basis of complex neurobehavioral conditions. PMID:25222617

Quantum approach of mesoscopic magnet dynamics with spin transfer torque

NASA Astrophysics Data System (ADS)

Wang, Yong; Sham, L. J.

2013-05-01

We present a theory of magnetization dynamics driven by spin-polarized current in terms of the quantum master equation. In the spin coherent state representation, the master equation becomes a Fokker-Planck equation, which naturally includes the spin transfer and quantum fluctuation. The current electron scattering state is correlated to the magnet quantum states, giving rise to quantum correction to the electron transport properties in the usual semiclassical theory. In the large-spin limit, the magnetization dynamics is shown to obey the Hamilton-Jacobi equation or the Hamiltonian canonical equations.

Tunable magnetotransport in Fe/hBN/graphene/hBN/Pt(Fe) epitaxial multilayers

NASA Astrophysics Data System (ADS)

Magnus Ukpong, Aniekan

2018-03-01

Theoretical and computational analysis of the magnetotransport properties and spin-transfer torque field-induced switching of magnetization density in vertically-stacked multilayers is presented. Using epitaxially-capped free layers of Pt and Fe, atom-resolved magnetic moments and spin-transfer torques are computed at finite bias. The calculations are performed within linear response approximation to the spin-density reformulation of the van der Waals density functional theory. Dynamical spin excitations are computed as a function of a spin-transfer torque induced magnetic field along the magnetic easy axis, and the corresponding spin polarization perpendicular to the easy axis is obtained. Bias-dependent giant anisotropic magnetoresistance of up to 3200% is obtained in the nonmagnetic-metal-capped Fe/hBN/graphene/hBN/Pt multilayer architecture. Since this specific heterostructure is not yet fabricated and characterized, the predicted high performance has not been demonstrated experimentally. Nevertheless, similar calculations performed on the Fe/hBN/Co stack show that the tunneling magnetoresistance obtained at the Fermi-level is in excellent agreement with results of recent magnetotransport measurements on magnetic tunnel junctions that contain the monolayer hBN tunnel region. The magnitude of the spin-transfer torque is found to increase as the tunneling spin current increases, and this activates the magnetization switching process due to increased charge accumulation. This mechanism causes substantial spin backflow, which manifests as rapid undulations in the bias-dependent tunneling spin currents. The implication of these findings on the design of nanoscale spintronic devices with spin-transfer torque tunable magnetization density is discussed. Insights derived from this study are expected to enhance the prospects for developing and integrating artificially assembled van der Waals multilayer heterostructures as the preferred material platform for efficient engineering of spin switches for spintronic applications.

Functional Magnetic Resonance Imaging Methods

PubMed Central

Chen, Jingyuan E.; Glover, Gary H.

2015-01-01

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

Basal ganglia lesions in subacute sclerosing panencephalitis

PubMed Central

Almeida, Kelson James; Brucki, Sonia Maria Dozzi; Duarte, Maria Irma Seixas; Pasqualucci, Carlos Augusto Gonçalves; Rosemberg, Sérgio; Nitrini, Ricardo

2012-01-01

The parieto-occipital region of the brain is the most frequently and severely affected in subacute sclerosing panencephalitis (SSPE). The basal ganglia, cerebellum and corpus callosum are less commonly involved. We describe a patient with SSPE confirmed by neuropathology based on brain magnetic resonance imaging showing extensive basal ganglia involvement and no significant involvement of other cortical structures. Though rarely described in SSPE, clinicians should be aware of this involvement. SSPE should be kept in mind when changes in basal ganglia signal are seen on brain magnetic resonance imaging with or without involvement of other regions of the human brain to avoid erroneous etiological diagnosis of other pathologies causing rapidly progressive dementia. PMID:29213810

On the topology of flux transfer events

NASA Technical Reports Server (NTRS)

Hesse, Michael; Birn, Joachim; Schindler, Karl

1990-01-01

A topological analysis is made of a simple model magnetic field of a perturbation at the magnetopause that shares magnetic properties with flux transfer events. The aim is to clarify a number of topological aspects that arise in the case of fully three-dimensional magnetic fields. It is shown that a localized perturbation at the magnetopause can in principle open a closed magnetosphere by establishing magnetic connections across the magnetopause by the formation of a ropelike magnetic field structure. For this purpose a global topological model of a closed magnetosphere is considered as the unperturbed state. The topological substructure of the model flux rope is discussed in detail.

Retinoblastoma and optic nerve enhancement in a brain magnetic resonance scan: is it always a metastasis?

PubMed

Correa-Acosta, A; González-Alviar, M E; Gaviria-Bravo, M L

2018-05-01

The case is presented on a girl with a unilateral retinoblastoma that required treatment with intra-arterial chemotherapy. In the nuclear magnetic resonance imaging of the brain performed 1 month after intra-arterial chemotherapy treatment, post-laminar optic nerve (ON) enhancement was observed, leading to the suspicion of an ON tumour infiltration. Additional examinations were requested by which a probable optic neuropathy was diagnosed. The ON enhancement in magnetic resonance imaging of the brain in retinoblastoma generally corresponds to tumour invasion of the ON. However, other diagnostic alternatives associated with the use of new treatments, such as intra-arterial chemotherapy, should be considered. Copyright © 2017 Sociedad Española de Oftalmología. Publicado por Elsevier España, S.L.U. All rights reserved.

Normalized power transmission between ABP and ICP in TBI.

PubMed

Shahsavari, S; Hallen, T; McKelvey, T; Ritzen, C; Rydenhag, B

2009-01-01

A new approach to study the pulse transmission between the cerebrovascular bed and the intracranial space is presented. In the proposed approach, the normalized power transmission between ABP and ICP has got the main attention rather than the actual power transmission. Evaluating the gain of the proposed transfer function at any single frequency can reveal how the percentage of contribution of that specific frequency component has been changed through the cerebrospinal system. The gain of the new transfer function at the fundamental cardiac frequency was utilized to evaluate the state of the brain in three TBI patients. Results were assessed using the reference evaluations achieved by a novel CT scan-based scoring scheme. In all three study cases, the gain of the transfer function showed a good capability to follow the trend of the CT scores and describe the brain state. Comparing the new transfer function with the traditional one and also the index of compensatory reserve, the proposed transfer function was found more informative about the state of the brain in the patients under study.

If the skull fits: magnetic resonance imaging and microcomputed tomography for combined analysis of brain and skull phenotypes in the mouse

PubMed Central

Blank, Marissa C.; Roman, Brian B.; Henkelman, R. Mark; Millen, Kathleen J.

2012-01-01

The mammalian brain and skull develop concurrently in a coordinated manner, consistently producing a brain and skull that fit tightly together. It is common that abnormalities in one are associated with related abnormalities in the other. However, this is not always the case. A complete characterization of the relationship between brain and skull phenotypes is necessary to understand the mechanisms that cause them to be coordinated or divergent and to provide perspective on the potential diagnostic or prognostic significance of brain and skull phenotypes. We demonstrate the combined use of magnetic resonance imaging and microcomputed tomography for analysis of brain and skull phenotypes in the mouse. Co-registration of brain and skull images allows comparison of the relationship between phenotypes in the brain and those in the skull. We observe a close fit between the brain and skull of two genetic mouse models that both show abnormal brain and skull phenotypes. Application of these three-dimensional image analyses in a broader range of mouse mutants will provide a map of the relationships between brain and skull phenotypes generally and allow characterization of patterns of similarities and differences. PMID:22947655

Brain tumor magnetic targeting and biodistribution of superparamagnetic iron oxide nanoparticles linked with 70-kDa heat shock protein study by nonlinear longitudinal response

NASA Astrophysics Data System (ADS)

Shevtsov, Maxim A.; Nikolaev, Boris P.; Ryzhov, Vyacheslav A.; Yakovleva, Ludmila Y.; Dobrodumov, Anatolii V.; Marchenko, Yaroslav Y.; Margulis, Boris A.; Pitkin, Emil; Guzhova, Irina V.

2015-08-01

Brain tumor targeting efficiency and biodistribution of the superparamagnetic nanoparticles conjugated with heat shock protein Hsp70 (SPION-Hsp70) were evaluated in experimental glioma model. Synthesized conjugates were characterized using the method of longitudinal nonlinear response of magnetic nanoparticles to a weak ac magnetic field with measurements of second harmonic of magnetization (NLR-M2). Cellular interaction of magnetic conjugates was analyzed in 9L glioma cell culture. The biodistribution of the nanoparticles and their accumulation in tumors was assessed by the latter approach as well. The efficacy of Hsp70-conjugates for contrast enhancement in the orthotopic model of 9L glioma was assessed by MR imaging (11 T). Magnetic nanoparticles conjugated with Hsp70 had the relaxivity properties of the MR-negative contrast agents. Morphological observation and cell viability test demonstrated good biocompatibility of Hsp70-conjugates. Analysis of the T2-weighted MR scans in tumor-bearing rats demonstrated the high efficacy of Hsp70-conjugates in contrast enhancement of the glioma in comparison to non-conjugated nanoparticles. High contrast enhancement of the glioma was provided by the accumulation of the SPION-Hsp70 particles in the glioma tissue (as shown by the histological assay). Biodistribution analysis by NLR-M2 measurements evidenced the many-fold increase (~40) in the tumor-to-normal brain uptake ratio in the Hsp70-conjugates treated animals. Biodistribution pattern of Hsp70-decorated nanoparticles differed from that of non-conjugated SPIONs. Coating of the magnetic nanoparticles with Hsp70 protein enhances the tumor-targeting ability of the conjugates that could be applied in the MR imaging of the malignant brain tumors.

[Effects of pulsed magnetic field on insulin-like growth factor-1 (IGF-1) in cerebrospinal fluid and effects of IGF-1 on functional recovery].

PubMed

Song, Cheng-xian; Fan, Jian-zhong; Wu, Hong-ying; Wei, Yi; Zhen, Jian-rong

2010-10-01

To study the effects of pulsed magnetic field on insulin-like growth factor-1 (IGF-1) level in the cerebrospinal fluid (CSF) and the association of IGF-1 alterations with the activities of daily living (ADL) of patients with brain injury. Sixty-five patients with brain injury were divided randomly into the control group (n=30) and magnetic therapy group (n=35), both receiving conventional therapy and in the latter group, daily pulsed magnetic field treatment (20-40 mT, 50 Hz, 20 min per time, 1 time per day) for 14 consecutive days were administered. On the first and 14th days of the treatment, 2 ml CSF was collected from the cases patients for IGF-1 measurement by radioimmunoassay, and Barthel index (BI) was used to assess the ADL of the patients. After a 14-day treatment, IGF-1 level in the CSF were significantly increased in the magnetic group in comparison with the level before the treatment and with those in the control group (P<0.05). IGF-1 in the CSF underwent no significant changes in the control group (P>0.05). The scores of BI increased significantly in both groups after the treatment (P<0.01), but the increment was more obvious in the magnetic therapy group (P<0.05). A significant positive correlation was found between IGF-1 level in the CSF and BI in these patients (r=0.283, P=0.022). Pulsed magnetic field might increase IGF-1 level in the CSF of patients with brain injury to promote the recovery of the patients ADL, suggesting its potential clinical value in the treatment of brain injury.

Enhanced blood-brain barrier transmigration using a novel transferrin embedded fluorescent magneto-liposome nanoformulation

NASA Astrophysics Data System (ADS)

Ding, Hong; Sagar, Vidya; Agudelo, Marisela; Pilakka-Kanthikeel, Sudheesh; Subba Rao Atluri, Venkata; Raymond, Andrea; Samikkannu, Thangavel; Nair, Madhavan P.

2014-02-01

The blood-brain barrier (BBB) is considered as the primary impediment barrier for most drugs. Delivering therapeutic agents to the brain is still a big challenge to date. In our study, a dual mechanism, receptor mediation combined with external non-invasive magnetic force, was incorporated into ferrous magnet-based liposomes for BBB transmigration enhancement. The homogenous magnetic nanoparticles (MNPs), with a size of ˜10 nm, were synthesized and confirmed by TEM and XRD respectively. The classical magnetism assay showed the presence of the characteristic superparamagnetic property. These MNPs encapsulated in PEGylated fluorescent liposomes as magneto-liposomes (MLs) showed mono-dispersion, ˜130 ± 10 nm diameter, by dynamic laser scattering (DLS) using the lipid-extrusion technique. Remarkably, a magnetite encapsulation efficiency of nearly 60% was achieved. Moreover, the luminescence and hydrodynamic size of the MLs was stable for over two months at 4 ° C. Additionally, the integrity of the ML structure remained unaffected through 120 rounds of circulation mimicking human blood fluid. After biocompatibility confirmation by cytotoxicity evaluation, these fluorescent MLs were further embedded with transferrin and applied to an in vitro BBB transmigration study in the presence or absence of external magnetic force. Comparing with magnetic force- or transferrin receptor-mediated transportation alone, their synergy resulted in 50-100% increased transmigration without affecting the BBB integrity. Consequently, confocal microscopy and iron concentration in BBB-composed cells further confirmed the higher cellular uptake of ML particles due to the synergic effect. Thus, our multifunctional liposomal magnetic nanocarriers possess great potential in particle transmigration across the BBB and may have a bright future in drug delivery to the brain.

Enhanced blood-brain barrier transmigration using a novel transferrin embedded fluorescent magneto-liposome nanoformulation.

PubMed

Ding, Hong; Sagar, Vidya; Agudelo, Marisela; Pilakka-Kanthikeel, Sudheesh; Atluri, Venkata Subba Rao; Raymond, Andrea; Samikkannu, Thangavel; Nair, Madhavan P

2014-02-07

The blood-brain barrier (BBB) is considered as the primary impediment barrier for most drugs. Delivering therapeutic agents to the brain is still a big challenge to date. In our study, a dual mechanism, receptor mediation combined with external non-invasive magnetic force, was incorporated into ferrous magnet-based liposomes for BBB transmigration enhancement. The homogenous magnetic nanoparticles (MNPs), with a size of ∼10 nm, were synthesized and confirmed by TEM and XRD respectively. The classical magnetism assay showed the presence of the characteristic superparamagnetic property. These MNPs encapsulated in PEGylated fluorescent liposomes as magneto-liposomes (MLs) showed mono-dispersion, ∼130 ± 10 nm diameter, by dynamic laser scattering (DLS) using the lipid-extrusion technique. Remarkably, a magnetite encapsulation efficiency of nearly 60% was achieved. Moreover, the luminescence and hydrodynamic size of the MLs was stable for over two months at 4 ° C. Additionally, the integrity of the ML structure remained unaffected through 120 rounds of circulation mimicking human blood fluid. After biocompatibility confirmation by cytotoxicity evaluation, these fluorescent MLs were further embedded with transferrin and applied to an in vitro BBB transmigration study in the presence or absence of external magnetic force. Comparing with magnetic force- or transferrin receptor-mediated transportation alone, their synergy resulted in 50-100% increased transmigration without affecting the BBB integrity. Consequently, confocal microscopy and iron concentration in BBB-composed cells further confirmed the higher cellular uptake of ML particles due to the synergic effect. Thus, our multifunctional liposomal magnetic nanocarriers possess great potential in particle transmigration across the BBB and may have a bright future in drug delivery to the brain.

Anatomic brain disease in hemodialysis patients: a cross-sectional study

USDA-ARS?s Scientific Manuscript database

Although dialysis patients are at high risk of stroke and have a high burden of cognitive impairment, there are few reports of anatomic brain findings in the hemodialysis population. Using magnetic resonance imaging of the brain, we compared the prevalence of brain abnormalities in hemodialysis pati...

MHD effects on heat transfer and entropy generation of nanofluid flow in an open cavity

NASA Astrophysics Data System (ADS)

Mehrez, Zouhaier; El Cafsi, Afif; Belghith, Ali; Le Quéré, Patrick

2015-01-01

The present numerical work investigates the effect of an external oriented magnetic field on heat transfer and entropy generation of Cu-water nanofluid flow in an open cavity heated from below. The governing equations are solved numerically by the finite-volume method. The study has been carried out for a wide range of solid volume fraction 0≤φ≤0.06, Hartmann number 0≤Ha≤100, Reynolds number 100≤Re≤500 and Richardson number 0.001≤Ri≤1 at three inclination angles of magnetic field γ: 0°, 45° and 90°. The numerical results are given by streamlines, isotherms, average Nusselt number, average entropy generation and Bejan number. The results show that flow behavior, temperature distribution, heat transfer and entropy generation are strongly affected by the presence of a magnetic field. The average Nusselt number and entropy generation, which increase by increasing volume fraction of nanoparticles, depend mainly on the Hartmann number and inclination angle of the magnetic field. The variation rates of heat transfer and entropy generation while adding nanoparticles or applying a magnetic field depend on the Richardson and Reynolds numbers.

