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1

Functional magnetic resonance imaging (FMRI) of the human brain  

Microsoft Academic Search

Functional magnetic resonance imaging (FMRI) can provide detailed images of human brain that reflect localized changes in cerebral blood flow and oxygenation induced by sensory, motor, or cognitive tasks. This review presents methods for gradient-recalled echo-planar functional magnetic resonance imaging (FMRI). Also included is a discussion of the hypothesized basis of FMRI, imaging hardware, a unique visual stimulation apparatus, image

Edgar A. DeYoe; Peter Bandettini; Jay Neitz; David Miller; Paula Winans

1994-01-01

2

The physics of functional magnetic resonance imaging (fMRI)  

NASA Astrophysics Data System (ADS)

Functional magnetic resonance imaging (fMRI) is a methodology for detecting dynamic patterns of activity in the working human brain. Although the initial discoveries that led to fMRI are only about 20 years old, this new field has revolutionized the study of brain function. The ability to detect changes in brain activity has a biophysical basis in the magnetic properties of deoxyhemoglobin, and a physiological basis in the way blood flow increases more than oxygen metabolism when local neural activity increases. These effects translate to a subtle increase in the local magnetic resonance signal, the blood oxygenation level dependent (BOLD) effect, when neural activity increases. With current techniques, this pattern of activation can be measured with resolution approaching 1 mm3 spatially and 1 s temporally. This review focuses on the physical basis of the BOLD effect, the imaging methods used to measure it, the possible origins of the physiological effects that produce a mismatch of blood flow and oxygen metabolism during neural activation, and the mathematical models that have been developed to understand the measured signals. An overarching theme is the growing field of quantitative fMRI, in which other MRI methods are combined with BOLD methods and analyzed within a theoretical modeling framework to derive quantitative estimates of oxygen metabolism and other physiological variables. That goal is the current challenge for fMRI: to move fMRI from a mapping tool to a quantitative probe of brain physiology.

Buxton, Richard B.

2013-09-01

3

Pediatric Functional Magnetic Resonance Imaging (fMRI): Issues and Applications  

Microsoft Academic Search

Functional magnetic resonance imaging (fMRI) represents a useful tool for studying brain functions and the neural basis of cognition in healthy children and in those in disease states. Functional magnetic resonance imaging is a relatively new use of existing magnetic resonance imaging technology that allows scientists and practitioners to observe the brain at work. It is based on the observation

Elizabeth Stief OShaughnessy; Madison M. Berl; Erin N. Moore; William D. Gaillard

2008-01-01

4

Audience response analysis using simultaneous electroencephalography (EEG) and functional magnetic resonance imaging (fMRI)  

US Patent & Trademark Office Database

Neuro-response data including Electroencephalography (EEG), Functional Magnetic Resonance Imaging (fMRI) is filtered, analyzed, and combined to evaluate the effectiveness of stimulus materials such as marketing and entertainment materials. A data collection mechanism including multiple modalities such as, Electroencephalography (EEG), Functional Magnetic Resonance Imaging (fMRI), Electrooculography (EOG), Galvanic Skin Response (GSR), etc., collects response data from subjects exposed to marketing and entertainment stimuli. A data cleanser mechanism filters the response data and removes cross-modality interference.

2013-07-23

5

Neural Signal Changes Associated with Cardiac and Respiratory Measures vs Boxcar Analysis in Functional Magnetic Resonance Imaging (fMRI).  

National Technical Information Service (NTIS)

Functional magnetic resonance imaging (FMRI) was used to measure signal changes in the brain during a respiratory challenge that elevated blood pressure. Subjects were scanned during a baseline period and during a Valsalva maneuver. Results were compared ...

K. E. Macey P. M. Macey M. A. Woo L. A. Henderson R. C. Frysinger

2001-01-01

6

Interhemispheric neuroplasticity following limb deafferentation detected by resting-state functional connectivity magnetic resonance imaging (fcMRI) and functional magnetic resonance imaging (fMRI)  

PubMed Central

Functional connectivity magnetic resonance imaging (fcMRI) studies in rat brain show brain reorganization following peripheral nerve injury. Subacute neuroplasticity was observed two weeks following transection of the four major nerves of the brachial plexus. Direct functional magnetic resonance imaging (fMRI) stimulation of the intact radial nerve reveals an activation pattern in the forelimb regions of the sensory and motor cortices that is significantly different from that observed in normal rats. Results of this fMRI experiment were used to determine seed voxel regions for fcMRI analysis. Intrahemispheric connectivities in the sensorimotor forelimb representations in both hemispheres are largely unaffected by deafferentation, whereas substantial disruption of interhemispheric sensorimotor cortical connectivity occurs. In addition, significant intra- and interhemispheric changes in connectivities of thalamic nuclei were found. These are the central findings of the study. They could not have been obtained from fMRI studies alone—both fMRI and fcMRI are needed. The combination provides a general marker for brain plasticity. The rat visual system was studied in the same animals as a control. No neuroplastic changes in connectivities were found in the primary visual cortex upon forelimb deafferentation. Differences were noted in regions responsible for processing multisensory visual-motor information. This incidental discovery is considered to be significant. It may provide insight into phantom limb epiphenomena.

Pawela, Christopher P.; Biswal, Bharat B.; Hudetz, Anthony G.; Li, Rupeng; Jones, Seth R.; Cho, Younghoon R.; Matloub, Hani S.; Hyde, James S.

2009-01-01

7

Improved assessment of significant activation in functional magnetic resonance imaging (fMRI): use of a cluster-size threshold.  

PubMed

The typical functional magnetic resonance (fMRI) study presents a formidable problem of multiple statistical comparisons (i.e., > 10,000 in a 128 x 128 image). To protect against false positives, investigators have typically relied on decreasing the per pixel false positive probability. This approach incurs an inevitable loss of power to detect statistically significant activity. An alternative approach, which relies on the assumption that areas of true neural activity will tend to stimulate signal changes over contiguous pixels, is presented. If one knows the probability distribution of such cluster sizes as a function of per pixel false positive probability, one can use cluster-size thresholds independently to reject false positives. Both Monte Carlo simulations and fMRI studies of human subjects have been used to verify that this approach can improve statistical power by as much as fivefold over techniques that rely solely on adjusting per pixel false positive probabilities. PMID:7596267

Forman, S D; Cohen, J D; Fitzgerald, M; Eddy, W F; Mintun, M A; Noll, D C

1995-05-01

8

High-field 4.23 tesla magnetic resonance imaging: initial experience in turbo-inversion recovery imaging and fMRI physics  

Microsoft Academic Search

High-field magnetic resonance imaging (MRI) offers functional, biochemical and physiological information. High field is advantageous for both fMRI signal generated from deoxyhemoglobin and blood oxygen, and intracellular sodium by inversion recovery MRI imaging. High field MRI was used to image human and primates for sodium MRI imaging.

Rakesh Sharma

2004-01-01

9

The Processing of First and Second-Order Motion in Human Visual Cortex Assessed by Functional Magnetic Resonance Imaging (fMRI)  

Microsoft Academic Search

We have examined the activity levels produced in various areas of the human occipital cortex in response to various motion stimuli using functional magnetic resonance imaging (fMRI) methods. In addition to standard luminance-defined (first-order) motion, three types of second-order motion were used. The areas examined were the motion area V5 (MT) and the following areas that were delineated using retinotopic

Andrew T. Smith; Mark W. Greenlee; Krish D. Singh; Falk M. Kraemer; Jurgen Hennig

1998-01-01

10

Discrete functional contributions of cerebral cortical foci in voluntary swallowing: a functional magnetic resonance imaging (fMRI) “Go, No-Go” study  

Microsoft Academic Search

Brain-imaging studies have shown that visually-cued, voluntary swallowing activates a distributed network of cortical regions including the precentral and postcentral gyri, anterior cingulate cortex (ACC), insula, frontoparietal operculum, cuneus and precuneus. To elucidate the functional contributions of these discrete activation foci for swallowing, a “Go, No-Go” functional magnetic resonance imaging (fMRI) paradigm was designed. Brain activation associated with visually-cued swallowing

Jillian A. Toogood; Amy M. Barr; Todd K. Stevens; Joseph S. Gati; Ravi S. Menon; Ruth E. Martin

2005-01-01

11

A new method to record and control for 2D-movement kinematics during functional magnetic resonance imaging (fMRI).  

PubMed

The recording of movement kinematics during functional magnetic resonance imaging (fMRI) experiments is complicated due to technical constraints of the imaging environment. Nevertheless, to study the functions of brain areas related to motor control, reliable and accurate records of movement trajectories and speed profiles are needed. We present a method designed to record and characterize the kinematic properties of drawing- and handwriting-like forearm movements during fMRI studies by recording pen stroke trajectories. The recording system consists of a translucent plastic board, a plastic pen containing fiber optics and a halogen light power source, a CCD camera, a video monitor and a PC with a video grabber card. Control experiments using a commercially available digitizer tablet have demonstrated the reliability of the data recorded during fMRI. Since the movement tracking signal is purely optical, there is no interaction with the MR (echoplanar) images. Thus, the method allows to obtain movement records with high spatial and temporal resolution which are suitable for the kinematic analysis of hand movements in fMRI studies. PMID:18706539

Hauptmann, Bjoern; Sosnik, Ronen; Smikt, Oded; Okon, Eli; Manor, David; Kushnir, Tammar; Flash, Tamar; Karni, Avi

2009-03-01

12

Relation between functional magnetic resonance imaging (fMRI) and single neuron, local field potential (LFP) and electrocorticography (ECoG) activity in human cortex  

PubMed Central

The relation between changes in the blood oxygen dependent metabolic changes imaged by functional magnetic resonance imaging (fMRI) and neural events directly recorded from human cortex from single neurons, local field potentials (LFPs) and electrocorticogram (ECoG) is critically reviewed, based on the published literature including findings from the authors' laboratories. All these data are from special populations, usually patients with medically refractory epilepsy, as this provides the major opportunity for direct cortical neuronal recording in humans. For LFP and ECoG changes are often sought in different frequency bands, for single neurons in frequency of action potentials. Most fMRI studies address issues of functional localization. The relation of those findings to localized changes in neuronal recordings in humans has been established in several ways. Only a few studies have directly compared changes in activity from the same sites in the same individual, using the same behavioral measure. More often the comparison has been between fMRI and electrophysiologic changes in populations recorded from the same functional anatomic system as defined by lesion effects; in a few studies those systems have been defined by fMRI changes such as the “default” network. The fMRI-electrophysiologic relationships have been evaluated empirically by colocalization of significant changes, and by quantitative analyses, often multiple linear regression. There is some evidence that the fMRI-electrophysiology relationships differ in different cortical areas, particularly primary motor and sensory cortices compared to association cortex, but also within areas of association cortex. Although crucial for interpretation of fMRI changes as reflecting neural activity in human cortex, controversy remains as to these relationships. Supported by: Dutch Technology Foundation and University of Utrecht Grant UGT7685, ERC-Advanced grant 320708 (NR) and NIH grant NS065186 (JO)

Ojemann, George A.; Ramsey, Nick F.; Ojemann, Jeffrey

2013-01-01

13

Iterative approach of dual regression with a sparse prior enhances the performance of independent component analysis for group functional magnetic resonance imaging (fMRI) data.  

PubMed

This study proposes an iterative dual-regression (DR) approach with sparse prior regularization to better estimate an individual's neuronal activation using the results of an independent component analysis (ICA) method applied to a temporally concatenated group of functional magnetic resonance imaging (fMRI) data (i.e., Tc-GICA method). An ordinary DR approach estimates the spatial patterns (SPs) of neuronal activation and corresponding time courses (TCs) specific to each individual's fMRI data with two steps involving least-squares (LS) solutions. Our proposed approach employs iterative LS solutions to refine both the individual SPs and TCs with an additional a priori assumption of sparseness in the SPs (i.e., minimally overlapping SPs) based on L(1)-norm minimization. To quantitatively evaluate the performance of this approach, semi-artificial fMRI data were created from resting-state fMRI data with the following considerations: (1) an artificially designed spatial layout of neuronal activation patterns with varying overlap sizes across subjects and (2) a BOLD time series (TS) with variable parameters such as onset time, duration, and maximum BOLD levels. To systematically control the spatial layout variability of neuronal activation patterns across the "subjects" (n=12), the degree of spatial overlap across all subjects was varied from a minimum of 1 voxel (i.e., 0.5-voxel cubic radius) to a maximum of 81 voxels (i.e., 2.5-voxel radius) across the task-related SPs with a size of 100 voxels for both the block-based and event-related task paradigms. In addition, several levels of maximum percentage BOLD intensity (i.e., 0.5, 1.0, 2.0, and 3.0%) were used for each degree of spatial overlap size. From the results, the estimated individual SPs of neuronal activation obtained from the proposed iterative DR approach with a sparse prior showed an enhanced true positive rate and reduced false positive rate compared to the ordinary DR approach. The estimated TCs of the task-related SPs from our proposed approach showed greater temporal correlation coefficients with a reference hemodynamic response function than those of the ordinary DR approach. Moreover, the efficacy of the proposed DR approach was also successfully demonstrated by the results of real fMRI data acquired from left-/right-hand clenching tasks in both block-based and event-related task paradigms. PMID:22939873

Kim, Yong-Hwan; Kim, Junghoe; Lee, Jong-Hwan

2012-12-01

14

Functional magnetic resonance imaging (fMRI) changes and saliva production associated with acupuncture at LI-2 acupuncture point: a randomized controlled study  

PubMed Central

Background Clinical studies suggest that acupuncture can stimulate saliva production and reduce xerostomia (dry mouth). We were interested in exploring the neuronal substrates involved in such responses. Methods In a randomized, sham acupuncture controlled, subject blinded trial, twenty healthy volunteers received true and sham acupuncture in random order. Cortical regions that were activated or deactivated during the interventions were evaluated by functional magnetic resonance imaging (fMRI). Saliva production was also measured. Results Unilateral manual acupuncture stimulation at LI-2, a point commonly used in clinical practice to treat xerostomia, was associated with bilateral activation of the insula and adjacent operculum. Sham acupuncture at an adjacent site induced neither activation nor deactivation. True acupuncture induced more saliva production than sham acupuncture. Conclusion Acupuncture at LI-2 was associated with neuronal activations absent during sham acupuncture stimulation. Neuroimaging signal changes appear correlated to saliva production.

Deng, Gary; Hou, Bob L; Holodny, Andrei I; Cassileth, Barrie R

2008-01-01

15

Functional Magnetic Resonance Imaging  

ERIC Educational Resources Information Center

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…

Voos, Avery; Pelphrey, Kevin

2013-01-01

16

Functional magnetic resonance imaging in pediatrics  

PubMed Central

Functional magnetic resonance imaging (fMRI) allows non-invasive assessment of human brain function in vivo by detecting blood flow differences. In this review, we want to illustrate the background and different aspects of performing functional magnetic resonance imaging (fMRI) in the pediatric age group. An overview over current and future applications of fMRI will be given, and typical problems, pitfalls, and benefits of doing fMRI in a pediatric age group are discussed. We conclude that fMRI can successfully be applied in children and holds great promise for both research and clinical purposes.

Wilke, Marko; Holland, Scott K.; Myseros, John S.; Schmithorst, Vincent J.; Ball, William S.

2005-01-01

17

Improving the spatial accuracy in functional magnetic resonance imaging (fMRI) based on the blood oxygenation level dependent (BOLD) effect: benefits from parallel imaging and a 32-channel head array coil at 1.5 Tesla.  

PubMed

Geometric distortions and low spatial resolution are current limitations in functional magnetic resonance imaging (fMRI). The aim of this study was to evaluate if application of parallel imaging or significant reduction of voxel size in combination with a new 32-channel head array coil can reduce those drawbacks at 1.5 T for a simple hand motor task. Therefore, maximum t-values (tmax) in different regions of activation, time-dependent signal-to-noise ratios (SNR(t)) as well as distortions within the precentral gyrus were evaluated. Comparing fMRI with and without parallel imaging in 17 healthy subjects revealed significantly reduced geometric distortions in anterior-posterior direction. Using parallel imaging, tmax only showed a mild reduction (7-11%) although SNR(t) was significantly diminished (25%). In 7 healthy subjects high-resolution (2 x 2 x 2 mm3) fMRI was compared with standard fMRI (3 x 3 x 3 mm3) in a 32-channel coil and with high-resolution fMRI in a 12-channel coil. The new coil yielded a clear improvement for tmax (21-32%) and SNR(t) (51%) in comparison with the 12-channel coil. Geometric distortions were smaller due to the smaller voxel size. Therefore, the reduction in tmax (8-16%) and SNR(t) (52%) in the high-resolution experiment seems to be tolerable with this coil. In conclusion, parallel imaging is an alternative to reduce geometric distortions in fMRI at 1.5 T. Using a 32-channel coil, reduction of the voxel size might be the preferable way to improve spatial accuracy. PMID:19713602

Fellner, C; Doenitz, C; Finkenzeller, T; Jung, E M; Rennert, J; Schlaier, J

2009-01-01

18

Mapping the central effects of chronic ketamine administration in an adolescent primate model by functional magnetic resonance imaging (fMRI).  

PubMed

Ketamine, a noncompetitive N-methyl-D-aspartic acid (NMDA) receptor antagonist, is capable of triggering excessive glutamate release and subsequent cortical excitation which may induce psychosis-like behavior and cognitive anomalies. Growing evidence suggests that acute ketamine administration can provoke dose-dependent positive and negative schizophrenia-like symptoms. While the acute effects of ketamine are primarily linked to aberrant activation of the prefrontal cortex and limbic structures with elevated glutamate and dopamine levels, the long-term effects of ketamine on brain functions and neurochemical homeostasis remain incompletely understood. In recent years, reports of ketamine abuse, especially among young individuals, have surged rapidly, with profound socioeconomic and health impacts. We herein investigated the chronic effects of ketamine on brain function integrity in an animal model of adolescent cynomolgus monkeys (Macaca fascicularis) by functional magnetic resonance imaging (fMRI). Immunohistochemical study was also conducted to examine neurochemical changes in the dopaminergic and cholinergic systems in the prefrontal cortex following chronic ketamine administration. Our results suggest that repeated exposure to ketamine markedly reduced neural activities in the ventral tegmental area, substantia nigra in midbrain, posterior cingulate cortex, and visual cortex in ketamine-challenged monkeys. In contrast, hyperfunction was observed in the striatum and entorhinal cortex. In terms of neurochemical and locomotive changes, chronically ketamine-challenged animals were found to have reduced tyrosine hydroxylase (TH) but not choline acetyltransferase (ChAT) levels in the prefrontal cortex, which was accompanied by diminished total movement compared with the controls. Importantly, the mesolimbic, mesocortical and entorhinal-striatal systems were found to be functionally vulnerable to ketamine's chronic effects. Dysfunctions of these neural circuits have been implicated in several neuropsychiatric disorders including depression, schizophrenia and attention deficit disorder (ADD). Collectively, our results support the proposition that repeated ketamine exposure can be exploited as a pharmacological paradigm for studying the central effects of ketamine relevant to neuropsychiatric disorders. PMID:22178134

Yu, Hongluan; Li, Qi; Wang, Defeng; Shi, Lin; Lu, Gang; Sun, Lin; Wang, Li; Zhu, Wei; Mak, Ying T; Wong, Naikei; Wang, Yixiang; Pan, Fang; Yew, David T

2012-01-01

19

Magnetic resonance imaging and magnetic resonance spectroscopy assessment of brain function in experimental animals and man  

Microsoft Academic Search

This paper introduces the basic principles and techniques of functional magnetic resonance imaging (fMRI) and spectroscopy (MRS). Examples are given of single event human fMRI studies on control subjects, and a graded activation protocol applied to Parkinsonian patients. Possibilities are discussed for using fMRI techniques to study the neural substrate of various pharmacological agents, including drugs of abuse.The application of

Peter G. Morris

1999-01-01

20

Voxel magnetic field disturbance from remote vasculature in BOLD fMRI  

Microsoft Academic Search

The mechanism of blood oxygenation-level dependent (BOLD) functional magnetic resonance imaging (fMRI) lies in the detection of blood-induced magnetic field disturbance during brain activity. A magnetic dipole induces a magnetic field in 3D space, which is represented by a 3D kernel that shows orientation-dependent decay in space (with a radial distant decay factor of 1\\/r3), bipolar values, and revolution symmetry.

Zikuan Chen; Zeyuan Chen; Vince Calhoun

2011-01-01

21

Evaluation of preprocessing steps to compensate for magnetic field distortions due to body movements in BOLD fMRI  

Microsoft Academic Search

Blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) is currently the dominant technique for non-invasive investigation of brain functions. One of the challenges with BOLD fMRI, particularly at high fields, is compensation for the effects of spatiotemporally varying magnetic field inhomogeneities (?B0) caused by normal subject respiration and, in some studies, movement of the subject during the scan to

Robert L. Barry; Joy M. Williams; L. Martyn Klassen; Jason P. Gallivan; Jody C. Culham; Ravi S. Menon

2010-01-01

22

Functional magnetic resonance imaging (fMRI) and effects of L-dopa on visual function in normal and amblyopic subjects.  

PubMed Central

PURPOSE: To evaluate the effects of a single dose of levodopa on visual cortex, based on functional MRI (fMRI), and on visual function, based on psychophysical tests, in amblyopic and normal subjects. METHOD: A prospective, randomized trial of a single dose of levodopa (2 mg/kg body weight) was undertaken in an institutional setting in nine normal and six amblyopic subjects, who were assessed at baseline and 90 minutes after levodopa ingestion. fMRI of occipital visual cortex was undertaken with a 1.5T GE MRI scanner utilizing the BOLD contrast technique. fMRI stimuli were two gratings (0.5, 2.0 cycles/degree of visual angle) that counterphased at 4 Hz. fMRI parameters for analysis included AREA and LEVEL of activation and a SUMMED score (AREA x LEVEL). Psychophysical tests included visual acuity, contrast sensitivity, stereoacuity, and binocular fusion. RESULTS: At baseline, AREA of activation (P = .05) and SUMMED score (P = .05) were significantly less in the amblyopic compared to the dominant eyes. Psychophysically, visual acuity and contrast sensitivity were significantly worse in the amblyopic eye. Following levodopa ingestion, there was significant decrease in LEVEL of activation in the amblyopic eye, even though visual acuity showed significant improvement (P = .03). Also, amblyopes showed a significant increase and normals showed some decrease in interocular difference in LEVEL of activation (P = .04). CONCLUSION: Unique information was obtained when fMRI was utilized to assess visual cortical function. While levodopa improved visual acuity in the amblyopic eye, it decreased the LEVEL of activation based on fMRI, a counterintuitive finding. The results highlight the value of utilizing fMRI to assess amblyopia and provide new directions for research.

Rogers, Gary L

2003-01-01

23

Functional magnetic resonance imaging: Clinical applications and potential  

Microsoft Academic Search

Demonstration that contrast in magnetic resonance images can be generated based on differences in blood oxygenation has led\\u000a to an explosion of interest in so-called functional magnetic resonance imaging (FMRI). FMRI can be used to map increases in\\u000a blood flow that accompany local synaptic activity in the brain. The technique has proved remarkably sensitive and has been\\u000a used to map

P. M. Matthews; S. Clare; J. Adcock

1999-01-01

24

Pitfalls in fMRI  

Microsoft Academic Search

Several different techniques allow a functional assessment of neuronal activations by magnetic resonance imaging (fMRI). The\\u000a by far most influential fMRI technique is based on a local T2*-sensitive hemodynamic response to neuronal activation, also\\u000a known as the blood oxygenation level dependent or BOLD effect. Consequently, the term ‘fMRI’ is often used synonymously with\\u000a BOLD imaging. Because interpretations of fMRI brain

Sven Haller; Andreas J. Bartsch

2009-01-01

25

Physiological monitoring of small animals during magnetic resonance imaging  

Microsoft Academic Search

Maintaining a stable physiologic state is essential when studying animal models of epilepsy with simultaneous electroencephalograph (EEG) and functional magnetic resonance imaging (fMRI) or EEG and magnetic resonance spectroscopy (MRS). To achieve and maintain such stability in rats in the MRI environment, a minimally invasive but comprehensive system was developed to monitor body temperature, heart rate, blood pressure, blood oxygen

Seyed M. Mirsattari; Frank Bihari; L. Stan Leung; Ravi S. Menon; Zheng Wang; John R. Ives; Robert Bartha

2005-01-01

26

Physiological monitoring of small animals during magnetic resonance imaging  

Microsoft Academic Search

Maintaining a stable physiologic state is essential when studying animal models of epilepsy with simultaneous electroencephalograph (EEG) and functional magnetic resonance imaging (fMRI) or EEG and magnetic resonance spectroscopy (MRS). To achieve and maintain such stability in rats in the MRI environment, a minimally invasive but comprehensive system was developed to monitor body temperature, heart rate, blood pressure, blood oxygen

Seyed M. Mirsattari; Frank Bihari; L. Stan Leung; Ravi S. Menon; Zheng Wang; John R. Ives; Robert Bartha

27

Transcranial magnetic stimulation assisted by neuronavigation of magnetic resonance images  

NASA Astrophysics Data System (ADS)

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.

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

2012-10-01

28

Pediatric magnetic resonance imaging  

SciTech Connect

This book defines the current clinical potential of magnetic resonance imaging and focuses on direct clinical work with pediatric patients. A section dealing with the physics of magnetic resonance imaging provides an introduction to enable clinicians to utilize the machine and interpret the images. Magnetic resonance imaging is presented as an appropriate imaging modality for pediatric patients utilizing no radiation.

Cohen, M.D.

1986-01-01

29

Functional magnetic resonance imaging of awake monkeys: some approaches for improving imaging quality  

Microsoft Academic Search

Functional magnetic resonance imaging (fMRI) at high magnetic field strength can suffer from serious degradation of image quality because of motion and physiological noise, as well as spatial distortions and signal losses due to susceptibility effects. Overcoming such limitations is essential for sensitive detection and reliable interpretation of fMRI data. These issues are particularly problematic in studies of awake animals.

Gang Chen; Feng Wang; Barbara C. Dillenburger; Robert M. Friedman; Li M. Chen; John C. Gore; Malcolm J. Avison; Anna W. Roe

30

Human brain somatic representation: a functional magnetic resonance mapping  

NASA Astrophysics Data System (ADS)

Central nervous system studies of injury and plasticity for the reorganization in the phantom limb sensation area presented. In particular functional magnetic resonance imaging (fMRI) mapping of the somatic and motor cortex of amputee patients, in the case of referred sensations. Using fMRI we can show the correlation between structure and functional field and study the reorganization due to plasticity in the brain. .

Romero-Romo, Juan; Rojas, Rafael; Salgado, Perla; Sánchez-Cortázar, Julián; Vazquez-Vela, Arturo; Barrios, Fernando A.

2001-10-01

31

Functional magnetic resonance imaging of the human brain  

Microsoft Academic Search

The current technical and methodological status of functional magnetic resonance imaging (fMRI) is reviewed. The mechanisms underlying the effects of deoxyhemoglobin concentration and cerebral blood flow changes are discussed, and methods for monitoring these changes are described and compared. Methods for post-processing fMRI data are outlined. Potential problems and solutions related to vessels and motion are discussed in detail.

Seong-Gi Kim; Kamil Ugurbil

1997-01-01

32

Functional magnetic resonance imaging studies of language  

Microsoft Academic Search

Functional neuroimaging of language builds on almost 150 years of study in neurology, psychology, linguistics, anatomy, and\\u000a physiology. In recent years, there has been an explosion of research using functional imaging technology, especially positron\\u000a emission tomography (PET) and functional magnetic resonance imaging (fMRI), to understand the relationship between brain mechanisms\\u000a and language processing. These methods combine highresolution anatomic images with

Steven L. Small; Martha W. Burton

2002-01-01

33

Functional Magnetic Resonance Imaging - Implications for Detection of Schizophrenia  

PubMed Central

Functional magnetic resonance imaging (fMRI) is an invaluable non-invasive instrument that has been used to investigate physiological disturbances that lead to manifest psychiatric illnesses. It is hoped that efficient application of fMRI can be utilised to characterise and diagnose mental illnesses such as schizophrenia. Although there are various fMRI research studies presenting very promising diagnosis results for schizophrenia, we believe that there is much to be done to develop effective diagnostic tools for clinical purposes. We present specific examples based mostly on our past and recent work together with various examples from the recent literature. We discuss where we currently stand in the efforts of fMRI being used for diagnosis of schizophrenia, examine common possible biases and offer some solutions with the hope that fMRI can be more efficiently used in diagnostic research.

Demirci, Oguz; Calhoun, Vince D

2010-01-01

34

Acoustic noise during functional magnetic resonance imaginga)  

PubMed Central

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

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

2007-01-01

35

Brain activation during manipulation of the myoelectric prosthetic hand: a functional magnetic resonance imaging study  

Microsoft Academic Search

Neuroimaging data, particularly functional magnetic resonance imaging (fMRI) findings, have not been reported in users of the myoelectric or electromyographic (EMG) prosthetic hand. We developed a virtual EMG prosthetic hand system to eliminate mutual signal noise interference between fMRI imaging and the EMG prosthesis. We used fMRI to localize activation in the human brain during manipulation of the virtual EMG

Masaharu Maruishi; Yoshiyuki Tanaka; Hiroyuki Muranaka; Toshio Tsuji; Yoshiaki Ozawa; Satoshi Imaizumi; Makoto Miyatani; Junichiro Kawahara

2004-01-01

36

Linear Systems Analysis of Functional Magnetic Resonance Imaging in Human V1  

Microsoft Academic Search

The linear transform model of functional magnetic resonance imaging (fMRI) hypothesizes that fMRI responses are propor- tional to local average neural activity averaged over a period of time. This work reports results from three empirical tests that support this hypothesis. First, fMRI responses in human pri- mary visual cortex (V1) depend separably on stimulus timing and stimulus contrast. Second, responses

Geoffrey M. Boynton; Stephen A. Engel; Gary H. Glover; David J. Heeger

1996-01-01

37

Operant-contingency-based preparation of children for functional magnetic resonance imaging.  

PubMed

Functional magnetic resonance imaging (fMRI) is used to study brain function during behavioral tasks. The participation of pediatric subjects is problematic because reliable task performance and control of head movement are simultaneously required. Differential reinforcement decreased head motion and improved vigilance task performance in 4 children (2 with behavioral disorders) undergoing simulated fMRI scans. Results show that behavior analysis techniques can improve child cooperation during fMRI procedures. PMID:12102139

Slifer, Keith J; Koontz, Kristine L; Cataldo, Michael F

2002-01-01

38

Operant-contingency-based preparation of children for functional magnetic resonance imaging.  