Preparation, characteristics, convection and applications of magnetic nanofluids: A review

NASA Astrophysics Data System (ADS)

Kumar, Aditya; Subudhi, Sudhakar

2018-02-01

Magnetic nanofluids (MNfs), the colloidal suspension of ferromagnetic nanomaterial, have been taken into research fascinatingly. After contemplating its distinctive interesting properties and unique eximious features it offers innumerous application not only in heat transfer field but also immensely prevalent in medical, biological, aerospace, electronics and solar sciences. This review paper epitomizes and perusing the research work done on heat transfer application of MNfs and encapsulate it for the future research support. Moreover, numerical and experimental, both the approaches has been included for the insightful analysis of phenomenon to apprehend augmentation in heat transfer by MNfs. This article first underlines the importance of appropriate methods of preparation of MNfs as well as its effects on the thermophysical properties of MNfs. Subsequently, the paper comprehended the descriptive analysis of augmentation of convection heat transfer and the effect of magnetic field on the behavior MNfs. Additionally, the effect of magnetic field intensity has been taken as a pertinent parameter and correlations have been developed for thermal conductivity, viscosity and heat transfer coefficient based on the reviewed data. The paper concluded with the tremendous applications of the MNfs and the futuristic plan to support the potential areas for future research.

Myo-inositol metabolism in appropriately grown and growth-restricted fetuses: a proton magnetic resonance spectroscopy study.

PubMed

Story, Lisa; Damodaram, Mellisa S; Supramaniam, Veena; Allsop, Joanna M; Mcguinness, Amy; Patel, Abhilasha; Wylezinska, Marzena; Kumar, Sailesh; Rutherford, Mary A

2013-09-01

Myo-inositol (Myo-ins) is a marker of neuroglial cells, being present in the astrocytes of brain tissue, but also functions as an osmolyte. Numbers of astrocytes are known to increase following injury to the brain. Growth-restricted fetuses are at increased risk of later neurodevelopmental impairments even in the absence of overt lesions and despite preserved/increased cerebral blood flow. This study aims to investigate brain Myo-ins metabolism in fetuses with intrauterine growth restriction (IUGR) and evidence of cerebral redistribution using magnetic resonance spectroscopy (MRS) at a short echo time. Biometry and Doppler assessment of blood flow was assessed using ultrasound in 28 fetuses with IUGR and 47 appropriately grown control subjects. MRI was used to exclude overt brain injury. Proton magnetic resonance spectroscopy of the fetal brain was then performed at an echo time of 42 ms to examine the Myo-ins:Choline (Cho), Myo-ins:Creatine (Cr) and Cho:Cr ratios. No alterations in brain Myo-ins:Cho, Myo-ins:Cr or Cho:Cr ratios were detected between appropriately grown and growth restricted fetuses. IUGR is not associated with a measureable difference in brain myo-inositol ratios. This may be due to the protective effects of preserved cerebral blood flow in growth restriction and comparable astrocyte numbers when compared to controls. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Magnetite pollution nanoparticles in the human brain

PubMed Central

Maher, Barbara A.; Karloukovski, Vassil; MacLaren, Donald A.; Foulds, Penelope G.; Allsop, David; Mann, David M. A.; Torres-Jardón, Ricardo; Calderon-Garciduenas, Lilian

2016-01-01

Biologically formed nanoparticles of the strongly magnetic mineral, magnetite, were first detected in the human brain over 20 y ago [Kirschvink JL, Kobayashi-Kirschvink A, Woodford BJ (1992) Proc Natl Acad Sci USA 89(16):7683–7687]. Magnetite can have potentially large impacts on the brain due to its unique combination of redox activity, surface charge, and strongly magnetic behavior. We used magnetic analyses and electron microscopy to identify the abundant presence in the brain of magnetite nanoparticles that are consistent with high-temperature formation, suggesting, therefore, an external, not internal, source. Comprising a separate nanoparticle population from the euhedral particles ascribed to endogenous sources, these brain magnetites are often found with other transition metal nanoparticles, and they display rounded crystal morphologies and fused surface textures, reflecting crystallization upon cooling from an initially heated, iron-bearing source material. Such high-temperature magnetite nanospheres are ubiquitous and abundant in airborne particulate matter pollution. They arise as combustion-derived, iron-rich particles, often associated with other transition metal particles, which condense and/or oxidize upon airborne release. Those magnetite pollutant particles which are <∼200 nm in diameter can enter the brain directly via the olfactory bulb. Their presence proves that externally sourced iron-bearing nanoparticles, rather than their soluble compounds, can be transported directly into the brain, where they may pose hazard to human health. PMID:27601646

Neuroprotection trek--the next generation: neuromodulation I. Techniques--deep brain stimulation, vagus nerve stimulation, and transcranial magnetic stimulation

NASA Technical Reports Server (NTRS)

Andrews, Russell J.

2003-01-01

Neuromodulation denotes controlled electrical stimulation of the central or peripheral nervous system. The three forms of neuromodulation described in this paper-deep brain stimulation, vagus nerve stimulation, and transcranial magnetic stimulation-were chosen primarily for their demonstrated or potential clinical usefulness. Deep brain stimulation is a completely implanted technique for improving movement disorders, such as Parkinson's disease, by very focal electrical stimulation of the brain-a technique that employs well-established hardware (electrode and pulse generator/battery). Vagus nerve stimulation is similar to deep brain stimulation in being well-established (for the treatment of refractory epilepsy), completely implanted, and having hardware that can be considered standard at the present time. Vagus nerve stimulation differs from deep brain stimulation, however, in that afferent stimulation of the vagus nerve results in diffuse effects on many regions throughout the brain. Although use of deep brain stimulation for applications beyond movement disorders will no doubt involve placing the stimulating electrode(s) in regions other than the thalamus, subthalamus, or globus pallidus, the use of vagus nerve stimulation for applications beyond epilepsy-for example, depression and eating disorders-is unlikely to require altering the hardware significantly (although stimulation protocols may differ). Transcranial magnetic stimulation is an example of an external or non-implanted, intermittent (at least given the current state of the hardware) stimulation technique, the clinical value of which for neuromodulation and neuroprotection remains to be determined.

Neuroprotection trek--the next generation: neuromodulation I. Techniques--deep brain stimulation, vagus nerve stimulation, and transcranial magnetic stimulation.

PubMed

Andrews, Russell J

2003-05-01

Neuromodulation denotes controlled electrical stimulation of the central or peripheral nervous system. The three forms of neuromodulation described in this paper-deep brain stimulation, vagus nerve stimulation, and transcranial magnetic stimulation-were chosen primarily for their demonstrated or potential clinical usefulness. Deep brain stimulation is a completely implanted technique for improving movement disorders, such as Parkinson's disease, by very focal electrical stimulation of the brain-a technique that employs well-established hardware (electrode and pulse generator/battery). Vagus nerve stimulation is similar to deep brain stimulation in being well-established (for the treatment of refractory epilepsy), completely implanted, and having hardware that can be considered standard at the present time. Vagus nerve stimulation differs from deep brain stimulation, however, in that afferent stimulation of the vagus nerve results in diffuse effects on many regions throughout the brain. Although use of deep brain stimulation for applications beyond movement disorders will no doubt involve placing the stimulating electrode(s) in regions other than the thalamus, subthalamus, or globus pallidus, the use of vagus nerve stimulation for applications beyond epilepsy-for example, depression and eating disorders-is unlikely to require altering the hardware significantly (although stimulation protocols may differ). Transcranial magnetic stimulation is an example of an external or non-implanted, intermittent (at least given the current state of the hardware) stimulation technique, the clinical value of which for neuromodulation and neuroprotection remains to be determined.

Clinical protocol. Gene therapy of Canavan disease: AAV-2 vector for neurosurgical delivery of aspartoacylase gene (ASPA) to the human brain.

PubMed

Janson, Christopher; McPhee, Scott; Bilaniuk, Larissa; Haselgrove, John; Testaiuti, Mark; Freese, Andrew; Wang, Dah-Jyuu; Shera, David; Hurh, Peter; Rupin, Joan; Saslow, Elizabeth; Goldfarb, Olga; Goldberg, Michael; Larijani, Ghassem; Sharrar, William; Liouterman, Larisa; Camp, Angelique; Kolodny, Edwin; Samulski, Jude; Leone, Paola

2002-07-20

This clinical protocol describes virus-based gene transfer for Canavan disease, a childhood leukodystrophy. Canavan disease, also known as Van Bogaert-Bertrand disease, is a monogeneic, autosomal recessive disease in which the gene coding for the enzyme aspartoacylase (ASPA) is defective. The lack of functional enzyme leads to an increase in the central nervous system of the substrate molecule, N-acetyl-aspartate (NAA), which impairs normal myelination and results in spongiform degeneration of the brain. No effective treatment currently exists; however, virus-based gene transfer has the potential to arrest or reverse the course of this otherwise fatal condition. This procedure involves neurosurgical administration of approximately 900 billion genomic particles (approximately 10 billion infectious particles) of recombinant adeno-associated virus (AAV) containing the aspartoacylase gene (ASPA) directly to affected regions of the brain in each of 21 patients with Canavan disease. Pre- and post-delivery assessments include a battery of noninvasive biochemical, radiological, and neurological tests. This gene transfer study represents the first clinical use of AAV in the human brain and the first instance of viral gene transfer for a neurodegenerative disease.

Using transcranial magnetic stimulation of the undamaged brain to identify lesion sites that predict language outcome after stroke.

PubMed

Lorca-Puls, Diego L; Gajardo-Vidal, Andrea; Seghier, Mohamed L; Leff, Alexander P; Sethi, Varun; Prejawa, Susan; Hope, Thomas M H; Devlin, Joseph T; Price, Cathy J

2017-06-01

Transcranial magnetic stimulation focused on either the left anterior supramarginal gyrus or opercular part of the left inferior frontal gyrus has been reported to transiently impair the ability to perform phonological more than semantic tasks. Here we tested whether phonological processing abilities were also impaired following lesions to these regions in right-handed, English speaking adults, who were investigated at least 1 year after a left-hemisphere stroke. When our regions of interest were limited to 0.5 cm3 of grey matter centred around sites that had been identified with transcranial magnetic stimulation-based functional localization, phonological impairments were observed in 74% (40/54) of patients with damage to the regions and 21% (21/100) of patients sparing these regions. This classification accuracy was better than that observed when using regions of interest centred on activation sites in previous functional magnetic resonance imaging studies of phonological processing, or transcranial magnetic stimulation sites that did not use functional localization. New regions of interest were generated by redefining the borders of each of the transcranial magnetic stimulation sites to include areas that were consistently damaged in the patients with phonological impairments. This increased the incidence of phonological impairments in the presence of damage to 85% (46/54) and also reduced the incidence of phonological impairments in the absence of damage to 15% (15/100). The difference in phonological processing abilities between those with and without damage to these 'transcranial magnetic stimulation-guided' regions remained highly significant even after controlling for the effect of lesion size. The classification accuracy of the transcranial magnetic stimulation-guided regions was validated in a second sample of 108 patients and found to be better than that for (i) functional magnetic resonance imaging-guided regions; (ii) a region identified from an unguided lesion overlap map; and (iii) a region identified from voxel-based lesion-symptom mapping. Finally, consistent with prior findings from functional imaging and transcranial magnetic stimulation in healthy participants, we show how damage to our transcranial magnetic stimulation-guided regions affected performance on phonologically more than semantically demanding tasks. The observation that phonological processing abilities were impaired years after the stroke, suggests that other brain regions were not able to fully compensate for the contribution that the transcranial magnetic stimulation-guided regions make to language tasks. More generally, our novel transcranial magnetic stimulation-guided lesion-deficit mapping approach shows how non-invasive stimulation of the healthy brain can be used to guide the identification of regions where brain damage is likely to cause persistent behavioural effects. © The Author (2017). Published by Oxford University Press on behalf of the Guarantors of Brain.

Molecular MRI differentiation between primary central nervous system lymphomas and high-grade gliomas using endogenous protein-based amide proton transfer MR imaging at 3 Tesla

PubMed Central

Jiang, Shanshan; Yu, Hao; Wang, Xianlong; Lu, Shilong; Li, Yufa; Feng, Lyujin; Zhang, Yi; Heo, Hye-Young; Lee, Dong-Hoon; Zhou, Jinyuan; Wen, Zhibo

2015-01-01

Objectives To show the ability of using the amide-proton-transfer-weighted (APTW) MRI signals as imaging biomarkers to differentiate primary central-nervous-system lymphomas (PCNSLs) from high-grade gliomas (HGGs). Methods Eleven patients with lymphomas and 21 patients with HGGs were examined. Magnetization-transfer (MT) spectra over an offset range of ±6 ppm and the conventional MT ratio (MTR) at 15.6 ppm were acquired. The APTW signals, total chemical-exchange-saturation-transfer signal (integral between 0 and 5 ppm, CESTtotal), and MTR signal were obtained and compared between PCNSLs and HGGs. The diagnostic performance was assessed with the receiver-operating-characteristic-curve analysis. Results The PCNSLs usually showed more homogeneous APTW hyperintensity (spatially compared to the normal brain tissue) than the HGGs. The APTWmax, APTWmax-min, and CESTtotal signal intensities were significantly lower (P < 0.05, 0.001, and 0.05, respectively), while the APTWmin and MTR were significantly higher (both P < 0.01) in PCNSL lesions than in HGG lesions. The APTW values in peritumoral oedema were significantly lower for PCNSLs than for HGGs (P < 0.01). APTWmax-min had the highest area under the receiver-operating-characteristic curve (0.963) and accuracy (94.1%) in differentiating PCNSLs from HGGs. Conclusions The protein-based APTW signal would be a valuable MRI biomarker by which to identify PCNSLs and HGGs presurgically. PMID:25925361

A Review of Transcranial Magnetic Stimulation and Multimodal Neuroimaging to Characterize Post-Stroke Neuroplasticity

PubMed Central

Auriat, Angela M.; Neva, Jason L.; Peters, Sue; Ferris, Jennifer K.; Boyd, Lara A.

2015-01-01

Following stroke, the brain undergoes various stages of recovery where the central nervous system can reorganize neural circuitry (neuroplasticity) both spontaneously and with the aid of behavioral rehabilitation and non-invasive brain stimulation. Multiple neuroimaging techniques can characterize common structural and functional stroke-related deficits, and importantly, help predict recovery of function. Diffusion tensor imaging (DTI) typically reveals increased overall diffusivity throughout the brain following stroke, and is capable of indexing the extent of white matter damage. Magnetic resonance spectroscopy (MRS) provides an index of metabolic changes in surviving neural tissue after stroke, serving as a marker of brain function. The neural correlates of altered brain activity after stroke have been demonstrated by abnormal activation of sensorimotor cortices during task performance, and at rest, using functional magnetic resonance imaging (fMRI). Electroencephalography (EEG) has been used to characterize motor dysfunction in terms of increased cortical amplitude in the sensorimotor regions when performing upper limb movement, indicating abnormally increased cognitive effort and planning in individuals with stroke. Transcranial magnetic stimulation (TMS) work reveals changes in ipsilesional and contralesional cortical excitability in the sensorimotor cortices. The severity of motor deficits indexed using TMS has been linked to the magnitude of activity imbalance between the sensorimotor cortices. In this paper, we will provide a narrative review of data from studies utilizing DTI, MRS, fMRI, EEG, and brain stimulation techniques focusing on TMS and its combination with uni- and multimodal neuroimaging methods to assess recovery after stroke. Approaches that delineate the best measures with which to predict or positively alter outcomes will be highlighted. PMID:26579069

Substantiating In Vivo Magnetic Brain Tumor Targeting of Cationic Iron Oxide Nanocarriers via Adsorptive Surface Masking

PubMed Central

Chertok, Beata; David, Allan E.; Moffat, Bradford A.; Yang, Victor C.