PubMed Central

Functional magnetic resonance imaging (fMRI) is used to study brain function during behavioral tasks. The participation of pediatric subjects is problematic because reliable task performance and control of head movement are simultaneously required. Differential reinforcement decreased head motion and improved vigilance task performance in 4 children (2 with behavioral disorders) undergoing simulated fMRI scans. Results show that behavior analysis techniques can improve child cooperation during fMRI procedures.

Slifer, Keith J; Koontz, Kristine L; Cataldo, Michael F

2002-01-01

39

Neuropsychiatric dynamics: the study of mental illness using functional magnetic resonance imaging  

Microsoft Academic Search

Functional magnetic resonance imaging (fMRI) is poised to make significant contributions to the study of neuropsychiatric illnesses. Whatever neural pathology attends such illnesses has proven subtle at best. By identifying predictable, regionally specific deficits in brain function, fMRI can suggest brain regions for detailed cellular analyses, provide valuable in vivo data regarding effective connectivity, provide a means to model the

Joseph H. Callicott; Daniel R. Weinberger

1999-01-01

40

Human Brain Language Areas Identified by Functional Magnetic Resonance Imaging  

Microsoft Academic Search

Functional magnetic resonance imaging (FMRI) was used to identify candidate language processing areas in the intact hu- man brain. Language was defined broadly to include both phonological and lexical-semantic functions and to exclude sensory, motor, and general executive functions. The language activation task required phonetic and semantic analysis of aurally presented words and was compared with a control task involving

Jeffrey R. Binder; Julie A. Frost; Thomas A. Hammeke; Robert W. Cox; Stephen M. Rao; Thomas Prieto

1997-01-01

41

Magnetic Resonance Imaging Outcomes From a Comprehensive Magnetic Resonance Study of Children With Fetal Alcohol Spectrum Disorders  

Microsoft Academic Search

Background: Magnetic resonance (MR) technology offers noninvasive methods for in vivo assessment of neuroabnormalities. Methods: A comprehensive neuropsychological ? psychiatric battery, coupled with MR imaging, (MRI), MR spectroscopy (MRS), and functional MRI (fMRI) assessments, were administered to children with fetal alcohol spectrum disorders (FASD) to determine if global and ? or focal abnor- malities could be identified, and distinguish diagnostic

Susan J. Astley; Elizabeth H. Aylward; Heather Carmichael Olson; Kimberly Kerns; Allison Brooks; Truman E. Coggins; Julian Davies; Susan Dorn; Beth Gendler; Tracy Jirikowic; Paul Kraegel; Kenneth Maravilla; Todd Richards

2009-01-01

42

Magnetic Resonance Imaging (MRI).  

National Technical Information Service (NTIS)

Magnetic resonance imaging (MRI) is a method of graphically representing the distribution of water and other hydrogen-rich molecules in the human body. Imaging parameters are complex. Although MR images may demonstrate anatomy as do conventional radiograp...

E. Feigenbaum

1985-01-01

43

Magnetic Resonance Facility.  

National Technical Information Service (NTIS)

Magnetic Resonance Facility capabilities and applications at NREL's National Bioenergy Center. Liquid and solid-state analysis capability for a variety of biomass, photovoltaic, and materials characterization applications across NREL. NREL scientists anal...

2012-01-01

44

Magnetic resonance imaging  

SciTech Connect

This book contains the following four major sections: physics and chemistry, relaxation/relaxometry, instrumentation, research areas. The authors discuss instrumentation and technical approaches in magnetic resonance (MR) imaging.

Partain, C.L.; Price, R.R.; Patton, J.A.; Kulkarni, M.V.; James, A.E.

1988-01-01

45

HIV and Aging Independently Affect Brain Function as Measured by Functional Magnetic Resonance Imaging  

PubMed Central

We investigated interactions between HIV and aging on brain function demands using functional magnetic resonance imaging (fMRI). A multiple regression model studied the association and interaction between fMRI measures, HIV serostatus, and age for 26 HIV infected (HIV+) and 25 seronegative (HIV?) subjects. While HIV serostatus and age independently affected fMRI measures, no interaction occurred. Functional brain demands in HIV+ subjects were equivalent to ~15–20 year older HIV? subjects. Frailty parallels between HIV and aging could result from continued immunological challenges depleting resources and triggering increased metabolic demands. fMRI could be a non-invasive biomarker to assess HIV in the brain.

Ances, Beau M.; Vaida, Florin; Yeh, Melinda J.; Liang, Christine L.; Buxton, Richard B.; Letendre, Scott; McCutchan, J. Allen; Ellis, Ronald J.

2009-01-01

46

Functional Magnetic Resonance Imaging for Language Mapping in Temporal Lobe Epilepsy  

PubMed Central

Functional magnetic resonance imaging (fMRI) is a noninvasive technique that is increasingly used to understand the cerebral cortical networks and organizations. In this paper, we describe the role of fMRI for mapping language networks in the presurgical workup of patients with medically intractable temporal lobe epilepsy (TLE). Studies comparing fMRI with the intracarotid sodium amobarbital (Wada) test and fMRI with intraoperative cortical stimulation mapping for language lateralization and/or localization in medically intractable TLE are discussed.

Wang, An; Peters, Terry M.; de Ribaupierre, Sandrine; Mirsattari, Seyed M.

2012-01-01

47

Magnetic Resonance Imaging of the Retina  

PubMed Central

This paper reviews recent developments in high-resolution magnetic resonance imaging (MRI) and its application to image anatomy, physiology, and function in the retina of animals. It describes technical issues and solutions in performing retinal MRI, anatomical MRI, blood oxygenation level-dependent functional MRI (fMRI), and blood-flow MRI both of normal retinas and of retinal degeneration. MRI offers unique advantages over existing retinal imaging techniques, including the ability to image multiple layers without depth limitation and to provide multiple clinically relevant data in a single setting. Retinal MRI has the potential to complement existing retinal imaging techniques.

Duong, Timothy Q.; Muir, Eric R.

2010-01-01

48

Noninvasive assessment of the injured human spinal cord by means of functional magnetic resonance imaging  

Microsoft Academic Search

Study design: A magnetic resonance imaging technique that enables indirect detection of neuronal activity has been developed for the spinal cord. In the present study, this method, spinal functional magnetic resonance imaging (fMRI), is applied to the first study of the injured spinal cord, with the goal of better clinical assessment of the entire cord.Objectives: The objectives of this project

P W Stroman; J Kornelsen; A Bergman; V Krause; K Ethans; K L Malisza; B Tomanek

2004-01-01

49

Interleaved transcranial magnetic stimulation and fMRI suggests that lamotrigine and valproic acid have different effects on corticolimbic activity  

Microsoft Academic Search

Rationale  Combined transcranial magnetic stimulation (TMS) and functional magnetic resonance imaging (fMRI) can be used to study anticonvulsant\\u000a drugs. A previous study showed that lamotrigine (LTG) inhibited brain activation induced when TMS was applied over motor cortex,\\u000a whereas it increased activation induced by TMS applied over prefrontal cortex.\\u000a \\u000a \\u000a \\u000a \\u000a Objectives  The present double-blind, placebo-controlled, crossover study in 30 healthy subjects again combined TMS

Xingbao Li; Raffaella Ricci; Charles H. Large; Berry Anderson; Ziad Nahas; Daryl E. Bohning; Mark S. George

2010-01-01

50

In vivo mapping of functional domains and axonal connectivity in cat visual cortex using magnetic resonance imaging  

Microsoft Academic Search

Noninvasive cognitive neuroimaging studies based on functional magnetic resonance imaging (fMRI) are of ever-increasing importance for basic and clinical neurosciences. The explanatory power of fMRI could be greatly expanded, however, if the pattern of the neuronal circuitry underlying functional activation could be made visible in an equally noninvasive manner. In this study, blood oxygenation level-dependent (BOLD)-based fMRI and diffusion tensor

Dae-Shik Kim; Mina Kim; Itamar Ronen; Elia Formisano; Keun-Ho Kim; Kamil Ugurbil; Susumu Mori; Rainer Goebel

2003-01-01

51

Development of a Clinical Functional Magnetic Resonance Imaging Service  

PubMed Central

One of the limitations of anatomical based imaging approaches is its relative inability to identify whether specific brain functions may be compromised by the location of brain lesions or contemplated brain surgeries. For this reason, methods for identifying the regions of eloquent brain that should not be disturbed are absolutely critical to the surgeon. By accurately identifying these regions preoperatively, virtually every pre-surgical decision from the surgical approach, operative goals (biopsy, sub-total vs. gross-total resection), and the potential need for awake craniotomy with intraoperative cortical-mapping is affected. Of the many techniques available to the surgeon, functional magnetic resonance imaging (fMRI) has become the primary modality of choice due to the ability of MRI to serve as a “one-stop shop” for assessing both anatomy and functionality of the brain. Given their prevalence, brain tumors serve as the model pathology for the included discussion; however, a similar case can be made for the use of fMRI in other neurological conditions, most notably epilepsy. The value of fMRI was validated in 2007 when the Centers for Medicare and Medicaid Services (CMS) established three new current procedural terminology (CPT) codes for clinical fMRI based upon its use for pre-therapeutic planning. In this article we will discuss the specific requirements for establishing an fMRI program, including specific software and hardware requirements. In addition, the nature of the fMRI CPT codes will be discussed.

Rigolo, Laura; Stern, Emily; Deaver, Pamela; Golby, Alexandra J.; Mukundan, Srinivasan

2013-01-01

52

Postnatal Changes in Functional Activities of the Pig’s Brain: A Combined Functional Magnetic Resonance Imaging and Immunohistochemical Study  

Microsoft Academic Search

Developmental changes in brain activation after pain stimulation and after passive movement of the hind paw were assessed by functional magnetic resonance imaging (fMRI) in pigs of postnatal ages 2, 4 and 6 months. Response patterns were correlated with histological maturation parameters. At 2 months, fMRI failed to detect brain activation after pain stimulation and revealed weak, but widespread activation

Marong Fang; Dietrich E. Lorke; Jicheng Li; Xiangyang Gong; Jason C. C. Yew; D. T. Yew

2005-01-01

53

Surface-based functional magnetic resonance imaging analysis of partial brain echo planar imaging data at 1.5 T  

Microsoft Academic Search

Surface-based functional magnetic resonance imaging (fMRI) analysis is more sensitive and accurate than volume-based analysis for detecting neural activation. However, these advantages are less important in practical fMRI experiments with commonly used 1.5-T magnetic resonance devices because of the resolution gap between the echo planar imaging data and the cortical surface models. We expected high-resolution segmented partial brain echo planar

Hang Joon Jo; Jong-Min Lee; Jae-Hun Kim; Chi-Hoon Choi; Do-Hyung Kang; Jun Soo Kwon; Sun I. Kim

2009-01-01

54

C-C4-01: Functional Magnetic Resonance Imaging (fMRI) and Diffusion Tensor Imaging (DTI): An Efficient, Non-invasive Alternative to Conventional Pre-surgical Planning in Neurosurgery  

PubMed Central

Background: Neurosurgical intervention often requires pre-surgical or intra-operative planning/mapping techniques that are invasive. For example, prior to temporal lobectomy for intractable epilepsy, patients often undergo a WADA test which involves anesthetizing one hemisphere of the brain at a time to localize memory and language functions. For other neurosurgical cases, electrophysiological intra-operative mapping of the cortex is often used during tumor resections proximal to eloquent cortex, or for localization of specific cortex (i.e., motor) when placing neurostimulators (e.g., for pain management). Less common, but emerging as a noninvasive planning tool, fMRI was designated in three CPT codes for pre-surgical planning purposes. Here, we examined the effectiveness of fMRI and DTI by comparing fMRI data to WADA test results (for epilepsy patients) and electrophysiological recordings (for tumor resections and motor cortex stimulator placement). We also examine the utility of DTI in the context of surgical intervention. Methods: We examined 8 intractable temporal lobe epilepsy (TLE) patients (5 males, 3 females; 6 left TLE, 2 right TLE) who underwent both WADA testing and fMRI language mapping for pre-surgical planning purposes, 1 tumor resection case in which the tumor was near the motor cortex and intra-operative electrophysiological mapping was employed, and 1 motor cortex neurostimulator case in which electrophysiological mapping was performed. All patients were enrolled in IRB-approved studies. FMRI data (language or motor) was obtained prior to surgical intervention and maps were used intra-operatively using BrainLab. Results: In all 8 epilepsy cases, language mapping data was concordant between fMRI and WADA test results. However, fMRI mapping allowed for discrete, focal localization of regions involved in language processes whereas WADA testing only delineated hemispheric dominance. In the tumor resection case, fMRI data was consistent with electrophysiological recordings obtained intra-operatively. Finally, fMRI data was used as the primary localization technique for the motor cortex neurostimulator, and confirmed with electrophysiological recordings. Conclusions: Here, we demonstrate the effectiveness of fMRI as a powerful pre-surgical planning tool that has the potential to replace invasive and costly conventional methods. FMRI maps can easily be uploaded and used intra-operatively during stereotactic neurosurgery for accurate localization of complex brain functions.

Robinson, Jennifer; Kirmani, Batool; Sanghera, Manjit; Phillips-Sabol, Jacqueline; Cruz, Daniel; Wright, Charles; Friehs, Gerhard

2010-01-01

55

Magnetic Resonance Imaging (MRI)  

MedlinePLUS

What is an MRI? MRI stands for Magnetic Resonance Imaging. It is an important tool used in many fields of medicine, and is capable of generating a detailed image of any part of the human body. As an analogy, think about a loaf of bread. You can’t see inside the loaf, so how would you go about finding ...

56

PACS-based functional magnetic resonance imaging.  

PubMed

The picture archiving and communication system (PACS) technology reaches its 10th anniversary. Retrospectively no one could foresee the impact the PACS would have to the health care enterprise, but it is common consent today, that PACS is the key technology crucial to daily clinical image operations and especially to image related basic and clinical research. During the past 10 years the PACS has been matured from a research and developmental stage into commercial products which are provided by all major modality and health care equipment vendors. The PACS, originally implemented in the Radiology Department, needs to grow and has already carried well beyond departmental limits conquering all image relevant areas inside the hospital. During the past 10 years a dramatic development in imaging techniques especially within MRI emerged. Advanced 3D- and 4D-MR imaging techniques result in much more images and more complex data objects than ever before which need to be implemented into the existing PACS. These new imaging techniques require intensive post-processing apart from the imaging modality which need to be integrated into the image workflow and the PACS implementation. Along with these new imaging techniques new clinical applications, e.g. stroke detection, and research applications, e.g. study of heart and brain function, in Neurology and Cardiology require changes to the traditional PACS concept. Therefore inter-disciplinary image distribution will become the high-water mark for the next 10 years in the PACS endeavor. This paper focuses on one new advanced imaging technique, functional magnetic resonance imaging (fMRI), and discusses how fMRI data is defined, what fMRI requires in terms of clinical and research applications and how to implement fMRI in the existing PACS. PMID:12620313

Erberich, Stephan G

2003-01-01

57

Magnetic Resonance Fingerprinting  

PubMed Central

Summary Magnetic Resonance (MR) is an exceptionally powerful and versatile measurement technique. The basic structure of an MR experiment has remained nearly constant for almost 50 years. Here we introduce a novel paradigm, Magnetic Resonance Fingerprinting (MRF) that permits the non-invasive quantification of multiple important properties of a material or tissue simultaneously through a new approach to data acquisition, post-processing and visualization. MRF provides a new mechanism to quantitatively detect and analyze complex changes that can represent physical alterations of a substance or early indicators of disease. MRF can also be used to specifically identify the presence of a target material or tissue, which will increase the sensitivity, specificity, and speed of an MR study, and potentially lead to new diagnostic testing methodologies. When paired with an appropriate pattern recognition algorithm, MRF inherently suppresses measurement errors and thus can improve accuracy compared to previous approaches.

Ma, Dan; Gulani, Vikas; Seiberlich, Nicole; Liu, Kecheng; Sunshine, Jeffrey L.; Duerk, Jeffrey L.; Griswold, Mark A.

2013-01-01

58

Multifractal analysis of Arterial Spin Labeling functional Magnetic Resonance Imaging of the brain  

Microsoft Academic Search

This work proposes a multifractal analysis of the time series derived from ASL fMRI (Arterial Spin Labeling functional Magnetic Resonance Imaging) to detect brain activated regions in response to an unknown stimulus. In contrast to standard model-based activation analysis, no prior knowledge of the expected haemodynamic response has to be assumed for extracting activation patterns from fMRI. The ASL time

Filipe Soares; Inês Sousa; Filipe Janela; João Seabra; Manuela Pereira; Mário M. Freire

2010-01-01

59

Percept-related activity in the human somatosensory system: functional magnetic resonance imaging studies  

Microsoft Academic Search

In this paper, we review blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) studies addressing the neural correlates of touch, thermosensation, pain and the mechanisms of their cognitive modulation in healthy human subjects. There is evidence that fMRI signal changes can be elicited in the parietal cortex by stimulation of single mechanoceptive afferent fibers at suprathreshold intensities for conscious

Carlo Adolfo Porro; Fausta Lui; Patrizia Facchin; Marta Maieron; Patrizia Baraldi

2004-01-01

60

The Visible Brain: Confidentiality and Privacy Implications of Functional Magnetic Resonance Imaging  

Microsoft Academic Search

Functional magnetic resonance imaging (fMRI) has built on a number of technologies, including electroencephalography, magnetoencephalography, positron emission tomography, and single-photon emission computed tomography, to become one of the decade’s most powerful tools for mapping sensory, motor, and cognitive function. Scientists also are using fMRI to study the neural correlates of a range of conditions, characteristics, and social behaviors, including severe

Stacey A. Tovino

2006-01-01

61

Brain Activity during Simulated Deception: An Event-Related Functional Magnetic Resonance Study  

Microsoft Academic Search

TheGuilty Knowledge Test (GKT) has been used extensively to model deception. An association between the brain evoked response potentials and lying on the GKT suggests that deception may be associated with changes in other measures of brain activity such as regional blood flow that could be anatomically localized with event-related functional magnetic resonance imaging (fMRI). Blood oxygenation level-dependent fMRI contrasts

D. D. Langleben; L. Schroeder; J. A. Maldjian; R. C. Gur; S. McDonald; J. D. Ragland; C. P. O'Brien; A. R. Childress

2002-01-01

62

Neuroanatomy of coprolalia in Tourette syndrome using functional magnetic resonance imaging  

Microsoft Academic Search

Objective: To determine the neural substrates of phonic tics in Tourette syndrome (TS) using functional magnetic resonance imaging (fMRI) and compare with a proposed tic-generating network (TGN). Patients: One with TS and one normal control. Methods: fMRI scans were obtained on the TS patient during which numerous unsuppressed phonic tics occurred and, along with the scanner noise, were recorded on

Larry Gates; James R. Clarke; Aidan Stokes; Ray Somorjai; Mark Jarmasz; Robert Vandorpe; Serdar M. Dursun

2004-01-01

63

Exploiting Temporal Information in Functional Magnetic Resonance Imaging Brain Data  

Microsoft Academic Search

Functional Magnetic Resonance Imaging(fMRI) has enabled scientists to look into the active human brain, leading to a flood of new data, thus encouraging the development of new data analysis methods. In this paper, we contribute a comprehensive framework for spatial and tem- poral exploration of fMRI data, and apply it to a challenging case study: separating drug addicted subjects from

Lei Zhang; Dimitris Samaras; Dardo Tomasi; Nelly Alia-klein; Lisa Cottone; Andreana Leskovjan; Nora D. Volkow; Rita Goldstein

2005-01-01

64

Experiences with functional magnetic resonance imaging at 1 tesla  

Microsoft Academic Search

Functional magnetic resonance imaging (fMRI) has been performed on a standard 1 T system using a pulse sequence developed to utilize blood oxygen level dependent (BOLD) contrast and an oV-line analysis routine using correlation techniques. The sequence and the data analysis routine have been validated by reproducing the conventional hand movement paradigm studies reported by numerous other workers. Our work

A P JONES; D G HUGHES; D S BRETTLE; L ROBINSON; J R SYKES; Q AZIZ; S HAMDY; D G THOMPSON; S W G DERBYSHIRE; A C N CHEN

1998-01-01

65

Hemodynamic Assessment of Carotid Stenosis by Functional Magnetic Resonance Imaging  

Microsoft Academic Search

Background: Functional magnetic resonance imaging (fMRI) is a method usually used to identify cortical representations of cerebral functions. Some studies and case reports suggest that stenoses of the brain-supplying arteries influence the BOLD (blood-oxygenation-level-dependent) signal. The objective of this study was to find out whether the BOLD signal differs in the ipsilateral hemisphere of patients with hemodynamically relevant and those

Ulf Jensen; Kathrin Börsch; Robert Stingele; Olav Jansen; Karsten Alfke

2008-01-01

66

Combining transcranial magnetic stimulation and FMRI to examine the default mode network.  

PubMed

The default mode network is a group of brain regions that are active when an individual is not focused on the outside world and the brain is at "wakeful rest." It is thought the default mode network corresponds to self-referential or "internal mentation". It has been hypothesized that, in humans, activity within the default mode network is correlated with certain pathologies (for instance, hyper-activation has been linked to schizophrenia and autism spectrum disorders whilst hypo-activation of the network has been linked to Alzheimer's and other neurodegenerative diseases. As such, noninvasive modulation of this network may represent a potential therapeutic intervention for a number of neurological and psychiatric pathologies linked to abnormal network activation. One possible tool to effect this modulation is Transcranial Magnetic Stimulation: a non-invasive neurostimulatory and neuromodulatory technique that can transiently or lastingly modulate cortical excitability (either increasing or decreasing it) via the application of localized magnetic field pulses. In order to explore the default mode network's propensity towards and tolerance of modulation, we will be combining TMS (to the left inferior parietal lobe) with functional magnetic resonance imaging (fMRI). Through this article, we will examine the protocol and considerations necessary to successfully combine these two neuroscientific tools. PMID:21248684

Halko, Mark A; Eldaief, Mark C; Horvath, Jared C; Pascual-Leone, Alvaro

2010-01-01

67

Nuclear Magnetic Resonance Gyroscope  

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

68

Breast magnetic resonance imaging.  

PubMed

Mammography has long been considered the gold standard for screening breast cancer. Although it reduces the risk of breast cancer mortality by enabling early diagnosis, it does not detect all breast cancers. Numerous breast imaging technologies are emerging as effective adjunctive diagnostic tools when mammography results are negative or inconclusive. Contrast-enhanced magnetic resonance (CE-MR) imaging, in particular, has demonstrated a high sensitivity and has proven to be most effective, especially with patients at high risk for developing breast cancer. This article discusses the clinical applications for breast MR imaging, use of CE-MR for breast cancer detection, and other emerging breast imaging technologies. PMID:22267704

Johnson, Marlene M

2012-01-01

69

Nuclear Magnetic Resonance Gyroscope  

NASA Astrophysics Data System (ADS)

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

Larsen, Michael

2011-06-01

70

Abdominal magnetic resonance elastography.  

PubMed

Magnetic resonance elastography (MRE) is a magnetic resonance imaging-based technique for quantitatively assessing the mechanical properties of tissues based on the propagation of shear waves. Multiple studies have described many potential applications of MRE, from characterizing tumors to detecting diffuse disease processes. Studies have shown that MRE can be successfully implemented to assess abdominal organs. The first clinical application of MRE to be well documented is the detection and characterization of hepatic fibrosis, which systematically increases the stiffness of liver tissue. In this diagnostic role, it offers a safer, less expensive, and potentially more accurate alternative to invasive liver biopsy. Emerging results suggest that measurements of liver and spleen stiffness may provide an indirect way to assess portal hypertension. Preliminary studies have demonstrated that it is possible to use MRE to evaluate the mechanical properties of other abdominal structures, such as the pancreas and kidneys. Steady technical progress in developing practical protocols for applying MRE in the abdomen and the pelvis provides opportunities to explore many other potential applications of this emerging technology. PMID:20010062

Yin, Meng; Chen, Jun; Glaser, Kevin J; Talwalkar, Jayant A; Ehman, Richard L

2009-04-01

71

Magnetic Resonance Imaging and Magnetic Resonance Angiography of Vertebrobasilar Dolichoectasia  

Microsoft Academic Search

We performed magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) in 16 patients with vertebrobasilar dolichoectasia (VBD). Five patients had compressive cranial nerve deficits and 11 patients presented with transient or permanent ischemic deficits related to the vertebrobasilar system. VBD did not present with distinct clinical findings and no clear correlation between basilar artery ectasia and the presence of

Franz T. Aichner; Stephan R. Felber; Günther G. Birbamer; Andrea Posch

1993-01-01

72

CASL fMRI of subcortico-cortical perfusion changes during memory-guided finger sequences  

Microsoft Academic Search

Arterial spin labeling (ASL) perfusion functional magnetic resonance imaging (fMRI) is an attractive alternative to BOLD fMRI. Nevertheless, current ASL fMRI techniques are limited by several factors that hamper more routine applications in humans. One of these factors is restricted brain coverage so that whole-brain ASL fMRI studies have never been reported. The present study tested the ability of a

Gaëtan Garraux; Mark Hallett; S. Lalith Talagala

2005-01-01

73

Localization of the motor hand area using transcranial magnetic stimulation and functional magnetic resonance imaging  

Microsoft Academic Search

Objective: The anatomical location of the motor area of the hand may be revealed using functional magnetic resonance imaging (fMRI). The motor cortex representation of the intrinsic hand muscles consists of a knob-like structure. This is omega- or epsilon-shaped in the axial plane and hook-shaped in the sagittal plane. As this knob lies on the surface of the brain, it

B Boroojerdi; H Foltys; T Krings; U Spetzger; A Thron; R Töpper

1999-01-01

74

Classification of magnetic resonance images  

Microsoft Academic Search

The aim of the paper is to compare classification error of the classifiers applied to magnetic resonance images for each descriptor used for feature extraction. We compared several Support Vector Machine (SVM) techniques, neural networks and k nearest neighbor classifier for classification of Magnetic Resonance Images (MRIs). Different descriptors are applied to provide feature extraction from the images. The dataset

Katarina Trojacanec; Gjorgji Madzarov; Dejan Gjorgjevikj; Suzana Loskovska

2010-01-01

75

Lying about facial recognition: An fMRI study  

Microsoft Academic Search

Novel deception detection techniques have been in creation for centuries. Functional magnetic resonance imaging (fMRI) is a neuroscience technology that non-invasively measures brain activity associated with behavior and cognition. A number of investigators have explored the utilization and efficiency of fMRI in deception detection. In this study, 18 subjects were instructed during an fMRI “line-up” task to either conceal (lie)

S. Bhatt; J. Mbwana; A. Adeyemo; A. Sawyer; A. Hailu; J. VanMeter

2009-01-01

76

MR-Eyetracker: a new method for eye movement recording in functional magnetic resonance imaging  

Microsoft Academic Search

We present a method for recording saccadic and pursuit eye movements in the magnetic resonance tomograph designed for visual\\u000a functional magnetic resonance imaging (fMRI) experiments. To reliably classify brain areas as pursuit or saccade related it\\u000a is important to carefully measure the actual eye movements. For this purpose, infrared light, created outside the scanner\\u000a by light-emitting diodes (LEDs), is guided

H. Kimmig; M. W. Greenlee; F. Huethe; T. Mergner

1999-01-01

77

Neuronal Clustering of Brain fMRI Images  

Microsoft Academic Search

Functional Magnetic Resonance Imaging (fMRI) allows the neuroscientists to observe the human brain in vivo. The current ap- proach consists in statistically validating their hypotheses. Data min- ing techniques provide an opportunity to help them in making up their hypotheses. This paper shows how a neuronal clustering technique can highlight active areas thanks to an appropriate distance between fMRI image

Nicolas Lachiche; Jean Hommet; Jerzy J. Korczak; Agnès Braud

2005-01-01

78

Lying about Facial Recognition: An fMRI Study  

ERIC Educational Resources Information Center

Novel deception detection techniques have been in creation for centuries. Functional magnetic resonance imaging (fMRI) is a neuroscience technology that non-invasively measures brain activity associated with behavior and cognition. A number of investigators have explored the utilization and efficiency of fMRI in deception detection. In this study,…

Bhatt, S.; Mbwana, J.; Adeyemo, A.; Sawyer, A.; Hailu, A.; VanMeter, J.

2009-01-01

79

Comparison of rhyming and word generation with FMRI  

Microsoft Academic Search

Functional magnetic resonance imaging (FMRI) has been successfully used to non-invasively map language function, but has several disadvantages. These include severe motion sensitivity, which limits overt verbal responses in behavioral paradigms, such as word generation. The lack of overt responses prevents behavioral validation, making data interpretation difficult. Our objective was to compare the FMRI activation patterns of a novel silent

Joseph T. Lurito; David A. Kareken; Mark J. Lowe; Shen Hsing A. Chen; Vincent P. Mathews

2000-01-01

80

Functional magnetic resonance imaging: imaging techniques and contrast mechanisms.  

PubMed Central

Functional magnetic resonance imaging (fMRI) is a widely used technique for generating images or maps of human brain activity. The applications of the technique are widespread in cognitive neuroscience and it is hoped they will eventually extend into clinical practice. The activation signal measured with fMRI is predicated on indirectly measuring changes in the concentration of deoxyhaemoglobin which arise from an increase in blood oxygenation in the vicinity of neuronal firing. The exact mechanisms of this blood oxygenation level dependent (BOLD) contrast are highly complex. The signal measured is dependent on both the underlying physiological events and the imaging physics. BOLD contrast, although sensitive, is not a quantifiable measure of neuronal activity. A number of different imaging techniques and parameters can be used for fMRI, the choice of which depends on the particular requirements of each functional imaging experiment. The high-speed MRI technique, echo-planar imaging provides the basis for most fMRI experiments. The problems inherent to this method and the ways in which these may be overcome are particularly important in the move towards performing functional studies on higher field MRI systems. Future developments in techniques and hardware are also likely to enhance the measurement of brain activity using MRI.

Howseman, A M; Bowtell, R W

1999-01-01

81

[Preoperative applications of cortical mapping with functional magnetic resonance].  