2009-01-01

Cationic magnetic nanoparticles are attractive as potential vehicles for tumor drug delivery due to their favorable interactions with both the tumor milieu and the therapeutic cargo. However, systemic delivery of these nanoparticles to the tumor site is compromised by their rapid plasma clearance. We developed a simple method for in vivo protection of cationic nanocarriers, using non-covalent surface masking with a conjugate of low molecular weight heparin and polyethylene glycol. Surface masking resulted in an 11-fold increase in plasma AUC and a 2-fold increase in the magnetic capture of systemically injected nanoparticles in orthotopic rodent brain tumors. Overall, the described methodology could expand the prospective applications for cationic magnetic nanoparticles in magnetically-mediated gene/drug delivery. PMID:19782394

Development of magneto-plasmonic nanoparticles for multimodal image-guided therapy to the brain.

PubMed

Tomitaka, Asahi; Arami, Hamed; Raymond, Andrea; Yndart, Adriana; Kaushik, Ajeet; Jayant, Rahul Dev; Takemura, Yasushi; Cai, Yong; Toborek, Michal; Nair, Madhavan

2017-01-05

Magneto-plasmonic nanoparticles are one of the emerging multi-functional materials in the field of nanomedicine. Their potential for targeting and multi-modal imaging is highly attractive. In this study, magnetic core/gold shell (MNP@Au) magneto-plasmonic nanoparticles were synthesized by citrate reduction of Au ions on magnetic nanoparticle seeds. Hydrodynamic size and optical properties of magneto-plasmonic nanoparticles synthesized with the variation of Au ions and reducing agent concentrations were evaluated. The synthesized magneto-plasmonic nanoparticles exhibited superparamagnetic properties, and their magnetic properties contributed to the concentration-dependent contrast in magnetic resonance imaging (MRI). The imaging contrast from the gold shell part of the magneto-plasmonic nanoparticles was also confirmed by X-ray computed tomography (CT). The transmigration study of the magneto-plasmonic nanoparticles using an in vitro blood-brain barrier (BBB) model proved enhanced transmigration efficiency without disrupting the integrity of the BBB, and showed potential to be used for brain diseases and neurological disorders.

Cognitive Priming and Cognitive Training: Immediate and Far Transfer to Academic Skills in Children.

PubMed

Wexler, Bruce E; Iseli, Markus; Leon, Seth; Zaggle, William; Rush, Cynthia; Goodman, Annette; Esat Imal, A; Bo, Emily

2016-09-12

Cognitive operations are supported by dynamically reconfiguring neural systems that integrate processing components widely distributed throughout the brain. The inter-neuronal connections that constitute these systems are powerfully shaped by environmental input. We evaluated the ability of computer-presented brain training games done in school to harness this neuroplastic potential and improve learning in an overall study sample of 583 second-grade children. Doing a 5-minute brain-training game immediately before math or reading curricular content games increased performance on the curricular content games. Doing three 20-minute brain training sessions per week for four months increased gains on school-administered math and reading achievement tests compared to control classes tested at the same times without intervening brain training. These results provide evidence of cognitive priming with immediate effects on learning, and longer-term brain training with far-transfer or generalized effects on academic achievement.

Cognitive Priming and Cognitive Training: Immediate and Far Transfer to Academic Skills in Children

PubMed Central

Wexler, Bruce E; Iseli, Markus; Leon, Seth; Zaggle, William; Rush, Cynthia; Goodman, Annette; Esat Imal, A.; Bo, Emily

2016-01-01

Cognitive operations are supported by dynamically reconfiguring neural systems that integrate processing components widely distributed throughout the brain. The inter-neuronal connections that constitute these systems are powerfully shaped by environmental input. We evaluated the ability of computer-presented brain training games done in school to harness this neuroplastic potential and improve learning in an overall study sample of 583 second-grade children. Doing a 5-minute brain-training game immediately before math or reading curricular content games increased performance on the curricular content games. Doing three 20-minute brain training sessions per week for four months increased gains on school-administered math and reading achievement tests compared to control classes tested at the same times without intervening brain training. These results provide evidence of cognitive priming with immediate effects on learning, and longer-term brain training with far-transfer or generalized effects on academic achievement. PMID:27615029

Tracing Activity Across the Whole Brain Neural Network with Optogenetic Functional Magnetic Resonance Imaging

PubMed Central

Lee, Jin Hyung

2011-01-01

Despite the overwhelming need, there has been a relatively large gap in our ability to trace network level activity across the brain. The complex dense wiring of the brain makes it extremely challenging to understand cell-type specific activity and their communication beyond a few synapses. Recent development of the optogenetic functional magnetic resonance imaging (ofMRI) provides a new impetus for the study of brain circuits by enabling causal tracing of activities arising from defined cell types and firing patterns across the whole brain. Brain circuit elements can be selectively triggered based on their genetic identity, cell body location, and/or their axonal projection target with temporal precision while the resulting network response is monitored non-invasively with unprecedented spatial and temporal accuracy. With further studies including technological innovations to bring ofMRI to its full potential, ofMRI is expected to play an important role in our system-level understanding of the brain circuit mechanism. PMID:22046160

Dynamics of the brain: Mathematical models and non-invasive experimental studies

NASA Astrophysics Data System (ADS)

Toronov, V.; Myllylä, T.; Kiviniemi, V.; Tuchin, V. V.

2013-10-01

Dynamics is an essential aspect of the brain function. In this article we review theoretical models of neural and haemodynamic processes in the human brain and experimental non-invasive techniques developed to study brain functions and to measure dynamic characteristics, such as neurodynamics, neurovascular coupling, haemodynamic changes due to brain activity and autoregulation, and cerebral metabolic rate of oxygen. We focus on emerging theoretical biophysical models and experimental functional neuroimaging results, obtained mostly by functional magnetic resonance imaging (fMRI) and near-infrared spectroscopy (NIRS). We also included our current results on the effects of blood pressure variations on cerebral haemodynamics and simultaneous measurements of fast processes in the brain by near-infrared spectroscopy and a very novel functional MRI technique called magnetic resonance encephalography. Based on a rapid progress in theoretical and experimental techniques and due to the growing computational capacities and combined use of rapidly improving and emerging neuroimaging techniques we anticipate during next decade great achievements in the overall knowledge of the human brain.

Synthesis of Natural Electric and Magnetic Time Series Using Impulse Responses of Inter-station Transfer Functions and a Reference

NASA Astrophysics Data System (ADS)

Wang, H.; Cheng, J.

2017-12-01

A method to Synthesis natural electric and magnetic Time series is proposed whereby the time series of local site are derived using an Impulse Response and a reference (STIR). The method is based on the assumption that the external source of magnetic fields are uniform, and the electric and magnetic fields acquired at the surface satisfy a time-independent linear relation in frequency domain.According to the convolution theorem, we can synthesize natural electric and magnetic time series using the impulse responses of inter-station transfer functions with a reference. Applying this method, two impulse responses need to be estimated: the quasi-MT impulse response tensor and the horizontal magnetic impulse response tensor. These impulse response tensors relate the local horizontal electric and magnetic components with the horizontal magnetic components at a reference site, respectively. Some clean segments of times series are selected to estimate impulse responses by using least-square (LS) method. STIR is similar with STIN (Wang, 2017), but STIR does not need to estimate the inter-station transfer functions, and the synthesized data are more accurate in high frequency, where STIN fails when the inter-station transfer functions are contaminated severely. A test with good quality of MT data shows that synthetic time-series are similar to natural electric and magnetic time series. For contaminated AMT example, when this method is used to remove noise present at the local site, the scatter of MT sounding curves are clear reduced, and the data quality are improved. *This work is funded by National Key R&D Program of China(2017YFC0804105),National Natural Science Foundation of China (41604064, 51574250), State Key Laboratory of Coal Resources and Safe Mining ,China University of Mining & Technology,(SKLCRSM16DC09)

Magnetically Recoverable Supported Ruthenium Catalyst for Hydrogenation of Alkynes and Transfer Hydrogenation of Carbonyl Compounds

EPA Science Inventory

A ruthenium (Ru) catalyst supported on magnetic nanoparticles (NiFe2O4) has been successfully synthesized and used for hydrogenation of alkynes at room temperature as well as transfer hydrogenation of a number of carbonyl compounds under microwave irradiation conditions. The cata...

Pulsed laser induced heat transfer from a phthalocyanine-based thin film to a Bi, Al-substituted DyIG substrate: photothermal demagnetization observed by magnetic circular dichroism and numerical analysis.

PubMed

Karasawa, Masanobu; Ishii, Kazuyuki

2018-05-03

We have investigated the demagnetization of a ferrimagnetic substrate, Bi, Al-substituted dysprosium iron garnet (Bi0.8Dy2.2Fe4.3Al0.7O12), based on selective pulsed laser irradiation of a molecular thin film consisting of μ-oxo-bis[hydroxyl{2,9(or 10),16(or 17),23(or 24)-tetra-tert-butylphthalocyanato}silicon] ((SiPc)2) and poly(vinylidene fluoride), and succeeded in reproducing photothermal energy transfer from a molecular thin film to an inorganic magnetic substrate in a submicrometer-order and a submicrosecond time scale using numerical analysis. After the instant temperature rise due to nanosecond pulsed laser irradiation of the (SiPc)2-based film, followed by heat transfer from the film to the neighboring magnetic substrate, demagnetization of the magnetic substrate was spectroscopically monitored by the decrease in its magnetic circular dichroism (MCD) intensity. The MCD intensity decreased with increasing pulsed laser energy, which reflects the fact that the submicrometer-order region of the substrate was demagnetized as a result of temperature rise reaching high Curie temperature. This heat transfer phenomenon resulting in the demagnetization of the magnetic substrate was numerically analyzed in a submicrometer-order and a submicrosecond time scale using the finite difference method: the demagnetized regions were calculated to be the same order of magnitude as those experimentally evaluated. These results would provide a more detailed understanding of photothermal energy transfer in organic-inorganic hybrid materials, which would be useful for developing photofunctional materials.

Magnetically Suspended Linear Pulse Motor for Semiconductor Wafer Transfer in Vacuum Chamber

NASA Technical Reports Server (NTRS)

Moriyama, Shin-Ichi; Hiraki, Naoji; Watanabe, Katsuhide; Kanemitsu, Yoichi

1996-01-01

This paper describes a magnetically suspended linear pulse motor for a semiconductor wafer transfer robot in a vacuum chamber. The motor can drive a wafer transfer arm horizontally without mechanical contact. In the construction of the magnetic suspension system, four pairs of linear magnetic bearings for the lift control are used for the guidance control as well. This approach allows us to make the whole motor compact in size and light in weight. The tested motor consists of a double-sided stator and a transfer arm with a width of 50 mm and a total length of 700 mm. The arm, like a ladder in shape, is designed as the floating element with a tooth width of 4 mm (a tooth pitch of 8 mm). The mover mass is limited to about 1.6 kg by adopting such an arm structure, and the ratio of thrust to mover mass reaches to 3.2 N/kg under a broad air gap (1 mm) between the stator teeth and the mover teeth. The performance testing was carried out with a transfer distance less than 450 mm and a transfer speed less than 560 mm/s. The attitude of the arm was well controlled by the linear magnetic bearings with a combined use, and consequently the repeatability on the positioning of the arm reached to about 2 micron. In addition, the positioning accuracy was improved up to about 30 micron through a compensation of the 128-step wave current which was used for the micro-step drive with a step increment of 62.5 micron.

MESSENGER observations of magnetic reconnection in Mercury's magnetosphere.

PubMed

Slavin, James A; Acuña, Mario H; Anderson, Brian J; Baker, Daniel N; Benna, Mehdi; Boardsen, Scott A; Gloeckler, George; Gold, Robert E; Ho, George C; Korth, Haje; Krimigis, Stamatios M; McNutt, Ralph L; Raines, Jim M; Sarantos, Menelaos; Schriver, David; Solomon, Sean C; Trávnícek, Pavel; Zurbuchen, Thomas H

2009-05-01

Solar wind energy transfer to planetary magnetospheres and ionospheres is controlled by magnetic reconnection, a process that determines the degree of connectivity between the interplanetary magnetic field (IMF) and a planet's magnetic field. During MESSENGER's second flyby of Mercury, a steady southward IMF was observed and the magnetopause was threaded by a strong magnetic field, indicating a reconnection rate ~10 times that typical at Earth. Moreover, a large flux transfer event was observed in the magnetosheath, and a plasmoid and multiple traveling compression regions were observed in Mercury's magnetotail, all products of reconnection. These observations indicate that Mercury's magnetosphere is much more responsive to IMF direction and dominated by the effects of reconnection than that of Earth or the other magnetized planets.

Traumatic Brain Injury Diffusion Magnetic Resonance Imaging Research Roadmap Development Project

DTIC Science & Technology

2012-10-01

Distribution Unlimited 13. SUPPLEMENTARY NOTES 14. ABSTRACT . Traumatic Brain Injury ( TBI ) is a public health problem of immense magnitude and...immediate importance that has become endemic among military personnel and veterans. Imaging biomarkers of TBI are needed to support diagnosis and therapy...and to predict TBI consequences while avoiding further injury. Diffusion magnetic resonance imaging has potential to become the non-invasive tool

Transfer of learning relates to intrinsic connectivity between hippocampus, ventromedial prefrontal cortex, and large-scale networks.

PubMed

Gerraty, Raphael T; Davidow, Juliet Y; Wimmer, G Elliott; Kahn, Itamar; Shohamy, Daphna

2014-08-20

An important aspect of adaptive learning is the ability to flexibly use past experiences to guide new decisions. When facing a new decision, some people automatically leverage previously learned associations, while others do not. This variability in transfer of learning across individuals has been demonstrated repeatedly and has important implications for understanding adaptive behavior, yet the source of these individual differences remains poorly understood. In particular, it is unknown why such variability in transfer emerges even among homogeneous groups of young healthy participants who do not vary on other learning-related measures. Here we hypothesized that individual differences in the transfer of learning could be related to relatively stable differences in intrinsic brain connectivity, which could constrain how individuals learn. To test this, we obtained a behavioral measure of memory-based transfer outside of the scanner and on a separate day acquired resting-state functional MRI images in 42 participants. We then analyzed connectivity across independent component analysis-derived brain networks during rest, and tested whether intrinsic connectivity in learning-related networks was associated with transfer. We found that individual differences in transfer were related to intrinsic connectivity between the hippocampus and the ventromedial prefrontal cortex, and between these regions and large-scale functional brain networks. Together, the findings demonstrate a novel role for intrinsic brain dynamics in flexible learning-guided behavior, both within a set of functionally specific regions known to be important for learning, as well as between these regions and the default and frontoparietal networks, which are thought to serve more general cognitive functions. Copyright © 2014 the authors 0270-6474/14/3411297-07$15.00/0.

Intermanual transfer effects in sequential tactuomotor learning: evidence for effector independent coding.

PubMed

van Mier, Hanneke I; Petersen, Steven E

2006-01-01

Results from our earlier brain imaging studies regarding motor learning have shown different areas activated during naive and practiced performance. When right handed participants moved a pen either with the dominant or non-dominant hand continuously through a cut-out maze as quickly and accurately as possible, practice resulted in decreased brain activity in right premotor and parietal areas as well as left cerebellum, while increased activity was found in the supplementary motor area (SMA). These lateralized practiced-related changes in brain activation suggest effector-independent abstract coding of information. To test this hypothesis more extensively, intermanual transfer of learning was examined in 24 male and female participants (12 right- and 12 left-handed) using the same maze-learning task. It was hypothesized that if an abstract representation of the movement is learned and stored, intermanual transfer effects should be more pronounced when participants transferred to a same maze as opposed to a mirror image of the maze. Errors and velocity were measured during the following conditions: initial naive performance (Naive); after practice on the maze (Prac); during intermanual transfer to the same maze (Transfer Identical); and to the mirror maze (Transfer Mirror). Transfer direction was tested from the dominant to non-dominant hand and vice versa. No significant differences were found between right- and left-handed participants, males and females, and transfer directions. However, intermanual transfer of learning was significantly greater to the identical maze as opposed to the mirror maze. These results showed that learning was indeed taking place at an abstract effector independent level.

Magnetization switching in ferromagnets by adsorbed chiral molecules without current or external magnetic field.

PubMed

Ben Dor, Oren; Yochelis, Shira; Radko, Anna; Vankayala, Kiran; Capua, Eyal; Capua, Amir; Yang, See-Hun; Baczewski, Lech Tomasz; Parkin, Stuart Stephen Papworth; Naaman, Ron; Paltiel, Yossi

2017-02-23

Ferromagnets are commonly magnetized by either external magnetic fields or spin polarized currents. The manipulation of magnetization by spin-current occurs through the spin-transfer-torque effect, which is applied, for example, in modern magnetoresistive random access memory. However, the current density required for the spin-transfer torque is of the order of 1 × 10 6  A·cm -2 , or about 1 × 10 25 electrons s -1 cm -2 . This relatively high current density significantly affects the devices' structure and performance. Here we demonstrate magnetization switching of ferromagnetic thin layers that is induced solely by adsorption of chiral molecules. In this case, about 10 13 electrons per cm 2 are sufficient to induce magnetization reversal. The direction of the magnetization depends on the handedness of the adsorbed chiral molecules. Local magnetization switching is achieved by adsorbing a chiral self-assembled molecular monolayer on a gold-coated ferromagnetic layer with perpendicular magnetic anisotropy. These results present a simple low-power magnetization mechanism when operating at ambient conditions.

Magnetization switching in ferromagnets by adsorbed chiral molecules without current or external magnetic field

PubMed Central

Ben Dor, Oren; Yochelis, Shira; Radko, Anna; Vankayala, Kiran; Capua, Eyal; Capua, Amir; Yang, See-Hun; Baczewski, Lech Tomasz; Parkin, Stuart Stephen Papworth; Naaman, Ron; Paltiel, Yossi

2017-01-01

Ferromagnets are commonly magnetized by either external magnetic fields or spin polarized currents. The manipulation of magnetization by spin-current occurs through the spin-transfer-torque effect, which is applied, for example, in modern magnetoresistive random access memory. However, the current density required for the spin-transfer torque is of the order of 1 × 106 A·cm−2, or about 1 × 1025 electrons s−1 cm−2. This relatively high current density significantly affects the devices' structure and performance. Here we demonstrate magnetization switching of ferromagnetic thin layers that is induced solely by adsorption of chiral molecules. In this case, about 1013 electrons per cm2 are sufficient to induce magnetization reversal. The direction of the magnetization depends on the handedness of the adsorbed chiral molecules. Local magnetization switching is achieved by adsorbing a chiral self-assembled molecular monolayer on a gold-coated ferromagnetic layer with perpendicular magnetic anisotropy. These results present a simple low-power magnetization mechanism when operating at ambient conditions. PMID:28230054

Nanofluid flow and heat transfer due to a stretching cylinder in the presence of magnetic field

NASA Astrophysics Data System (ADS)

Ashorynejad, H. R.; Sheikholeslami, M.; Pop, I.; Ganji, D. D.

2013-03-01

In this paper, flow and heat transfer of a nanofluid over a stretching cylinder in the presence of magnetic field has been investigated. The governing partial differential equations with the corresponding boundary conditions are reduced to a set of ordinary differential equations with the appropriate boundary conditions using similarity transformation, which is then solved numerically by the fourth order Runge-Kutta integration scheme featuring a shooting technique. Different types of nanoparticles as copper (Cu), silver (Ag), alumina (Al2O3) and titanium oxide (TiO2) with water as their base fluid has been considered. The influence of significant parameters such as nanoparticle volume fraction, nanofluids type, magnetic parameter and Reynolds number on the flow and heat transfer characteristics is discussed. It was found that the Nusselt number increases as each of Reynolds number or nanoparticles volume fraction increase, but it decreases as magnetic parameter increase. Also it can be found that choosing copper (for small of magnetic parameter) and alumina (for large values of magnetic parameter) leads to the highest cooling performance for this problem.

Nanomaterials for regulating cancer and stem cell fate

NASA Astrophysics Data System (ADS)

Shah, Birju P.

The realm of nanomedicine has grown exponentially over the past few decades. However, there are several obstacles that need to be overcome, prior to the wide-spread clinical applications of these nanoparticles, such as (i) developing well-defined nanoparticles of varying size, morphology and composition to enable various clinical applications; (ii) overcome various physiological barriers encountered in order to deliver the therapeutics to the target location; and (iii) real-time monitoring of the nano-therapeutics within the human body for tracking their uptake, localization and effect. Hence, this dissertation focuses on developing multimodal nanotechnology-based approaches to overcome the above-mentioned challenges and thus enable regulation of cancer and stem cell fate. The initial part of this dissertation describes the development of multimodal magnetic core-shell nanoparticles (MCNPs), comprised of a highly magnetic core surrounded by a thin gold shell, thus combining magnetic and plasmonic properties. These nanoparticles were utilized for mainly two applications: (i) Magnetically-facilitated delivery of siRNA and plasmid DNA for effective stem cell differentiation and imaging and (ii) Combined hyperthermia and targeted delivery of a mitochondria-targeting peptide for enhancing apoptosis in cancer cells. The following part of this dissertation presents the generation of a multi-functional cyclodextrin-conjugated polymeric delivery platform (known as DexAMs), for co-delivery of anticancer drugs and siRNAs in a target-specific manner to brain tumor cells. This combined delivery of chemotherapeutics and siRNA resulted in a synergistic effect on the apoptosis of brain tumor cells, as compared to the individual treatments. The final part of this thesis presents development of stimuli-responsive uorescence resonance energy transfer (FRET)-based mesoporous silica nanoparticles for real-time monitoring of drug release in cells. The stimuli-responsive behavior of these nanoparticles resulted in change in the FRET signal, thus allowing for real time monitoring of drug release. Taken together, these nanomaterial-based approaches combine therapeutic and imaging modalities within a single nanoplatform and as a result have the potential for regulating cancer and stem cell fate such as proliferation, differentiation and apoptosis as well as allowing for real-time monitoring of these events in a non-invasive manner.

Poynting vector analysis for wireless power transfer between magnetically coupled coils with different loads.

PubMed

Guo, Yunsheng; Li, Jiansheng; Hou, Xiaojuan; Lv, Xiaolong; Liang, Hao; Zhou, Ji; Wu, Hongya

2017-04-07

Wireless power transfer is a nonradiative type of transmission that is performed in the near-field region. In this region, the electromagnetic fields that are produced by both the transmitting and receiving coils are evanescent fields, which should not transmit energy. This then raises the question of how the energy can be transferred. Here we describe a theoretical study of the two evanescent field distributions at different terminal loads. It is shown that the essential principle of wireless energy transfer is the superposition of the two evanescent fields, and the resulting superimposed field is mediated through the terminal load. If the terminal load is either capacitive or inductive, then the superimposed field cannot transfer the energy because its Poynting vector is zero; in contrast, if the load is resistive, energy can then be conveyed from the transmitting coil to the receiving coil. The simulation results for the magnetic field distributions and the time-domain current waveforms agree very well with the results of the theoretical analysis. This work thus provides a comprehensive understanding of the energy transfer mechanism involved in the magnetic resonant coupling system.

Review of heat transfer problems associated with magnetically-confined fusion reactor concepts

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

Hoffman, M.A.; Werner, R.W.; Carlson, G.A.

1976-04-01

Conceptual design studies of possible fusion reactor configurations have revealed a host of interesting and sometimes extremely difficult heat transfer problems. The general requirements imposed on the coolant system for heat removal of the thermonuclear power from the reactor are discussed. In particular, the constraints imposed by the fusion plasma, neutronics, structure and magnetic field environment are described with emphasis on those aspects which are unusual or unique to fusion reactors. Then the particular heat transfer characteristics of various possible coolants including lithium, flibe, boiling alkali metals, and helium are discussed in the context of these general fusion reactor requirements.more » Some specific areas where further experimental and/or theoretical work is necessary are listed for each coolant along with references to the pertinent research already accomplished. Specialized heat transfer problems of the plasma injection and removal systems are also described. Finally, the challenging heat transfer problems associated with the superconducting magnets are reviewed, and once again some of the key unsolved heat transfer problems are enumerated.« less

Engineered core-shell magnetic nanoparticle for MR dual-modal tracking and safe magnetic manipulation of ependymal cells in live rodents

NASA Astrophysics Data System (ADS)

Peng, Yung-Kang; Lui, Cathy N. P.; Chen, Yu-Wei; Chou, Shang-Wei; Chou, Pi-Tai; Yung, Ken K. L.; Edman Tsang, S. C.

2018-01-01

Tagging recognition group(s) on superparamagnetic iron oxide is known to aid localisation (imaging), stimulation and separation of biological entities using magnetic resonance imaging (MRI) and magnetic agitation/separation (MAS) techniques. Despite the wide applicability of iron oxide nanoparticles in T 2-weighted MRI and MAS, the quality of the images and safe manipulation of the exceptionally delicate neural cells in a live brain are currently the key challenges. Here, we demonstrate the engineered manganese oxide clusters-iron oxide core-shell nanoparticle as an MR dual-modal contrast agent for neural stem cells (NSCs) imaging and magnetic manipulation in live rodents. As a result, using this engineered nanoparticle and associated technologies, identification, stimulation and transportation of labelled potentially multipotent NSCs from a specific location of a live brain to another by magnetic means for self-healing therapy can therefore be made possible.

Clinical Applications of Transcranial Magnetic Stimulation in Pediatric Neurology.

PubMed

Narayana, Shalini; Papanicolaou, Andrew C; McGregor, Amy; Boop, Frederick A; Wheless, James W

2015-08-01

Noninvasive brain stimulation is now an accepted technique that is used as a diagnostic aid and in the treatment of neuropsychiatric disorders in adults, and is being increasingly used in children. In this review, we will discuss the basic principles and safety of one noninvasive brain stimulation method, transcranial magnetic stimulation. Improvements in the spatial accuracy of transcranial magnetic stimulation are described in the context of image-guided transcranial magnetic stimulation. The article describes and provides examples of the current clinical applications of transcranial magnetic stimulation in children as an aid in the diagnosis and treatment of neuropsychiatric disorders and discusses future potential applications. Transcranial magnetic stimulation is a noninvasive tool that is safe for use in children and adolescents for functional mapping and treatment, and for many children it aids in the preoperative evaluation and the risk-benefit decision making. © The Author(s) 2014.

Multivariate information-theoretic measures reveal directed information structure and task relevant changes in fMRI connectivity.

PubMed

Lizier, Joseph T; Heinzle, Jakob; Horstmann, Annette; Haynes, John-Dylan; Prokopenko, Mikhail

2011-02-01

The human brain undertakes highly sophisticated information processing facilitated by the interaction between its sub-regions. We present a novel method for interregional connectivity analysis, using multivariate extensions to the mutual information and transfer entropy. The method allows us to identify the underlying directed information structure between brain regions, and how that structure changes according to behavioral conditions. This method is distinguished in using asymmetric, multivariate, information-theoretical analysis, which captures not only directional and non-linear relationships, but also collective interactions. Importantly, the method is able to estimate multivariate information measures with only relatively little data. We demonstrate the method to analyze functional magnetic resonance imaging time series to establish the directed information structure between brain regions involved in a visuo-motor tracking task. Importantly, this results in a tiered structure, with known movement planning regions driving visual and motor control regions. Also, we examine the changes in this structure as the difficulty of the tracking task is increased. We find that task difficulty modulates the coupling strength between regions of a cortical network involved in movement planning and between motor cortex and the cerebellum which is involved in the fine-tuning of motor control. It is likely these methods will find utility in identifying interregional structure (and experimentally induced changes in this structure) in other cognitive tasks and data modalities.

Regulatory T cells are strong promoters of acute ischemic stroke in mice by inducing dysfunction of the cerebral microvasculature.

PubMed

Kleinschnitz, Christoph; Kraft, Peter; Dreykluft, Angela; Hagedorn, Ina; Göbel, Kerstin; Schuhmann, Michael K; Langhauser, Friederike; Helluy, Xavier; Schwarz, Tobias; Bittner, Stefan; Mayer, Christian T; Brede, Marc; Varallyay, Csanad; Pham, Mirko; Bendszus, Martin; Jakob, Peter; Magnus, Tim; Meuth, Sven G; Iwakura, Yoichiro; Zernecke, Alma; Sparwasser, Tim; Nieswandt, Bernhard; Stoll, Guido; Wiendl, Heinz

2013-01-24

We have recently identified T cells as important mediators of ischemic brain damage, but the contribution of the different T-cell subsets is unclear. Forkhead box P3 (FoxP3)-positive regulatory T cells (Tregs) are generally regarded as prototypic anti-inflammatory cells that maintain immune tolerance and counteract tissue damage in a variety of immune-mediated disorders. In the present study, we examined the role of Tregs after experimental brain ischemia/reperfusion injury. Selective depletion of Tregs in the DEREG mouse model dramatically reduced infarct size and improved neurologic function 24 hours after stroke and this protective effect was preserved at later stages of infarct development. The specificity of this detrimental Treg effect was confirmed by adoptive transfer experiments in wild-type mice and in Rag1(-/-) mice lacking lymphocytes. Mechanistically, Tregs induced microvascular dysfunction in vivo by increased interaction with the ischemic brain endothelium via the LFA-1/ICAM-1 pathway and platelets and these findings were confirmed in vitro. Ablation of Tregs reduced microvascular thrombus formation and improved cerebral reperfusion on stroke, as revealed by ultra-high-field magnetic resonance imaging at 17.6 Tesla. In contrast, established immunoregulatory characteristics of Tregs had no functional relevance. We define herein a novel and unexpected role of Tregs in a primary nonimmunologic disease state.

GABA and glutamate levels correlate with MTR and clinical disability: Insights from multiple sclerosis.

PubMed

Nantes, Julia C; Proulx, Sébastien; Zhong, Jidan; Holmes, Scott A; Narayanan, Sridar; Brown, Robert A; Hoge, Richard D; Koski, Lisa

2017-08-15

Converging areas of research have implicated glutamate and γ-aminobutyric acid (GABA) as key players in neuronal signalling and other central functions. Further research is needed, however, to identify microstructural and behavioral links to regional variability in levels of these neurometabolites, particularly in the presence of demyelinating disease. Thus, we sought to investigate the extent to which regional glutamate and GABA levels are related to a neuroimaging marker of microstructural damage and to motor and cognitive performance. Twenty-one healthy volunteers and 47 people with multiple sclerosis (all right-handed) participated in this study. Motor and cognitive abilities were assessed with standard tests used in the study of multiple sclerosis. Proton magnetic resonance spectroscopy data were acquired from sensorimotor and parietal regions of the brains' left cerebral hemisphere using a MEGA-PRESS sequence. Our analysis protocol for the spectroscopy data was designed to account for confounding factors that could contaminate the measurement of neurometabolite levels due to disease, such as the macromolecule signal, partial volume effects, and relaxation effects. Glutamate levels in both regions of interest were lower in people with multiple sclerosis. In the sensorimotor (though not the parietal) region, GABA concentration was higher in the multiple sclerosis group compared to controls. Lower magnetization transfer ratio within grey and white matter regions from which spectroscopy data were acquired was linked to neurometabolite levels. When adjusting for age, normalized brain volume, MTR, total N-acetylaspartate level, and glutamate level, significant relationships were found between lower sensorimotor GABA level and worse performance on several tests, including one of upper limb motor function. This work highlights important methodological considerations relevant to analysis of spectroscopy data, particularly in the afflicted human brain. These findings support that regional neurotransmitter levels are linked to local microstructural integrity and specific behavioral abilities that can be affected in diseases such as multiple sclerosis. Copyright © 2017 Elsevier Inc. All rights reserved.