PubMed

The authors describe a clinical experience in cortical brain mapping by Functional Magnetic Resonance Imaging (FMRI) with a 1.0 T MR scanner with BOLD technique and echo-planar imaging (EPI). A brief review is made of the theoretical basis of the BOLD technique and of the different functional tasks used. The main clinical applications of FMRI cortical mapping regarding the sensorimotor cortex of the hand and of language are mentioned. The experiment involves 29 patients, 16 with gliomas (G), 7 with mesial temporal sclerosis (MT S) and 6 with arteriovenous malformations (AVM) The most frequent clinical applications were the determination of the topographic relationship of the cerebral lesions with these eloquent cortices as well as the presurgical lateralization of language in medically intractable epileptic patients. The results are discussed in order to assess the FMRI cortical mapping role as a noninvasive method for presurgical planning, regarding the evaluation of the potential neurosurgical risks and the identification of viable cortex regions displaced or reorganized as a consequence of disease. Additionally, FMRI cortical mapping can also assess the atypical speech representations and the language lateralization of the patients. PMID:11321972

Cravo, I; Palma, T; Conceição, C; Evangelista, P

2001-01-01

82

Low field magnetic resonance imaging  

DOEpatents

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

Pines, Alexander (Berkeley, CA); Sakellariou, Dimitrios (Billancourt, FR); Meriles, Carlos A. (Fort Lee, NJ); Trabesinger, Andreas H. (London, GB)

2010-07-13

83

Brain processing of visual sexual stimuli in healthy men: a functional magnetic resonance imaging study  

Microsoft Academic Search

The brain plays a central role in sexual motivation. To identify cerebral areas whose activation was correlated with sexual desire, eight healthy male volunteers were studied with functional magnetic resonance imaging (fMRI). Visual stimuli were sexually stimulating photographs (S condition) and emotionally neutral photographs (N condition). Subjective responses pertaining to sexual desire were recorded after each condition. To image the

Harold Mouras; Serge Stoléru; Jacques Bittoun; Dominique Glutron; Mélanie Pélégrini-Issac; Anne-Lise Paradis; Yves Burnod

2003-01-01

84

AFNI: Software for Analysis and Visualization of Functional Magnetic Resonance Neuroimages  

Microsoft Academic Search

A package of computer programs for analysis and visualization of three-dimensional human brain functional magnetic resonance imaging (FMRI) results is described. The software can color overlay neural activation maps onto higher resolution anatomical scans. Slices in each cardinal plane can be viewed simultaneously. Manual placement of markers on anatomical landmarks allows transformation of anatomical and functional scans into stereotaxic (Talairach–Tournoux)

Robert W. Cox

1996-01-01

85

Cognitive impairment after traumatic brain injury: a functional magnetic resonance imaging study using the Stroop task  

Microsoft Academic Search

The anterior cingulate cortex (ACC) plays a key role in cognition, motor function, and emotion processing. However, little is known about how traumatic brain injury (TBI) affects the ACC system. Our purpose was to compare, by functional magnetic resonance imaging (fMRI) studies, the patterns of cortical activation in patients with cognitive impairment after TBI and those of normal subjects. Cortical

Akio Soeda; Toshihiko Nakashima; Ayumi Okumura; Kazuo Kuwata; Jun Shinoda; Toru Iwama

2005-01-01

86

Functional Analysis of Human MT and Related Visual Cortical Areas Using Magnetic Resonance Imaging  

Microsoft Academic Search

Using noninvasive functional magnetic resonance imaging (fMRI) techniques, we analyzed the responses in human area MT with regard to visual motion, color, and luminance contrast sensitivity, and retinotopy. As in previous PET studies, we found that area MT responded selectively to moving (compared to stationary) stimuli. The location of human MT in the present fMRl results is consistent with that

Roger B. H. Tootell; John B. Reppas; Kenneth K. Kwong; Rafael Malach; Richard T. Born; Thomas J. Brady; Bruce R. Rosen; John W. Belliveaul

1995-01-01

87

The Hippocampal Formation Participates in Novel Picture Encoding: Evidence from Functional Magnetic Resonance Imaging  

Microsoft Academic Search

Considerable evidence exists to support the hypothesis that the hippocampus and related medial temporal lobe structures are crucial for the encoding and storage of information in long-term memory. Few human imaging studies, however, have successfully shown signal intensity changes in these areas during encoding or retrieval. Using functional magnetic resonance imaging (fMRI), we studied normal human subjects while they performed

Chantal E. Stern; Suzanne Corkin; R. Gilberto Gonzalez; Alexander R. Guimaraes; John R. Baker; Peggy J. Jennings; Cindy A. Carr; Robert M. Sugiura; Vasanth Vedantham; Bruce R. Rosen

1996-01-01

88

Neural Correlates of Successful Encoding Identified Using Functional Magnetic Resonance Imaging  

Microsoft Academic Search

Neural activity that occurs during the creation of a new memory trace can be observed using functional magnetic resonance imaging (fMRI). Event-related designs have been used to dem- onstrate that activity in prefrontal and medial temporal lobe areas is associated with successful memory storage. Here we contrasted activity associated with encoding success and en- coding effort. Participants viewed a series

Paul J. Reber; Robert M. Siwiec; Darren R. Gitleman; Todd B. Parrish; Ken A. Paller

2002-01-01

89

A Functional Magnetic Resonance Imaging Study of Neural Dissociations between Brand and Person Judgments  

Microsoft Academic Search

Functional magnetic resonance imaging (fMRI) was used to investigate whether semantic judgments about products and persons are processed similarly. Our results suggest they are not: comparisons of neural correlates of product versus human descriptor judgments indicated greater activation in the medial prefrontal cortex regions for persons; for products, activation was greater in the left inferior prefrontal cortex, an area known

Carolyn Yoon; Fred Feinberg

2006-01-01

90

Functional Magnetic Resonance Imaging of Cognitive Processing in Young Adults with Down Syndrome  

ERIC Educational Resources Information Center

The authors used functional magnetic resonance imaging (fMRI) to investigate neural activation during a semantic-classification/object-recognition task in 13 persons with Down syndrome and 12 typically developing control participants (age range = 12-26 years). A comparison between groups suggested atypical patterns of brain activation for the…

Jacola, Lisa M.; Byars, Anna W.; Chalfonte-Evans, Melinda; Schmithorst, Vincent J.; Hickey, Fran; Patterson, Bonnie; Hotze, Stephanie; Vannest, Jennifer; Chiu, Chung-Yiu; Holland, Scott K.; Schapiro, Mark B.

2011-01-01

91

Localization of the Cortical Response to Smiling Using New Imaging Paradigms with Functional Magnetic Resonance Imaging  

Microsoft Academic Search

Functional magnetic resonance imaging (fMRI) can serve to localize activity in the cerebral cortex. The present study was performed to develop a quantitative means of describing the cortical location activated during voluntary smiling in multiple subjects and to determine whether this location is specific to smiling when compared with other motor tasks. Five human subjects were instructed to smile or

Arun K. Gosain; Rasmus M. Birn; James S. Hyde

2001-01-01

92

A Functional Magnetic Resonance Imaging Investigation of Verbal Working Memory in Adolescents with Specific Language Impairment  

ERIC Educational Resources Information Center

This study used neuroimaging and behavioral techniques to examine the claim that processing capacity limitations underlie specific language impairment (SLI). Functional magnetic resonance imaging (fMRI) was used to investigate verbal working memory in adolescents with SLI and normal language (NL) controls. The experimental task involved a modified…

Weismer, Susan Ellis; Plante, Elena; Jones, Maura; Tomblin, Bruce J.

2005-01-01

93

Assessing the working memory network: Studies with functional magnetic resonance imaging and structural equation modeling  

Microsoft Academic Search

A considerable body of evidence supports the notion that the neurofunctional substrate of working memory is not only related to the integrity of the prefrontal cortex, but also to the concerted interplay of widespread interacting networks including the parietal cortex, subcortical regions and cerebellar areas. Modern functional brain imaging techniques such as functional magnetic resonance imaging (fMRI) have provided a

R. G. M. Schlösser; G. Wagner; H. Sauer

2006-01-01

94

Nuclear magnetic resonance contrast agents  

DOEpatents

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

Smith, Paul H. (Los Alamos, NM); Brainard, James R. (Los Alamos, NM); Jarvinen, Gordon D. (Los Alamos, NM); Ryan, Robert R. (Los Alamos, NM)

1997-01-01

95

Nuclear magnetic resonance contrast agents  

DOEpatents

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

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

1997-12-30

96

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

ERIC Educational Resources Information Center

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

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

2000-01-01

97

Recent developments in optimal experimental designs for functional magnetic resonance imaging  

PubMed Central

Functional magnetic resonance imaging (fMRI) is one of the leading brain mapping technologies for studying brain activity in response to mental stimuli. For neuroimaging studies utilizing this pioneering technology, there is a great demand of high-quality experimental designs that help to collect informative data to make precise and valid inference about brain functions. This paper provides a survey on recent developments in experimental designs for fMRI studies. We briefly introduce some analytical and computational tools for obtaining good designs based on a specified design selection criterion. Research results about some commonly considered designs such as blocked designs, and m-sequences are also discussed. Moreover, we present a recently proposed new type of fMRI designs that can be constructed using a certain type of Hadamard matrices. Under certain assumptions, these designs can be shown to be statistically optimal. Some future research directions in design of fMRI experiments are also discussed.

Kao, Ming-Hung; Temkit, M'hamed; Wong, Weng Kee

2014-01-01

98

Functional magnetic resonance imaging of the central auditory pathway following speech and pure-tone stimuli.  

PubMed

Functional magnetic resonance imaging (FMRI) is a new noninvasive technique for imaging cerebral function. Studies of the human central auditory pathway examined responses in eight normal hearing volunteers following auditory stimuli, including narrative speech and pure-tone audiometry. The activation demonstrated by FMRI is modeled on an increase in regional blood flow with increased neuronal activity. The FMRI signals represent deoxyhemoglobin concentration changes in capillaries within the region of the brain that is activated. Brain activation was imaged in the superior temporal gyrus during text reading and pure tones. Activation in both text and pure-tone presentation did not vary with the intensity of the auditory stimulus and elicited a dominant response in the left temporal lobe. These observations demonstrate the capability of FMRI to correlate anatomic and functional relationships in the human central auditory pathway. PMID:8523982

Millen, S J; Haughton, V M; Yetkin, Z

1995-12-01

99

Molecular-level functional magnetic resonance imaging of dopaminergic signaling.  

PubMed

We demonstrate a technique for mapping brain activity that combines molecular specificity and spatial coverage using a neurotransmitter sensor detectable by magnetic resonance imaging (MRI). This molecular functional MRI (fMRI) method yielded time-resolved volumetric measurements of dopamine release evoked by reward-related lateral hypothalamic brain stimulation of rats injected with the neurotransmitter sensor. Peak dopamine concentrations and release rates were observed in the anterior nucleus accumbens core. Substantial dopamine transients were also present in more caudal areas. Dopamine-release amplitudes correlated with the rostrocaudal stimulation coordinate, suggesting participation of hypothalamic circuitry in modulating dopamine responses. This work provides a foundation for development and application of quantitative molecular fMRI techniques targeted toward numerous components of neural physiology. PMID:24786083

Lee, Taekwan; Cai, Lili X; Lelyveld, Victor S; Hai, Aviad; Jasanoff, Alan

2014-05-01

100

Neuropsychiatric dynamics: the study of mental illness using functional magnetic resonance imaging.  

PubMed

Functional magnetic resonance imaging (fMRI) is poised to make significant contributions to the study of neuropsychiatric illnesses. Whatever neural pathology attends such illnesses has proven subtle at best. By identifying predictable, regionally specific deficits in brain function, fMRI can suggest brain regions for detailed cellular analyses, provide valuable in vivo data regarding effective connectivity, provide a means to model the effects of various drug challenge paradigms, and characterize intermediate phenotypes in the search for the genes underlying mental illness. Nonetheless, as promising as fMRI appears to be in terms of its relative safety, repeatability, ability to generate individual brain maps and widespread availability, it is still subject to a number of unresolved conceptual conundrums inherited from earlier neuroimaging work. For example, functional neuroimaging has not generated any pathognomic findings in mental illness, has not established a clear link between neurophysiology and observable behavior, and has not resolved the potential confounds of medication. In this article, we will review the relevant historical background preceding fMRI, address methodological considerations in fMRI, and summarize recent fMRI findings in psychiatry. Finally, fMRI is being used to simplify the complex genetics of neuropsychiatric illness by generating quantitative and qualitative brain phenotypes. PMID:10401590

Callicott, J H; Weinberger, D R

1999-05-01

101

Ethics in fMRI Studies  

Microsoft Academic Search

Functional magnetic resonance imaging (fMRI) has surfaced as a powerful method to study brain function in humans. While the\\u000a involvement of neuroradiologists in fMRI studies in the clinical setting is obvious, in neuroscience research most of the\\u000a investigators are not specialists trained in reading brain images. Advances in neuroimaging are increasingly intersecting\\u000a with issues of ethical, legal, and social interest.

Daniela Seixas; Margarida Ayres Basto

2008-01-01

102

Primary Motor and Sensory Cortex Activation during Motor Performance and Motor Imagery: A Functional Magnetic Resonance Imaging Study  

Microsoft Academic Search

The intensity and spatial distribution of functional activation in the left precentral and postcentral gyri during actual motor performance (MP) and mental representation (motor imagery (MI)) of self-paced finger-to-thumb opposition movements of the dominant hand were investigated in fourteen right- handed volunteers by functional magnetic resonance imag- ing (fMRI) techniques. Significant increases in mean normal- ized fMRI signal intensities over

Carlo A. Porro; Maria Pia Francescato; Valentina Cettolo; Mathew E. Diamond; Patrizia Baraldi; Chiava Zuiani; Massimo Bazzocchi

1996-01-01

103

Functional Magnetic Resonance Imaging Brain Mapping in Psychiatry: Methodological Issues Illustrated in a Study of Working Memory in Schizophrenia  

Microsoft Academic Search

Functional magnetic resonance imaging (fMRI) is a potential paradigm shift in psychiatric neuroimaging. The technique provides individual, rather than group-averaged, functional neuroimaging data, but subtle methodological confounds represent unique challenges for psychiatric research. As an exemplar of the unique potential and problems of fMRI, we present a study of 10 inpatients with schizophrenia and 10 controls performing a novel “n

Joseph H Callicott; Nicolas F Ramsey; Kathleen Tallent; Alessandro Bertolino; Michael B Knable; Richard Coppola; Terry Goldberg; Peter van Gelderen; Venkata S Mattay; Joseph A Frank; Chrit TW Moonen; Daniel R Weinberger

1998-01-01

104

Transcranial direct current stimulation and simultaneous functional magnetic resonance imaging.  

PubMed

Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique that uses weak electrical currents administered to the scalp to manipulate cortical excitability and, consequently, behavior and brain function. In the last decade, numerous studies have addressed short-term and long-term effects of tDCS on different measures of behavioral performance during motor and cognitive tasks, both in healthy individuals and in a number of different patient populations. So far, however, little is known about the neural underpinnings of tDCS-action in humans with regard to large-scale brain networks. This issue can be addressed by combining tDCS with functional brain imaging techniques like functional magnetic resonance imaging (fMRI) or electroencephalography (EEG). In particular, fMRI is the most widely used brain imaging technique to investigate the neural mechanisms underlying cognition and motor functions. Application of tDCS during fMRI allows analysis of the neural mechanisms underlying behavioral tDCS effects with high spatial resolution across the entire brain. Recent studies using this technique identified stimulation induced changes in task-related functional brain activity at the stimulation site and also in more distant brain regions, which were associated with behavioral improvement. In addition, tDCS administered during resting-state fMRI allowed identification of widespread changes in whole brain functional connectivity. Future studies using this combined protocol should yield new insights into the mechanisms of tDCS action in health and disease and new options for more targeted application of tDCS in research and clinical settings. The present manuscript describes this novel technique in a step-by-step fashion, with a focus on technical aspects of tDCS administered during fMRI. PMID:24796646

Meinzer, Marcus; Lindenberg, Robert; Darkow, Robert; Ulm, Lena; Copland, David; Flöel, Agnes

2014-01-01

105

Magnetic Resonance Detection Method and and Apparatus.  

National Technical Information Service (NTIS)

A method and apparatus is described for detecting magnetic resonance of a sample. The apparatus uses an exceptionally stable tunnel diode rf oscillator incorporating a LC reentrant cavity resonator. The method entails measuring a magnetic resonance of the...

C. T. Van Degrift D. B. Utton

1977-01-01

106

Biological magnetic resonance: vol. 5  

SciTech Connect

This book discusses magnetic resonance techniques (NMR and ESR) as applied to biochemical research. Topics considered include the applications of carbon-13 NMR spectroscopy in investigations of metabolic pathways in vivo, the use of nitrogen-15 NMR in studies of systems of biological interest, phosphorus-31 NMR investigations of enzyme systems, the principles and state-of-the-art advances in the use of oxygen isotopes in phosphorus-31 and oxygen-17 NMR studies of biophosphates, and electron spin resonance and nuclear magnetic resonance studies of lipid-protein interactions in membranes.

Berliner, L.J.; Reuben, J.

1983-01-01

107

Basics of magnetic resonance imaging  

SciTech Connect

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

Oldendorf, W.; Oldendorf, W. Jr.

1988-01-01

108

Phase stability in fMRI time series: effect of noise regression, off-resonance correction and spatial filtering techniques.  

PubMed

Although the majority of fMRI studies exploit magnitude changes only, there is an increasing interest regarding the potential additive information conveyed by the phase signal. This integrated part of the complex number furnished by the MR scanners can also be used for exploring direct detection of neuronal activity and for thermography. Few studies have explicitly addressed the issue of the available signal stability in the context of phase time-series, and therefore we explored the spatial pattern of frequency specific phase fluctuations, and evaluated the effect of physiological noise components (heart beat and respiration) on the phase signal. Three categories of retrospective noise reduction techniques were explored and the temporal signal stability was evaluated in terms of a physiologic noise model, for seven fMRI measurement protocols in eight healthy subjects at 3T, for segmented CSF, gray and white matter voxels. We confirmed that for most processing methods, an efficient use of the phase information is hampered by the fact that noise from physiological and instrumental sources contributes significantly more to the phase than to the magnitude instability. Noise regression based on the phase evolution of the central k-space point, RETROICOR, or an orthonormalized combination of these were able to reduce their impact, but without bringing phase stability down to levels expected from the magnitude signal. Similar results were obtained after targeted removal of scan-to-scan variations in the bulk magnetic field by the dynamic off-resonance in k-space (DORK) method and by the temporal off-resonance alignment of single-echo time series technique (TOAST). We found that spatial high-pass filtering was necessary, and in vivo a Gaussian filter width of 20mm was sufficient to suppress physiological noise and bring the phase fluctuations to magnitude levels. Stronger filters brought the fluctuations down to levels dictated by thermal noise contributions, and for 62.5mm(3) voxels the phase stability was as low as 5 mrad (0.27°). In conditions of low SNR(o) and high temporal sampling rate (short TR); we achieved an upper bound for the phase instabilities at 0.0017 ppm, which is close to the dHb contribution to the GM/WM phase contrast. PMID:22079450

Hagberg, Gisela E; Bianciardi, Marta; Brainovich, Valentina; Cassara, Antonino Mario; Maraviglia, Bruno

2012-02-15

109

Mechanical detection of magnetic resonance  

NASA Astrophysics Data System (ADS)

CONVENTIONAL techniques for measuring magnetic resonance involve the detection of electromagnetic signals induced in a coil or microwave cavity by the collective precession of magnetic moments (from nuclei or electrons) excited by an alternating magnetic field. In a different approach1, isolated electron spins have been detected by scanning tunnelling microscopy, with the spin precession inducing a radiofrequency modulation in the tunnelling current. Here, we describe a new and extremely sensitive method of detection, the principles of which derive from magnetic force microscopy2-5 and a recent proposal6,7 by one of us (J.A.S.). We measure the small, oscillatory magnetic force (10-14 N) acting on a paramagnetic sample (a few grains of diphenylpicrylhydrazil, weighing < 30 ng) which has been excited into magnetic resonance in the presence of an inhomogeneous magnetic field. This force is detected by optically sensing the angstrom-scale vibration of a micromechanical cantilever on which the sample is mounted. The sensitivity of this technique to the spatial distribution of the spins suggests that mechanical detection of magnetic resonance has the potential for imaging microscopic samples in three dimensions. So far, we have achieved a spatial resolution of 19 ?m in one dimension.

Rugar, D.; Yannoni, C. S.; Sidles, J. A.

1992-12-01

110

Real-Time Functional Magnetic Resonance Imaging  

Microsoft Academic Search

A recursive algorithm suitable for functional magnetic reso- nance imaging (FMRI) calculations is presented. The correla- tion coefficient of a time course of images with a reference time series, with the mean and any linear trend projected out, may be computed with 22 operations per voxel, per image; the storage overhead is four numbers per voxel. A statistical model for

Robert W. Cox; Andrzej Jesmanowicz; James S. Hyde

1995-01-01

111

Functional magnetic resonance imaging of eye dominance at 4 tesla.  

PubMed

We studied eye dominance in visual cortex and lateral geniculate nucleus (LGN) using functional magnetic resonance imaging (fMRI) at a very high magnetic field (4 tesla). Eight normal volunteers were studied with fMRI at 4 tesla during alternating monocular visual stimulation. The acquisition was repeated twice in 4 subjects to confirm reproducibility. In addition, magnetic resonance signal intensities during three conditions (right eye stimulation, left eye stimulation, and control condition) were compared to determine whether the observed area was truly or relatively monocular in 2 subjects. In both the individual and group analyses, the anterior striate cortex was consistently activated by the contralateral eye more than the ipsilateral eye. Additionally, we found evidence that there were areas in the bilateral LGN which were more active during the stimulation of the contralateral eye than during the stimulation of the ipsilateral eye. The activated areas were reproducible, and the mean ratio of the overlapping area was 0.71 for the repeated scans. The additional experiment revealed that the area in the anterior visual cortex could be divided into two parts, one truly monocular and the other relatively monocular. Our finding confirmed previous fMRI results at 1.5 tesla showing that eye dominance was observed in the contralateral anterior visual cortex. However, the eye dominance in the visual cortex was found not only in the most anterior area corresponding to the monocular temporal crescent but also in the more posterior area, presumably showing the greater sensitivity of the temporal visual field (nasal retina) as compared with the nasal visual field (temporal retina) in the peripheral visual field (peripheral retina). In addition, it is suggested that the nasotemporal asymmetry of the retina and the visual fields is represented in the LGN as well as in the visual cortex. PMID:11586061

Miki, A; Liu, G T; Englander, S A; van Erp, T G; Bonhomme, G R; Aleman, D O; Liu, C S; Haselgrove, J C

2001-01-01

112

Functional magnetic resonance imaging in rodents: an unique tool to study in vivo pharmacologic neuromodulation.  

PubMed

When new compounds targeting the brain are developed, it is important to assess both the acute and chronic effects on brain functioning. This can be done non-invasively using a technique called functional magnetic resonance imaging (fMRI). This review discusses the possibilities of both stimulation-based and resting state fMRI to study pharmacological modulations of the rodent brain. Moreover, attention is given to the use of anesthetics which could importantly influence the outcome of both techniques. PMID:23856429

Jonckers, Elisabeth; Van der Linden, Annemie; Verhoye, Marleen

2013-10-01

113

Abnormal pontine activation in pathological laughing as shown by functional magnetic resonance imaging  

PubMed Central

To explore the aetiology of pathological laughing, a 65?year?old woman with pathological laughing was examined by 3?T functional magnetic resonance imaging (fMRI) before and after treatment with drugs. Here, we report that the patient consistently showed exaggerated pontine activation during the performance of three tasks before treatment, whereas abnormal pontine activation was no longer found after successful treatment with the selective serotonin reuptake inhibitor, paroxetine. Our findings in this first fMRI study of pathological laughing suggest that serotonergic replacement decreases the aberrant activity in a circuit that involves the pons.

Kosaka, H; Omata, N; Omori, M; Shimoyama, T; Murata, T; Kashikura, K; Takahashi, T; Murayama, J; Yonekura, Y; Wada, Y

2006-01-01

114

Generalized relative entropy in functional magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

The generalized Kullback-Leibler distance Dq ( q is the Tsallis parameter) is shown to be an useful measure for analysis of functional magnetic resonance imaging (fMRI) data series. This generalized form of entropy is used to evaluate the “distance” between the probability functions p1 and p2 of the signal levels related to periods of stimulus and non-stimulus in event-related fMRI experiments. The probability densities of the mean distance D (averaged over the N epochs of the entire experiment) are obtained through numerical simulations for different values of signal-to-noise ratio (SNR) and found to be fitted very well by Gamma distributions ( ?2<0.0008) for small values of N ( N<30). These distributions allow us to determine the sensitivity and specificity of the method by construction of the receiver operating characteristic (ROC) curves. The performance of the method is also investigated in terms of the parameters q and L (number of signal levels) and our results indicate that the optimum choice is q=0.8 and L=3. The entropic index q is found to exert control on both sensitivity and specificity of the method. As q ( q>0) is raised, sensitivity increases but specificity decreases. Finally, the method is applied in the analysis of a real event-related fMRI motor stimulus experiment and the resulting maps show activation in primary and secondary motor brain areas.

Cabella, Brenno C. T.; Sturzbecher, Marcio J.; de Araujo, Draulio B.; Neves, Ubiraci P. C.

2009-01-01

115

Quality Map Thresholding for Denoising of Complex-Valued fMRI Data and Its Application to ICA of fMRI  

Microsoft Academic Search

Although functional magnetic resonance imaging (fMRI) data are acquired as complex-valued images, traditionally most fMRI\\u000a studies only use the magnitude of the data. FMRI analysis in the complex domain promises to provide more statistically significant\\u000a information; however, the noisy nature of the phase poses a challenge for successful study of fMRI by complex-valued signal\\u000a processing algorithms. In this paper, we

Pedro A. Rodriguez; Nicolle M. Correa; Tom Eichele; Vince D. Calhoun; Tülay Adal?

116

Functional Magnetic Resonance Imaging in Narcolepsy and the Kleine-Levin Syndrome  

PubMed Central

This work aims at reviewing the present state of the art when it comes to understanding the pathophysiology of narcolepsy and the Kleine–Levin syndrome (KLS) from a neuroimaging point of view. This work also aims at discussing future perspectives of functional neuroimaging in these sleep disorders. We focus on functional magnetic resonance imaging (fMRI), which is a technique for in vivo measurements of brain activation in neuronal circuitries under healthy and pathological conditions. fMRI has significantly increased the knowledge on the affected neuronal circuitries in narcolepsy and the Kleine–Levin syndrome. It has been shown that narcolepsy is accompanied with disturbances of the emotional and the closely related reward systems. In the Kleine Levin syndrome, fMRI has identified hyperactivation of the thalamus as a potential biomarker that could be used in the diagnostic procedure. The fMRI findings in both narcolepsy and the Kleine–Levin syndrome are in line with previous structural and functional imaging studies. We conclude that fMRI in combination with multi-modal imaging can reveal important details about the pathophysiology in narcolepsy and the Kleine–Levin syndrome. In the future, fMRI possibly gives opportunities for diagnostic support and prediction of treatment response in individual patients.

Engstrom, Maria; Hallbook, Tove; Szakacs, Attila; Karlsson, Thomas; Landtblom, Anne-Marie

2014-01-01

117

A Computational Multiresolution BOLD fMRI Model  

Microsoft Academic Search

Blood oxygenation level-dependent (BOLD) func- tional magnetic resonance imaging (fMRI) is a widely used method for brain mapping. BOLD fMRI signal detection is based on an in- travoxel dephasing mechanism. This model involves bulk nuclear spin precession in a BOLD-induced inhomogeneous magnetic field within a millimeter-resolution voxel, that is, BOLD signal forma- tion spans a huge spatial scale range from

Zikuan Chen; Vince Calhoun

2011-01-01

118

Magnetic resonance apparatus  

DOEpatents

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

Jackson, Jasper A. (Los Alamos, NM); Cooper, Richard K. (Los Alamos, NM)

1982-01-01

119

Nuclear Magnetic Resonance Massmetric Flowmeter.  

National Technical Information Service (NTIS)

Based on earlier research work in the measurement of jet and rocket propellants by means of Nuclear Magnetic Resonance (NMR), a propellant mass flow meter based on the NMR principle was designed and constructed. The mass flow measurement is derived by mul...

J. H. Battocletti W. H. Vander Heyden W. K. Genthe

1972-01-01

120

Interventional cardiovascular magnetic resonance imaging  

PubMed Central

Magnetic resonance imaging (MRI) provides structural and functional cardiovascular information with excellent soft tissue contrast. Real-time MRI can guide transcatheter cardiovascular interventions in large animal models, and may prove superior to x-ray and adjunct modalities for peripheral vascular, structural heart and cardiac electrophysiology applications. We describe technical considerations, pre-clinical work and early clinical studies in this emerging field.

Raman, Venkatesh K.; Lederman, Robert J.

2008-01-01

121

Event-related fMRI in Cognition  

PubMed Central

A primary advantage of functional magnetic resonance imaging (fMRI) over other techniques in neuroscience is its flexibility. Researchers have used fMRI to study a remarkable diversity of topics, from basic processes of perception and memory, to the complex mechanisms of economic decision making and moral cognition. The chief contributor to this experimental flexibility – indeed, to the growth of fMRI itself – has been the development of event-related experimental designs and associated analyses. The core idea of an event-related design, as first articulated in the late 1990s, is the separation of cognitive processes into discrete points in time (i.e., “events”) allowing differentiation of their associated fMRI signals. By modeling brain function as a series of transient changes, rather than as an ongoing state, event-related fMRI allowed researchers to create much more complex paradigms and more dynamic analysis methods. Yet, this flexibility came with a cost. As the complexity of experimental designs increased, fMRI analyses became increasingly abstracted from the original data, which in turn has had consequences both positive (e.g., greater use of model-based fMRI) and negative (e.g., fewer articles plot the timing of activation). And, as event-related methods have become ubiquitous, they no longer represent a distinct category of fMRI research. In a real sense, event-related fMRI has now become, simply, fMRI.

Huettel, Scott A.

2011-01-01

122

Magnetic resonance apparatus  

DOEpatents

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

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

1980-10-10

123

Magnetic Resonance Studies of Coal. Volume III.  

National Technical Information Service (NTIS)

Electron spin resonance (ESR) and Electron-Nuclear Double Resonance (ENDOR) techniques have been used to study natural radical centers in Alabama coals. Also Nuclear Magnetic Resonance (NMR) techniques have been used for a preliminary study of the hydroge...