Carcinoma-astrocyte gap junctions promote brain metastasis by cGAMP transfer

PubMed Central

Jin, Xin; Valiente, Manuel; Er, Ekrem Emrah; Lopez-Soto, Alejandro; Jacob, Leni; Patwa, Ruzeen; Shah, Hardik; Xu, Ke; Cross, Justin R.; Massagué, Joan

2016-01-01

SUMMARY Brain metastasis represents a substantial source of morbidity and mortality in various cancers, and is characterized by high resistance to chemotherapy. Here we define the role of the most abundant cell type in the brain, the astrocyte, in promoting brain metastasis. Breast and lung cancer cells express protocadherin 7 (PCDH7) to favor the assembly of carcinoma-astrocyte gap junctions composed of connexin 43 (Cx43). Once engaged with the astrocyte gap-junctional network, brain metastatic cancer cells employ these channels to transfer the second messenger cGAMP to astrocytes, activating the STING pathway and production of inflammatory cytokines IFNα and TNFα. As paracrine signals, these factors activate the STAT1 and NF-κB pathways in brain metastatic cells, which support tumour growth and chemoresistance. The orally bioavailable modulators of gap junctions meclofenamate and tonabersat break this paracrine loop, and we provide proof-of-principle for the applicability of this therapeutic strategy to treat established brain metastasis. PMID:27225120

Carcinoma-astrocyte gap junctions promote brain metastasis by cGAMP transfer.

PubMed

Chen, Qing; Boire, Adrienne; Jin, Xin; Valiente, Manuel; Er, Ekrem Emrah; Lopez-Soto, Alejandro; Jacob, Leni; Patwa, Ruzeen; Shah, Hardik; Xu, Ke; Cross, Justin R; Massagué, Joan

2016-05-26

Brain metastasis represents a substantial source of morbidity and mortality in various cancers, and is characterized by high resistance to chemotherapy. Here we define the role of the most abundant cell type in the brain, the astrocyte, in promoting brain metastasis. We show that human and mouse breast and lung cancer cells express protocadherin 7 (PCDH7), which promotes the assembly of carcinoma-astrocyte gap junctions composed of connexin 43 (Cx43). Once engaged with the astrocyte gap-junctional network, brain metastatic cancer cells use these channels to transfer the second messenger cGAMP to astrocytes, activating the STING pathway and production of inflammatory cytokines such as interferon-α (IFNα) and tumour necrosis factor (TNF). As paracrine signals, these factors activate the STAT1 and NF-κB pathways in brain metastatic cells, thereby supporting tumour growth and chemoresistance. The orally bioavailable modulators of gap junctions meclofenamate and tonabersat break this paracrine loop, and we provide proof-of-principle that these drugs could be used to treat established brain metastasis.

Evaluation of the induced electric field and compliance procedure for a wireless power transfer system in an electrical vehicle.

PubMed

Laakso, Ilkka; Hirata, Akimasa

2013-11-07

In this study, an induced electric field in a human body is evaluated for the magnetic field leaked from a wireless power transfer system for charging an electrical vehicle. The magnetic field from the wireless power transfer system is modelled computationally, and its effectiveness is confirmed by comparison with the field measured in a previous study. The induced electric field in a human standing around the vehicle is smaller than the allowable limit prescribed in international guidelines, although the magnetic field strength in the human body is locally higher than the allowable external field strength. Correlation between the external magnetic field and the induced electric field is confirmed to be reasonable at least in the standing posture, which is the case discussed in the international standard. Based on this finding, we discussed and confirmed the applicability of a three-point magnetic field measurement at heights of 0.5, 1.0, and 1.5 m for safety compliance.

Spin Transfer torques in Antiferromagnets

NASA Astrophysics Data System (ADS)

Saidaoui, Hamed; Waintal, Xavier; Manchon, Aurelien; Spsms, Cea, Grenoble France Collaboration

2013-03-01

Spin Transfer Torque (STT) has attracted tremendously growing interest in the past two decades. Consisting on the transfer of spin angular momentum of a spin polarized current to local magnetic moments, the STT gives rise to a complex dynamics of the magnetization. Depending on the the structure, the STT shows a dominated In plane component for spin valves, whereas both components coexist for magnetic tunneling junctions (MTJ). For latter case the symmetry of the structure is considered to be decisive in identifying the nature and behavior of the torque. In the present study we are interested in magnetic structures where we substitute either one or both of the magnetic layers by antiferromagnets (AF). We use Non-equilibrium Green's function formalism applied on a tight-binding model to investigate the nature of the spin torque. We notice the presence of two types of torque exerted on (AF), a torque which tends to rotate the order parameter and another one that competes with the exchange interaction. We conclude by comparison with previous works.

Does placental inflammation relate to brain lesions and volume in preterm infants?

PubMed

Reiman, Milla; Kujari, Harry; Maunu, Jonna; Parkkola, Riitta; Rikalainen, Hellevi; Lapinleimu, Helena; Lehtonen, Liisa; Haataja, Leena

2008-05-01

To evaluate the association between histologic inflammation of placenta and brain findings in ultrasound examinations and regional brain volumes in magnetic resonance imaging in very-low-birth-weight (VLBW) or in very preterm infants. VLBW or very preterm infants (n = 121) were categorized into 3 groups according to the most pathologic brain finding on ultrasound examinations until term. The brain magnetic resonance imaging performed at term was analyzed for regional brain volumes. The placentas were analyzed for histologic inflammatory findings. Histologic chorioamnionitis on the fetal side correlated to brain lesions in univariate but not in multivariate analyses. Low gestational age was the only significant risk factor for brain lesions in multivariate analysis (P < .0001). Histologic chorioamnionitis was not associated with brain volumes in multivariate analyses. Female sex, low gestational age, and low birth weight z score correlated to smaller volumes in total brain tissue (P = .001, P = .0002, P < .0001, respectively) and cerebellum (P = .047, P = .003, P = .001, respectively). In addition, low gestational age and low-birth-weight z score correlated to a smaller combined volume of basal ganglia and thalami (P = .0002). Placental inflammation does not appear to correlate to brain lesions or smaller regional brain volumes in VLBW or in very preterm infants at term age.

Effects of extremely low frequency magnetic field on oxidative balance in brain of rats.

PubMed

Ciejka, Elzbieta; Kleniewska, P; Skibska, B; Goraca, A

2011-12-01

Extremely low frequency magnetic field (ELF-MF) may result in oxidative DNA damage and lipid peroxidation with an ultimate effect on a number of systemic disturbances and cell death. The aim of the study is to assess the effect of ELF-MF parameters most frequently used in magnetotherapy on reactive oxygen species generation (ROS) in brain tissue of experimental animals depending on the time of exposure to this field. The research material included adult male Sprague-Dawley rats, aged 3-4 months. The animals were divided into 3 groups: I - control (shame) group; II - exposed to the following parameters of the magnetic field: 7 mT, 40 Hz, 30 min/day, 10 days; III - exposed to the ELF-MF parameters of 7 mT, 40 Hz, 60 min/day, 10 days. The selected parameters of oxidative stress: thiobarbituric acid reactive substances (TBARS), hydrogen peroxide (H(2)O(2)), total free sulphydryl groups (-SH groups) and protein in brain homogenates were measured after the exposure of rats to the magnetic field. ELF-MF parameters of 7 mT, 40 Hz, 30 min/day for 10 days caused a significant increase in lipid peroxidation and insignificant increase in H(2)O(2) and free -SH groups. The same ELF-MF parameters but applied for 60 min/day caused a significant increase in free -SH groups and protein concentration in the brain homogenates indicating the adaptive mechanism. The study has shown that ELF-MF applied for 30 min/day for 10 days can affect free radical generation in the brain. Prolongation of the exposure to ELF-MF (60/min/day) caused adaptation to this field. The effect of ELF-MF irradiation on oxidative stress parameters depends on the time of animal exposure to magnetic field.

Emerging Imaging Tools for Use with Traumatic Brain Injury Research

PubMed Central

Wilde, Elisabeth A.; Tong, Karen A.; Holshouser, Barbara A.

2012-01-01

Abstract This article identifies emerging neuroimaging measures considered by the inter-agency Pediatric Traumatic Brain Injury (TBI) Neuroimaging Workgroup. This article attempts to address some of the potential uses of more advanced forms of imaging in TBI as well as highlight some of the current considerations and unresolved challenges of using them. We summarize emerging elements likely to gain more widespread use in the coming years, because of 1) their utility in diagnosis, prognosis, and understanding the natural course of degeneration or recovery following TBI, and potential for evaluating treatment strategies; 2) the ability of many centers to acquire these data with scanners and equipment that are readily available in existing clinical and research settings; and 3) advances in software that provide more automated, readily available, and cost-effective analysis methods for large scale data image analysis. These include multi-slice CT, volumetric MRI analysis, susceptibility-weighted imaging (SWI), diffusion tensor imaging (DTI), magnetization transfer imaging (MTI), arterial spin tag labeling (ASL), functional MRI (fMRI), including resting state and connectivity MRI, MR spectroscopy (MRS), and hyperpolarization scanning. However, we also include brief introductions to other specialized forms of advanced imaging that currently do require specialized equipment, for example, single photon emission computed tomography (SPECT), positron emission tomography (PET), encephalography (EEG), and magnetoencephalography (MEG)/magnetic source imaging (MSI). Finally, we identify some of the challenges that users of the emerging imaging CDEs may wish to consider, including quality control, performing multi-site and longitudinal imaging studies, and MR scanning in infants and children. PMID:21787167

Relationship between temperature variability and brain injury on magnetic resonance imaging in cooled newborn infants after perinatal asphyxia.

PubMed

Brotschi, B; Gunny, R; Rethmann, C; Held, U; Latal, B; Hagmann, C

2017-09-01

The objective of the study was whether temperature management during therapeutic hypothermia correlates with the severity of brain injury assessed on magnetic resonance imaging in term infants with hypoxic-ischemic encephalopathy. Prospectively collected register data from the National Asphyxia and Cooling Register of Switzerland were analyzed. Fifty-five newborn infants were cooled for 72 h with a target temperature range of 33 to 34 °C. Individual temperature variability (odds ratio (OR) 40.17 (95% confidence interval (CI) 1.37 to 1037.67)) and percentage of temperatures within the target range (OR 0.95 (95% CI 0.90 to 0.98)) were associated with the severity of brain injury seen on magnetic resonance imaging (MRI). Neither the percentage of measured temperatures above (OR 1.08 (95% CI 0.96 to 1.21)) nor below (OR 0.99 (95% CI 0.92 to 1.07) the target range was associated with the severity of brain injury seen on MRI. In a national perinatal asphyxia cohort, temperature variability and percentage of temperatures within the target temperature range were associated with the severity of brain injury.

Measurement of the Dynamic Shear Modulus of Mouse Brain Tissue In Vivo By Magnetic Resonance Elastography

PubMed Central

Atay, Stefan M.; Kroenke, Christopher D.; Sabet, Arash; Bayly, Philip V.

2008-01-01

In this study, the magnetic resonance elastography (MRE) technique was used to estimate the dynamic shear modulus of mouse brain tissue in vivo. The technique allows visualization and measurement of mechanical shear waves excited by lateral vibration of the skull. Quantitative measurements of displacement in three dimensions (3-D) during vibration at 1200 Hz were obtained by applying oscillatory magnetic field gradients at the same frequency during an MR imaging sequence. Contrast in the resulting phase images of the mouse brain is proportional to displacement. To obtain estimates of shear modulus, measured displacement fields were fitted to the shear wave equation. Validation of the procedure was performed on gel characterized by independent rheometry tests and on data from finite element simulations. Brain tissue is, in reality, viscoelastic and nonlinear. The current estimates of dynamic shear modulus are strictly relevant only to small oscillations at a specific frequency, but these estimates may be obtained at high frequencies (and thus high deformation rates), non-invasively throughout the brain. These data complement measurements of nonlinear viscoelastic properties obtained by others at slower rates, either ex vivo or invasively. PMID:18412500

Resonant-cavity antenna for plasma heating

DOEpatents

Perkins, F.W. Jr.; Chiu, S.C.; Parks, P.; Rawls, J.M.

1984-01-10

This invention relates generally to a method and apparatus for transferring energy to a plasma immersed in a magnetic field, and relates particularly to an apparatus for heating a plasma of low atomic number ions to high temperatures by transfer of energy to plasma resonances, particularly the fundamental and harmonics of the ion cyclotron frequency of the plasma ions. This invention transfers energy from an oscillating radio-frequency field to a plasma resonance of a plasma immersed in a magnetic field.

Unlocking the Secrets of the Brain, Part II: A Continuing Look at Techniques for Exploring the Brain.

ERIC Educational Resources Information Center

Powledge, Tabitha M.

1997-01-01

Describes techniques for delving into the brain including positron emission tomography (PET), single photon emission computed tomography (SPECT), electroencephalogram (EEG), magnetoencephalography (MEG), transcranial magnetic stimulation (TMS), and low-tech indirect studies. (JRH)

Controlling the column spacing in isothermal magnetic advection to enable tunable heat and mass transfer.

DOE PAGES

Solis, Kyle Jameson; Martin, James E.

2012-11-01

Isothermal magnetic advection is a recently discovered method of inducing highly organized, non-contact flow lattices in suspensions of magnetic particles, using only uniform ac magnetic fields of modest strength. The initiation of these vigorous flows requires neither a thermal gradient nor a gravitational field and so can be used to transfer heat and mass in circumstances where natural convection does not occur. These advection lattices are comprised of a square lattice of antiparallel flow columns. If the column spacing is sufficiently large compared to the column length, and the flow rate within the columns is sufficiently large, then one wouldmore » expect efficient transfer of both heat and mass. Otherwise, the flow lattice could act as a countercurrent heat exchanger and only mass will be efficiently transferred. Although this latter case might be useful for feeding a reaction front without extracting heat, it is likely that most interest will be focused on using IMA for heat transfer. In this paper we explore the various experimental parameters of IMA to determine which of these can be used to control the column spacing. These parameters include the field frequency, strength, and phase relation between the two field components, the liquid viscosity and particle volume fraction. We find that the column spacing can easily be tuned over a wide range, to enable the careful control of heat and mass transfer.« less

Brain training game improves executive functions and processing speed in the elderly: a randomized controlled trial.

PubMed

Nouchi, Rui; Taki, Yasuyuki; Takeuchi, Hikaru; Hashizume, Hiroshi; Akitsuki, Yuko; Shigemune, Yayoi; Sekiguchi, Atsushi; Kotozaki, Yuka; Tsukiura, Takashi; Yomogida, Yukihito; Kawashima, Ryuta

2012-01-01

The beneficial effects of brain training games are expected to transfer to other cognitive functions, but these beneficial effects are poorly understood. Here we investigate the impact of the brain training game (Brain Age) on cognitive functions in the elderly. Thirty-two elderly volunteers were recruited through an advertisement in the local newspaper and randomly assigned to either of two game groups (Brain Age, Tetris). This study was completed by 14 of the 16 members in the Brain Age group and 14 of the 16 members in the Tetris group. To maximize the benefit of the interventions, all participants were non-gamers who reported playing less than one hour of video games per week over the past 2 years. Participants in both the Brain Age and the Tetris groups played their game for about 15 minutes per day, at least 5 days per week, for 4 weeks. Each group played for a total of about 20 days. Measures of the cognitive functions were conducted before and after training. Measures of the cognitive functions fell into four categories (global cognitive status, executive functions, attention, and processing speed). Results showed that the effects of the brain training game were transferred to executive functions and to processing speed. However, the brain training game showed no transfer effect on any global cognitive status nor attention. Our results showed that playing Brain Age for 4 weeks could lead to improve cognitive functions (executive functions and processing speed) in the elderly. This result indicated that there is a possibility which the elderly could improve executive functions and processing speed in short term training. The results need replication in large samples. Long-term effects and relevance for every-day functioning remain uncertain as yet. UMIN Clinical Trial Registry 000002825.

Using Proton Magnetic Resonance Imaging and Spectroscopy to Understand Brain "Activation"

ERIC Educational Resources Information Center

Baslow, Morris H.; Guilfoyle, David N.

2007-01-01

Upon stimulation, areas of the brain associated with specific cognitive processing tasks may undergo observable physiological changes, and measures of such changes have been used to create brain maps for visualization of stimulated areas in task-related brain "activation" studies. These perturbations usually continue throughout the period of the…

Brain-Based Learning. Research Brief

ERIC Educational Resources Information Center

Walker, Karen

2005-01-01

What does brain-based research say about how adolescents learn? The 1990s was declared as the Decade of the Brain by President Bush and Congress. With the advancement of MRIs (Magnetic Resonance Imagining) and PET (positron emission tomography) scans, it has become much easier to study live healthy brains. As a result, the concept of…

Graph Analysis of Functional Brain Networks for Cognitive Control of Action in Traumatic Brain Injury

ERIC Educational Resources Information Center

Caeyenberghs, Karen; Leemans, Alexander; Heitger, Marcus H.; Leunissen, Inge; Dhollander, Thijs; Sunaert, Stefan; Dupont, Patrick; Swinnen, Stephan P.

2012-01-01

Patients with traumatic brain injury show clear impairments in behavioural flexibility and inhibition that often persist beyond the time of injury, affecting independent living and psychosocial functioning. Functional magnetic resonance imaging studies have shown that patients with traumatic brain injury typically show increased and more broadly…

IgLON5-Associated Encephalitis With Atypical Brain Magnetic Resonance Imaging and Cerebrospinal Fluid Changes.

PubMed

Montagna, Massimiliano; Amir, Rizvana; De Volder, Ilse; Lammens, Martin; Huyskens, Jef; Willekens, Barbara

2018-01-01

IgLON5-associated encephalitis is a syndrome with different clinical presentations consisting of sleep dysfunction, bulbar dysfunction, chorea, and progressive supranuclear palsy-like symptoms whereas dysautonomy and cognitive decline usually appear in later stages of the disease. We report a case of a patient with IgLON5-associated encephalitis presenting with rapidly progressive cognitive decline and atypical inflammatory lesions on brain magnetic resonance imaging, oligoclonal bands on cerebrospinal fluid, anti-IgLON5 antibodies exclusively of the IgG1 class, and a fierce inflammatory reaction on brain biopsy, who responded favorably to immunotherapy.

Magnetically guided central nervous system delivery and toxicity evaluation of magneto-electric nanocarriers

PubMed Central

Kaushik, Ajeet; Jayant, Rahul D.; Nikkhah-Moshaie, Roozbeh; Bhardwaj, Vinay; Roy, Upal; Huang, Zaohua; Ruiz, Ariel; Yndart, Adriana; Atluri, Venkata; El-Hage, Nazira; Khalili, Kamel; Nair, Madhavan

2016-01-01

Least component-based delivery of drug-tagged-nanocarriers across blood-brain-barriers (BBB) will allow site-specific and on-demand release of therapeutics to prevent CNS diseases. We developed a non-invasive magnetically guided delivery of magneto-electric nanocarriers (MENCs), ~20 nm, 10 mg/kg, across BBB in C57Bl/J mice. Delivered MENCs were uniformly distributed inside the brain, and were non-toxic to brain and other major organs, such as kidney, lung, liver, and spleen, and did not affect hepatic, kidney and neurobehavioral functioning. PMID:27143580

Low-current-density spin-transfer switching in Gd{sub 22}Fe{sub 78}-MgO magnetic tunnel junction

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

Kinjo, Hidekazu, E-mail: kinjou.h-lk@nhk.or.jp; Machida, Kenji; Aoshima, Ken-ichi

2014-05-28

Magnetization switching of a relatively thick (9 nm) Gd-Fe free layer was achieved with a low spin injection current density of 1.0 × 10{sup 6} A/cm{sup 2} using MgO based magnetic tunnel junction devices, fabricated for light modulators. At about 560 × 560 nm{sup 2} in size, the devices exhibited a tunneling magnetoresistance ratio of 7%. This low-current switching is mainly attributed to thermally assisted spin-transfer switching in consequence of its thermal magnetic behavior arising from Joule heating.

Magnetic and optoelectronic properties of gold nanocluster-thiophene assembly.

PubMed

Qin, Wei; Lohrman, Jessica; Ren, Shenqiang

2014-07-07

Nanohybrids consisting of Au nanocluster and polythiophene nanowire assemblies exhibit unique thermal-responsive optical behaviors and charge-transfer controlled magnetic and optoelectronic properties. The ultrasmall Au nanocluster enhanced photoabsorption and conductivity effectively improves the photocurrent of nanohybrid based photovoltaics, leading to an increase of power conversion efficiency by 14 % under AM 1.5 illumination. In addition, nanohybrids exhibit electric field controlled spin resonance and magnetic field sensing behaviors, which open up the potential of charge-transfer complex system where the magnetism and optoelectronics interact. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

IS VOYAGER 1 INSIDE AN INTERSTELLAR FLUX TRANSFER EVENT?

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

Schwadron, N. A.; McComas, D. J., E-mail: n.schwadron@unh.edu

Plasma wave observations from Voyager 1 have recently shown large increases in plasma density, to about 0.1 cm{sup –3}, consistent with the density of the local interstellar medium. However, corresponding magnetic field observations continue to show the spiral magnetic field direction observed throughout the inner heliosheath. These apparently contradictory observations may be reconciled if Voyager 1 is inside an interstellar flux transfer event—similar to flux transfer events routinely seen at the Earth's magnetopause. If this were the case, Voyager 1 remains inside the heliopause and based on the Voyager 1 observations we can determine the polarity of the interstellar magnetic field for the first time.

Wireless power transfer based on dielectric resonators with colossal permittivity

NASA Astrophysics Data System (ADS)

Song, Mingzhao; Belov, Pavel; Kapitanova, Polina

2016-11-01

Magnetic resonant wireless power transfer system based on dielectric disk resonators made of colossal permittivity (ɛ = 1000) and low loss (tan δ = 2.5 × 10-4) microwave ceramic is experimentally investigated. The system operates at the magnetic dipole mode excited in the resonators providing maximal power transfer efficiency of 90% at the frequency 232 MHz. By applying an impedance matching technique, the efficiency of 50% is achieved within the separation between the resonators d = 16 cm (3.8 radii of the resonator). The separation, misalignment and rotation dependencies of wireless power transfer efficiency are experimentally studied.

Brain magnetic resonance imaging with contrast dependent on blood oxygenation

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

Ogawa, S.; Lee, T.M.; Kay, A.R.

1990-12-01

Paramagnetic deoxyhemoglobin in venous blood is a naturally occurring contrast agent for magnetic resonance imaging (MRI). By accentuating the effects of this agent through the use of gradient-echo techniques in high yields, the authors demonstrate in vivo images of brain microvasculature with image contrast reflecting the blood oxygen level. This blood oxygenation level-dependent (BOLD) contrast follows blood oxygen changes induced by anesthetics, by insulin-induced hypoglycemia, and by inhaled gas mixtures that alter metabolic demand or blood flow. The results suggest that BOLD contrast can be used to provide in vivo real-time maps of blood oxygenation in the brain under normalmore » physiological conditions. BOLD contrast adds an additional feature to magnetic resonance imaging and complement other techniques that are attempting to provide position emission tomography-like measurements related to regional neural activity.« less

Brain Magnetic Resonance Imaging with Contrast Dependent on Blood Oxygenation

NASA Astrophysics Data System (ADS)

Ogawa, S.; Lee, T. M.; Kay, A. R.; Tank, D. W.

1990-12-01

Paramagnetic deoxyhemoglobin in venous blood is a naturally occurring contrast agent for magnetic resonance imaging (MRI). By accentuating the effects of this agent through the use of gradient-echo techniques in high fields, we demonstrate in vivo images of brain microvasculature with image contrast reflecting the blood oxygen level. This blood oxygenation level-dependent (BOLD) contrast follows blood oxygen changes induced by anesthetics, by insulin-induced hypoglycemia, and by inhaled gas mixtures that alter metabolic demand or blood flow. The results suggest that BOLD contrast can be used to provide in vivo real-time maps of blood oxygenation in the brain under normal physiological conditions. BOLD contrast adds an additional feature to magnetic resonance imaging and complements other techniques that are attempting to provide positron emission tomography-like measurements related to regional neural activity.

Creutzfeldt-Jakob Disease

MedlinePlus

... CJD: Electroencephalogram (EEG) measures the brain's patterns of electrical activity similar to the way an electrocardiogram (ECG) measures the heart's electrical activity. Brain magnetic resonance imaging (MRI) can detect ...

Randomized Double-Blind Placebo-Controlled Trial of Bevacizumab Therapy for Radiation Necrosis of the Central Nervous System

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

Levin, Victor A., E-mail: vlevin49@comcast.ne; Bidaut, Luc; Hou, Ping

Purpose: To conduct a controlled trial of bevacizumab for the treatment of symptomatic radiation necrosis of the brain. Methods and Materials: A total of 14 patients were entered into a placebo-controlled randomized double-blind study of bevacizumab for the treatment of central nervous system radiation necrosis. All patients were required to have radiographic or biopsy proof of central nervous system radiation necrosis and progressive neurologic symptoms or signs. Eligible patients had undergone irradiation for head-and-neck carcinoma, meningioma, or low- to mid-grade glioma. Patients were randomized to receive intravenous saline or bevacizumab at 3-week intervals. The magnetic resonance imaging findings 3 weeksmore » after the second treatment and clinical signs and symptoms defined the response or progression. Results: The volumes of necrosis estimated on T{sub 2}-weighted fluid-attenuated inversion recovery and T{sub 1}-weighted gadolinium-enhanced magnetic resonance imaging scans demonstrated that although no patient receiving placebo responded (0 of 7), all bevacizumab-treated patients did so (5 of 5 randomized and 7 of 7 crossover) with decreases in T{sub 2}-weighted fluid-attenuated inversion recovery and T{sub 1}-weighted gadolinium-enhanced volumes and a decrease in endothelial transfer constant. All bevacizumab-treated patients-and none of the placebo-treated patients-showed improvement in neurologic symptoms or signs. At a median of 10 months after the last dose of bevacizumab in patients receiving all four study doses, only 2 patients had experienced a recurrence of magnetic resonance imaging changes consistent with progressive radiation necrosis; one patient received a single additional dose of bevacizumab and the other patient received two doses. Conclusion: The Class I evidence of bevacizumab efficacy from the present study in the treatment of central nervous system radiation necrosis justifies consideration of this treatment option for people with radiation necrosis secondary to the treatment of head-and-neck cancer and brain cancer.« less

Clinical safety of 3-T brain magnetic resonance imaging in newborns.

PubMed

Fumagalli, Monica; Cinnante, Claudia Maria; Calloni, Sonia Francesca; Sorrentino, Gabriele; Gorla, Ilaria; Plevani, Laura; Pesenti, Nicola; Sirgiovanni, Ida; Mosca, Fabio; Triulzi, Fabio

2018-03-29

The effects and potential hazards of brain magnetic resonance imaging (MRI) at 3 T in newborns are debated. Assess the impact of 3-T MRI in newborns on body temperature and physiological parameters. Forty-nine newborns, born preterm and at term, underwent 3-T brain MRI at term-corrected age. Rectal and skin temperature, oxygen saturation and heart rate were recorded before, during and after the scan. A statistically significant increase in skin temperature of 0.6 °C was observed at the end of the MRI scan (P<0.01). There was no significant changes in rectal temperature, heart rate or oxygen saturation. Core temperature, heart rate and oxygen saturation in newborns were not affected by 3-T brain MR scanning.

Brain Neuromodulation Techniques: A Review.

PubMed

Lewis, Philip M; Thomson, Richard H; Rosenfeld, Jeffrey V; Fitzgerald, Paul B

2016-08-01

The modulation of brain function via the application of weak direct current was first observed directly in the early 19th century. In the past 3 decades, transcranial magnetic stimulation and deep brain stimulation have undergone clinical translation, offering alternatives to pharmacological treatment of neurological and neuropsychiatric disorders. Further development of novel neuromodulation techniques employing ultrasound, micro-scale magnetic fields and optogenetics is being propelled by a rapidly improving understanding of the clinical and experimental applications of artificially stimulating or depressing brain activity in human health and disease. With the current rapid growth in neuromodulation technologies and applications, it is timely to review the genesis of the field and the current state of the art in this area. © The Author(s) 2016.

Bacterial lipopolysaccharide-induced systemic inflammation alters perfusion of white matter-rich regions without altering flow in brain-irrigating arteries: Relationship to blood-brain barrier breakdown?

PubMed

Dhaya, Ibtihel; Griton, Marion; Raffard, Gérard; Amri, Mohamed; Hiba, Bassem; Konsman, Jan Pieter

2018-01-15

To better understand brain dysfunction during sepsis, cerebral arterial blood flow was assessed with Phase Contrast Magnetic Resonance Imaging, perfusion with Arterial Spin Labeling and structure with diffusion-weighted Magnetic Resonance Imaging in rats after intraperitoneal administration of bacterial lipopolysaccharides. Although cerebral arterial flow was not altered, perfusion of the corpus callosum region and diffusion parallel to its fibers were higher after lipopolysaccharide administration as compared to saline injection. In parallel, lipopolysaccharide induced perivascular immunoglobulin-immunoreactivity in white matter. These findings indicate that systemic inflammation can result in increased perfusion, blood-brain barrier breakdown and altered water diffusion in white matter. Copyright © 2017 Elsevier B.V. All rights reserved.

FDTD-based Transcranial Magnetic Stimulation model applied to specific neurodegenerative disorders.

PubMed

Fanjul-Vélez, Félix; Salas-García, Irene; Ortega-Quijano, Noé; Arce-Diego, José Luis

2015-01-01

Non-invasive treatment of neurodegenerative diseases is particularly challenging in Western countries, where the population age is increasing. In this work, magnetic propagation in human head is modelled by Finite-Difference Time-Domain (FDTD) method, taking into account specific characteristics of Transcranial Magnetic Stimulation (TMS) in neurodegenerative diseases. It uses a realistic high-resolution three-dimensional human head mesh. The numerical method is applied to the analysis of magnetic radiation distribution in the brain using two realistic magnetic source models: a circular coil and a figure-8 coil commonly employed in TMS. The complete model was applied to the study of magnetic stimulation in Alzheimer and Parkinson Diseases (AD, PD). The results show the electrical field distribution when magnetic stimulation is supplied to those brain areas of specific interest for each particular disease. Thereby the current approach entails a high potential for the establishment of the current underdeveloped TMS dosimetry in its emerging application to AD and PD. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

A chiral-based magnetic memory device without a permanent magnet

PubMed Central

Dor, Oren Ben; Yochelis, Shira; Mathew, Shinto P.; Naaman, Ron; Paltiel, Yossi

2013-01-01

Several technologies are currently in use for computer memory devices. However, there is a need for a universal memory device that has high density, high speed and low power requirements. To this end, various types of magnetic-based technologies with a permanent magnet have been proposed. Recent charge-transfer studies indicate that chiral molecules act as an efficient spin filter. Here we utilize this effect to achieve a proof of concept for a new type of chiral-based magnetic-based Si-compatible universal memory device without a permanent magnet. More specifically, we use spin-selective charge transfer through a self-assembled monolayer of polyalanine to magnetize a Ni layer. This magnitude of magnetization corresponds to applying an external magnetic field of 0.4 T to the Ni layer. The readout is achieved using low currents. The presented technology has the potential to overcome the limitations of other magnetic-based memory technologies to allow fabricating inexpensive, high-density universal memory-on-chip devices. PMID:23922081

A chiral-based magnetic memory device without a permanent magnet.

PubMed

Ben Dor, Oren; Yochelis, Shira; Mathew, Shinto P; Naaman, Ron; Paltiel, Yossi

2013-01-01

Several technologies are currently in use for computer memory devices. However, there is a need for a universal memory device that has high density, high speed and low power requirements. To this end, various types of magnetic-based technologies with a permanent magnet have been proposed. Recent charge-transfer studies indicate that chiral molecules act as an efficient spin filter. Here we utilize this effect to achieve a proof of concept for a new type of chiral-based magnetic-based Si-compatible universal memory device without a permanent magnet. More specifically, we use spin-selective charge transfer through a self-assembled monolayer of polyalanine to magnetize a Ni layer. This magnitude of magnetization corresponds to applying an external magnetic field of 0.4 T to the Ni layer. The readout is achieved using low currents. The presented technology has the potential to overcome the limitations of other magnetic-based memory technologies to allow fabricating inexpensive, high-density universal memory-on-chip devices.