I. Miyagawa C. Alexander

1981-01-01

124

Delta Relaxation Enhanced Magnetic Resonance  

NASA Astrophysics Data System (ADS)

Generally speaking, targeted molecular imaging has always been difficult to perform with magnetic resonance. The difficulty does not arise with the magnetic resonance imaging (MRI) technique or equipment itself, but rather with the targeted contrast agents, which the method requires. Also referred to as activatable contrast agents, or MRI probes, targeted contrast agents are pharmaceuticals that will selectively bind to a particular biological (target) molecule. They are used to highlight a certain tissue or the difference between healthy and diseased tissue. Unfortunately, nearly all MRI probes are non-specific, causing localized increases in MR image intensity in both the unbound and target-bound states. Therefore, brightening in a conventional MRI image, following probe injection, does not positively indicate the presence of the target molecule. Herein, a novel method known as delta relaxation enhanced magnetic resonance (dreMR, pronounced "dreamer") is presented that utilizes variable magnetic field technology to produce image contrast related to the dependence of the sample's longitudinal relaxation rates upon the strength of the main magnetic field of the MRI scanner. Since only bound contrast agent shows significant magnetic field dependence, it is an indicator of the bound probe, which is in turn a marker for the target molecule. This work details the development of the dreMR method, focusing on the specialized hardware necessary to provide a clinical, static-field MRI the ability to modulate its main magnetic field throughout an MRI sequence. All modifications were performed in such a manner that the host MRI system was not degraded or permanently modified in any way. The three parts of this technology are: the insertable electromagnet, the power supply system and the control system. The insertable electromagnet modifies the magnetic field, the power system drives the electromagnet, and the control system generates the magnetic field waveform envelope and synchronizes this waveform with the rest of the MRI pulse sequence. On two separate dreMR systems, images were obtained having contrast which was directly proportional to the magnetic field dependence of the sample's relaxation rates. This contrast unambiguously indicated the presence of the bound probe, and its imaging therefore yields a map of the targeted biological molecule. Keywords Magnetic Resonance Imaging; Field-Cycled MRI; MR Probe; Targeted Contrast Agent; Gadolinium; Insert Coil; Power Supply; Relaxation Rate; Relaxivity; Actively Shielded; dreMR; Delta Relaxation Enhanced MRI; MRI Hardware; Gradient Echo; Spin Echo; Spoiled Gradient; Echo iv

Alford, Jamu K.

125

Changes in fMRI magnitude data and phase data observed in block-design and event-related tasks  

Microsoft Academic Search

Functional magnetic resonance imaging (fMRI) data are acquired as a complex image pair including magnitude and phase information. The vast majority of fMRI experiments do not attempt to take advantage of the time varying phase information. The phase of the MRI signal is related to the local magnetic field changes, suggesting it may contain useful information about the source of

Sunil Kumar Arja; Zhaomei Feng; Zikuan Chen; Arvind Caprihan; Kent A. Kiehl; Tülay Adali; Vince D. Calhoun

2010-01-01

126

Performing functional magnetic resonance imaging in patients with Parkinson's disease treated with deep brain stimulation.  

PubMed

Deep brain stimulation (DBS) is a relatively novel treatment in advanced Parkinson's disease (PD). Functional magnetic resonance imaging (fMRI) is a useful technique for examining the effects of DBS both within the basal ganglia and its cortical connectivity. There are technical difficulties in imaging patients with PD, and the DBS itself can generate image artifacts. We describe aspects related to optimizing the fMRI acquisition parameters in patients with DBS and the results of sensorimotor activation tasks performed by four PD patients during hand, foot, and tongue movements, both before and after DBS implant. Provided that all safety conditions are followed, it is possible to perform fMRI in patients with PD and DBS. The standard DBS surgical procedure has to be slightly modified in order to reduce image artifacts. The event-related design provided increased power to detect sensorimotor cortex and basal ganglia activation. PMID:16671094

Arantes, Paula R; Cardoso, Ellison F; Barreiros, Maria A; Teixeira, Manoel J; Gonçalves, Márcia R; Barbosa, Egberto R; Sukwinder, Sukhi Shergill; Leite, Claudia C; Amaro, Edson

2006-08-01

127

Functional magnetic resonance imaging and evoked potential correlates of conscious and unconscious vision in parietal extinction patients  

Microsoft Academic Search

We describe recent functional magnetic resonance imaging (fMRI) and event-related potential (ERP) studies of visual extinction in patients with right parietal damage who can detect isolated visual stimuli on either side, yet often miss contralesional (left) stimuli during bilateral stimulation. We consider the neural fate of such extinguished visual stimuli and how neural responses differ for consciously detected versus extinguished

Jon Driver; Patrik Vuilleumier; Martin Eimer; Geraint Rees

2001-01-01

128

Laterality in Metaphor Processing: Lack of Evidence from Functional Magnetic Resonance Imaging for the Right Hemisphere Theory  

ERIC Educational Resources Information Center

We investigated processing of metaphoric sentences using event-related functional magnetic resonance imaging (fMRI). Seventeen healthy subjects (6 female, 11 male) read 60 novel short German sentence pairs with either metaphoric or literal meaning and performed two different tasks: judging the metaphoric content and judging whether the sentence…

Rapp, Alexander M.; Leube, Dirk T.; Erb, Michael; Grodd, Wolfgang; Kircher, Tilo T. J.

2007-01-01

129

Lateralized auditory spatial perception and the contralaterality of cortical processing as studied with functional magnetic resonance imaging and magnetoencephalography  

Microsoft Academic Search

Functional magnetic resonance imaging (fMRI) and magnetoencephalography (MEG) were used to study the relationships between lateralized auditory perception in humans and the contralaterality of processing in auditory cortex. Subjects listened to rapidly presented streams of short FM-sweep tone bursts to detect infrequent, slightly deviant tone bursts. The stimulus streams consisted of either monaural stimuli to one ear or the other

Marty G. Woldorff; Claus Tempelmann; Juergen Fell; Carola Tegeler; Hermann Hinrichs; Henning Scheich

1999-01-01

130

A case of persistent visual hallucinations of faces following LSD abuse: A functional Magnetic Resonance Imaging study  

Microsoft Academic Search

In this study, we report the case of a patient experiencing hallucinations of faces that could be reliably precipitated by looking at trees. Using functional Magnetic Resonance Imaging (fMRI), we found that face hallucinations were associated with increased and decreased neural activity in a number of cortical regions. Within the same fusiform face area, however, we found significant decreased and

Giuseppe Iaria; Christopher J. Fox; Michael Scheel; Robert M. Stowe; Jason J. S. Barton

2010-01-01

131

Paradoxical correlation between signal in functional magnetic resonance imaging and deoxygenated haemoglobin content in capillaries: a new theoretical explanation  

Microsoft Academic Search

Signal increases in functional magnetic resonance imaging (fMRI) are believed to be a result of decreased paramagnetic deoxygenated haemoglobin (deoxyHb) content in the neural activation area. However, discrepancies in this canonical blood oxygenation level dependent (BOLD) theory have been pointed out in studies using optical techniques, which directly measure haemoglobin changes. To explain the discrepancies, we developed a new theory

Toru Yamamoto; Toshinori Kato

2002-01-01

132

A Critical Review of ERP and fMRI Evidence on L2 Syntactic Processing  

ERIC Educational Resources Information Center

The current review focuses on recent event-related brain potential (ERPs) and functional magnetic resonance imaging (fMRI) in L2 syntactic processing data. To this end, critical factors influencing both the dynamics of neural mechanisms (ERPs) and critical functional brain correlates (fMRI) are discussed. These entail the critical period…

Kotz, Sonja A.

2009-01-01

133

Medial temporal lobe activations in fMRI and PET studies of episodic encoding and retrieval  

Microsoft Academic Search

Early neuroimaging studies often failed to obtain evidence of medial temporal lobe (MTL) activation during episodic encoding or retrieval, but a growing number of studies using functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) have provided such evidence. We review data from fMRI studies that converge on the conclusion that posterior MTL is associated with episodic encoding; too

Daniel L. Schacter; Anthony D. Wagner

1999-01-01

134

In vivo static field perturbations in magnetic resonance  

NASA Astrophysics Data System (ADS)

Fundamental magnetic resonance (MR) theory assumes the spatial homogeneity of a dominating static magnetic field B = B 0?. When this assumption is violated, a myriad of artifacts and compromising factors are introduced to MR spectra and images. Though in vivo nuclear magnetic resonance (NMR) is one of the most widely used scientific and diagnostic tools in medicine and biology, it remains haunted by the continual and persistant ghost of B0 inhomogeneity. An inclusive list of in vivo NMR applications severely impacted by B0 inhomogeneity could go on ad infinitum. Examples of such applications include neurosurgical utility in functional magnetic resonance imaging (fMRI), cerebral metabolic flux mapping, cerebral diffusion tractography, and abdominal diagnostic imaging. Given this wide impact on in vivo NMR, significant effort has been exerted in developing methods of compensating B0 inhomogeneity. Complicating this task is the sample-specific nature of in vivo B 0 inhomogeneity and its exacerbation with ever increasing B 0 field strengths. State of the art B 0 inhomogeneity compensation is currently at a critical juncture where homogenization demands are overwhelming the outer capabilities of existing technology and methods. This thesis addresses the B 0 inhomogeneity problem in the mammalian brain and presents novel solutions to the homogenization technology stalemate.

Koch, Kevin Matthew

135

Magnetic resonance imaging in lissencephaly  

Microsoft Academic Search

In a patient with clinical manifestations suggestive of brain malformation, computer-assisted tomography (CT) showed lissencephaly:\\u000a agyria, pachygyria, absent opercularization, and colpocephaly. The patient did not have seizures or a typical EEG of hypsarrhythmia.\\u000a By magnetic resonance imaging (MRI), using a long inversion-recovery sequence, it was possible to verify the CT-findings and\\u000a to demonstrate heterotopic grey matter and missing claustrum. By

M. Krawinkel; H.-J. Steen; B. Terwey

1987-01-01

136

Magnetic resonance neurography: technical considerations.  

PubMed

Proper performance of magnetic resonance neurography (MRN) is essential not only to make the examination easier to interpret but also for its accurate evaluation. This article outlines the technical considerations of MRN, various imaging pulse sequences available on current scanners, as well as their relative advantages and disadvantages. In addition, a guide to the optimal use of high-resolution and high-contrast MRN technique is provided, which will aid clinicians in attaining a good-quality examination. PMID:24210313

Chhabra, Avneesh; Flammang, Aaron; Padua, Abraham; Carrino, John A; Andreisek, Gustav

2014-02-01

137

Quantitative nuclear magnetic resonance spectrometry  

Microsoft Academic Search

The purities of the widely-used herbicide glyphosate (N-(phosphonomethyl)glycine), and the insecticide profenofos (O-(4-bromo-2-chlorophenyl) O-ethyl S-propyl phosphorothioate) were determined by 1H and 31P quantitative nuclear magnetic resonance (QNMR) spectrometry using an internal standard. QNMR does not need a standard reference of the same target analyte, in contrast to chromatographic methods, but only a compound containing the nucleus of interest. Sodium acetate

Tareq Saed Al Deen; D Brynn Hibbert; James M Hook; Robert J Wells

2002-01-01

138

Mapping of neural activity produced by thermal pain in the healthy human spinal cord and brain stem: a functional magnetic resonance imaging study  

Microsoft Academic Search

Functional magnetic resonance imaging (fMRI) has greatly advanced our current understanding of pain, although most studies to date have focused on imaging of cortical structures. In the present study, we have used fMRI at 3 T to investigate the neural activity evoked by thermal sensation and pain (42°C and 46°C) throughout the entire lower neuroaxis from the first synapse in

Catherine M. Cahill; Patrick W. Stroman

2011-01-01

139

Normalization of Functional Magnetic Resonance Images by Classified Cerebrospinal Fluid Cluster  

Microsoft Academic Search

For functional magnetic resonance imaging (fMRI) time series data, traditional intensity normalization techniques may introduce negative correlation with the neurological stimulation in non-activated voxels, and hence may cause incorrect identification of the activated\\/deactivated region. In this study, we present a modified proportional scaling method for intensity normalization using segmented specific tissue. In particular, the mean intensity across the classified cerebrospinal

Zhenghui Hu; Pengcheng Shi

2006-01-01

140

Growth Hormone Deficiency and Memory Functioning in Adults Visualized by Functional Magnetic Resonance Imaging  

Microsoft Academic Search

Cognitive functioning, especially memory performance, is known to be impaired in patients with childhood-onset growth hormone deficiency (CO-GHD), and growth hormone substitution has been found to counteract this memory impairment. Neuropsychological and functional magnetic resonance imagining (fMRI) data acquired during a working memory task in 13 childhood-onset GH-deficient patients were compared with 13 age, sex and education level matched healthy

Lucia I. Arwert; Dick J. Veltman; Jan Berend Deijen; P. Sytze van Dam; Henriette A. Delemarre-van deWaal; Madeleine L. Drent

2005-01-01

141

Functional Magnetic Resonance Imaging of Effects of a Nicotinic Agonist in Schizophrenia  

Microsoft Academic Search

3-(2,4-Dimethoxybenzylidene)-anabaseine (DMXB-A) is a partial agonist at ?7-nicotinic acetylcholine receptors and is now in early clinical development for treatment of deficits in neurocognition and sensory gating in schizophrenia. During its initial phase 2 test, functional magnetic resonance imaging (fMRI) studies were conducted to determine whether the drug had its intended effect on hippocampal inhibitory interneurons. Increased hemodynamic activity in the

Jason R Tregellas; Ann Olincy; Lynn Johnson; Jody Tanabe; Shireen Shatti; Laura F Martin; Debra Singel; Yiping P Du; Ferenc Soti; William R Kem; Robert Freedman; JR Tregellas

2010-01-01

142

Striatal recruitment during an implicit sequence learning task as measured by functional magnetic resonance imaging  

Microsoft Academic Search

Prior research has repeatedly implicated the striatum in implicit sequence learning; however, imaging findings have been inconclusive with respect to the sub-territories and laterality involved. Using functional magnetic resonance imaging (fMRI), we studied brain activation profiles associated with performance of the serial reaction time task (SRT) in 10 normal right-handed males. Behavioral results indicate that significant implicit learning occurred, uncontaminated

Scott L. Rauch; Paul J. Whalen; Cary R. Savage; Tim Curran; Adair Kendrick; Halle D. Brown; George Bush; Hans C. Breiter; Bruce R. Rosen

1997-01-01

143

Functional magnetic resonance imaging of the ascending stages of the auditory system in dogs  

PubMed Central

Background Functional magnetic resonance imaging (fMRI) is a technique able to localize neural activity in the brain by detecting associated changes in blood flow. It is an essential tool for studying human functional neuroanatomy including the auditory system. There are only a few studies, however, using fMRI to study canine brain functions. In the current study ten anesthetized dogs were scanned during auditory stimulation. Two functional sequences, each in combination with a suitable stimulation paradigm, were used in each subject. Sequence 1 provided periods of silence during which acoustic stimuli could be presented unmasked by scanner noise (sparse temporal sampling) whereas in sequence 2 the scanner noise was present throughout the entire session (continuous imaging). The results obtained with the two different functional sequences were compared. Results This study shows that with the proper experimental setup it is possible to detect neural activity in the auditory system of dogs. In contrast to human fMRI studies the strongest activity was found in the subcortical parts of the auditory pathways. Especially sequence 1 showed a high reliability in detecting activated voxels in brain regions associated with the auditory system. Conclusion These results indicate that fMRI is applicable for studying the canine auditory system and could become an additional method for the clinical evaluation of the auditory function of dogs. Additionally, fMRI is an interesting technique for future studies concerned with canine functional neuroanatomy.

2013-01-01

144

Use of Functional Magnetic Resonance Imaging in the Early Identification of Alzheimer's Disease  

PubMed Central

A growing body of evidence suggests that a preclinical phase of Alzheimer’s disease (AD) exists several years or more prior to the overt manifestation of clinical symptoms and is characterized by subtle neuropsychological and brain changes. Identification of individuals prior to the development of significant clinical symptoms is imperative in order to have the greatest treatment impact by maintaining cognitive abilities and preserving quality of life. Functional magnetic resonance imaging (fMRI) offers considerable promise as a non-invasive tool for detecting early functional brain changes in asymptomatic adults. In fact, evidence to date indicates that functional brain decline precedes structural decline in preclinical samples. Therefore, fMRI may offer the unique ability to capture the dynamic state of change in the degenerating brain. This review examines the clinical utility of blood oxygen level dependent (BOLD) fMRI in those at risk for AD as well as in early AD. We provide an overview of fMRI findings in at-risk groups by virtue of genetic susceptibility or mild cognitive decline followed by an appraisal of the methodological issues concerning the diagnostic usefulness of fMRI in early AD. We conclude with a discussion of future directions and propose that BOLD-fMRI in combination with cerebral blood flow or diffusion techniques will provide a more complete accounting of the neurovascular changes that occur in preclinical AD and thus improve our ability to reliably detect early brain changes prior to disease onset.

Wierenga, Christina E.; Bondi, Mark W.

2007-01-01

145

Tracking Cognitive Change over 24 Weeks with Longitudinal Functional Magnetic Resonance Imaging in Alzheimer's Disease  

PubMed Central

Background Previous studies have revealed that functional magnetic resonance imaging (fMRI) blood oxygen level-dependent (BOLD) signal in specific brain regions correlates with cross-sectional performance on standardized clinical trial measures in Alzheimer's disease (AD); however, the relationship between longitudinal change in fMRI-BOLD signal and neuropsychological performance remains unknown. Objective: To identify changes in regional fMRI-BOLD activity that tracks change in neuropsychological performance in mild AD dementia over 6 months. Methods Twenty-four subjects (mean age 71.6) with mild AD dementia (mean Mini Mental State Examination 21.7, Global Clinical Dementia Rating 1.0) on stable donepezil dosing participated in two task-related fMRI sessions consisting of a face-name paired associative encoding memory paradigm 24 weeks apart during a randomized placebo-controlled pharmaco-fMRI drug study. Regression analysis was used to identify regions where the change in fMRI activity for Novel > Repeated stimulus contrast was associated with the change scores on postscan memory tests and the Free and Cued Selective Reminding Test (FCSRT). Results Correlations between changes in postscan memory accuracy and changes in fMRI activity were observed in regions including the angular gyrus, parahippocampal gyrus, inferior frontal gyrus and cerebellum. Correlations between changes in FCSRT-free recall and changes in fMRI were observed in regions including the inferior parietal lobule, precuneus, hippocampus and parahippocampal gyrus. Conclusion Changes in encoding-related fMRI activity in regions implicated in mnemonic networks correlated with changes in psychometric measures of episodic memory retrieval performed outside the scanner. These exploratory results support the potential of fMRI activity to track cognitive change and detect signals of short-term pharmacologic effect in early-phase AD studies.

McLaren, Donald G.; Sreenivasan, Aishwarya; Diamond, Eli L.; Mitchell, Meghan B.; Van Dijk, Koene R.A.; DeLuca, Amy N.; O'Brien, Jacqueline L.; Rentz, Dorene M.; Sperling, Reisa A.; Atri, Alireza

2012-01-01

146

Using fMRI to Study Recovery from Acquired Dysphasia  

Microsoft Academic Search

We have used functional magnetic resonance imaging (fMRI) to characterize brain activations associated with two distinct language tasks performed by a 28-year-old woman after partial recovery from dysphasia due to a left frontal hemispheric ischemic stroke. MRI showed that her ischemic lesion extended posteriorly from the left inferior frontal to the perisylvian cortex. fMRI scans of both language tasks revealed

Gemma A. Calvert; Michael J. Brammer; Robin G. Morris; Steve C. R. Williams; Nigel King; Paul M. Matthews

2000-01-01

147

Wide-range nuclear magnetic resonance detector  

NASA Technical Reports Server (NTRS)

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

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

1972-01-01

148

Principles of nuclear magnetic resonance.  

PubMed

The basic principles of nuclear magnetic resonance (NMR) are discussed. The concepts presented include a qualitative quantum-mechanical approach to NMR spectroscopy and a classical-mechanical approach to time-dependent NMR phenomena (relaxation effects). The spectroscopic concepts discussed include absorption of radiation by matter, spin and energy quantization , chemical shift, and spin-spin splitting. The time-dependent phenomena include the concepts of T1 and T2, the spin-lattice and spin-spin relaxation time, and Fourier-transform NMR spectroscopy. PMID:6726415

Koutcher, J A; Burt, C T

1984-01-01

149

Magnetic resonance imaging of acquired cardiac disease.  

PubMed Central

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

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

1996-01-01

150

Superconducting microwave resonator for millikelvin magnetic resonance force microscopy  

NASA Astrophysics Data System (ADS)

We have fabricated a superconducting resonator capable of generating a strong microwave magnetic field in a small (100 ?m) volume for low temperature magnetic resonance experiments. While the resonator was specifically developed for use at millikelvin temperatures in a dilution refrigerator, where the total cooling power is limited to a few hundred microwatts, it is also useful at temperatures up to 5 K. The resonator consists of a 220 ?m diameter, 2-1/2 turn niobium coil resonating with a short section of niobium microstripline. At a resonance frequency of 3 GHz, the loaded Q of the resonator was 780. The field strength was characterized by performing electron spin nutations. Operating at 100 mK with 320 ?W of dissipated power, the resonator generated a field of 4 G at a distance of 100 ?m from the coil.

Mamin, H. J.; Budakian, R.; Rugar, D.

2003-05-01

151

Informing brain connectivity with optogenetic functional magnetic resonance imaging.  

PubMed

Optogenetic functional magnetic resonance imaging (ofMRI) is a novel approach that combines optogenetic control of neural circuits with high-field functional MRI. Optogenetics is a neuro-modulation technology in which light-activated trans-membrane conductance regulators are introduced into specifically targeted cell types to allow temporally precise, millisecond-scale activity modulation in vivo. By combining optogenetic control with fMRI readout, neural activity arising from specific circuit elements defined by genetic identity, cell body location, and axonal projection targets can be monitored in vivo across the whole brain. These unique features of ofMRI open new vistas for in vivo characterization of the dense plexus of neural connections according to their type and functionality. PMID:22326987

Lee, Jin Hyung

2012-10-01

152

Deciphering laminar-specific neural inputs with line-scanning fMRI.  

PubMed

Using a line-scanning method during functional magnetic resonance imaging (fMRI), we obtained high temporal (50-ms) and spatial (50-?m) resolution information along the cortical thickness and showed that the laminar position of fMRI onset coincides with distinct neural inputs in rat somatosensory and motor cortices. This laminar-specific fMRI onset allowed us to identify the neural inputs underlying ipsilateral fMRI activation in the barrel cortex due to peripheral denervation-induced plasticity. PMID:24240320

Yu, Xin; Qian, Chunqi; Chen, Der-yow; Dodd, Stephen J; Koretsky, Alan P

2014-01-01

153

Quality Map Thresholding for De-noising of Complex-Valued fMRI Data and Its Application to ICA of fMRI.  

PubMed

Although functional magnetic resonance imaging (fMRI) data are acquired as complex-valued images, traditionally most fMRI studies only use the magnitude of the data. FMRI analysis in the complex domain promises to provide more statistically significant information; however, the noisy nature of the phase poses a challenge for successful study of fMRI by complex-valued signal processing algorithms. In this paper, we introduce a physiologically motivated de-noising method that uses phase quality maps to successfully identify and eliminate noisy areas in the fMRI data so they can be used in individual and group studies. Additionally, we show how the developed de-noising method improves the results of complex-valued independent component analysis of fMRI data, a very successful tool for blind source separation of biomedical data. PMID:21949563

Rodriguez, Pedro A; Correa, Nicolle M; Eichele, Tom; Calhoun, Vince D; Adali, Tülay

2009-09-01

154

Society for Cardiovascular Magnetic Resonance guidelines for reporting cardiovascular magnetic resonance examinations  

PubMed Central

These reporting guidelines are recommended by the Society for Cardiovascular Magnetic Resonance (SCMR) to provide a framework for healthcare delivery systems to disseminate cardiac and vascular imaging findings related to the performance of cardiovascular magnetic resonance (CMR) examinations.

Hundley, W Gregory; Bluemke, David; Bogaert, Jan G; Friedrich, Matthias G; Higgins, Charles B; Lawson, Mark A; McConnell, Michael V; Raman, Subha V; van Rossum, Albert C; Flamm, Scott; Kramer, Christopher M; Nagel, Eike; Neubauer, Stefan

2009-01-01

155

MAGNETIC RESONANCE ELASTOGRAPHY: A REVIEW  

PubMed Central

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

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

2011-01-01

156

Extension of dVCA model and its application in estimating fMRI components  

NASA Astrophysics Data System (ADS)

General linear model (GLM) and independent component analysis (ICA) are widely used methods in the community of functional magnetic resonance imaging (fMRI) data analysis. GLM and ICA are all assuming that fMRI components are location locked. Here we extend the Differentially variable component analysis (dVCA) and introduce it into fMRI data to analyze the transient changes during fMRI experiments which are ignored in GLM and ICA. We apply the extended dVCA to model fMRI images as the linear combination of ongoing activity and multiple fMRI components. We test our extended dVCA method on simulated images that mimicked the fMRI slice images containing two components, and employ the iterative maximum a posteriori (MAP) solution succeed to estimate each component's time-invariant spatial patterns, and its time-variant amplitude scaling factors and location shifts. The extended dVCA algorithm also identify two fMRI components that reflect the fact of hemispheric asymmetry for motor area in another test with fMRI data acquired with the block design task of right/left hand finger tapping alternately. This work demonstrates that our extended dVCA method is robustness to detect the variability of the fMRI components that maybe existent during the fMRI experiments.

Zhang, Gaoyan; Zhang, Jiacai; Yao, Li; Zhao, Xiaojie

2010-03-01

157

Magnetic Resonance Force Microscopy with Magnetic Tiped Cantilevers  

Microsoft Academic Search

Magnetic resonance force microscopy has been performed, until recently, by attaching the sample under study to a fragile microcantilever. Increasing the resolution, force-sensitivity and practicality of the technique, demands both reducing the size of the magnetic particle and measuring magnetic resonance as an excitation of magnetic-tip cantilevers. To lift the sample-on-cantilever restriction we have succesfully attached and controllably magnetized a

John A. Marohn; Raul Fainchtein; Doran D. Smith

1998-01-01

158

A mechanical analog of nuclear magnetic resonance  

NSDL National Science Digital Library

A mechanical analog apparatus for teaching Nuclear Magnetic Resonance is assembled of PVC, an air-bearing, a magnetic sphere, two sheet magnets, and a pair of Helmholtz coils. The magnetic sphere spins in the air-bearing due to turbine torque and acts as an ensemble of protons in the NMR system. The Helmholtz coils allow us to supply an AC magnetic field to perturb the sphere and search for resonance. The sheet magnets are on a slide. By moving them closer or further from the air bearing, we adjust the magnetic field at the sphere. The field at the air bearing is relatively uniform.

Masters, Mark F.

2013-02-13

159

Test-retest reliability in fMRI: Or how I learned to stop worrying and love the variability.  

PubMed

This paper briefly recounts the details of one of the first studies of whole brain, single subject variability in functional Magnetic Resonance Imaging (fMRI). In this paper I will not attempt to provide an overview of fMRI reliability, but will instead revisit the choices we made in performing our experiment as we did. PMID:22261373

McGonigle, David J

2012-08-15

160

Regression Models for Identifying Noise Sources in Magnetic Resonance Images  

PubMed Central

Stochastic noise, susceptibility artifacts, magnetic field and radiofrequency inhomogeneities, and other noise components in magnetic resonance images (MRIs) can introduce serious bias into any measurements made with those images. We formally introduce three regression models including a Rician regression model and two associated normal models to characterize stochastic noise in various magnetic resonance imaging modalities, including diffusion-weighted imaging (DWI) and functional MRI (fMRI). Estimation algorithms are introduced to maximize the likelihood function of the three regression models. We also develop a diagnostic procedure for systematically exploring MR images to identify noise components other than simple stochastic noise, and to detect discrepancies between the fitted regression models and MRI data. The diagnostic procedure includes goodness-of-fit statistics, measures of influence, and tools for graphical display. The goodness-of-fit statistics can assess the key assumptions of the three regression models, whereas measures of influence can isolate outliers caused by certain noise components, including motion artifacts. The tools for graphical display permit graphical visualization of the values for the goodness-of-fit statistic and influence measures. Finally, we conduct simulation studies to evaluate performance of these methods, and we analyze a real dataset to illustrate how our diagnostic procedure localizes subtle image artifacts by detecting intravoxel variability that is not captured by the regression models.

Zhu, Hongtu; Li, Yimei; Ibrahim, Joseph G.; Shi, Xiaoyan; An, Hongyu; Chen, Yashen; Gao, Wei; Lin, Weili; Rowe, Daniel B.; Peterson, Bradley S.

2009-01-01

161

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

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

162

Chemical Principles Revisited. Proton Magnetic Resonance Spectroscopy.  

ERIC Educational Resources Information Center

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

McQuarrie, Donald A.

1988-01-01

163

Functional Magnetic Resonance Imaging and Pediatric Anxiety  

ERIC Educational Resources Information Center

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

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

2008-01-01

164

[Cardiac magnetic resonance imaging (MRI)].  

PubMed

TECHNOLOGICAL PROGRESS: Although cardiac magnetic resonance imaging (MRI) is now recognised as the imaging method of choice for the morphological study of the heart, recent technological progress have widened its indications to functional analysis of the heart rate, perfusion and contractility. FUNCTIONAL ASSESSMENT: The possibility of conducting pharmacological stress tests enhances the functional exploration of cardiac perfusion and contractility. The rapid sequences in apnea, tissue marking and injection of contrast products are all elements that help to refine the study of the locoregional consequences of an ischemia: does the myocardial tissue contract normally? Is it sufficiently perfused? Is it still viable? THE BENEFITS OF A NON-INVASIVE TECHNIQUE: The MRI offers clinicians a non-invasive and non-radiating imaging technique that is the perfect supplement to echocardiography. A reliable angio-coronary LRI technique would, for the first time, permit exploration of the coronary vascularisation, tissue perfusion and resulting contractility. PMID:15387389

Vignaux, Olivier

2004-07-31

165

Coronary artery magnetic resonance angiography.  

PubMed

Coronary magnetic resonance angiography (coronary MRA) continues to advance rapidly from both a technical and clinical perspective. Coronary MRA has benefited directly from improvements in spatial resolution, contrast definition, and advances in motion correction, which have furthered its routine use in evaluating coronary artery bypass grafts and anomalous coronary arteries. Work in refining the techniques for more accurate identification of coronary artery disease (CAD) continues, with advances in navigator-gated and breath-hold motion correction techniques, novel k-space strategies (e.g., spiral and radial k-space filling), development and application of intravascular contrast agents, and imaging at higher field strengths. Ultimately, these developments may lead to the routine application of coronary MRA as a screening tool for CAD. This article reviews the development of coronary MRA, discusses the requirements and tools necessary for optimal visualization of the coronary arteries, and describes the application of coronary MRA to acquired and congenital CAD. PMID:15170777

Flamm, Scott D; Muthupillai, Raja

2004-06-01

166

Magnetic resonance imaging of cholangiocarcinoma.  