Hemoglobin magnetism in aqueous solution probed by muon spin relaxation and future applications to brain research

PubMed Central

Nagamine, Kanetada; Shimomura, Koichiro; Miyadera, Haruo; Kim, Yong-Jae; Scheicher, Ralph Hendrik; Das, Tara Prasad; Schultz, Jerome Samson

2007-01-01

A marked difference in spin relaxation behavior due to hemoglobin magnetism was found for positive muons (μ+) in deoxyhemoglobin in comparison with that observed in oxyhemoglobin in aqueous solution at room temperature under zero and external longitudinal magnetic fields upto 0.4 Tesla. At the same time, small but significant unique relaxation pattern was observed in nonmagnetic oxyhemoglobin. Combined with our previous measurements on hemoglobin in human blood, application of this type of measurement to the studies of the level of oxygenation in various regions of the human brain is suggested. PMID:24019590

In Vivo Assessment of Neurotransmitters and Modulators with Magnetic Resonance Spectroscopy: Application to Schizophrenia

PubMed Central

Wijtenburg, S. Andrea; Yang, Shaolin; Fischer, Bernard A.; Rowland, Laura M.

2015-01-01

In vivo measurement of neurotransmitters and modulators is now feasible with advanced proton magnetic resonance spectroscopy (1H-MRS) techniques. This review provides a basic tutorial of MRS, describes the methods available to measure brain glutamate, glutamine, γ-aminobutyric acid, glutathione, N-acetylaspartylglutamate, glycine, and serine at magnetic field strengths of 3Tesla or higher, and summarizes the neurochemical findings in schizophrenia. Overall, 1H-MRS holds great promise for producing biomarkers that can serve as treatment targets, prediction of disease onset, or illness exacerbation in schizophrenia and other brain diseases. PMID:25614132

Determination of regional brain temperature using proton magnetic resonance spectroscopy to assess brain-body temperature differences in healthy human subjects.

PubMed

Childs, Charmaine; Hiltunen, Yrjö; Vidyasagar, Rishma; Kauppinen, Risto A

2007-01-01

Proton magnetic resonance spectroscopy ((1)H MRS) was used to determine brain temperature in healthy volunteers. Partially water-suppressed (1)H MRS data sets were acquired at 3T from four different gray matter (GM)/white matter (WM) volumes. Brain temperatures were determined from the chemical-shift difference between the CH(3) of N-acetyl aspartate (NAA) at 2.01 ppm and water. Brain temperatures in (1)H MRS voxels of 2 x 2 x 2 cm(3) showed no substantial heterogeneity. The volume-averaged temperature from single-voxel spectroscopy was compared with body temperatures obtained from the oral cavity, tympanum, and temporal artery regions. The mean brain parenchyma temperature was 0.5 degrees C cooler than readings obtained from three extra-brain sites (P < 0.01). (1)H MRS imaging (MRSI) data were acquired from a slice encompassing the single-voxel volumes to assess the ability of spectroscopic imaging to determine regional brain temperature within the imaging slice. Brain temperature away from the center of the brain determined by MRSI differed from that obtained by single-voxel MRS in the same brain region, possibly due to a poor line width (LW) in MRSI. The data are discussed in the light of proposed brain-body temperature gradients and the use of (1)H MRSI to monitor brain temperature in pathologies, such as brain trauma.

Unwarping confocal microscopy images of bee brains by nonrigid registration to a magnetic resonance microscopy image.

PubMed

Rohlfing, Torsten; Schaupp, Frank; Haddad, Daniel; Brandt, Robert; Haase, Axel; Menzel, Randolf; Maurer, Calvin R

2005-01-01

Confocal microscopy (CM) is a powerful image acquisition technique that is well established in many biological applications. It provides 3-D acquisition with high spatial resolution and can acquire several different channels of complementary image information. Due to the specimen extraction and preparation process, however, the shapes of imaged objects may differ considerably from their in vivo appearance. Magnetic resonance microscopy (MRM) is an evolving variant of magnetic resonance imaging, which achieves microscopic resolutions using a high magnetic field and strong magnetic gradients. Compared to CM imaging, MRM allows for in situ imaging and is virtually free of geometrical distortions. We propose to combine the advantages of both methods by unwarping CM images using a MRM reference image. Our method incorporates a sequence of image processing operators applied to the MRM image, followed by a two-stage intensity-based registration to compute a nonrigid coordinate transformation between the CM images and the MRM image. We present results obtained using CM images from the brains of 20 honey bees and a MRM image of an in situ bee brain. Copyright 2005 Society of Photo-Optical Instrumentation Engineers.

A Scalable Framework For Segmenting Magnetic Resonance Images

PubMed Central

Hore, Prodip; Goldgof, Dmitry B.; Gu, Yuhua; Maudsley, Andrew A.; Darkazanli, Ammar

2009-01-01

A fast, accurate and fully automatic method of segmenting magnetic resonance images of the human brain is introduced. The approach scales well allowing fast segmentations of fine resolution images. The approach is based on modifications of the soft clustering algorithm, fuzzy c-means, that enable it to scale to large data sets. Two types of modifications to create incremental versions of fuzzy c-means are discussed. They are much faster when compared to fuzzy c-means for medium to extremely large data sets because they work on successive subsets of the data. They are comparable in quality to application of fuzzy c-means to all of the data. The clustering algorithms coupled with inhomogeneity correction and smoothing are used to create a framework for automatically segmenting magnetic resonance images of the human brain. The framework is applied to a set of normal human brain volumes acquired from different magnetic resonance scanners using different head coils, acquisition parameters and field strengths. Results are compared to those from two widely used magnetic resonance image segmentation programs, Statistical Parametric Mapping and the FMRIB Software Library (FSL). The results are comparable to FSL while providing significant speed-up and better scalability to larger volumes of data. PMID:20046893

Ruthenium supported on magnetic nanoparticles: An efficient and recoverable catalyst for hydrogenation of alkynes and transfer hydrogenation of carbonyl compounds

EPA Science Inventory

Ruthenium supported on surface modified magnetic nanoparticles (NiFe2O4) has been successfully synthesized and applied for hydrogenation of alkynes at room temperature as well as transfer hydrogenation of a number of carbonyl compounds under microwave irradiation conditions. The ...

Serial Magnetization Transfer Imaging in Acute Optic Neuritis

ERIC Educational Resources Information Center

Hickman, S. J.; Toosy, A. T.; Jones, S. J.; Altmann, D. R.; Miszkiel, K. A.; MacManus, D. G.; Barker, G. J.; Plant, G. T.; Thompson, A. J.; Miller, D.H.

2004-01-01

In serial studies of multiple sclerosis lesions, reductions in magnetization transfer ratio (MTR) are thought to be due to demyelination and axonal loss, with later rises due to remyelination. This study followed serial changes in MTR in acute optic neuritis in combination with clinical and electrophysiological measurements to determine if the MTR…

In-situ electric field in human body model in different postures for wireless power transfer system in an electrical vehicle.

PubMed

Shimamoto, Takuya; Laakso, Ilkka; Hirata, Akimasa

2015-01-07

The in-situ electric field of an adult male model in different postures is evaluated for exposure to the magnetic field leaked from a wireless power transfer system in an electrical vehicle. The transfer system is located below the centre of the vehicle body and the transferred power and frequency are 7 kW and 85 kHz, respectively. The in-situ electric field is evaluated for a human model (i) crouching near the vehicle, (ii) lying on the ground with or without his arm stretched, (iii) sitting in the driver's seat, and (iv) standing on a transmitting coil without a receiving coil. In each scenario, the maximum in-situ electric fields are lower than the allowable limit prescribed by international guidelines, although the local magnetic field strength in regions of the human body is higher than the allowable external magnetic field strength. The highest in-situ electric field is observed when the human body model is placed on the ground with his arm extended toward the coils, because of a higher magnetic field around the arm.

Fermi Level shifting, Charge Transfer and Induced Magnetic Coupling at La0.7Ca0.3MnO3/LaNiO3 Interface

PubMed Central

Ning, Xingkun; Wang, Zhanjie; Zhang, Zhidong

2015-01-01

A large magnetic coupling has been observed at the La0.7Ca0.3MnO3/LaNiO3 (LCMO/LNO) interface. The x-ray photoelectron spectroscopy (XPS) study results show that Fermi level continuously shifted across the LCMO/LNO interface in the interface region. In addition, the charge transfer between Mn and Ni ions of the type Mn3+ − Ni3+ → Mn4+ − Ni2+ with the oxygen vacancies are observed in the interface region. The intrinsic interfacial charge transfer can give rise to itinerant electrons, which results in a “shoulder feature” observed at the low binding energy in the Mn 2p core level spectra. Meanwhile, the orbital reconstruction can be mapped according to the Fermi level position and the charge transfer mode. It can be considered that the ferromagnetic interaction between Ni2+ and Mn4+ gives rise to magnetic regions that pin the ferromagnetic LCMO and cause magnetic coupling at the LCMO/LNO interface. PMID:25676088

Brain aging: Evaluation of pH using phosphorus magnetic resonance spectroscopy.

PubMed

Cichocka, Monika; Kozub, Justyna; Urbanik, Andrzej

2018-02-02

Very important aspects of aging include age-related changes occurring in the brain. The aim of the present study was to identify the standard pH value in the entire brain volume using phosphorus magnetic resonance spectroscopy in healthy individuals of both sexes in different age groups, and then to determine whether there are differences in these values. A total of 65 individuals aged 20-32 years (mean age 24.5 ± 2.1 years, 31 women and 34 men) and 31 individuals aged 60-81 years (mean age 64.9 ± 5.5 years, 17 women and 14 men) were studied. The phosphorus magnetic resonance spectroscopy examination was carried out using a 1.5-T magnetic resonance system. The signal was acquired from the volume of interest that covered the whole brain. A vast majority of the examined individuals had slightly alkaline brain pH regardless of age. In the ≥20 years group, pH was 7.09 ± 0.11, and in the ≥60 years group, the average pH was 7.03 ± 0.05. This comparison of the pH identified in all the tested individuals shows a negative correlation of pH with age. The present findings might provide a valuable basis for further research into "healthy aging" as well as pathology in older adults. Geriatr Gerontol Int 2018; ••: ••-••. © 2018 Japan Geriatrics Society.

Impact of SQUIDs on functional imaging in neuroscience

NASA Astrophysics Data System (ADS)

Della Penna, Stefania; Pizzella, Vittorio; Romani, Gian Luca

2014-04-01

This paper provides an overview on the basic principles and applications of magnetoencephalography (MEG), a technique that requires the use of many SQUIDs and thus represents one of the most important applications of superconducting electronics. Since the development of the first SQUID magnetometers, it was clear that these devices could be used to measure the ultra-low magnetic signals associated with the bioelectric activity of the neurons of the human brain. Forty years on from the first measurement of magnetic alpha rhythm by David Cohen, MEG has become a fundamental tool for the investigation of brain functions. The simple localization of cerebral sources activated by sensory stimulation performed in the early years has been successively expanded to the identification of the sequence of neuronal pool activations, thus decrypting information of the hierarchy underlying cerebral processing. This goal has been achieved thanks to the development of complex instrumentation, namely whole head MEG systems, allowing simultaneous measurement of magnetic fields all over the scalp with an exquisite time resolution. The latest trends in MEG, such as the study of brain networks, i.e. how the brain organizes itself in a coherent and stable way, are discussed. These sound applications together with the latest technological developments aimed at implementing systems able to record MEG signals and magnetic resonance imaging (MRI) of the head with the same set-up pave the way to high performance systems for brain functional investigation in the healthy and the sick population.

Tissue microstructure features derived from anomalous diffusion measurements in magnetic resonance imaging.

PubMed

Yu, Qiang; Reutens, David; O'Brien, Kieran; Vegh, Viktor

2017-02-01

Tissue microstructure features, namely axon radius and volume fraction, provide important information on the function of white matter pathways. These parameters vary on the scale much smaller than imaging voxels (microscale) yet influence the magnetic resonance imaging diffusion signal at the image voxel scale (macroscale) in an anomalous manner. Researchers have already mapped anomalous diffusion parameters from magnetic resonance imaging data, but macroscopic variations have not been related to microscale influences. With the aid of a tissue model, we aimed to connect anomalous diffusion parameters to axon radius and volume fraction using diffusion-weighted magnetic resonance imaging measurements. An ex vivo human brain experiment was performed to directly validate axon radius and volume fraction measurements in the human brain. These findings were validated using electron microscopy. Additionally, we performed an in vivo study on nine healthy participants to map axon radius and volume fraction along different regions of the corpus callosum projecting into various cortical areas identified using tractography. We found a clear relationship between anomalous diffusion parameters and axon radius and volume fraction. We were also able to map accurately the trend in axon radius along the corpus callosum, and in vivo findings resembled the low-high-low-high behaviour in axon radius demonstrated previously. Axon radius and volume fraction measurements can potentially be used in brain connectivity studies and to understand the implications of white matter structure in brain diseases and disorders. Hum Brain Mapp 38:1068-1081, 2017. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Interhemispheric Information Transfer: A New Diagnostic Method for Mild Traumatic Brain Injury

DTIC Science & Technology

2011-10-01

brain tumors, meningitis, cerebral palsy, encephalitis, brain abscesses , vascular malformations, cerebrovascular disease, Alzheimer’s disease...disease including head trauma with loss of consciousness 2) Having a contraindication to MRI such as pregnancy, breast feeding, surgical clips

Establishing upper limits on neuronal activity-evoked pH changes with APT-CEST MRI at 7 T.

PubMed

Khlebnikov, Vitaliy; Siero, Jeroen C W; Bhogal, Alex A; Luijten, Peter R; Klomp, Dennis W J; Hoogduin, Hans

2018-07-01

To detect neuronal activity-evoked pH changes by amide proton transfer-chemical exchange saturation transfer (APT-CEST) MRI at 7 T. Three healthy subjects participated in the study. A low-power 3-dimensional APT-CEST sequence was optimized through the Bloch-McConnell equations. pH sensitivity of the sequence was estimated both in phantoms and in vivo. The feasibility of pH-functional MRI was tested in Bloch-McConnell-simulated data using the optimized sequence. In healthy subjects, the visual stimuli were used to evoke transient pH changes in the visual cortex, and a 3-dimensional APT-CEST volume was acquired at the pH-sensitive frequency offset of 3.5 ppm every 12.6 s. In theory, a three-component general linear model was capable of separating the effects of blood oxygenation level-dependent contrast and pH. The Bloch-McConnell equations indicated that a change in pH of 0.03 should be measurable at the experimentally determined temporal signal-to-noise ratio of 108. However, only a blood oxygenation level-dependent effect in the visual cortex could be discerned during the visual stimuli experiments performed in the healthy subjects. The results of this study suggest that if indeed there are any transient brain pH changes in response to visual stimuli, those are under 0.03 units pH change, which is extremely difficult to detect using the existent techniques. Magn Reson Med 80:126-136, 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.

Traumatic Brain Injury Diffusion Magnetic Resonance Imaging Research Roadmap Development Project

DTIC Science & Technology

2011-10-01

promising technology on the horizon is the Diffusion Tensor Imaging ( DTI ). Diffusion tensor imaging ( DTI ) is a magnetic resonance imaging (MRI)-based...in the brain. The potential for DTI to improve our understanding of TBI has not been fully explored and challenges associated with non-existent...processing tools, quality control standards, and a shared image repository. The recommendations will be disseminated and pilot tested. A DTI of TBI

Eccentric figure-eight coils for transcranial magnetic stimulation.

PubMed

Sekino, Masaki; Ohsaki, Hiroyuki; Takiyama, Yoshihiro; Yamamoto, Keita; Matsuzaki, Taiga; Yasumuro, Yoshihiro; Nishikawa, Atsushi; Maruo, Tomoyuki; Hosomi, Koichi; Saitoh, Youichi

2015-01-01

Previously we proposed an eccentric figure-eight coil that can cause threshold stimulation in the brain at lower driving currents. In this study, we performed numerical simulations and magnetic stimulations to healthy subjects for evaluating the advantages of the eccentric coil. The simulations were performed using a simplified spherical brain model and a realistic human brain model. We found that the eccentric coil required a driving current intensity of approximately 18% less than that required by the concentric coil to cause comparable eddy current densities within the brain. The eddy current localization of the eccentric coil was slightly higher than that of the concentric coil. A prototype eccentric coil was designed and fabricated. Instead of winding a wire around a bobbin, we cut eccentric-spiral slits on the insulator cases, and a wire was woven through the slits. The coils were used to deliver magnetic stimulation to healthy subjects; among our results, we found that the current slew rate corresponding to motor threshold values for the concentric and eccentric coils were 86 and 78 A/µs, respectively. The results indicate that the eccentric coil consistently requires a lower driving current to reach the motor threshold than the concentric coil. Future development of compact magnetic stimulators will enable the treatment of some intractable neurological diseases at home. © 2014 Wiley Periodicals, Inc.