PubMed

Cholangiocarcinoma arises from the bile ducts and is the most common primary malignancy of the biliary tree. Cholangiocarcinoma is classified according to its growth pattern: mass-forming, periductal-infiltrating, or intraductal-growing type. The majority of cholangiocarcinomas occur at the common hepatic duct (CHD) and its bifurcation, also referred to as Klatskin's tumor, but they also can occur in more peripheral branches within the hepatic parenchyma. Microscopically, cholangiocarcinoma represents an adenocarcinoma with a glandular appearance arising from the epithelium of the bile ducts. On magnetic resonance (MR) images, cholangiocarcinomas appear hypointense on T1-weighted images, and hyperintense on T2-weighted images. Central hypointensity can be seen on T2-weighted images and correspond to fibrosis. On dynamic MR images, cholangiocarcinomas show moderate peripheral enhancement followed by progressive and concentric filling in the tumor with contrast material. Pooling of contrast within the tumor on delayed MR images is suggestive of peripheral cholangiocarcinoma. The role of MR imaging in hilar cholangiocarcinoma is to confirm/reach a diagnosis and to assess resectability. Hilar cholangiocarcinoma shows the same signal intensity pattern of peripheral tumors both on T1- and T2-weighted images. On magnetic resonance cholangiopancreatography (MRCP) images, hilar cholangiocarcinoma appears as a moderately irregular thickening of the bile duct wall (>/=5 mm) with symmetric upstream dilation of the intrahepatic bile ducts. The aim of preoperative investigation in Klatskin tumors typically requires the evaluation of the level of biliary obstruction, the intrahepatic tumor spread, and the vascular involvement; it also needs to show any atrophy-hypertrophy complex. Because of its intrinsic high tissue contrast and multiplanar capability, MR imaging and MRCP are able to detect and preoperatively assess patients with cholangiocarcinoma, investigating all involved structures such as bile ducts, vessels and hepatic parenchyma. The main reason for surgical/imaging discrepancy is represented by the microscopic diffusion along the mucosa and in the perineural space. PMID:15192788

Manfredi, Riccardo; Barbaro, Brunella; Masselli, Gabriele; Vecchioli, Amorino; Marano, Pasquale

2004-05-01

167

Magnetic resonance imaging of acetabular labral tears.  

PubMed

The acetabular labrum plays an important role in hip biomechanical function and stability. Labral tears can result in appreciable clinical symptoms and joint dysfunction and may predispose the hip to chondral damage and osteoarthritis. Magnetic resonance imaging is an effective tool for detecting and characterizing labral tears. Direct magnetic resonance arthrography is the most commonly used and validated technique for evaluating the labrum. However, indirect magnetic resonance arthrography and non-arthrographic magnetic resonance imaging are two less invasive and less resource-intensive techniques that should also be considered. Orthopaedic surgeons and radiologists should strive to develop and implement minimally and noninvasive diagnostic magnetic resonance imaging protocols for the investigation of labral pathology. PMID:21543685

Rakhra, Kawan S

2011-05-01

168

Magnetic resonance imaging of glioblastoma using aptamer conjugated magnetic nanoparticles  

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

169

Multidimensionally encoded magnetic resonance imaging.  

PubMed

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

Lin, Fa-Hsuan

2013-07-01

170

FMRI Effective Connectivity and TMS Chronometry: Complementary Accounts of Causality in the Visuospatial Judgment Network  

Microsoft Academic Search

BackgroundWhile traditionally quite distinct, functional neuroimaging (e.g. functional magnetic resonance imaging: fMRI) and functional interference techniques (e.g. transcranial magnetic stimulation: TMS) increasingly address similar questions of functional brain organization, including connectivity, interactions, and causality in the brain. Time-resolved TMS over multiple brain network nodes can elucidate the relative timings of functional relevance for behavior (“TMS chronometry”), while fMRI functional or

Tom A. de Graaf; Christianne Jacobs; Alard Roebroeck; Alexander T. Sack; Bernhard T. Baune

2009-01-01

171

Linear constraint minimum variance beamformer functional magnetic resonance inverse imaging  

PubMed Central

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

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

2011-01-01

172

Statistical Improvements in Functional Magnetic Resonance Imaging Analyses Produced by Censoring High-Motion Data Points  

PubMed Central

Subject motion degrades the quality of task functional magnetic resonance imaging (fMRI) data. Here, we test two classes of methods to counteract the effects of motion in task fMRI data: (1) a variety of motion regressions and (2) motion censoring (“motion scrubbing”). In motion regression, various regressors based on realignment estimates were included as nuisance regressors in general linear model (GLM) estimation. In motion censoring, volumes in which head motion exceeded a threshold were withheld from GLM estimation. The effects of each method were explored in several task fMRI data sets and compared using indicators of data quality and signal-to-noise ratio. Motion censoring decreased variance in parameter estimates within- and across-subjects, reduced residual error in GLM estimation, and increased the magnitude of statistical effects. Motion censoring performed better than all forms of motion regression and also performed well across a variety of parameter spaces, in GLMs with assumed or unassumed response shapes. We conclude that motion censoring improves the quality of task fMRI data and can be a valuable processing step in studies involving populations with even mild amounts of head movement.

Siegel, Joshua S.; Power, Jonathan D.; Dubis, Joseph W.; Vogel, Alecia C.; Church, Jessica A.; Schlaggar, Bradley L.; Petersen, Steven E.

2013-01-01

173

Statistical improvements in functional magnetic resonance imaging analyses produced by censoring high-motion data points.  

PubMed

Subject motion degrades the quality of task functional magnetic resonance imaging (fMRI) data. Here, we test two classes of methods to counteract the effects of motion in task fMRI data: (1) a variety of motion regressions and (2) motion censoring ("motion scrubbing"). In motion regression, various regressors based on realignment estimates were included as nuisance regressors in general linear model (GLM) estimation. In motion censoring, volumes in which head motion exceeded a threshold were withheld from GLM estimation. The effects of each method were explored in several task fMRI data sets and compared using indicators of data quality and signal-to-noise ratio. Motion censoring decreased variance in parameter estimates within- and across-subjects, reduced residual error in GLM estimation, and increased the magnitude of statistical effects. Motion censoring performed better than all forms of motion regression and also performed well across a variety of parameter spaces, in GLMs with assumed or unassumed response shapes. We conclude that motion censoring improves the quality of task fMRI data and can be a valuable processing step in studies involving populations with even mild amounts of head movement. PMID:23861343

Siegel, Joshua S; Power, Jonathan D; Dubis, Joseph W; Vogel, Alecia C; Church, Jessica A; Schlaggar, Bradley L; Petersen, Steven E

2014-05-01

174

Surface-based analysis methods for high-resolution functional magnetic resonance imaging  

PubMed Central

Functional magnetic resonance imaging (fMRI) has become a popular technique for studies of human brain activity. Typically, fMRI is performed with >3-mm sampling, so that the imaging data can be regarded as two-dimensional samples that average through the 1.5—4-mm thickness of cerebral cortex. The increasing use of higher spatial resolutions, <1.5-mm sampling, complicates the analysis of fMRI, as one must now consider activity variations within the depth of the brain tissue. We present a set of surface-based methods to exploit the use of high-resolution fMRI for depth analysis. These methods utilize white-matter segmentations coupled with deformable-surface algorithms to create a smooth surface representation at the gray-white interface and pial membrane. These surfaces provide vertex positions and normals for depth calculations, enabling averaging schemes that can increase contrast-to-noise ratio, as well as permitting the direct analysis of depth profiles of functional activity in the human brain.

Khan, Rez; Zhang, Qin; Darayan, Shayan; Dhandapani, Sankari; Katyal, Sucharit; Greene, Clint; Bajaj, Chandra; Ress, David

2011-01-01

175

Functional magnetic resonance imaging reflects changes in brain functioning with sedation.  

PubMed

Functional magnetic resonance imaging (fMRI) studies have demonstrated localized brain activation during cognitive tasks. Brain activation increases with task complexity and decreases with familiarity. This study investigates how sleepiness alters the relationship between brain activation and task familiarity. We hypothesize that sleepiness prevents the reduction in activation associated with practice. Twenty-nine individuals rated their sleepiness using the Stanford Sleepiness Scale before fMRI. During imaging, subjects performed the Paced Auditory Serial Addition Test, a continuous mental arithmetic task. A positive correlation was observed between self-rated sleepiness and frontal brain activation. Fourteen subjects participated in phase 2. Sleepiness was induced by evening dosing with chlorpheniramine (CP) (8 mg or 12 mg) and terfenadine (60 mg) in the morning for 3 days before the second fMRI scan. The Multiple Sleep Latency Test (MSLT) was also performed. Results revealed a significant increase in fMRI activation in proportion to the dose of CP. In contrast, for all subjects receiving placebo there was a reduction in brain activation. MSLT revealed significant daytime sleepiness for subjects receiving CP. These findings suggest that sleepiness interferes with efficiency of brain functioning. The sleepy or sedated brain shows increased oxygen utilization during performance of a familiar cognitive task. Thus, the beneficial effect of prior task exposure is lost under conditions of sedation. Copyright 2000 John Wiley & Sons, Ltd. PMID:12404614

Starbuck, Victoria N; Kay, Gary G; Platenberg, R. Craig; Lin, Chin-Shoou; Zielinski, Brandon A

2000-12-01

176

Magnetic nanostructures as amplifiers of transverse fields in magnetic resonance.  

PubMed

We introduce the concept of amplifying the transverse magnetic fields produced and/or detected with inductive coils in magnetic resonance settings by using the reversible transverse susceptibility properties of magnetic nanostructures. First, we describe the theoretical formalism of magnetic flux amplification through the coil in the presence of a large perpendicular DC magnetic field (typical of magnetic resonance systems) achieved through the singularity in the reversible transverse susceptibility in anisotropic single domain magnetic nanoparticles. We experimentally demonstrate the concept of transverse magnetic flux amplification in an inductive coil system using oriented nanoparticles with uni-axial magnetic anisotropy. We also propose a composite ferromagnetic/anti-ferromagnetic core/shell nanostructure system with uni-directional magnetic anisotropy that, in principle, provides maximal transverse magnetic flux amplification. PMID:16039099

Barbic, Mladen; Scherer, Axel

2005-09-01

177

A Demonstration Model of Magnetic Resonance  

ERIC Educational Resources Information Center

Describes a simple and inexpensive model to demonstrate the pulsed magnetic resonance phenomenon. Gives the details of construction of the device which can provide a direct demonstration of the precessional motion of a magnetic moment in a steady magnetic field. (Author/GS)

Sandhu, H. S.; Peemoeller, H.

1974-01-01

178

Simultaneous acquisition of corrugator electromyography and functional magnetic resonance imaging: A new method for objectively measuring affect and neural activity concurrently  

Microsoft Academic Search

The development of functional neuroimaging of emotion holds the promise to enhance our understanding of the biological bases of affect and improve our knowledge of psychiatric diseases. However, up to this point, researchers have been unable to objectively, continuously and unobtrusively measure the intensity and dynamics of affect concurrently with functional magnetic resonance imaging (fMRI). This has hindered the development

Aaron S. Heller; Lawrence L. Greischar; Ann Honor; Michael J. Anderle; Richard J. Davidson

2011-01-01

179

Reducing the Effects of Background Noise during Auditory Functional Magnetic Resonance Imaging of Speech Processing: Qualitative and Quantitative Comparisons between Two Image Acquisition Schemes and Noise Cancellation  

ERIC Educational Resources Information Center

Purpose: The intense sound generated during functional magnetic resonance imaging (fMRI) complicates studies of speech and hearing. This experiment evaluated the benefits of using active noise cancellation (ANC), which attenuates the level of the scanner sound at the participant's ear by up to 35 dB around the peak at 600 Hz. Method: Speech and…

Blackman, Graham A.; Hall, Deborah A.

2011-01-01

180

Magnetic resonance elastometry using a single-sided permanent magnet  

NASA Astrophysics Data System (ADS)

In this paper, we describe a magnetic resonance method of measuring material elasticity using a single-sided magnet with a permanent static field gradient. This method encodes sample velocity in a reciprocal space using Hahn spin-echoes with variable timing. The experimental results show a strong correlation between magnetic resonance signal attenuation and elasticity when an oscillating force is applied on the sample. This relationship in turn provides us with information about the displacement velocity experienced by the sample, which is inversely proportional to Young's modulus. The proposed method shows promise in offering a portable and cost-effective magnetic resonance elastography system.

Tan, Carl S.; Marble, Andrew E.; Ono, Yuu

2012-04-01

181

Modern Miracle Medical Machines: Magnetic Resonance Imaging  

NSDL National Science Digital Library

This learning activity teaches the physics of magnetic resonance imaging and NMR. It begins with instruction on the basics of magnetism, electromagnetism, and resonance and applies these topics to the operation of magnetic resonance equipment for medical diagnostics. This activity includes both hands-on exercises and computer visualizations. Information on the construction of the measurement apparatus is available in the instructor resources for the Modern Miracle Medical Machines web site. This one of a growing set of activities developed by the Kansas State University Physics Education Research group on the physics of modern medicine.

Murphy, Sytil K.

2010-06-08

182

Role of Ongoing, Intrinsic Activity of Neuronal Populations for Quantitative Neuroimaging of Functional Magnetic Resonance Imaging-Based Networks  

PubMed Central

Abstract A primary objective in neuroscience is to determine how neuronal populations process information within networks. In humans and animal models, functional magnetic resonance imaging (fMRI) is gaining increasing popularity for network mapping. Although neuroimaging with fMRI—conducted with or without tasks—is actively discovering new brain networks, current fMRI data analysis schemes disregard the importance of the total neuronal activity in a region. In task fMRI experiments, the baseline is differenced away to disclose areas of small evoked changes in the blood oxygenation level-dependent (BOLD) signal. In resting-state fMRI experiments, the spotlight is on regions revealed by correlations of tiny fluctuations in the baseline (or spontaneous) BOLD signal. Interpretation of fMRI-based networks is obscured further, because the BOLD signal indirectly reflects neuronal activity, and difference/correlation maps are thresholded. Since the small changes of BOLD signal typically observed in cognitive fMRI experiments represent a minimal fraction of the total energy/activity in a given area, the relevance of fMRI-based networks is uncertain, because the majority of neuronal energy/activity is ignored. Thus, another alternative for quantitative neuroimaging of fMRI-based networks is a perspective in which the activity of a neuronal population is accounted for by the demanded oxidative energy (CMRO2). In this article, we argue that network mapping can be improved by including neuronal energy/activity of both the information about baseline and small differences/fluctuations of BOLD signal. Thus, total energy/activity information can be obtained through use of calibrated fMRI to quantify differences of ?CMRO2 and through resting-state positron emission tomography/magnetic resonance spectroscopy measurements for average CMRO2.

Herman, Peter; Sanganahalli, Basavaraju G.; Coman, Daniel; Blumenfeld, Hal; Rothman, Douglas L.

2011-01-01

183

Revealing human ocular dominance columns using high-resolution functional magnetic resonance imaging.  

PubMed

In this review, I will recall some events at the time when we conducted a high-resolution functional magnetic resonance imaging (fMRI) study mapping ocular dominance columns in humans (Cheng et al., 2001). In particular, I will comment on why and how we had to deal with several key issues in the experimental procedure that we developed in this study, including the adoption of prolonged monocular stimulation, the treatment of large surface veins and the prescription of imaging slice on selected subjects. I will then touch upon several key developments after our work was published and give my thoughts on the challenges that the field of high-resolution fMRI faces. PMID:21914484

Cheng, Kang

2012-08-15

184

Magnetic Resonance Imaging of Glutamate  

PubMed Central

Glutamate (Glu) exhibits a pH and concentration dependent chemical exchange saturation transfer effect (CEST) between its -amine group and bulk water, here termed GluCEST. GluCEST asymmetry is observed at ~3 parts per million downfield from bulk water. Following middle cerebral artery occlusion in the rat brain, an approximately 100% elevation of GluCEST in the ipsilateral side compared to the contralateral side was observed, and is predominantly due to pH changes. In a rat brain tumor model with blood brain barrier disruption, intravenous Glu injection resulted in a clear elevation of GluCEST and a comparable increase in the proton magnetic resonance spectroscopy signal of Glu. GluCEST maps from healthy human brain at 7T were also obtained. These results demonstrate the feasibility and potential of GluCEST for mapping relative changes in Glu concentration as well as pH in vivo. Potential contributions from other brain metabolites to the GluCEST effect are also discussed.

Cai, Kejia; Haris, Mohammad; Singh, Anup; Kogan, Feliks; Greenberg, Joel H.; Hariharan, Hari; Detre, John A.; Reddy, Ravinder

2011-01-01

185

Ferromagnetic Resonance Imaging with Magnetic Resonance Force Microscopy  

NASA Astrophysics Data System (ADS)

Magnetic resonance force microscopy achieves very high resolution three-dimensional imaging capabilities of magnetic resonance imaging by taking advantage of very high sensitivity mechanical force detection. This enables non-contacting, microscopic studies and imaging of a broad range of materials. As a consequence of the strong interactions between spins, the assumptions underlying conventional MRI are not applicable to FMR imaging. However, using a new approach to localizing the resonant volume in an FMR measurement founded on the strong, nonuniform magnetic field of the micromagnetic probe tip, we have demonstrated scanned probe Ferromagnetic Resonance (FMR) imaging [1]. The scanned probe FMR images obtained in patterned ferromagnetic films are well explained by detailed numerical modeling. In addition to illuminating the mechanisms underlying localized FMR, the model provides the basis for submicron scanned probe FMR imaging of films and buried ferromagnetic elements. This work was supported by the U.S. Department of Energy through Grant No. DE-FG02-03ER46054. [1] ``Local Ferromagnetic Resonance Imaging with Magnetic Resonance Force Microscopy,'' Yu. Obukhov, D.V. Pelekhov, J. Kim, P. Banerjee, I. Martin, E. Nazaretski, R. Movshovich, S. An, T.J. Gramila, S. Batra, and P. C. Hammel, Phys. Rev. Lett. 100(19), 197601 (2008).

Pelekhov, Denis

2009-03-01

186

Optimization of Blocked Designs in fMRI Studies  

ERIC Educational Resources Information Center

Blocked designs in functional magnetic resonance imaging (fMRI) are useful to localize functional brain areas. A blocked design consists of different blocks of trials of the same stimulus type and is characterized by three factors: the length of blocks, i.e., number of trials per blocks, the ordering of task and rest blocks, and the time between…

Maus, Barbel; van Breukelen, Gerard J. P.; Goebel, Rainer; Berger, Martijn P. F.

2010-01-01

187

Activation detection on FMRI time series using hidden Markov model  

Microsoft Academic Search

This paper introduces several unsupervised learning methods for analyzing functional magnetic resonance imaging (fMRI) data based on hidden Markov model (HMM). Unlike the conventional general linear model (GLM) method, which aims at modelling the blood oxygen level-depend (BOLD) response of a voxel as a function of time, HMM approach is focused on capturing the first order statistical evolution among the

Rong Duan; Hong Man; Wei Jiang; Wen-Ching Liu

2005-01-01

188

Coronary computed tomography and magnetic resonance imaging.  

PubMed

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

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

2009-04-01

189

Coronary Computed Tomography and Magnetic Resonance Imaging  

PubMed Central

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

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

2009-01-01

190

Miniature Magnet for Electron Spin Resonance Experiments  

ERIC Educational Resources Information Center

Describes commercially available permanent magnets that have been incorporated in a compact and inexpensive structure providing both field sweep and modulation suitable for electron spin resonance at microwave frequencies. (MLH)

Rupp, L. W.; And Others

1976-01-01

191

International Society for Magnetic Resonance in Medicine  

MedlinePLUS

... Links Workshop & Educational Course Series ISMRM Workshop on Functional MRI: Emerging Techniques & New Interpretations 22-25 June ... Are The International Society for Magnetic Resonance in Medicine is a nonprofit professional association dedicated to promoting ...

192

Mathematical Foundations for Magnetic Resonance Imaging.  

National Technical Information Service (NTIS)

Over the past decade, the technical development of Magnetic Resonance Imaging (MRI) has been very rapid. This report provides the theoretical framework for the understanding and the design of new imaging sequences, and points out limitations of achievable...

S. Mansson

1995-01-01

193

The Retinotopic Organization of Primate Dorsal V4 and Surrounding Areas: A Functional Magnetic Resonance Imaging Study in Awake Monkeys  

Microsoft Academic Search

Using functional magnetic resonance imaging (fMRI), we mapped the retinotopic organization throughout the visual cortex of fixating monkeys. The retinotopy observed in areas V1, V2, and V3 was completely consistent with the classical view. V1 and V3 were bordered rostrally by a vertical meridian representation, and V2 was bordered by a horizontal meridian. More anterior in occipital cortex, both areas

Denis Fize; Wim Vanduffel; Koen Nelissen; Katrien Denys; Christophe Chef d'Hotel; Olivier Faugeras; Guy A. Orban

2003-01-01

194

Functional Magnetic Resonance Imaging of Compensatory Neural Recruitment in Aging and Risk for Alzheimer’s Disease: Review and Recommendations  

Microsoft Academic Search

There has been a recent proliferation of functional magnetic resonance imaging (fMRI) studies that interpret between-group or within-group differences in brain response patterns as evidence for compensatory neural recruitment. However, it is currently a challenge to determine whether these observed differences are truly attributable to compensatory neural recruitment or whether they are indicative of some other cognitive or physiological process.

S. Duke Han; Katherine J. Bangen; Mark W. Bondi

2009-01-01

195

Tracking Cognitive Change over 24 Weeks with Longitudinal Functional Magnetic Resonance Imaging in Alzheimer’s Disease  

Microsoft Academic Search

Background: Previous studies have revealed that functional magnetic resonance imaging (fMRI) blood oxygen level-dependent (BOLD) signal in specific brain regions correlates with cross-sectional performance on standardized clinical trial measures in Alzheimer’s disease (AD); however, the relationship between longitudinal change in fMRI-BOLD signal and neuropsychological performance remains unknown. Objective: To identify changes in regional fMRI-BOLD activity that tracks change in neuropsychological

Donald G. McLaren; Aishwarya Sreenivasan; Eli L. Diamond; Meghan B. Mitchell; Koene R. A. Van Dijk; Amy N. DeLuca; Jacqueline L. O’Brien; Dorene M. Rentz; Reisa A. Sperling; Alireza Atri

2012-01-01

196

Spectacular shrinking deficit: insights from multimodal magnetic resonance imaging after embolic middle cerebral artery occlusion in Sprague–Dawley rats  

Microsoft Academic Search

Almost no data is available on the serial changes in the brain after spectacular shrinking deficit (SSD) that may help understand this relatively rare clinical phenomenon. Quantitative diffusion-(DWI), perfusion-(PWI), T1-(T1WI), T2-weighted (T2WI), and functional magnetic resonance imaging (fMRI) were performed before, during, and up to 7 days after embolic middle cerebral artery occlusion (eMCAO) in male Sprague–Dawley rats (n=9). Region

Nils Henninger; Kenneth M. Sicard; Marc Fisher

2007-01-01

197

Effects of noise from functional magnetic resonance imaging on auditory event-related potentials in working memory task  

Microsoft Academic Search

The effects of functional magnetic resonance imaging (fMRI) acoustic noise were investigated on the parameters of event-related responses (ERPs) elicited during auditory matching-to-sample location and pitch working memory tasks. Stimuli were tones with varying location (left or right) and frequency (high or low). Subjects were instructed to memorize and compare either the locations or frequencies of the stimuli with each

Nikolai Novitski; Irina Anourova; Sami Martinkauppi; Hannu J Aronen; Risto Näätänen; Synnöve Carlson

2003-01-01

198

Magnetic resonance elastography of liver: clinical applications.  

PubMed

Magnetic resonance elastography (MRE) has been successfully implemented in the assessment of diffuse liver diseases. Currently, MRE is the most accurate noninvasive technique for detection and staging of liver fibrosis with a potential to replace liver biopsy. Magnetic resonance elastography is able to differentiate isolated fatty liver disease from steatohepatitis with or without fibrosis. Potential clinical applications include the differentiation of benign and malignant focal liver masses and the assessment of treatment response in diffuse liver diseases. PMID:24270110

Venkatesh, Sudhakar K; Yin, Meng; Ehman, Richard L

2013-01-01

199

Magnetic Resonance Elastography of Liver: Clinical Applications  

PubMed Central

Magnetic resonance elastography (MRE) has been successfully implemented in the assessment of diffuse liver diseases. Currently, MRE is the most accurate noninvasive technique for detection and staging of liver fibrosis with a potential to replace liver biopsy. Magnetic resonance elastography is able to differentiate isolated fatty liver disease from steatohepatitis with or without fibrosis. Potential clinical applications include the differentiation of benign and malignant focal liver masses and the assessment of treatment response in diffuse liver diseases.

Venkatesh, Sudhakar K.; Yin, Meng; Ehman, Richard L.

2014-01-01

200

Neuropsychological Predictors of BOLD Response During a Spatial Working Memory Task in Adolescents: What Can Performance Tell Us About fMRI Response Patterns?  

Microsoft Academic Search

The relationship between standardized neuropsychological test performance and functional magnetic resonance imaging (fMRI) response during cognitive tasks is largely unknown. This exploratory investigation examined the relationship between neuropsychological test performance and fMRI response to a spatial working memory (SWM) task among 49 typically developing adolescents. Participants were administered a variety of neuropsychological tests in the domains of working memory, visuospatial

Bonnie J. Nagel; Valerie C. Barlett; Alecia D. Schweinsburg; Susan F. Tapert

2005-01-01

201

Nuclear Magnetic Resonance in Liquid Crystal Solvents  

Microsoft Academic Search

Since the discovery by Saupe and Englert that a nematic phase is a satisfactory solvent for high resolution nuclear magnetic resonance (NMR) studies, the variety of liquid crystal phases which have been found useful in NMR experiments has greatly increased. The resonance studies have increased our understanding of the structure of the solvent mesophases, and of their interactions with solute

Lawrence C. Snyder; Saul Meiboom

1969-01-01

202

The Direct Detection of a Single Evoked Action Potential with Magnetic Resonance Spectroscopy in Lumbricus Terrestris  

PubMed Central

Functional MRI (fMRI) indirectly measures neural activity by detecting the signal change associated with the hemodynamic response following brain activation. In order to alleviate the temporal and spatial specificity problems associated with fMRI, a number of attempts have been made to detect neural magnetic fields (NMFs) with MRI directly, but have thus far provided conflicting results. In the present study, we used magnetic resonance to detect axonal NMFs in the median giant fiber of the earthworm, Lumbricus terrestris, by examining the free-induction decay (FID) with a sampling interval of 0.32 ms. The earthworm nerve cords were isolated from the vasculature and stimulated at the threshold of action potential generation. FIDs were acquired shortly after the stimulation and simultaneous field potential recordings identified the presence or absence of single evoked action potentials. FIDs acquired when the stimulus did not evoke an action potential were summed as background. The phase of the background-subtracted FID exhibited a systematic change, with a peak phase difference of [-1.2 ± 0.3] ×10-5 radians occurring at a time corresponding to the timing of the action potential. In addition, we calculated the possible changes in the FID magnitude and phase due to a simulated action potential using a volume conductor model. The measured phase difference matched the theoretical prediction well in both amplitude and temporal characteristics. This study provides the first evidence for the direct detection of a magnetic field from an evoked action potential using magnetic resonance.

Poplawsky, Alexander J.; Dingledine, Raymond

2011-01-01

203

Functional magnetic resonance imaging and somatosensory evoked potentials in rats with a neonatally induced freeze lesion of the somatosensory cortex.  

PubMed

Brain plasticity is an important mechanism for functional recovery from a cerebral lesion. The authors aimed to visualize plasticity in adult rats with a neonatal freeze lesion in the somatosensory cortex using functional magnetic resonance imaging (fMRI), and hypothesized activation outside the primary projection area. A freeze lesion was induced in the right somatosensory cortex of newborn Wistar rats (n = 12). Sham-operated animals (n = 7) served as controls. After 6 or 7 months, a neurologic examination was followed by recording of somatosensory evoked potentials (SSEPs) and magnetic resonance experiments (anatomical images, fMRI with blood oxygen level-dependent contrast and perfusion-weighted imaging) with electrical forepaw stimulation under alpha-chloralose anesthesia. Lesioned animals had no obvious neurologic deficits. Anatomical magnetic resonance images showed a malformed cortex or hyperintense areas (cysts) in the lesioned hemisphere. SSEPs were distorted and smaller in amplitude, and fMRI activation was significantly weaker in the lesioned hemisphere. Only in a few animals were cortical areas outside the primary sensory cortex activated. The results are discussed in respect to an apparent absence of plasticity, loss of excitable tissue, the excitability of the lesioned hemisphere, altered connectivity, and a disturbed coupling of increased neuronal activity to the hemodynamic response. PMID:15625415

Schwindt, Wolfram; Burke, Michael; Pillekamp, Frank; Luhmann, Heiko J; Hoehn, Mathias

2004-12-01

204

PTFOS: Flexible and Absorbable Intracranial Electrodes for Magnetic Resonance Imaging  

PubMed Central

Intracranial electrocortical recording and stimulation can provide unique knowledge about functional brain anatomy in patients undergoing brain surgery. This approach is commonly used in the treatment of medically refractory epilepsy. However, it can be very difficult to integrate the results of cortical recordings with other brain mapping modalities, particularly functional magnetic resonance imaging (fMRI). The ability to integrate imaging and electrophysiological information with simultaneous subdural electrocortical recording/stimulation and fMRI could offer significant insight for cognitive and systems neuroscience as well as for clinical neurology, particularly for patients with epilepsy or functional disorders. However, standard subdural electrodes cause significant artifact in MRI images, and concerns about risks such as cortical heating have generally precluded obtaining MRI in patients with implanted electrodes. We propose an electrode set based on polymer thick film organic substrate (PTFOS), an organic absorbable, flexible and stretchable electrode grid for intracranial use. These new types of MRI transparent intracranial electrodes are based on nano-particle ink technology that builds on our earlier development of an EEG/fMRI electrode set for scalp recording. The development of MRI-compatible recording/stimulation electrodes with a very thin profile could allow functional mapping at the individual subject level of the underlying feedback and feed forward networks. The thin flexible substrate would allow the electrodes to optimally contact the convoluted brain surface. Performance properties of the PTFOS were assessed by MRI measurements, finite difference time domain (FDTD) simulations, micro-volt recording, and injecting currents using standard electrocortical stimulation in phantoms. In contrast to the large artifacts exhibited with standard electrode sets, the PTFOS exhibited no artifact due to the reduced amount of metal and conductivity of the electrode/trace ink and had similar electrical properties to a standard subdural electrode set. The enhanced image quality could enable routine MRI exams of patients with intracranial electrode implantation and could also lead to chronic implantation solutions.

Bonmassar, Giorgio; Fujimoto, Kyoko; Golby, Alexandra J.

2012-01-01

205

Target image search using fMRI signals  

NASA Astrophysics Data System (ADS)

Recent neural signal decoding studies based on functional magnetic resonance imaging (fMRI) have identified the specific image presenting to the subject from a set of potential images, and some studies extend neural decoding into image reconstruction, i.e. image contents that the subject perceived were decoded from the fMRI signals recorded during the subject looking at images. In this paper, we decoded the target images using fMRI signals and described a target image searching method based on the relationship between target image stimuli and fMRI activity. We recorded fMRI data during a serial visual stimuli image presentation task, some of the stimuli images were target images and the rest images were non-target ones. Our fMRI data analysis results showed that in the serial visual presentation task, target images elicited a stereotypical response in the fMRI, which can be detected by multi-voxel pattern analysis (MVPA). Classifiers designed with support vector machine (SVM) used this response to decipher target images from non-target images. The leave-one-run-out cross-validation showed that we can pick out the target images with a possibility far above the chance level, which indicate that there's a neural signatures correlated with the target image recognition process in the human systems.

Xiong, Shi; Song, Sutao; Zhan, Yu; Zhang, Jiacai

2014-03-01

206

Magnetic-Resonance Studies of Coal. Volume IV.  

National Technical Information Service (NTIS)

As part of a continuing magnetic resonance characterization of geologically-selected coals, Electron Spin Resonance (ESR) and Nuclear Magnetic Resonance (NMR) studies have been conducted on coal seams which lie within the Pratt group of the Warrior Basin....

I. Miyagawa C. Alexander

1982-01-01

207

Fano resonances in magnetic metamaterials  

SciTech Connect

We study the scattering of magnetoinductive plane waves by internal (external) capacitive (inductive) defects coupled to a one-dimensional split-ring resonator array. We examine a number of simple defect configurations where Fano resonances occur and study the behavior of the transmission coefficient as a function of the controllable external parameters. We find that for embedded capacitive defects, the addition of a small amount of coupling to second neighbors is necessary for the occurrence of Fano resonance. For external inductive defects, Fano resonances are commonplace, and they can be tuned by changing the relative orientation or distance between the defect and the SSR array.

Naether, Uta; Molina, Mario I. [Departmento de Fisica, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago (Chile) and Center for Optics and Photonics (CEFOP), Casilla 4016, Concepcion (Chile)

2011-10-15

208

Magnetic resonance in radiating or absorbing atoms  

Microsoft Academic Search

Investigation of atomic energy levels using magnetic resonance ; techniques is discussed. A review is presenied of some of the studies of atomic ; vapors in connection with level structures and the mutual interactions of light ; oscillating magnetic fields and the effects of collisions. (auth);

F. Bitter

1962-01-01

209

Homodyne detection in magnetic resonance imaging  

Microsoft Academic Search

Magnetic detection of complex images in magnetic resonance imaging (MRI) is immune to the effects of incidental phase variations, although in some applications information is lost or images are degraded. It is suggested that synchronous detection or demodulation can be used in MRI systems in place of magnitude detection to provide complete suppression of undesired quadrature components, to preserve polarity

Douglas C. Noll; Dwight G. Nishimura; Albert Macovski

1991-01-01

210

Pulse Shaping for Localized Magnetic Resonance Tagging.  

National Technical Information Service (NTIS)

Magnetic resonance tagging is usually achieved by means of a train of non-selective radio-frequency pulses separated by gradient pulses. Thus, the modulation of the M(sub z) magnetization component expands all over the imaging plane. It has been proposed ...

V. N. Ikonomidou G. D. Sergiadis

2001-01-01

211

Pressure Activated Driver for Magnetic Resonance Elastography.  

National Technical Information Service (NTIS)

A driver for use in applying an oscillating stress to a subject undergoing a magnetic resonance elastography (MRE) examination includes a passive actuator located in the bore of the magnet and in contact with the subject. A remotely located acoustic drive...

M. A. Dresner P. J. Rossman R. L. Ehman T. C. Hulshizer

2004-01-01

212

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

PubMed

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

van de Groep, J; Polman, A

2013-11-01

213

Investigation of laser polarized xenon magnetic resonance  

NASA Technical Reports Server (NTRS)

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

Walsworth, Ronald L.

1998-01-01

214

Scanning ferromagnetic resonance microscopy and resonant heating of magnetite nanoparticles: Demonstration of thermally detected magnetic resonance  

NASA Astrophysics Data System (ADS)

We report a 9 GHz microwave scanning probe based on a slit aperture for spatially resolved magnetic resonance detection. We use patterned layers of dispersed magnetite Fe3O4 nanoparticles and demonstrate low-field ferromagnetic resonance images with a spatial resolution of 15 ?m. We also demonstrate localized heating of magnetite nanoparticles via ferromagnetic resonance absorption which can be controlled by an external dc magnetic field. Using our microwave probe as a transmitter and a temperature sensor (thermocouple or infrared detector), we show thermally detected magnetic resonance at room temperature.

Sakran, F.; Copty, A.; Golosovsky, M.; Davidov, D.; Monod, P.

2004-05-01

215

Magnetic resonance imaging and magnetic resonance spectroscopic imaging of prostate cancer  

Microsoft Academic Search

Magnetic resonance imaging (MRI) and magnetic resonance spectroscopic imaging (MRSI) are evolving techniques that offer noninvasive evaluation of anatomic and metabolic features of prostate cancer. The ability of MRI to determine the location and extent of the tumor and to identify metastatic spread is useful in the pretreatment setting, enabling treatment decision-making that is evidence-based. MRSI of the prostate gland

Renata Huzjan; Evis Sala; Hedvig Hricak

2005-01-01

216

Magnetic resonance imaging: effects of magnetic field strength  

SciTech Connect

Magnetic resonance images of the head, abdomen, and pelvis of normal adult men were obtained using varying magnetic field strength, and measurements of T1 and T2 relaxations and of signal-to-noise (SN) ratios were determined. For any one spin echo sequence, gray/white matter contrast decreases and muscle/fat contrast increases with field. SN levels rise rapidly up to 3.0 kgauss and then change more slowly, actually dropping for muscle. The optimum field for magnetic resonance imaging depends on tissue type, body part, and imaging sequence, so that it does not have a unique value. Magnetic resonance systems that operate in the 3.0-5.0 kgauss range achieve most or all of the gains that can be achieved by higher magnetic fields.

Crooks, L.E.; Arakawa, M.; Hoenninger, J.; McCarten, B.; Watts, J.; Kaufman, L.

1984-04-01

217

A toolbox for model-free analysis of fMRI data  

Microsoft Academic Search

We introduce MFBOX (Model-free Toolbox), a Matlab toolbox for analyzing multivariate data sets in an explorative fashion. Its main focus lies on the analysis of functional Nuclear Magnetic Resonance Imaging (fMRI) data sets with various model-free or data-driven techniques. In this context, it can also be used as plugin for SPM5, a popular tool in regression-based fMRI analysis. The toolbox

Peter Gruber; C. Kohler; Fabian J. Theis

2007-01-01

218

A Statistical Framework for Optimal Design Matrix Generation With Application to fMRI  

Microsoft Academic Search

The general linear model (GLM) is a well established tool for analyzing\\u000afunctional magnetic resonance imaging (fMRI) data. Most fMRI analyses via GLM\\u000aproceed in a massively univariate fashion where the same design matrix is used\\u000afor analyzing data from each voxel. A major limitation of this approach is the\\u000alocally varying nature of signals of interest as well as

Gautam V. Pendse; Richard Baumgartner; Adam J. Schwarz; Alexandre Coimbra; David Borsook; Lino Becerra

2010-01-01

219

Order Selection of the Linear Mixing Model for Complex-Valued FMRI Data  

Microsoft Academic Search

Functional magnetic resonance imaging (fMRI) data are originally acquired as complex-valued images, which motivates the use\\u000a of complex-valued data analysis methods. Due to the high dimension and high noise level of fMRI data, order selection and\\u000a dimension reduction are important procedures for multivariate analysis methods such as independent component analysis (ICA).\\u000a In this work, we develop a complex-valued order selection

Wei Xiong; Yi-Ou Li; Nicolle Correa; Xi-Lin Li; Vince D. Calhoun; Tülay Adal?

220

Imaging Cognition II: An Empirical Review of 275 PET and fMRI Studies  

Microsoft Academic Search

Positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) have been extensively used to explore the functional neuroanatomy of cognitive functions. Here we review 275 PET and fMRI studies of attention (sustained, selective, Stroop, orientation, divided), perception (object, face, space\\/motion, smell), imagery (object, space\\/ motion), language (written\\/spoken word recognition, spoken\\/ no spoken response), working memory (verbal\\/numeric, object, spatial, problem

Roberto Cabeza; Lars Nyberg

2000-01-01

221

Analysis of fMRI data by blind separation into independent spatial components  

Microsoft Academic Search

r r Abstract: Current analytical techniques applied to functional magnetic resonance imaging (fMRI) data require a priori knowledge or specific assumptions about the time courses of processes contributing to the measured signals. Here we describe a new method for analyzing fMRI data based on the independent component analysis (ICA) algorithm of Bell and Sejnowski ((1995): Neural Comput 7:1129-1159). We decomposed

Martin J. Mckeown; Scott Makeig; Greg G. Brown; Sandra S. Kindermann; Anthony J. Bell; Terrence J. Sejnowski

1998-01-01

222

Evaluating requirements for spatial resolution of fMRI for neurosurgical planning  

Microsoft Academic Search

Abstract: The unambiguous localization of eloquent functional areas is necessary to decrease the neuro-logical morbidity of neurosurgical procedures. We explored the minimum spatial resolution requirements for functional magnetic resonance imaging (fMRI) data acquisition when brain mapping is used in neurosurgical planning and navigation. Using a 1.5 Tesla clinical MRI scanner, eight patients with brain tumors underwent fMRI scans using spatial

Seung-Schik Yoo; Ion-Florin Talos; Alexandra J. Golby; Peter Mc L. Black; Lawrence P. Panych

2004-01-01

223

Magnetic resonance elastography: Inversions in bounded media.  

PubMed

Magnetic resonance elastography is a noninvasive imaging technique capable of quantifying and spatially resolving the shear stiffness of soft tissues by visualization of synchronized mechanical wave displacement fields. However, magnetic resonance elastography inversions generally assume that the measured tissue motion consists primarily of shear waves propagating in a uniform, infinite medium. This assumption is not valid in organs such as the heart, eye, bladder, skin, fascia, bone and spinal cord, in which the shear wavelength approaches the geometric dimensions of the object. The aim of this study was to develop and test mathematical inversion algorithms capable of resolving shear stiffness from displacement maps of flexural waves propagating in bounded media such as beams, plates, and spherical shells, using geometry-specific equations of motion. Magnetic resonance elastography and finite element modeling of beam, plate, and spherical shell phantoms of various geometries were performed. Mechanical testing of the phantoms agreed with the stiffness values obtained from finite element modeling and magnetic resonance elastography data, and a linear correlation of r(2) >or= 0.99 was observed between the stiffness values obtained using magnetic resonance elastography and finite element modeling data. In conclusion, we have demonstrated new inversion methods for calculating shear stiffness that may be more appropriate for waves propagating in bounded media. PMID:19780146

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

2009-12-01

224

Magnetic Resonance Imaging of Dendrite Currents  

NASA Astrophysics Data System (ADS)

The action currents of active dendrites generate their own magnetic field, which can cause the phase of the spins to change. Many investigators have attempted to detect neural and dendritic currents directly using magnetic resonance imaging. Such a measurement of action currents would be remarkable, since it would allow functional imaging of neural activity using the high spatial resolution of MRI and avoid an ill-posed inverse problem to determine the current sources. Measurement of the magnetic field of neural currents would better follow the distribution of neural activity in time and space. Our goal in this presentation is to use the calculated magnetic field of a dendrite to estimate the resulting phase shift in the magnetic resonance signal. We find the phase shift produced by a collection of simultaneously active dendrites is below the threshold for detection using current MRI technology.

Jay, William; Dolasinski, Brian; Wijesinghe, Ranjith; Roth, Bradley

2011-10-01

225

Soft X-ray resonant magnetic scattering of magnetic nanostructures  

NASA Astrophysics Data System (ADS)

Soft X-ray resonant magnetic scattering offers a unique element-, site- and valence-specific probe to study magnetic structures on the nanoscopic length scale. This new technique, which combines X-ray scattering with X-ray magnetic circular and linear dichroism, is ideally suited to investigate magnetic superlattices and magnetic domain structures. The theoretical analysis of the polarization dependence to determine the vector magnetization profile is presented. This is illustrated with examples studying the closure domains in self-organising magnetic domain structures, the magnetic order in patterned samples, and the local configuration of magnetic nano-objects using coherent X-rays. To cite this article: G. van der Laan, C. R. Physique 9 (2008).

van der Laan, Gerrit

2008-06-01

226

The Diversity of Nuclear Magnetic Resonance Spectroscopy  

NASA Astrophysics Data System (ADS)

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

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

227

Stepped impedance resonators for high-field magnetic resonance imaging.  

PubMed

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

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

2014-02-01

228

Magnetic Resonance Imaging (MRI) -- Head  

MedlinePLUS Videos and Cool Tools

... x-ray contrast material, drugs, food, or the environment, or if you have asthma. The contrast material ... are also screened for safety in the magnetic environment. Children will be given appropriately sized earplugs or ...

229

Cardiovascular magnetic resonance for the clinical cardiologist  

PubMed Central

Cardiovascular magnetic resonance is a noninvasive imaging modality that provides superior anatomical and functional information in the absence of ionizing radiation. The cardiovascular magnetic resonance imaging program has been active at the Quebec Heart Institute at Laval Hospital for two years, now providing advanced imaging studies to over 42 referral centres from eastern and central Quebec as well as providing training for national and international fellows. The program benefits from the collborative work of cardiologists and radiologists, who both bring to the table their unique expertise. The following text reviews current clinical applications useful in the daily practice of the cardiovascular specialist.

Larose, Eric; Rodes-Cabau, Josep; Delarochelliere, Robert; Barbeau, Gerald; Noel, Bernard; Bertrand, Olivier

2007-01-01

230

Granular convection observed by magnetic resonance imaging  

SciTech Connect

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

Ehrichs, E.E.; Jaeger, H.M.; Knight, J.B.; Nagel, S.R.; Karczmar, G.S.; Kuperman, V.Yu. [Univ. of Chicago, IL (United States)

1995-03-17

231

Magnetic resonance imaging of shoulder arthropathies.  

PubMed

The role of magnetic resonance imaging in evaluating shoulder arthropathies is evolving. This article reviews 4 of the major arthropathies: septic arthritis, rheumatoid arthritis, calcium pyrophosphate dihydrate (CPPD) deposition disease, and hydroxyapatite disease (HAD), with special attention to their magnetic resonance imaging features. Comfort with identifying these entities allows appropriate and prompt treatment, which is critical for joint preservation in the case of infection, for maximal therapeutic efficacy of disease-modifying drugs in the case of rheumatoid arthritis, and for expediting symptomatic relief in the cases of CPPD deposition disease and HAD. PMID:22469408

Sussmann, A Ross; Cohen, Jodi; Nomikos, George C; Schweitzer, Mark E

2012-05-01

232

Imaging in breast cancer: Magnetic resonance spectroscopy  

PubMed Central

A technique called in vivo magnetic resonance spectroscopy (MRS) can be performed along with magnetic resonance imaging (MRI) to obtain information about the chemical content of breast lesions. This information can be used for several clinical applications, such as monitoring the response to cancer therapies and improving the accuracy of lesion diagnosis. Initial MRS studies of breast cancer show promising results, and a growing number of research groups are incorporating the technique into their breast MRI protocols. This article introduces 1H-MRS of the breast, reviews the literature, discusses current methods and technical issues, and describes applications for treatment monitoring and lesion diagnosis.

Bolan, Patrick J; Nelson, Michael T; Yee, Douglas; Garwood, Michael

2005-01-01

233

A computational multiresolution BOLD fMRI model.  

PubMed

Blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) is a widely used method for brain mapping. BOLD fMRI signal detection is based on an intravoxel dephasing mechanism. This model involves bulk nuclear spin precession in a BOLD-induced inhomogeneous magnetic field within a millimeter-resolution voxel, that is, BOLD signal formation spans a huge spatial scale range from Angstrom to millimeter. In this letter, we present a computational model for multiresolution BOLD fMRI simulation, which consists of partitioning the nuclear spin pool into spin packets at a mesoscopic scale (?10(-6) m), and calculating multiresolution voxel signals by grouping spin packets at a macroscopic scale range (10(-5) to 10(-3) m). Under a small-angle approximation, we find that the BOLD signal intensity is related to its phase counterpart (or BOLD fieldmap) across two spatial resolution levels. PMID:21652281

Chen, Zikuan; Calhoun, Vince

2011-10-01

234

A computational multiresolution BOLD fMRI model  

PubMed Central

Blood oxygenation level dependent (BOLD) functional magnetic resonance imaging (fMRI) is a widely used method for brain mapping. BOLD fMRI signal detection is based on an intravoxel dephasing mechanism. This model involves bulk nuclear spin precession in a BOLD-induced inhomogeneous magnetic field within a millimeter-resolution voxel, that is, BOLD signal formation spans a huge spatial scale range from Angstrom to millimeter. In this letter, we present a computational model for multiresolution BOLD fMRI simulation, which consists of partitioning the nuclear spin pool into spin packets at a mesoscopic scale (~10?6m), and calculating multiresolution voxel signals by grouping spin packets at a macroscopic scale range (10?5-10?3m). Under a small angle approximation, we find that the BOLD signal intensity is related to its phase counterpart (or BOLD fieldmap) across two spatial resolution levels.

Chen, Zikuan; Calhoun, Vince

2011-01-01

235

Microwave Magnetic Resonance Spectrum of Oxygen  

Microsoft Academic Search

The complex magnetic-resonance spectrum of oxygen gas is observed at 9340 Mc\\/sec in magnetic fields up to 9000 oersted. Some 40 lines are resolved. A partial analysis of the spectrum is made with the help of Henry's recent Zeeman theory of O2. Other lines are identified by the temperature dependence of the relative intensities. Line widths are measured by several

Robert Beringer; J. G. Castle

1951-01-01

236

Video: Proton Nuclear Magnetic Resonance (NMR)  

NSDL National Science Digital Library

This video, distributed on YouTube by the Royal Society of Chemistry, describes the basic principles of Nuclear Magnetic Resonance. This video is a good primer and would be very useful to supplement introductory lectures on NMR. The video covers the basic theory behind a 1H spectrum and goes through actually acquiring a spectrum. The top-off look of the instrument is useful and how the superconducting magnet is mounted. Running time for the video is 8:43.

2011-06-03

237

Development of a simple pressure and heat stimulator for intra- and interdigit functional magnetic resonance imaging.  

PubMed

For this study, we developed a simple pressure and heat stimulator that can quantitatively control pressure and provide heat stimulation to intra- and interdigit areas. The developed stimulator consists of a control unit, drive units, and tactors. The control unit controls the stimulation parameters, such as stimulation types, intensity, time, and channel, and transmits a created signal of stimulation to the drive units. The drive units operate pressure and heat tactors in response to commands from the control unit. The pressure and heat tactors can display various stimulation intensities quantitatively, apply stimulation continuously, and adjust the stimulation areas. Additionally, they can easily be attached to and detached from the digits. The developed pressure and heat stimulator is small in total size, easy to install, and inexpensive to manufacture. The new stimulator operated stably in a magnetic resonance imaging (MRI) environment without affecting the obtained images. A preliminary functional magnetic resonance imaging (fMRI) experiment confirmed that differences in activation of somatosensory areas were induced from the pressure and heat stimulation. The developed pressure and heat stimulator is expected to be utilized for future intra- and interdigit fMRI studies on pressure and heat stimulation. PMID:23861087

Kim, Hyung-Sik; Choi, Mi-Hyun; Kim, Hyun-Joo; Hong, Sang-Pyo; Park, Jang-Yeon; Jun, Jae-Hoon; Yi, Jeong-Han; Chung, Yoon-Gi; Kim, Sung-Phil; Park, Jong-Rak; Lim, Dae-Woon; Chung, Soon-Cheol

2014-06-01

238

Multivariate Strategies in Functional Magnetic Resonance Imaging  

ERIC Educational Resources Information Center

We discuss aspects of multivariate fMRI modeling, including the statistical evaluation of multivariate models and means for dimensional reduction. In a case study we analyze linear and non-linear dimensional reduction tools in the context of a "mind reading" predictive multivariate fMRI model.

Hansen, Lars Kai

2007-01-01

239

Longitudinal fMRI analysis: A review of methods  

PubMed Central

Functional magnetic resonance imaging (fMRI) investigations of a longitudinal nature, where participants are scanned repeatedly over time and imaging data are obtained at more than one time-point, are essential to understanding functional changes and development in healthy and pathological brains. The main objective of this paper is to provide a brief summary of common longitudinal analysis approaches, develop an overview of fMRI by introducing how such data manifest, and explore the statistical challenges that arise at the intersection of these two techniques.

Skup, Martha

2011-01-01

240

Longitudinal fMRI analysis: A review of methods  

PubMed Central

Functional magnetic resonance imaging (fMRI) investigations of a longitudinal nature, where participants are scanned repeatedly over time and imaging data are obtained at more than one time-point, are essential to understanding functional changes and development in healthy and pathological brains. The main objective of this paper is to provide a brief summary of common longitudinal analysis approaches, develop an overview of fMRI by introducing how such data manifest, and explore the statistical challenges that arise at the intersection of these two techniques.

Skup, Martha

2010-01-01

241

An improved nuclear magnetic resonance spectrometer  

NASA Technical Reports Server (NTRS)

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

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

1967-01-01

242

Current technical development of magnetic resonance imaging  

Microsoft Academic Search

The impact of MRI continues to grow due to progress in all phases of the development cycle. Since its initial use for human imaging approximately 20 years ago, magnetic resonance imaging (MRI) has developed into a widely used clinical imaging modality. Now, at the start of the 21st century, the number of MRI systems worldwide is in excess of 10,800.

Stephen J. Riederer

2000-01-01

243

Nuclear Magnetic Resonance Technology for Medical Studies.  

ERIC Educational Resources Information Center

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

Budinger, Thomas F.; Lauterbur, Paul C.

1984-01-01

244

Clinical impact of shoulder magnetic resonance imaging  

Microsoft Academic Search

The clinical impact of magnetic resonance imaging (MRI) of the shoulder is dependent upon the clinical diagnosisand clinical indications for surgical management. MRI of the shoulder is very useful in defining the anatomic pathology associated with shoulder pain and disability. The clinical impact of MRI is improved when it is obtained under well defined criteria which should be based upon

Joseph P. Iannotti; Gerald R. Williams

1997-01-01

245

Magnetic resonance imaging of painful shoulder arthroplasty  

Microsoft Academic Search

Specialized magnetic resonance imaging (MRI) was performed in 42 painful shoulder arthroplasties, 22 of which underwent subsequent revision surgery, allowing surgical confirmation of the pathology identified on MRI. One hemiarthroplasty was excluded because of motion artifact, leaving 21 studies (19 patients) to be correlated retrospectively to the surgical findings. At the time of revision surgery, there were full-thickness rotator cuff

John W Sperling; Hollis G Potter; Edward V Craig; Evan Flatow; Russell F Warren

2002-01-01

246

Nuclear magnetic resonance in rare earth metals  

Microsoft Academic Search

This article describes the study, by nuclear magnetic resonance, of both static and dynamical aspects of the hyperfine interaction in rare earth metals, and illustrates the categories of information that can be obtained by using nuclei as microscopic probes in metallic media. The systems discussed include not only the pure rare earth metals but also their alloys and their metallic

M. A. H. McCausland; I. S. Mackenzie

1979-01-01

247

Scatter-based magnetic resonance elastography  

Microsoft Academic Search

Elasticity is a sensitive measure of the microstructural constitution of soft biological tissues and increasingly used in diagnostic imaging. Magnetic resonance elastography (MRE) uniquely allows in vivo measurement of the shear elasticity of brain tissue. However, the spatial resolution of MRE is inherently limited as the transformation of shear wave patterns into elasticity maps requires the solution of inverse problems.

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

2009-01-01

248

Vibration safety limits for magnetic resonance elastography  

Microsoft Academic Search

Magnetic resonance elastography (MRE) has been demonstrated to have potential as a clinical tool for assessing the stiffness of tissue in vivo. An essential step in MRE is the generation of acoustic mechanical waves within a tissue via a coupled mechanical driver. Motivated by an increasing volume of human imaging trials using MRE, the objectives of this study were to

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

2008-01-01

249

Image processing for magnetic-resonance elastography  

Microsoft Academic Search

A newly developed magnetic resonance imaging technique can directly visualize propagating acoustic strain waves in tissue-like materials. By estimating the local wavelength of the acoustic wave pattern, quantitative values of shear modulus can be calculated and images generated that depict tissue elasticity or stiffness. Since tumors are significantly stiffer than normal tissue (the basis of their detection by palpation), this

Armando Manduca; R. Muthupillai; P. J. Rossman; James F. Greenleaf; Richard L. Ehman

1996-01-01

250

Image analysis for magnetic resonance elastography  

Microsoft Academic Search

A newly developed magnetic resonance imaging technique can directly visualize propagating acoustic strain waves in tissue-like materials. By estimating the local wavelength of the acoustic wave pattern, quantitative values of shear modulus can be calculated and images generated that depict tissue elasticity or stiffness. Since tumors are significantly stiffer than normal tissue (the basis of their detection by palpation), this

A. Manduca; R. Muthupillai; P. J. Rossman; J. F. Greenleaf; R. L. Ehman

1996-01-01

251

Local wavelength estimation for magnetic resonance elastography  

Microsoft Academic Search

A newly developed magnetic resonance imaging technique can directly visualize propagating acoustic strain waves in tissue-like materials. By estimating the local wavelength of the acoustic wave pattern, quantitative values of shear modulus can be calculated and images generated that depict tissue elasticity or stiffness. Since tumors are significantly stiffer than normal tissue (the basis of their detection by palpation), this

A. Manduca; R. Muthupillai; P. J. Rossman; J. F. Greenleaf; R. L. Ehman

1996-01-01

252

Parallel Magnetic Resonance Imaging using Neural Networks  

Microsoft Academic Search

ABSTRACT Magnetic resonance imaging of dynamic,events such as cognitive tasks in the brain, requires high spatial and temporal resolution. In order to increase the resolution in both domains simultaneously, par- allel imaging schemes have been in existence, where multiple re- ceiver coils are used, each of which needs to acquire only a frac- tion of the total available signal. In

Neelam Sinha; Manojkumar Saranathan; Kalpathi R. Ramakrishnan; Sundaram Suresh

2007-01-01

253

The role of fetal magnetic resonance imaging  

Microsoft Academic Search

The role of magnetic resonance imaging (MRI) in fetal imaging is expanding. The depth of structural information provided by MRI means it is more than just a useful adjunct to ultrasound, as several structures are more clearly visualised and many of the limitations of ultrasound are avoided. Currently, MRI is most frequently utilised with reference to the fetal central nervous

C Wright; C P Sibley; P N Baker

2010-01-01

254

Coolant quality for magnetic resonance imaging systems  

Microsoft Academic Search

As radiologists demand increased power, speed and duty cycle from their magnetic resonance imaging (MRI) systems, thermal management of the gradient sub-system becomes more challenging. A heat exchanger in the MRI system cools heat-generating components by pumping water through hollow copper tubing, which also carries high electrical currents. Water is used as a coolant because of its high specific heat

Julie Wong; Garron K Morris

2008-01-01

255

Magnetic resonance elastography of the brain  

Microsoft Academic Search

The purpose of this study was to obtain normative data using magnetic resonance elastography (MRE) (a) to obtain estimates of the shear modulus of human cerebral tissue in vivo and (b) to assess a possible age dependence of the shear modulus of cerebral tissue in healthy adult volunteers. MR elastography studies were performed on tissue-simulating gelatin phantoms and 25 healthy

Scott A. Kruse; Gregory H. Rose; Kevin J. Glaser; Armando Manduca; Joel P. Felmlee; Clifford R. Jack; Richard L. Ehman

2008-01-01

256

Magnetic resonance imaging of the knee  

Microsoft Academic Search

Magnetic resonance imaging (MRI) is an accepted non invasive modality for evaluation of soft tissue pathology without exposure to ionizing radiation. Current appli cations demonstrate excellent visualization of the anat omy and pathology of various organs. Preliminary stud ies in the knee reveal fine resolution of anatomy and pathology involving the meniscus. The purpose of this study is to determine

D. W. Jackson; L. D. Jennings; R. M. Maywood; P. E. Berger

1988-01-01

257

Myocardial tissue tagging with cardiovascular magnetic resonance  

Microsoft Academic Search

Cardiovascular magnetic resonance (CMR) is currently the gold standard for assessing both global and regional myocardial function. New tools for quantifying regional function have been recently developed to characterize early myocardial dysfunction in order to improve the identification and management of individuals at risk for heart failure. Of particular interest is CMR myocardial tagging, a non-invasive technique for assessing regional

Monda L Shehata; Susan Cheng; Nael F Osman; David A Bluemke; João AC Lima

2009-01-01

258

Magnetic resonance imaging of orbital tumors  

Microsoft Academic Search

This contribution provides an overview of diseases of eye and orbit and their appearance on magnetic resonance imaging. In recent years the diagnosis of eye and orbit pathology has profited significantly from increasingly sophisticated technical developments in the field of tomographic methods. Due to the small size of the examination area the improvement in spatial resolution and soft tissue contrast

A. J. Lemke; I. Kazi; R. Felix

2006-01-01

259

Sports Health Magnetic Resonance Imaging Challenge  

PubMed Central

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

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

2010-01-01

260

Magnetic resonance applications in atherosclerotic vascular disease  

Microsoft Academic Search

Magnetic resonance imaging of the cardiovascular system offers great promise in the detection and characterization of the\\u000a anatomic, physiologic, and biochemical consequences of atherosclerosis. This review will focus on the potential applications\\u000a of MRI for evaluating atherosclerosis of the abdominal aorta and iliofemoral vessels.