Silent music reading: auditory imagery and visuotonal modality transfer in singers and non-singers.

PubMed

Hoppe, Christian; Splittstößer, Christoph; Fliessbach, Klaus; Trautner, Peter; Elger, Christian E; Weber, Bernd

2014-11-01

In daily life, responses are often facilitated by anticipatory imagery of expected targets which are announced by associated stimuli from different sensory modalities. Silent music reading represents an intriguing case of visuotonal modality transfer in working memory as it induces highly defined auditory imagery on the basis of presented visuospatial information (i.e. musical notes). Using functional MRI and a delayed sequence matching-to-sample paradigm, we compared brain activations during retention intervals (10s) of visual (VV) or tonal (TT) unimodal maintenance versus visuospatial-to-tonal modality transfer (VT) tasks. Visual or tonal sequences were comprised of six elements, white squares or tones, which were low, middle, or high regarding vertical screen position or pitch, respectively (presentation duration: 1.5s). For the cross-modal condition (VT, session 3), the visuospatial elements from condition VV (session 1) were re-defined as low, middle or high "notes" indicating low, middle or high tones from condition TT (session 2), respectively, and subjects had to match tonal sequences (probe) to previously presented note sequences. Tasks alternately had low or high cognitive load. To evaluate possible effects of music reading expertise, 15 singers and 15 non-musicians were included. Scanner task performance was excellent in both groups. Despite identity of applied visuospatial stimuli, visuotonal modality transfer versus visual maintenance (VT>VV) induced "inhibition" of visual brain areas and activation of primary and higher auditory brain areas which exceeded auditory activation elicited by tonal stimulation (VT>TT). This transfer-related visual-to-auditory activation shift occurred in both groups but was more pronounced in experts. Frontoparietal areas were activated by higher cognitive load but not by modality transfer. The auditory brain showed a potential to anticipate expected auditory target stimuli on the basis of non-auditory information and sensory brain activation rather mirrored expectation than stimulation. Silent music reading probably relies on these basic neurocognitive mechanisms. Copyright © 2014 Elsevier Inc. All rights reserved.

Interhemispheric Transfer Time Asymmetry of Visual Information Depends on Eye Dominance: An Electrophysiological Study

PubMed Central

Chaumillon, Romain; Blouin, Jean; Guillaume, Alain

2018-01-01

The interhemispheric transfer of information is a fundamental process in the human brain. When a visual stimulus appears eccentrically in one visual-hemifield, it will first activate the contralateral hemisphere but also the ipsilateral one with a slight delay due to the interhemispheric transfer. This interhemispheric transfer of visual information is believed to be faster from the right to the left hemisphere in right-handers. Such an asymmetry is considered as a relevant fact in the context of the lateralization of the human brain. We show here using current source density (CSD) analyses of visually evoked potential (VEP) that, in right-handers and, to a lesser extent in left-handers, this asymmetry is in fact dependent on the sighting eye dominance, the tendency we have to prefer one eye for monocular tasks. Indeed, in right-handers, a faster interhemispheric transfer of visual information from the right to left hemisphere was observed only in participants with a right dominant eye (DE). Right-handers with a left DE showed the opposite pattern, with a faster transfer from the left to the right hemisphere. In left-handers, albeit a smaller number of participants has been tested and hence confirmation is required, only those with a right DE showed an asymmetrical interhemispheric transfer with a faster transfer from the right to the left hemisphere. As a whole these results demonstrate that eye dominance is a fundamental determinant of asymmetries in interhemispheric transfer of visual information and suggest that it is an important factor of brain lateralization. PMID:29515351

Interhemispheric Transfer Time Asymmetry of Visual Information Depends on Eye Dominance: An Electrophysiological Study.

PubMed

Chaumillon, Romain; Blouin, Jean; Guillaume, Alain

2018-01-01

The interhemispheric transfer of information is a fundamental process in the human brain. When a visual stimulus appears eccentrically in one visual-hemifield, it will first activate the contralateral hemisphere but also the ipsilateral one with a slight delay due to the interhemispheric transfer. This interhemispheric transfer of visual information is believed to be faster from the right to the left hemisphere in right-handers. Such an asymmetry is considered as a relevant fact in the context of the lateralization of the human brain. We show here using current source density (CSD) analyses of visually evoked potential (VEP) that, in right-handers and, to a lesser extent in left-handers, this asymmetry is in fact dependent on the sighting eye dominance, the tendency we have to prefer one eye for monocular tasks. Indeed, in right-handers, a faster interhemispheric transfer of visual information from the right to left hemisphere was observed only in participants with a right dominant eye (DE). Right-handers with a left DE showed the opposite pattern, with a faster transfer from the left to the right hemisphere. In left-handers, albeit a smaller number of participants has been tested and hence confirmation is required, only those with a right DE showed an asymmetrical interhemispheric transfer with a faster transfer from the right to the left hemisphere. As a whole these results demonstrate that eye dominance is a fundamental determinant of asymmetries in interhemispheric transfer of visual information and suggest that it is an important factor of brain lateralization.

Direct enhancement of nitrogen-15 targets at high-field by fast ADAPT-SABRE

NASA Astrophysics Data System (ADS)

Roy, Soumya S.; Stevanato, Gabriele; Rayner, Peter J.; Duckett, Simon B.

2017-12-01

Signal Amplification by Reversible Exchange (SABRE) is an attractive nuclear spin hyperpolarization technique capable of huge sensitivity enhancement in nuclear magnetic resonance (NMR) detection. The resonance condition of SABRE hyperpolarization depends on coherent spin mixing, which can be achieved naturally at a low magnetic field. The optimum transfer field to spin-1/2 heteronuclei is technically demanding, as it requires field strengths weaker than the earth's magnetic field for efficient spin mixing. In this paper, we illustrate an approach to achieve strong 15N SABRE hyperpolarization at high magnetic field by a radio frequency (RF) driven coherent transfer mechanism based on alternate pulsing and delay to achieve polarization transfer. The presented scheme is found to be highly robust and much faster than existing related methods, producing ∼ 3 orders of magnitude 15N signal enhancement within 2 s of RF pulsing.

Direct enhancement of nitrogen-15 targets at high-field by fast ADAPT-SABRE.

PubMed

Roy, Soumya S; Stevanato, Gabriele; Rayner, Peter J; Duckett, Simon B

2017-12-01

Signal Amplification by Reversible Exchange (SABRE) is an attractive nuclear spin hyperpolarization technique capable of huge sensitivity enhancement in nuclear magnetic resonance (NMR) detection. The resonance condition of SABRE hyperpolarization depends on coherent spin mixing, which can be achieved naturally at a low magnetic field. The optimum transfer field to spin-1/2 heteronuclei is technically demanding, as it requires field strengths weaker than the earth's magnetic field for efficient spin mixing. In this paper, we illustrate an approach to achieve strong 15 N SABRE hyperpolarization at high magnetic field by a radio frequency (RF) driven coherent transfer mechanism based on alternate pulsing and delay to achieve polarization transfer. The presented scheme is found to be highly robust and much faster than existing related methods, producing ∼3 orders of magnitude 15 N signal enhancement within 2 s of RF pulsing. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

Enhancement of Spin-transfer torque switching via resonant tunneling

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

Chatterji, Niladri; Tulapurkar, Ashwin A.; Muralidharan, Bhaskaran

We propose the use of resonant tunneling as a route to enhance the spin-transfer torque switching characteristics of magnetic tunnel junctions. The proposed device structure is a resonant tunneling magnetic tunnel junction based on a MgO-semiconductor heterostructure sandwiched between a fixed magnet and a free magnet. Using the non-equilibrium Green's function formalism coupled self consistently with the Landau-Lifshitz-Gilbert-Slonczewski equation, we demonstrate enhanced tunnel magneto-resistance characteristics as well as lower switching voltages in comparison with traditional trilayer devices. Two device designs based on MgO based heterostructures are presented, where the physics of resonant tunneling leads to an enhanced spin transfer torquemore » thereby reducing the critical switching voltage by up to 44%. It is envisioned that the proof-of-concept presented here may lead to practical device designs via rigorous materials and interface studies.« less

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

Miyawaki, Daisuke; Murakami, Masao; Demizu, Yusuke

Purpose: To assess the incidence of early delayed or late morbidity of Brain after particle therapy for skull base tumors and head-and-neck cancers. Methods and Materials: Between May 2001 and December 2005, 59 patients with cancerous invasion of the skull base were treated with proton or carbon ion therapy at the Hyogo Ion Beam Medical Center. Adverse events were assessed according to the magnetic resonance imaging findings (late effects of normal tissue-subjective, objective, management, analytic [LENT-SOMA]) and symptoms (Common Terminology Criteria for Adverse Events [CTCAE], version 3.0). Dose-volume histograms were used to analyze the relationship between the dose and volumemore » of the irradiated brain and the occurrence of brain injury. The median follow-up time was 33 months. Results: Of the 48 patients treated with proton therapy and 11 patients treated with carbon ion radiotherapy, 8 (17%) and 7 (64%), respectively, developed radiation-induced brain changes (RIBCs) on magnetic resonance imaging (LENT-SOMA Grade 1-3). Four patients (7%) had some clinical symptoms, such as vertigo and headache (CTCAE Grade 2) or epilepsy (CTCAE Grade 3). The actuarial occurrence rate of RIBCs at 2 and 3 years was 20% and 39%, respectively, with a significant difference in the incidence between the proton and carbon ion radiotherapy groups. The dose-volume histogram analyses revealed significant differences between Brain lobes with and without RIBCs in the actuarial volume of brain lobes receiving high doses. Conclusion: Particle therapies produced minimal symptomatic brain toxicities, but sequential evaluation with magnetic resonance imaging detected a greater incidence of RIBCs. Significant differences were observed in the irradiated brain volume between Brain lobes with and without RIBCs.« less

Microbleeds in postmortem brains of patients with Alzheimer disease: a T2*-weighted gradient-echo 7.0 T magnetic resonance imaging study.

PubMed

De Reuck, Jacques L; Cordonnier, Charlotte; Deramecourt, Vincent; Auger, Florent; Durieux, Nicolas; Bordet, Regis; Maurage, Claude-Alain; Leys, Didier; Pasquier, Florence

2013-01-01

This study aims to determine the distribution and to quantify microbleeds (MBs) in postmortem brains of patients with Alzheimer disease (AD) on T2*-weighted gradient-echo 7.0 T magnetic resonance imaging. Twenty-eight AD brains were compared with 5 controls. The AD brains were subdivided further: 18 without and 10 with additional severe cerebral amyloid angiopathy (AD-CAA). The distribution and the number of cortical focal signal intensity losses, representing MBs, were assessed on coronal sections at the frontal, the central, and the occipital level of a cerebral hemisphere. MBs prevailed in the central sections (P=0.005) of AD brains without CAA, whereas in AD-CAA brains, they were more frequent in all coronal sections (P≤0.002). They prevailed in the deep cortical layers of the AD brains and of the controls (P≤0.03). They were significantly increased in all cortical layers of the AD-CAA brains (P≤0.04), compared with the controls. MBs prevalence in brains of AD patients had a different topographic distribution according to the absence or presence of severe CAA.

Liquid neon heat transfer as applied to a 30 tesla cryomagnet

NASA Technical Reports Server (NTRS)

Papell, S. S.; Hendricks, R. C.

1975-01-01

Since superconducting magnets cooled by liquid helium are limited to magnetic fields of about 18 teslas, the design of a 30 tesla cryomagnet necessitates forced convection liquid neon heat transfer in small coolant channels. As these channels are too small to handle the vapor flow if the coolant were to boil, the design philosophy calls for suppressing boiling by subjecting the fluid to high pressures. Forced convection heat transfer data are obtained by using a blowdown technique to force the fluid vertically through a resistance-heated instrumented tube. The data are obtained at inlet temperatures between 28 and 34 K and system pressures between 28 to 29 bars. Data correlation is limited to a very narrow range of test conditions, since the tests were designed to simulate the heat transfer characteristics in the coolant channels of the 30 tesla cryomagnet concerned. The results can therefore be applied directly to the design of the magnet system.-

Advances in cryogenic engineering. Volume 27 - Proceedings of the Cryogenic Engineering Conference, San Diego, CA, August 11-14, 1981

NASA Technical Reports Server (NTRS)

Fast, R. W. (Editor)

1982-01-01

Applications of superconductivity are considered, taking into account MHD and fusion, generators, transformers, transmission lines, magnets for physics, cryogenic techniques, electrtronics, and aspects of magnet stability. Advances related to heat transfer in He I are discussed along with subjects related to theat transfer in He II, refrigeration of superconducting systems, refrigeration and liquefaction, dilution and magnetic refrigerators, refrigerators for space applications, mass transfer and flow phenomena, and the properties of fluids. Developments related to cryogenic applications are also explored, giving attention to bulk storage and transfer of cryogenic fluids, liquefied natural gas operations, space science and technology, and cryopumping. Topics related to cryogenic instrumentation and controls include the production and use of high grade silicon diode temperature sensors, the choice of strain gages for use in a large superconducting alternator, microprocessor control of cryogenic pressure, and instrumentation, data acquisition and reduction for a large spaceborne helium dewar.

Magnetic MIMO Signal Processing and Optimization for Wireless Power Transfer

NASA Astrophysics Data System (ADS)

Yang, Gang; Moghadam, Mohammad R. Vedady; Zhang, Rui

2017-06-01

In magnetic resonant coupling (MRC) enabled multiple-input multiple-output (MIMO) wireless power transfer (WPT) systems, multiple transmitters (TXs) each with one single coil are used to enhance the efficiency of simultaneous power transfer to multiple single-coil receivers (RXs) by constructively combining their induced magnetic fields at the RXs, a technique termed "magnetic beamforming". In this paper, we study the optimal magnetic beamforming design in a multi-user MIMO MRC-WPT system. We introduce the multi-user power region that constitutes all the achievable power tuples for all RXs, subject to the given total power constraint over all TXs as well as their individual peak voltage and current constraints. We characterize each boundary point of the power region by maximizing the sum-power deliverable to all RXs subject to their minimum harvested power constraints. For the special case without the TX peak voltage and current constraints, we derive the optimal TX current allocation for the single-RX setup in closed-form as well as that for the multi-RX setup. In general, the problem is a non-convex quadratically constrained quadratic programming (QCQP), which is difficult to solve. For the case of one single RX, we show that the semidefinite relaxation (SDR) of the problem is tight. For the general case with multiple RXs, based on SDR we obtain two approximate solutions by applying time-sharing and randomization, respectively. Moreover, for practical implementation of magnetic beamforming, we propose a novel signal processing method to estimate the magnetic MIMO channel due to the mutual inductances between TXs and RXs. Numerical results show that our proposed magnetic channel estimation and adaptive beamforming schemes are practically effective, and can significantly improve the power transfer efficiency and multi-user performance trade-off in MIMO MRC-WPT systems.

Heat transfer through the flat surface of Rutherford superconducting cable samples with novel pattern of electrical insulation immersed in He II

NASA Astrophysics Data System (ADS)

Strychalski, M.; Chorowski, M.; Polinski, J.

2014-05-01

Future accelerator magnets will be exposed to heat loads that exceed even by an order of magnitude presently observed heat fluxes transferred to superconducting magnet coils. To avoid the resistive transition of the superconducting cables, the efficiency of heat transfer between the magnet structure and the helium must be significantly increased. This can be achieved through the use of novel concepts of the cable’s electrical insulation wrapping, characterized by an enhanced permeability to helium while retaining sufficient electrical resistivity. This paper presents measurement results of the heat transfer through Rutherford NbTi cable samples immersed in a He II bath and subjected to the pressure loads simulating the counteracting of the Lorentz forces observed in powered magnets. The Rutherford cable samples that were tested used different electrical insulation wrapping schemes, including the scheme that is presently used and the proposed scheme for future LHC magnets. A new porous polyimide cable insulation with enhanced helium permeability was proposed in order to improve the evacuation of heat form the NbTi coil to He II bath. These tests were performed in a dedicated Claudet-type cryostat in pressurized He II at 1.9 K and 1 bar.