George E. Wesbey; Charles B. Higgins; James D. Hale; Peter E. Valk

1986-01-01

261

Magnetic Resonance Neurography in Extraspinal Sciatica  

Microsoft Academic Search

Background: Sciatica without evidence of lumbosa- cral root compression is often attributed to piriformis syndrome. However, specific diagnostic tools have not been available to demonstrate sciatic nerve entrapment by the piriformis muscle. Objective: To evaluate the use of magnetic resonance (MR) neurography in identifying abnormalities of the sciatic nerve in patients with unexplained sciatica. Design: Case series from a retrospective

Aaron M. Lewis; Robert Layzer; J. W. Engstrom; Nicholas M. Barbaro; Cynthia T. Chin

2006-01-01

262

Magnetic resonance imaging in patients with panhypopituitarism  

Microsoft Academic Search

Primary panhypopituitarism consists of functional deficiency of the anterior pituitary lobe, which appears during infancy or adolescence. The magnetic resonance findings in 10 patients with a history of primary hopopituitarism are presented. The findings include: reduced pituitary size in all cases: partially (8 cases) or totally (2 cases) empty sella; thin (4 cases), partially visible (3 cases) or absent (2

R. S. Pozzi Mucelli; F. Frezza; S. Magnaldi; G. Proto

1992-01-01

263

Magnetic resonance imaging of the carpal tunnel.  

PubMed

Eleven wrists in eight patients with carpal tunnel syndrome were investigated by electrophysiological studies and magnetic resonance imaging (M.R.I.). The operative findings in ten wrists correlated with the M.R.I. evidence of synovial disease, carpal tunnel stenosis and median nerve compression. PMID:2366024

Healy, C; Watson, J D; Longstaff, A; Campbell, M J

1990-05-01

264

Electrically detected magnetic resonance applied to polyaniline  

Microsoft Academic Search

The transport properties of polyaniline films have been investigated by electrically detected magnetic resonance (EDMR) in different protonation states. In polyaniline, a spin-dependent interchain tunneling involving a polaron-polaron transition is found. The EDMR signal in polyaniline is found to be dependent on the DC electric field, protonation level as well as the atmosphere. For low electric fields, and samples with

C. A. Brunello; R. M. Faria

1999-01-01

265

Off-center magnetic resonance imaging with permanent magnets  

NASA Astrophysics Data System (ADS)

Magnets for magnetic resonance imaging are currently designed as structures that are symmetric with respect to the geometric center O of the magnet cavity. This symmetry results in a symmetric field configuration, where point O coincides with the imaging center S defined as the point where the field gradient is zero. However, in many clinical applications such as breast or spine imaging, the region of interest is displaced from the geometric center. We present a design method for yokeless permanent magnets, where the position of point S is dictated by the imaging requirements. The magnet is composed of uniformly magnetized triangular prisms and it does not require a ferromagnetic yoke to channel the magnetic flux. Given an arbitrary polygonal cavity, the design depends on the position of point F, where the magnetostatic potential is assumed to be equal to the magnetostatic potential of the external medium. For a long magnet, the position of the imaging center S coincides with point F. As an example of the off-center design, we analyze a three-dimensional yokeless magnet with cavity of width=length=80 cm and height=45 cm. The magnet generates a field above 0.5 T when constructed using the NdFeB alloy of remanence larger than 1.3 T. The off-center configuration offers flexibility in magnet design that makes it possible to focus on a particular region of the human body, without increasing magnet cavity, magnet size, or its weight

Abele, Manlio G.; Rusinek, Henry

2008-04-01

266

The Reporting of Observational Clinical Functional Magnetic Resonance Imaging Studies: A Systematic Review  

PubMed Central

Introduction Complete reporting assists readers in confirming the methodological rigor and validity of findings and allows replication. The reporting quality of observational functional magnetic resonance imaging (fMRI) studies involving clinical participants is unclear. Objectives We sought to determine the quality of reporting in observational fMRI studies involving clinical participants. Methods We searched OVID MEDLINE for fMRI studies in six leading journals between January 2010 and December 2011.Three independent reviewers abstracted data from articles using an 83-item checklist adapted from the guidelines proposed by Poldrack et al. (Neuroimage 2008; 40: 409–14). We calculated the percentage of articles reporting each item of the checklist and the percentage of reported items per article. Results A random sample of 100 eligible articles was included in the study. Thirty-one items were reported by fewer than 50% of the articles and 13 items were reported by fewer than 20% of the articles. The median percentage of reported items per article was 51% (ranging from 30% to 78%). Although most articles reported statistical methods for within-subject modeling (92%) and for between-subject group modeling (97%), none of the articles reported observed effect sizes for any negative finding (0%). Few articles reported justifications for fixed-effect inferences used for group modeling (3%) and temporal autocorrelations used to account for within-subject variances and correlations (18%). Other under-reported areas included whether and how the task design was optimized for efficiency (22%) and distributions of inter-trial intervals (23%). Conclusions This study indicates that substantial improvement in the reporting of observational clinical fMRI studies is required. Poldrack et al.'s guidelines provide a means of improving overall reporting quality. Nonetheless, these guidelines are lengthy and may be at odds with strict word limits for publication; creation of a shortened-version of Poldrack's checklist that contains the most relevant items may be useful in this regard.

Guo, Qing; Parlar, Melissa; Truong, Wanda; Hall, Geoffrey; Thabane, Lehana; McKinnon, Margaret; Goeree, Ron; Pullenayegum, Eleanor

2014-01-01

267

Interaction of magnetic resonators studied by the magnetic field enhancement  

SciTech Connect

It is the first time that the magnetic field enhancement (MFE) is used to study the interaction of magnetic resonators (MRs), which is more sensitive than previous parameters–shift and damping of resonance frequency. To avoid the coherence of lattice and the effect of Bloch wave, the interaction is simulated between two MRs with same primary phase when the distance is changed in the range of several resonance wavelengths, which is also compared with periodic structure. The calculated MFE oscillating and decaying with distance with the period equal to resonance wavelength directly shows the retardation effect. Simulation also shows that the interaction at normal incidence is sensitive to the phase correlation which is related with retardation effect and is ultra-long-distance interaction when the two MRs are strongly localized. When the distance is very short, the amplitude of magnetic resonance is oppressed by the strong interaction and thus the MFE can be much lower than that of single MR. This study provides the design rules of metamaterials for engineering resonant properties of MRs.

Hou, Yumin, E-mail: ymhou@pku.edu.cn [State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871 (China)] [State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871 (China)

2013-12-15

268

Nuclear Magnetic Resonance or Magnetic Resonance Imaging: Analysis of a New Technology.  

National Technical Information Service (NTIS)

The purpose of this study was to determine the need for nuclear magnetic resonance imaging in South Carolina. The study was conducted by (1) literature search, (2) contacts with vendors, (3) analysis of existing studies and (4) correspondence with physici...

1984-01-01

269

Nuclear magnetic resonance properties of lunar samples.  

NASA Technical Reports Server (NTRS)

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

Kline, D.; Weeks, R. A.

1972-01-01

270

Magnetic resonance imaging with magnetic resonance cholangiopancreatography accurately predicts resectability of pancreatic carcinoma  

Microsoft Academic Search

Accurate preoperative staging of pancreatic malignancy aids in directing appropriate therapy and avoids unnecessary invasive\\u000a procedures. We evaluated the accuracy of magnetic resonance imaging (MRI) with magnetic resonance cholangiopancreatography\\u000a (MRCP) in determining resectability of pancreatic malignancy. Twenty-one patients with suspected pancreatic malignancy underwent\\u000a dynamic, contrast-en-hanced breath-hold MRI with MRCP prior to surgical evaluation. Results of this study were correlated\\u000a with

Steven N. Hochwald; Neil M. Rofsky; Michael Dobryansky; Peter Shamamian; Stuart G. Marais

1999-01-01

271

Musical training-induced functional reorganization of the adult brain: functional magnetic resonance imaging and transcranial magnetic stimulation study on amateur string players.  

PubMed

We used the combined technique of functional magnetic resonance imaging (fMRI) and transcranial magnetic stimulation (TMS) to observe changes that occur in adult brains after the practice of stringed musical instruments. We carried out fMRI on eight volunteers (aged 20-22 years): five novices and three individuals who had discontinued practice for more than 5 years. The motor paradigm contained a repetitive lift-abduction/fall-adduction movement of the left/right little finger, carried out with maximum efforts without pacing. The sensory paradigm was to stimulate the same little finger using a string. In parallel to the fMRI acquisition, TMS motor maps for the little finger were obtained using a frameless stereotactic neuronavigation system. After the baseline study, each participant began to learn a stringed instrument. Newly developed fMRI activations for the left little finger were observed 6 months after practice at multiple brain regions including inferior parietal lobule, premotor area (PMA), left precuneus, right anterior superior temporal gyrus, and posterior middle temporal gyrus. In contrast, new activations were rarely observed for the right little finger. The TMS study revealed new motor representation sites for the left little finger in the PMA or supplementary motor area (SMA). Unexpectedly, TMS motor maps for the right little finger were reduced significantly. Among new fMRI activations for sensory stimuli of the left little finger, the cluster of highest activation was located in the SMA. Collectively, these data provide insight into orchestrated reorganization of the sensorimotor and temporal association cortices contributing to the skillful fingering and musical processing after the practice of playing stringed instruments. PMID:15449354

Kim, Dong-Eog; Shin, Min-Jung; Lee, Kyoung-Min; Chu, Kon; Woo, Sung Ho; Kim, Young Ro; Song, Eun-Cheol; Lee, Jun-Won; Park, Seong-Ho; Roh, Jae-Kyu

2004-12-01

272

Magnetic resonance in the differential diagnosis of dementia  

Microsoft Academic Search

Summary.   Magnetic resonance became an important tool for the differential diagnosis of dementia. Magnetic resonance imaging is the\\u000a preferred method to exclude treatable entities accompagnied by dementing symptoms. New techniques including diffusion and\\u000a perfusion magnetic resonance imaging are helpful for the differentiation between vascular dementia and degenerative disorders.\\u000a Magnetic Resonance spectroscopy evolves as a tool for the diagnosis of different

S. R. Felber

2002-01-01

273

Magnetic Earth Ionosphere Resonant Frequencies  

NASA Technical Reports Server (NTRS)

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

Spaniol, Craig

1994-01-01

274

SEVEN TOPICS IN FUNCTIONAL MAGNETIC RESONANCE IMAGING  

PubMed Central

Functional MRI (fMRI) is a non-invasive brain imaging methodology that started in 1991 and allows human brain activation to be imaged at high resolution within only a few minutes. Because it has extremely high sensitivity, is relatively easy to implement, and can be performed on most standard clinical MRI scanners. It continues to grow at an explosive rate throughout the world. Over the years, at any given time, fMRI has been defined by only a handful of major topics that have been the focus of researchers using and developing the methodology. In this review, I attempt to take a snapshot of the field of fMRI as it is in mid-2009 by discussing the seven topics that I feel are most on the minds of fMRI researchers. The topics are, in no particular order or grouping: (1) Clinical impact, (2) Utilization of individual functional maps, (3) fMRI signal interpretation, (4) Pattern effect mapping and decoding, (5) Endogenous oscillations, (6) MRI technology, and (7) Alternative functional contrast mechanisms. Most of these topics are highly interdependent, each advancing as the others advance. While most fMRI involves applications towards clinical or neuroscience questions, all applications are fundamentally dependent on advances in basic methodology as well as advances in our understanding of the relationship between neuronal activity and fMRI signal changes. This review neglects almost completely an in-depth discussion of applications. Rather the discussions are on the methods and interpretation.

BANDETTINI, PETER A.

2010-01-01

275

Dipolar Broadening of Magnetic Resonance Lines in Magnetically Diluted Crystals  

Microsoft Academic Search

Calculations are given for the frequency moments associated with the dipolar broadening of magnetic resonance lines in crystals having lattice points populated at random by identical paramagnetic ions or nuclei. It is found that for fractional magnetic population f>0.1 the line shape is approximately Gaussian with a width proportional to f12; for f<0.01 the line shape is approximately Lorentzian with

C. Kittel; Elihu Abrahams

1953-01-01

276

Magnetic resonance imaging: effects of magnetic field strength  

Microsoft Academic Search

Magnetic resonance images of the head, abdomen, and pelvis of normal adult men were obtained using varying magnetic field strength, and measurements of T1 and T2 relaxations and of signal-to-noise (SN) ratios were determined. For any one spin echo sequence, gray\\/white matter contrast decreases and muscle\\/fat contrast increases with field. SN levels rise rapidly up to 3.0 kgauss and then

L. E. Crooks; M. Arakawa; J. Hoenninger; B. McCarten; J. Watts; L. Kaufman

1984-01-01

277

Neonatal life support during magnetic resonance imaging.  

PubMed

Magnetic resonance techniques are required frequently for the assessment of the brain of ill neonates. In the present study, the effects of a 1.5 T MR scanner on devices for life support were assessed. A ventilator (Dräger Babylog 2000) was tested in the 1.5 T magnet, using a neonatal ventilation tester and 1.5-5 m tubes. In a special MR incubator, temperature and humidity were measured at 1-min intervals. Infusion was tested with the pump outside the magnet room: infusion rates and time to alarm were tested with 7-m tubes. The ventilator performed normally at a magnetic field line of 2 mT, although the alarms failed. The incubator created a temperature of 35.9 degrees C and humidity of 40.7%, which was acceptable for examinations of 45 min. The alarm limits of the infusion pump placed outside the magnet at 7 m were within company limits. The study indicates that magnetic resonance examinations can be performed safely in ill preterm neonates who require life-support devices. PMID:12102325

Groenendaal, F; Leusink, C; Nijenhuis, M; Janssen, M J H

2002-01-01

278

Magnetic resonance relaxation properties of superparamagnetic particles.  

PubMed

Nanometric crystals of maghemite are known to exhibit superparamagnetism. Because of the significance of their magnetic moment, maghemite nanoparticles are exceptional contrast agents and are used for magnetic resonance imaging (of the liver, spleen, lymph nodes), for magnetic resonance angiography and for molecular and cellular imaging. The relaxivity of these agents depends on their size, saturation magnetization and magnetic field and also on their degree of clustering. There are different types of maghemite particles whose relaxation characteristics are suited to a specific MRI application. The relaxation induced by maghemite particles is caused by the diffusion of water protons in the inhomogeneous field surrounding the particles. This is well described by a theoretical model that takes magnetite crystal anisotropy and Néel relaxation into account. Another type of superparamagnetic compound is ferritin, the iron-storing protein: it contains a superparamagnetic ferrihydrite core. Even if the resulting magnetic moment of ferritin is far smaller than for magnetite nanoparticles, its massive presence in different organs darkens T(2)-weighted MR images, allowing the noninvasive estimation of iron content, thanks to MRI. The relaxation induced by ferritin in aqueous solutions has been demonstrated to be caused by the exchange of protons between bulk water protons and the surface of the ferrihydrite crystal. However, in vivo, the relaxation properties of ferritin are still unexplained, probably because of protein clustering. PMID:20049798

Gossuin, Yves; Gillis, Pierre; Hocq, Aline; Vuong, Quoc L; Roch, Alain

2009-01-01

279

Magnetic resonance of calcified tissues  

NASA Astrophysics Data System (ADS)

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

Wehrli, Felix W.

2013-04-01

280

Magnetic resonance of calcified tissues.  

PubMed

MRI of the human body is largely made possible by the favorable relaxation properties of protons of water and triacyl glycerides prevalent in soft tissues. Hard tissues--key among them bone--are generally less amenable to measurement with in vivo MR imaging techniques, not so much as a result of the lower proton density but rather due to the extremely short life-times of the proton signal in water bound to solid-like entities, typically collagen, or being trapped in micro-pores. Either mechanism can enhance T2 relaxation by up to three orders of magnitude relative to their soft-tissue counterparts. Detection of these protons requires solid-state techniques that have emerged in recent years and that promise to add a new dimension to the study of hard tissues. Alternative approaches to probe calcified tissues exploit their characteristic magnetic properties. Bone, teeth and extra-osseous calcium-containing biomaterials are unique in that they are more diamagnetic than all other tissues and thus yield information indirectly by virtue of the induced magnetic fields present in their vicinity. Progress has also been made in methods allowing very high-resolution structural imaging of trabecular and cortical bone relying on detection of the surrounding soft-tissues. This brief review, much of it drawn from work conducted in the author's laboratory, seeks to highlight opportunities with focus on early-stage developments for image-based assessment of structure, function, physiology and mechanics of calcified tissues in humans via liquid and solid-state approaches, including proton, deuteron and phosphorus NMR and MRI. PMID:23414678

Wehrli, Felix W

2013-04-01

281

Magnetic resonance diagnostic markers in clinically sporadic prion disease: a combined brain magnetic resonance imaging and spectroscopy  

Microsoft Academic Search

The intra vitam diagnosis of prion disease is challenging and a definite diagnosis still requires neuropathological examination in non-familial cases. Magnetic resonance imaging has gained increasing importance in the diagnosis of prion disease. The aim of this study was to compare the usefulness of different magnetic resonance imaging sequences and proton magnetic resonance spectroscopy in the differential diagnosis of patients

Raffaele Lodi; Piero Parchi; Caterina Tonon; David Manners; Sabina Capellari; Rosaria Strammiello; Rita Rinaldi; Claudia Testa; Emil Malucelli; Barbara Mostacci; Giovanni Rizzo; Giulia Pierangeli; Pietro Cortelli; Pasquale Montagna; Bruno Barbiroli

2009-01-01

282

Magnetic resonance imaging with an optical atomicmagnetometer  

SciTech Connect

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

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

2006-05-09

283

Magnetic resonance imaging: effects of magnetic field strength.  

PubMed

Magnetic resonance images of the head, abdomen, and pelvis of normal adult men were obtained using varying magnetic field strength, and measurements of T1 and T2 relaxations and of signal-to-noise (SN) ratios were determined. The T1 relaxation of gray matter, white matter, and muscle increases and T2 decreases with field strength, while T1 of fat remains relatively constant and T2 increases. As a consequence, for any one spin echo sequence, gray/white matter contrast decreases and muscle/fat contrast increases with field. SN levels rise rapidly up to 3.0 kgauss and then change more slowly, actually dropping for muscle. The optimum field for magnetic resonance imaging depends on tissue type, body part, and imaging sequence, so that it does not have a unique value. Magnetic resonance systems that operate in the 3.0-5.0 kgauss range achieve most or all of the gains that can be achieved by higher magnetic fields. PMID:6701302

Crooks, L E; Arakawa, M; Hoenninger, J; McCarten, B; Watts, J; Kaufman, L

1984-04-01

284

Simultaneous measurements of kinematics and fMRI: compatibility assessment and case report on recovery evaluation of one stroke patient  

Microsoft Academic Search

BACKGROUND: Correlating the features of the actual executed movement with the associated cortical activations can enhance the reliability of the functional Magnetic Resonance Imaging (fMRI) data interpretation. This is crucial for longitudinal evaluation of motor recovery in neurological patients and for investigating detailed mutual interactions between activation maps and movement parameters. Therefore, we have explored a new set-up combining fMRI

Claudia Casellato; Simona Ferrante; Marta Gandolla; Nicola Volonterio; Giancarlo Ferrigno; Giuseppe Baselli; Tiziano Frattini; Alberto Martegani; Franco Molteni; Alessandra Pedrocchi

2010-01-01

285

Activation of Cortical and Cerebellar Motor Areas during Executed and Imagined Hand Movements: An fMRI Study  

Microsoft Academic Search

Brain activation during executed (EM) and imagined movements (IM) of the right and left hand was studied in 10 healthy right-handed subjects using functional magnetic resonance imagining (fMRI). Low electromyographic (EMG) activity of the musculi flexor digitorum superficialis and high vividness of the imagined movements were trained prior to image acquisition. Regional cerebral activation was measured by fMRI during EM

Martin Lotze; Pedro Montoya; Michael Erb; Ernst Hülsmann; Herta Flor; Uwe Klose; Niels Birbaumer; Wolfgang Grodd

1999-01-01

286

A quantitative analysis of noncircularity for complex-valued fMRI based on semi-blind ICA  

Microsoft Academic Search

The spatial components included in complex-valued functional magnetic resonance imaging (fMRI) data are generally assumed to be noncircular signals. In this paper, we try to quantitatively investigate the noncircularity of fMRI with a measure called the degree of impropriety (DOI). Two semi-blind complex ICA algorithms, the kurtosis maximization (KM) algorithm suitable for separating noncircular sources and the complex fastICA algorithm

Jia-Chen Wang; Qiu-Hua Lin; Fengyu Cong; Vince D. Calhoun

2011-01-01

287

The application of independent component analysis with projection method to two-task fMRI data over multiple subjects  

Microsoft Academic Search

Spatial Independent component analysis (sICA) has been successfully used to analyze functional magnetic resonance (fMRI) data. However, the application of ICA was limited in multi-task fMRI data due to the potential spatial dependence between task-related components. Long et al. (2009) proposed ICA with linear projection (ICAp) method and demonstrated its capacity to solve the interaction among task-related components in multi-task

Rui Li; Mingqi Hui; Li Yao; Kewei Chen; Zhiying Long

2011-01-01

288

Neural correlates of viewing paintings: evidence from a quantitative meta-analysis of functional magnetic resonance imaging data.  

PubMed

Many studies involving functional magnetic resonance imaging (fMRI) have exposed participants to paintings under varying task demands. To isolate neural systems that are activated reliably across fMRI studies in response to viewing paintings regardless of variation in task demands, a quantitative meta-analysis of fifteen experiments using the activation likelihood estimation (ALE) method was conducted. As predicted, viewing paintings was correlated with activation in a distributed system including the occipital lobes, temporal lobe structures in the ventral stream involved in object (fusiform gyrus) and scene (parahippocampal gyrus) perception, and the anterior insula-a key structure in experience of emotion. In addition, we also observed activation in the posterior cingulate cortex bilaterally-part of the brain's default network. These results suggest that viewing paintings engages not only systems involved in visual representation and object recognition, but also structures underlying emotions and internalized cognitions. PMID:24704947

Vartanian, Oshin; Skov, Martin

2014-06-01

289

Simultaneous Measurement of Magnetic Resonance and Neuronal Signals  

Microsoft Academic Search

Nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) at ultra low magnetic fields (ULF, ˜ microT) have advantages over their counterparts at higher magnetic fields, despite the reduction in signal strength. Among these advantages are that the instrumentation uses superconducting quantum interference devices (SQUIDs), and is now compatible with simultaneous measurements of biomagnetic signals, such as magnetoencephalography (MEG). This

Michelle Espy

2007-01-01

290

Foundations of Advanced Magnetic Resonance Imaging  

PubMed Central

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

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

2005-01-01

291

Nuclear magnetic resonance imaging in Marfan's syndrome.  

PubMed

Detection and evaluation of aortic root and other cardiovascular abnormalities in patients with Marfan's syndrome are important in determining appropriate therapy and preventing premature mortality. To evaluate the role of nuclear magnetic resonance imaging (NMR) in this syndrome, 10 patients were evaluated using a 0.35 tesla commercial nuclear magnetic resonance imaging system. Findings from these studies were compared with data from other noninvasive tests as well as surgical follow-up. Results from these examinations indicate that NMR-derived measurements of aortic root diameter agree closely with echocardiographic measurements. In addition, NMR provides more complete anatomic detail than does echocardiography and can be utilized to assess and follow up virtually all patients with this syndrome. PMID:3794112

Schaefer, S; Peshock, R M; Malloy, C R; Katz, J; Parkey, R W; Willerson, J T

1987-01-01

292

Combined Confocal and Magnetic Resonance Microscopy  

SciTech Connect

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

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

2002-05-12

293

Cardiovascular magnetic resonance in heart failure.  

PubMed

Imaging has a central role in the evaluation of patients with heart failure (HF). Cardiovascular magnetic resonance (CMR) is rapidly evolving as a versatile imaging modality that often provides additional information to echocardiography in patients with suspected or known HF. CMR is the only imaging modality that has the ability to assess, without exposure to ionizing radiation, cardiac function, structure (tissue characterization), perfusion, and viability. Moreover, magnetic resonance spectroscopy techniques can assess the pathophysiologic role of deranged cardiac energetics in HF. In this review we discuss the role of CMR in the evaluation of patients with HF giving particular emphasis to recent developments and the additional information that can be obtained with this imaging modality, over and above standard echocardiography. PMID:21360113

Karamitsos, Theodoros D; Neubauer, Stefan

2011-06-01

294

Magnetic resonances in nano-scale metamaterials  

NASA Astrophysics Data System (ADS)

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

Hao, Zhao; Liddle, Alex; Martin, Michael

2006-03-01

295

Vibration criteria for a magnetic resonance imager  

NASA Astrophysics Data System (ADS)

One instrument used in clinical medicine to create a high-contrast image of the body's soft tissues involves the principle of nuclear magnetic resonance. The machine is called a magnetic resonance imager (MRI). The MRI scanning process is analogous to optical devices in that it is somewhat sensitive to vibration. This paper describes some field tests intended to quantify the effect of vibration upon image quality as heavy vehicles passed near two on-grade MRI installations. The measured field data are compared to recently published criteria and also are correlated with test images created by the MRI during the vibration events. The paper includes recommendations for improving the format of the manufacturer's vibration specification.

Nash, Anthony

1994-10-01

296

Nuclear magnetic resonance imaging of the pancreas  

SciTech Connect

Nuclear magnetic resonance (NMR) images were obtained from 12 patients with pancreatic disease, and from 40 patients in a control group. Correlation of the images with ultrasound examinations and with laparotomy in five cases indicates that NMR is accurate in the demonstration of pancreatic pathology. Though the images bear close similarity to those obtained by conventional computed tomography (CT), further investigations are needed to delineate the true accuracy of NMR.

Smith, F.W.; Reid, A.; Hutchison, J.M.S.; Mallard, J.R.

1980-03-01

297

Laser magnetic resonance of sulphur radicals  

Microsoft Academic Search

High rotational transitions of the radical NS have been observed using an FIR optically-pumped laser-magnetic-resonance (LMR) spectrometer. The spectra were recorded at wavelengths of 680 and 514 microns (from C2H3Br and DCOF lasers, respectively) and have been assigned to individual Zeeman components of the rotational transitions J = 8.5 to 9.5 and J = 11.5 to 12.5 in the lowest

J. R. Anacona; P. B. Davies

1985-01-01

298

Nuclear magnetic resonance imaging: Basic principles  

SciTech Connect

This book discusses the complicated physics of magnetic resonance imaging and explains the basic principles of data acquisition and image reconstruction techniques. The MR imaging photographs are provided with explanation and there are samples of images literally from head to toe. In this book, the author uses many analogies to more familiar physical phenomena, such as sound waves, to help explain NMR, and these are often ingenious and effective.

Young, S.W.

1985-01-01

299

Magnetic Resonance Imaging of Acute Stroke  

Microsoft Academic Search

In the investigation of ischemic stroke, conventional structural magnetic resonance (MR) techniques (e.g., T1-weighted imaging, T2-weighted imaging, and proton density-weighted imaging) are valuable for the assessment of infarct extent and location beyond the first 12 to 24 hours after onset, and can be combined with MR angiography to noninvasively assess the intracranial and extracranial vasculature. However, during the critical first

Alison E. Baird; Steven Warach

1998-01-01

300

Cardiovascular Magnetic Resonance in Heart Failure  

Microsoft Academic Search

Imaging has a central role in the evaluation of patients with heart failure (HF). Cardiovascular magnetic resonance (CMR)\\u000a is rapidly evolving as a versatile imaging modality that often provides additional information to echocardiography in patients\\u000a with suspected or known HF. CMR is the only imaging modality that has the ability to assess, without exposure to ionizing\\u000a radiation, cardiac function, structure

Theodoros D. Karamitsos; Stefan Neubauer

2011-01-01

301

Magnetic resonance urography: a pictorial overview  

Microsoft Academic Search

Magnetic resonance urography (MRU) can be performed on the basis of two different imaging strategies: static-fluid MRU, based on heavily T2 weighted turbo spin echo (TSE) sequences, and gadolinium-enhanced excretory MRU. Both MR urographic techniques in combination with standard MRI permit a comprehensive examination of the entire urinary tract. This pictorial review illustrates the MRU features of the a wide

R Garcia-Valtuille; A I GARCIA-VALTUILLE; F ABASCAL; L CEREZAL; M C ARGUELLO

2006-01-01

302

Wide-range dynamic magnetic resonance elastography  

Microsoft Academic Search

Tissue mechanical parameters have been shown to be highly sensitive to disease by elastography. Magnetic resonance elastography (MRE) in the human body relies on the low-dynamic range of tissue mechanics <100Hz. In contrast, MRE suited for investigations of mice or small tissue samples requires vibration frequencies 10–20 times higher than those used in human MRE. The dispersion of the complex

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

2011-01-01

303

Magnetic resonance imaging assessment of cardiac function  

Microsoft Academic Search

Measurements of left ventricular function at rest and during stress are useful for identifying myocardial ischemia, injury,\\u000a and the risk of subsequent myocardial infarction. Without ionizing radiation or intravascular contrast administration, magnetic\\u000a resonance imaging techniques can be used to acquire precise measurements of left ventricular function. This relatively new\\u000a development may enhance a physician’s ability to provide care to patients

W. Gregory Hundley; Craig A. Hamilton; Pairoj Rerkpattanapipat

2003-01-01

304

Cardiac Magnetic Resonance in Hypertrophic Cardiomyopathy  

Microsoft Academic Search

Hypertrophic cardiomyopathy is a fascinating and complex disorder with substantial variability in phenotypic expression and\\u000a natural progression. Recently, there has been substantial research demonstrating incremental utility of cardiac magnetic resonance in the diagnosis\\u000a and treatment of this disease. With the increasing utilization of multimodality imaging, our understanding of the subtle morphologic\\u000a differences and their prognostic implications is only going to

Milind Y. Desai; Ashwat Dhillon; Andrew C. Y. To

2011-01-01

305

Nuclear magnetic resonance quantum information processing  

PubMed Central

For the past decade, nuclear magnetic resonance (NMR) has been established as a main experimental technique for testing quantum protocols in small systems. This Theme Issue presents recent advances and major challenges of NMR quantum information possessing (QIP), including contributions by researchers from 10 different countries. In this introduction, after a short comment on NMR-QIP basics, we briefly anticipate the contents of this issue.

Serra, R. M.; Oliveira, I. S.

2012-01-01

306

Imaging Conditioned Fear Circuitry Using Awake Rodent fMRI  

PubMed Central

Functional magnetic resonance imaging (fMRI) is a powerful method for exploring emotional and cognitive brain responses in humans. However rodent fMRI has not previously been applied to the analysis of learned behaviour in awake animals, limiting its use as a translational tool. Here we have developed a novel paradigm for studying brain activation in awake rats responding to conditioned stimuli using fMRI. Using this method we show activation of the amygdala and related fear circuitry in response to a fear-conditioned stimulus and demonstrate that the magnitude of fear circuitry activation is increased following early life stress, a rodent model of affective disorders. This technique provides a new translatable method for testing environmental, genetic and pharmacological manipulations on emotional and cognitive processes in awake rodent models.

Brydges, Nichola M.; Whalley, Heather C.; Jansen, Maurits A.; Merrifield, Gavin D.; Wood, Emma R.; Lawrie, Stephen M.; Wynne, Sara-Madge; Day, Mark; Fleetwood-Walker, Sue; Steele, Douglas; Marshall, Ian; Hall, Jeremy; Holmes, Megan C.

2013-01-01

307

Magnetic resonance acoustic radiation force imaging  

PubMed Central

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

McDannold, Nathan; Maier, Stephan E.

2008-01-01

308

Magnetic resonance venography and liver transplant complications.  

PubMed

Hepatic vein stenosis is a rare but serious complication following liver transplantation. Multiple modalities can be utilized to image the hepatic vasculature. Magnetic resonance venography (MRV) provides certain advantages over ultrasound, computed tomography angiography and digital subtraction venography. MRV utilizes the same imaging principles of magnetic resonance angiography in order to image the venous system. Blood pool contrast agents, specifically gadofosveset trisodium, allow for steady state imaging up to 1 h following injection, with improved visualisation of vital venous structures by utilising delayed steady state imaging. Additionally, the inherent physics properties of magnetic resonance imaging also provide excellent soft tissue detail and thus help define the extent of complications that often plague the post-liver transplant patient. This case report describes the use of gadofosveset trisodium in a patient with hepatic venous stenosis following liver transplantation. Initial venography failed to outline the stenoses and thus MRV using a blood pool contrast agent was utilised in order to delineate the anatomy and plan a therapeutic endovascular procedure. PMID:24106414

Strovski, Evgeny; Liu, Dave; Scudamore, Charles; Ho, Stephen; Yoshida, Eric; Klass, Darren

2013-09-28

309

Travelling-wave nuclear magnetic resonance.  

PubMed

Nuclear magnetic resonance (NMR) is one of the most versatile experimental methods in chemistry, physics and biology, providing insight into the structure and dynamics of matter at the molecular scale. Its imaging variant-magnetic resonance imaging (MRI)-is widely used to examine the anatomy, physiology and metabolism of the human body. NMR signal detection is traditionally based on Faraday induction in one or multiple radio-frequency resonators that are brought into close proximity with the sample. Alternative principles involving structured-material flux guides, superconducting quantum interference devices, atomic magnetometers, Hall probes or magnetoresistive elements have been explored. However, a common feature of all NMR implementations until now is that they rely on close coupling between the detector and the object under investigation. Here we show that NMR can also be excited and detected by long-range interaction, relying on travelling radio-frequency waves sent and received by an antenna. One benefit of this approach is more uniform coverage of samples that are larger than the wavelength of the NMR signal-an important current issue in MRI of humans at very high magnetic fields. By allowing a significant distance between the probe and the sample, travelling-wave interaction also introduces new possibilities in the design of NMR experiments and systems. PMID:19225521

Brunner, David O; De Zanche, Nicola; Fröhlich, Jürg; Paska, Jan; Pruessmann, Klaas P

2009-02-19

310

New Insights into the Hemodynamic Blood Oxygenation Level Dependent Response through Combination of Functional Magnetic Resonance Imaging and Optical Recording in Gerbil Barrel Cortex  

Microsoft Academic Search

Fast, low-angle shoot functional magnetic resonance imaging (fMRI), based on the blood oxygenation level-dependent (BOLD) effect, was combined with optical recording of intrinsic signals (ORIS) and 2-deoxyglucose labeling in gerbil barrel cortex. We observed over the activated barrel a positive BOLD signal and increased levels of deoxyhemoglobin and total he- moglobin during each period of prolonged (30 sec) D2 vibrissal

Andreas Hess; Detlef Stiller; Thomas Kaulisch; Peter Heil; Henning Scheich

2000-01-01

311

Evaluation of Spatial Working Memory Function in Children and Adults with Fetal Alcohol Spectrum Disorders: A Functional Magnetic Resonance Imaging Study  

Microsoft Academic Search

Magnetic resonance imaging (MRI) and functional MRI stud- ies involving n-back spatial working memory (WM) tasks were conducted in adults and children with Fetal Alcohol Spectrum Disorders (FASD), and in age- and sex-matched controls. FMRI experiments demonstrated consistent activations in regions of the brain associated with working memory. Children with FASD displayed greater inferior-middle frontal lobe activity, while greater superior

KRISZTINA L. MALISZA; AVA-ANN ALLMAN; DEBORAH SHILOFF; LORNA JAKOBSON; SALLY LONGSTAFFE; ALBERT E. CHUDLEY

2005-01-01

312

What is Involved and What is Necessary for Complex Linguistic and Nonlinguistic Auditory Processing: Evidence from Functional Magnetic Resonance Imaging and Lesion Data  

Microsoft Academic Search

We used functional magnetic resonance imaging (fMRI) in conjunction with a voxel-based approach to lesion symptom mapping to quantitatively evaluate the similarities and dif- ferences between brain areas involved in language and envi- ronmental sound comprehension. In general, we found that language and environmental sounds recruit highly overlapping cortical regions, with cross-domain differences being graded rather than absolute. Within language-based

Frederic Dick; Ayse Pinar Saygin; Gaspare Galati; Sabrina Pitzalis; Simone Bentrovato; Simona D'amico; Stephen Wilson; Elizabeth Bates; Luigi Pizzamiglio

2007-01-01

313

Too Many Trees to See the Forest: Performance, Event-related Potential, and Functional Magnetic Resonance Imaging Manifestations of Integrative Congenital Prosopagnosia  

Microsoft Academic Search

Neuropsychological, event-related potential (ERP), and func- tional magnetic resonance imaging (fMRI) methods were com- bined to provide a comprehensive description of performance and neurobiological profiles for K.W., a case of congenital proso- pagnosia. We demonstrate that K.W.'s visual perception is characterized by almost unprecedented inability to identify faces, a large bias toward local features, and an extreme deficit in global\\/

Shlomo Bentin; Joseph M. Degutis; Mark D'esposito; Lynn C. Robertson

2007-01-01

314

Differential magnetic resonance signal change in human sensorimotor cortex to finger movements of different rate of the dominant and subdominant hand  

Microsoft Academic Search

Functional magnetic resonance tomography (fMRI) analysis of unimanual and bimanual sequential movements in righthanders showed the following effects. First, a rate-dependent activation of the somato-motor cortex was confirmed, with faster movement rates producing higher activation both in terms of signal intensity and number of activated voxels. Second, the right hemisphere showed more activation than the left hemisphere during unimanual tasks.

L Jäncke; M Peters; G Schlaug; S Posse; H Steinmetz; H.-W Müller-Gärtner

1998-01-01

315

Magnetic Resonance Microscopy of Collagen Mineralization  

PubMed Central

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

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

2008-01-01

316

Physiological Noise in Brainstem fMRI  

PubMed Central

The brainstem is directly involved in controlling blood pressure, respiration, sleep/wake cycles, pain modulation, motor, and cardiac output. As such it is of significant basic science and clinical interest. However, the brainstem’s location close to major arteries and adjacent pulsatile cerebrospinal fluid filled spaces, means that it is difficult to reliably record functional magnetic resonance imaging (fMRI) data from. These physiological sources of noise generate time varying signals in fMRI data, which if left uncorrected can obscure signals of interest. In this Methods Article we will provide a practical introduction to the techniques used to correct for the presence of physiological noise in time series fMRI data. Techniques based on independent measurement of the cardiac and respiratory cycles, such as retrospective image correction (RETROICOR, Glover et al., 2000), will be described and their application and limitations discussed. The impact of a physiological noise model, implemented in the framework of the general linear model, on resting fMRI data acquired at 3 and 7?T is presented. Data driven approaches based such as independent component analysis (ICA) are described. MR acquisition strategies that attempt to either minimize the influence of physiological fluctuations on recorded fMRI data, or provide additional information to correct for their presence, will be mentioned. General advice on modeling noise sources, and its effect on statistical inference via loss of degrees of freedom, and non-orthogonality of regressors, is given. Lastly, different strategies for assessing the benefit of different approaches to physiological noise modeling are presented.

Brooks, Jonathan C. W.; Faull, Olivia K.; Pattinson, Kyle T. S.; Jenkinson, Mark

2013-01-01

317

Neurophysiological architecture of functional magnetic resonance images of human brain.  

PubMed

We investigated large-scale systems organization of the whole human brain using functional magnetic resonance imaging (fMRI) data acquired from healthy volunteers in a no-task or 'resting' state. Images were parcellated using a prior anatomical template, yielding regional mean time series for each of 90 regions (major cortical gyri and subcortical nuclei) in each subject. Significant pairwise functional connections, defined by the group mean inter-regional partial correlation matrix, were mostly either local and intrahemispheric or symmetrically interhemispheric. Low-frequency components in the time series subtended stronger inter-regional correlations than high-frequency components. Intrahemispheric connectivity was generally related to anatomical distance by an inverse square law; many symmetrical interhemispheric connections were stronger than predicted by the anatomical distance between bilaterally homologous regions. Strong interhemispheric connectivity was notably absent in data acquired from a single patient, minimally conscious following a brainstem lesion. Multivariate analysis by hierarchical clustering and multidimensional scaling consistently defined six major systems in healthy volunteers-- corresponding approximately to four neocortical lobes, medial temporal lobe and subcortical nuclei- - that could be further decomposed into anatomically and functionally plausible subsystems, e.g. dorsal and ventral divisions of occipital cortex. An undirected graph derived by thresholding the healthy group mean partial correlation matrix demonstrated local clustering or cliquishness of connectivity and short mean path length compatible with prior data on small world characteristics of non-human cortical anatomy. Functional MRI demonstrates a neurophysiological architecture of the normal human brain that is anatomically sensible, strongly symmetrical, disrupted by acute brain injury, subtended predominantly by low frequencies and consistent with a small world network topology. PMID:15635061

Salvador, Raymond; Suckling, John; Coleman, Martin R; Pickard, John D; Menon, David; Bullmore, Ed

2005-09-01

318

Electron Spin Magnetic Resonance Force Microscopy of Nitroxide Spin Labels  

NASA Astrophysics Data System (ADS)

Nitroxide spin labels are widely used in electron spin resonance studies of biological and polymeric systems. Magnetic resonance force microscopy (MRFM) is a magnetic resonance technique that couples the high spatial resolution of a scanning probe microscope with the species selectivity of magnetic resonance. We report on our investigations of 4-amino TEMPO, a nitroxide spin label, by force-gradient MRFM. Our microscope operates at high vacuum in liquid helium, using a custom fabricated ultra-soft silicon cantilever in the magnet-on-cantilever geometry. An 18 GHz gap coupled microstripline resonator supplies the transverse field.

Moore, Eric W.; Lee, Sanggap; Hickman, Steven A.; Wright, Sarah J.; Marohn, John A.

2009-03-01

319

Model-independent method for fMRI analysis  

Microsoft Academic Search

This paper presents a fast method for delineation of activated areas of the brain from functional magnetic resonance imaging (fMRI) time series data. The steps of the work accomplished are as follows. 1) It is shown that the detection performance evaluated by the area under the receiver operating characteristic curve is directly related to the signal-to-noise ratio (SNR) of the

Hamid Soltanian-Zadeh; Donald J. Peck; David O. Hearshen; Renee R. Lajiness-O'Neill

2004-01-01

320

Intensity coding of auditory stimuli: an fMRI study  

Microsoft Academic Search

The effect of stimulus intensity (sound pressure level, SPL) of auditory stimuli on the BOLD response in the auditory cortex was investigated in 14 young and healthy subjects, with no hearing abnormalities, using echo-planar, functional magnetic resonance imaging (fMRI) during a verbal and a non-verbal auditory discrimination task. The stimuli were presented block-wise at three different intensities: 95, 85 and

L JÄncke; N. J Shah; S Posse; M Grosse-Ryuken; H.-W MÜller-GÄrtner

1998-01-01

321

Changes in fMRI Following Cognitive Rehabilitation in Severe Traumatic Brain Injury: A Case Study  

Microsoft Academic Search

Objective: To illustrate the relationship between changes in neuropsychological testing and changes in functional magnetic resonance imaging (fMRI) before and after cognitive rehabilitation therapy (CRT). Study Design: Single case study. Setting: Outpatient treatment center. Participant: A woman with history of severe traumatic brain injury (TBI) 16 years before study. Intervention: Individualized CRT using a developmental metacognitive model. Main Outcome Measures:

Linda Laatsch; Deborah Little; Keith Thulborn

2004-01-01

322

Prognostic Value of fMRI in Recovery of Hand Function in Subcortical Stroke Patients  

Microsoft Academic Search

The first objective of the study was to determine whether functional magnetic resonance imaging (fMRI) signal was correlated with motor performance at different stages of poststroke recovery. The second objective was to assess the existence of prognostic factors for recovery in early functional MR images. Eight right-handed patients with pure motor deficit secondary to a first lacunar infarct localized on

Isabelle Loubinoux; S. Dechaumont-Palacin; E. Castel-Lacanal; X. De Boissezon; Philippe Marque; J. Pariente; J.-F. Albucher; I. Berry; F. Chollet

2007-01-01

323

Brain activity underlying emotional valence and arousal: A response-related fMRI study  

Microsoft Academic Search

Emotional behavior is organized along two psychophysiologic dimensions: (1) valence, varying from negative to positive, and (2) arousal, varying from low to high. Behavioral responses along these dimensions are assumed to be mediated by different brain circuits. We recorded startle reflex modulation and skin conductance responses in healthy volunteers during functional magnetic resonance imaging (fMRI) while they viewed a set

Silke Anders; Martin Lotze; Michael Erb; Wolfgang Grodd; Niels Birbaumer

2004-01-01

324

Brain Systems Mediating Aversive Conditioning: an Event-Related fMRI Study  

Microsoft Academic Search

We have used event-related functional magnetic resonance imaging (fMRI) to characterize neural responses associated with emotional learning. Employing a classical conditioning paradigm in which faces were conditioned by pairing with an aversive tone (US), we compared responses evoked by conditioned (CS+) and nonconditioned (CS?) stimuli. Pairing 50% of the CS+ with the US enabled us to constrain our analysis to

Christian Büchel; Jond Morris; Raymond J Dolan; Karl J Friston

1998-01-01

325

Quantitative evaluation of hemodynamic response after hypercapnia among different brain territories by fMRI  

Microsoft Academic Search

The brain vascular system has an autoregulatory mechanism that maintains blood perfusion within normal limits at the capillary level. Partially due to its clinical importance, it is of interest to better understand the mechanisms involved in vascular regulation. Therefore, using functional magnetic resonance imaging (fMRI), we quantitatively investigated hemodynamic response characteristics of regions supplied by the main cerebral arteries, during

R. F. Leoni; K. C. Mazzeto-Betti; K. C. Andrade; D. B. de Araujo

2008-01-01

326

Effects of electroacupuncture versus manual acupuncture on the human brain as measured by fMRI  

Microsoft Academic Search

The goal of this functional magnetic resonance imaging (fMRI) study was to compare the central effects of electroacupuncture at different frequencies with traditional Chinese manual acupuncture. Although not as time-tested as manual acupuncture, electroacupuncture does have the advantage of setting stimulation frequency and intensity objectively and quantifiably. Manual acupuncture, electroacupuncture at 2 Hz and 100 Hz, and tactile control stimulation

Vitaly Napadow; Nikos Makris; Jing Liu; Norman W. Kettner; Kenneth K. Kwong; Kathleen K. S. Hui

2005-01-01

327

Origin of Negative Blood Oxygenation Level-Dependent fMRI Signals  

Microsoft Academic Search

Summary: Functional magnetic resonance imaging (fMRI) techniques are based on the assumption that changes in spike activity are accompanied by modulation in the blood oxygen- ation level-dependent (BOLD) signal. In addition to conven- tional increases in BOLD signals, sustained negative BOLD signal changes are occasionally observed and are thought to reflect a decrease in neural activity. In this study, the

Noam Harel; Sang-Pil Lee; Tsukasa Nagaoka; Dae-Shik Kim; Seong-Gi Kim

2002-01-01

328

Puzzlingly High Correlations in fMRI Studies of Emotion, Personality, and Social Cognition  

ERIC Educational Resources Information Center

Functional Magnetic Resonance Imaging (fMRI) studies of emotion, personality, and social cognition have drawn much attention in recent years, with high-profile studies frequently reporting extremely high (e.g., > 8) correlations between behavioral and self-report measures of personality or emotion and measures of brain activation. We show that…

Vul, Edward; Harris, Christine; Winkielman, Piotr; Pashler, Harold

2009-01-01

329

Neuroanatomical Distribution of Five Semantic Components of Verbs: Evidence from fMRI  

ERIC Educational Resources Information Center

The Simulation Framework, also known as the Embodied Cognition Framework, maintains that conceptual knowledge is grounded in sensorimotor systems. To test several predictions that this theory makes about the neural substrates of verb meanings, we used functional magnetic resonance imaging (fMRI) to scan subjects' brains while they made semantic…

Kemmerer, David; Castillo, Javier Gonzalez; Talavage, Thomas; Patterson, Stephanie; Wiley, Cynthia

2008-01-01

330

Using fMRI to Study Conceptual Change: Why and How?  

ERIC Educational Resources Information Center

Although the use of brain imaging techniques, such as functional magnetic resonance imaging (fMRI) is increasingly common in educational research, only a few studies regarding science learning have so far taken advantage of this technology. This paper aims to facilitate the design and implementation of brain imaging studies relating to science…

Masson, Steve; Potvin, Patrice; Riopel, Martin; Foisy, Lorie-Marlene Brault; Lafortune, Stephanie

2012-01-01

331

INFERRING INDIVIDUAL DIFFERENCES IN FMRI: FINDING BRAIN REGIONS WITH SIGNIFICANT WITHIN SUBJECT CORRELATION  

Microsoft Academic Search

Functional magnetic resonance imaging studies answer questions about activation effects in populations of subjects. To begin with, this involves appro- priate modeling of the fMRI data at the within-subject level. This is followed by extending the model to multiple subjects. There have been several attempts toward this extension, all of which have focused on inference on a single effect of

Sumitra Purkayastha; Tor D. Wager; Thomas E. Nichols

2008-01-01

332

Segmented spin-echo pulses to increase fMRI signal: Repeated intrinsic diffusional enhancement  

Microsoft Academic Search

Since its inception, functional magnetic resonance imaging (fMRI) has seen rapid progress in the application to neurosci- ence. Common gradient-recalled acquisition methods are sus- ceptible to static field inhomogeneities, resulting in signal loss at the medial temporal area important for memory function or at the basal ganglia area for motor control. In addition, they are susceptible to the contaminating signals

Allen W. Song; Hui Mao; Raja Muthupillai; Frank Haist; W. Thomas Dixon

1999-01-01

333

Dual-Tasking Alleviated Sleep Deprivation Disruption in Visuomotor Tracking: An fMRI Study  

ERIC Educational Resources Information Center

Effects of dual-responding on tracking performance after 49-h of sleep deprivation (SD) were evaluated behaviorally and with functional magnetic resonance imaging (fMRI). Continuous visuomotor tracking was performed simultaneously with an intermittent color-matching visual detection task in which a pair of color-matched stimuli constituted a…

Gazes, Yunglin; Rakitin, Brian C.; Steffener, Jason; Habeck, Christian; Butterfield, Brady; Basner, Robert C.; Ghez, Claude; Stern, Yaakov

2012-01-01

334

Modeling the hemodynamic response in fMRI using smooth FIR filters  

Microsoft Academic Search

Modeling the hemodynamic response in functional magnetic resonance (fMRI) experiments is an important aspect of the analysis of functional neuroimages. This has been done in the past using parametric response function, from a limited family. In this contribution, the authors adopt a semi-parametric approach based on finite impulse response (FIR) filters. In order to cope with the increase in the

Cyril Goutte; Finn Årup Nielsen; K. H. Hansen

2000-01-01

335

Auditory Verb Perception Recruits Motor Systems in the Developing Brain: An fMRI Investigation  

ERIC Educational Resources Information Center

This study investigated neural activation patterns during verb processing in children, using fMRI (functional Magnetic Resonance Imaging). Preschool children (aged 4-6) passively listened to lists of verbs and adjectives while neural activation was measured. Findings indicated that verbs were processed differently than adjectives, as the verbs…

James, Karin Harman; Maouene, Josita

2009-01-01

336

Perceiving Age and Gender in Unfamiliar Faces: An fMRI Study on Face Categorization  

ERIC Educational Resources Information Center

Efficient processing of unfamiliar faces typically involves their categorization (e.g., into old vs. young or male vs. female). However, age and gender categorization may pose different perceptual demands. In the present study, we employed functional magnetic resonance imaging (fMRI) to compare the activity evoked during age vs. gender…

Wiese, Holger; Kloth, Nadine; Gullmar, Daniel; Reichenbach, Jurgen R.; Schweinberger, Stefan R.

2012-01-01

337

Neural Changes after Phonological Treatment for Anomia: An fMRI Study  

ERIC Educational Resources Information Center

Functional magnetic resonance imaging (fMRI) was used to investigate the neural processing characteristics associated with word retrieval abilities after a phonologically-based treatment for anomia in two stroke patients with aphasia. Neural activity associated with a phonological and a semantic task was compared before and after treatment with…

Rochon, Elizabeth; Leonard, Carol; Burianova, Hana; Laird, Laura; Soros, Peter; Graham, Simon; Grady, Cheryl

2010-01-01

338

Seeing Chinese Characters in Action: An fMRI Study of the Perception of Writing Sequences  

ERIC Educational Resources Information Center

The Chinese character is composed of a finite set of strokes whose order in writing follows consensual principles and is learnt through school education. Using functional magnetic resonance imaging (fMRI), this study investigates the neural activity associated with the perception of writing sequences by asking participants to observe…

Yu, Hongbo; Gong, Lanyun; Qiu, Yinchen; Zhou, Xiaolin

2011-01-01

339

Generalized likelihood ratio detection for fMRI using complex data  

Microsoft Academic Search

The majority of functional magnetic resonance imaging (fMRI) studies obtain functional information using statistical tests based on the magnitude image reconstructions. Recently, a complex correlation (CC) test was proposed based on the complex image data in order to take advantage of phase information in the signal. However, the CC test ignores additional phase information in the baseline component of the

Fangyuan Y. Nan; Robert D. Nowak

1999-01-01

340

Brain Correlates of Aesthetic Expertise: A Parametric fMRI Study  

ERIC Educational Resources Information Center

Several studies have demonstrated that acquired expertise influences aesthetic judgments. In this paradigm we used functional magnetic resonance imaging (fMRI) to study aesthetic judgments of visually presented architectural stimuli and control-stimuli (faces) for a group of architects and a group of non-architects. This design allowed us to test…

Kirk, Ulrich; Skov, Martin; Christensen, Mark Schram; Nygaard, Niels

2009-01-01

341

What Has fMRI Told Us about the Development of Cognitive Control through Adolescence?  

ERIC Educational Resources Information Center

Cognitive control, the ability to voluntarily guide our behavior, continues to improve throughout adolescence. Below we review the literature on age-related changes in brain function related to response inhibition and working memory, which support cognitive control. Findings from studies using functional magnetic resonance imaging (fMRI) indicate…

Luna, Beatriz; Padmanabhan, Aarthi; O'Hearn, Kirsten

2010-01-01

342

Independent component analysis of fMRI group studies by self-organizing clustering  

Microsoft Academic Search

Independent component analysis (ICA) is a valuable technique for the multivariate data-driven analysis of functional magnetic resonance imaging (fMRI) data sets. Applications of ICA have been developed mainly for single subject studies, although different solutions for group studies have been proposed. These approaches combine data sets from multiple subjects into a single aggregate data set before ICA estimation and, thus,

Fabrizio Easposito; Tommaso Scarabino; Aapo Hyvarinen; Johan Himberg; Elia Formisano; Silvia Comani; Gioacchino Tedeschi; Rainer Goebel; Erich Seifritz; Francesco Di Salle

2005-01-01

343

Automated quality assurance routines for fMRI data applied to a multicenter study  

Microsoft Academic Search

Standard procedures to achieve quality assessment (QA) of functional magnetic resonance imaging (fMRI) data are of great importance. A standardized and fully automated procedure for QA is presented that allows for classification of data quality and the detection of artifacts by inspecting temporal variations. The application of the procedure on phantom measurements was used to check scanner and stimulation hardware

Tony Stöcker; Frank Schneider; Martina Klein; Ute Habel; Thilo Kellermann; Karl Zilles; N. Jon Shah

2005-01-01

344

Are Errors Differentiable from Deceptive Responses when Feigning Memory Impairment? An fMRI Study  

ERIC Educational Resources Information Center

Previous neuroimaging studies have suggested that the neural activity associated with truthful recall, with false memory, and with feigned memory impairment are different from one another. Here, we report a functional magnetic resonance imaging (fMRI) study that addressed an important but yet unanswered question: Is the neural activity associated…

Lee, Tatia M. C.; Au, Ricky K. C.; Liu, Ho-Ling; Ting, K. H.; Huang, Chih-Mao; Chan, Chetwyn C. H.

2009-01-01

345

Visual–spatial ability and fMRI cortical activation in surgery residents  

Microsoft Academic Search

BackgroundWe previously reported that a particular type of visual–spatial ability, mental rotation of visual forms, correlates with surgical performance in residents. In the current study, we used functional magnetic resonance imaging (fMRI) to identify patterns of cortical activation associated with mental rotation ability in those same residents.

Kyle R. Wanzel; Dimitri J. Anastakis; Mary Pat McAndrews; Ethan D. Grober; Ravi S. Sidhu; Keri Taylor; David J. Mikulis; Stanley J. Hamstra

2007-01-01

346

fMRI response to blue light delivery in the naïve brain: Implications for combined optogenetic fMRI studies.  

PubMed

The combination of optogenetics and functional magnetic resonance imaging (fMRI) is referred to as opto-fMRI. Optogenetics utilises genetic engineering to introduce light sensitive actuator proteins into cells. Functional MRI (fMRI) is a specialist form of magnetic resonance imaging concerned with imaging changes in blood flow and oxygenation, linked to regional variation in metabolic activity, in the brain. This study describes a methodological concern regarding the effects of light delivery into the brain for the purposes of opto-fMRI. We show that blue light delivery to the naïve rat brain causes profound fMRI responses, despite the absence of optogenetic activation. We demonstrate that these fMRI responses are dependent upon laser power and show that the laser causes significant heating. We identify how heating impacts upon the MR signal causing NMR frequency shifts, and T1 and T2* changes. This study brings attention to a possible confounder which must be taken into account when opto-fMRI experiments are designed. PMID:23128081

Christie, Isabel N; Wells, Jack A; Southern, Paul; Marina, Nephtali; Kasparov, Sergey; Gourine, Alexander V; Lythgoe, Mark F

2012-11-01

347

Magnetic Field Effects on High Quality Factor Superconducting Coplanar Resonators  

NASA Astrophysics Data System (ADS)

Superconducting coplanar waveguide resonators have proven to be invaluable tools in studying some of the same decoherence mechanisms as those found in superconducting qubits. Prior improvements in fabrication led to resonator internal quality factors (Qi's) in excess of 10 million at high power, enabling us to sensitively probe environmental effects on the resonance frequency and Qi. We have found these resonators to be very susceptible to applied and stray magnetic fields, with measurable changes in the resonator's Qi and resonance frequency from fields as small as a few milligauss. I will present more recent measurements of resonators in magnetic fields.

Megrant, Anthony; Neill, Charles; Barends, Rami; Chen, Yu; Chiaro, Ben; Kelly, Julian; Mariantoni, Matteo; Mutus, Josh; O'Malley, Peter; Sank, Daniel; Vainsencher, Amit; Wenner, James; White, Ted; Low, David; Ohya, Shinobu; Palmstrom, Christopher; Martinis, John; Cleland, Andrew

2013-03-01

348

Magnetic resonance spectroscopy of the human brain  

NASA Astrophysics Data System (ADS)

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.

Strózik-Kotlorz, D.

2014-01-01

349

Resting-state fMRI as a biomarker for Alzheimer's disease?  

PubMed

Previous work indicates that resting-state functional magnetic resonance imaging (fMRI) is sensitive to functional brain changes related to Alzheimer's disease (AD) pathology across the clinical spectrum. Cross-sectional studies have found functional connectivity differences in the brain's default mode network in aging, mild cognitive impairment, and AD. In addition, two recent longitudinal studies have shown that functional connectivity changes track AD progression. This earlier work suggests that resting-state fMRI may be a promising biomarker for AD. However, some key issues still need to be addressed before resting-state fMRI can be successfully applied clinically. In a previous issue of Alzheimer's Research & Therapy, Vemuri and colleagues discuss the use of resting-state fMRI in the study of AD. In this commentary, I will highlight and expand upon some of their main conclusions. PMID:22423634

Damoiseaux, Jessica S

2012-01-01

350

Principal Feature Analysis: A Multivariate Feature Selection Method for fMRI Data  

PubMed Central

Brain decoding with functional magnetic resonance imaging (fMRI) requires analysis of complex, multivariate data. Multivoxel pattern analysis (MVPA) has been widely used in recent years. MVPA treats the activation of multiple voxels from fMRI data as a pattern and decodes brain states using pattern classification methods. Feature selection is a critical procedure of MVPA because it decides which features will be included in the classification analysis of fMRI data, thereby improving the performance of the classifier. Features can be selected by limiting the analysis to specific anatomical regions or by computing univariate (voxel-wise) or multivariate statistics. However, these methods either discard some informative features or select features with redundant information. This paper introduces the principal feature analysis as a novel multivariate feature selection method for fMRI data processing. This multivariate approach aims to remove features with redundant information, thereby selecting fewer features, while retaining the most information.

Zeng, Ying; Tong, Li; Yan, Bin

2013-01-01

351

Optimized wireless power transfer to RFID sensors via magnetic resonance  

Microsoft Academic Search

Wireless powering of sensors through the strongly coupled magnetic resonance (SCMR) method at the RFID frequency of 27.2 MHz is studied here. The proposed system comprises of two single resonant loops and two self-resonant helical coils, in contrast to the two resonant loops traditionally used in RFID systems. The system is designed using simulation software and is validated by measurements.

Stavros V. Georgakopoulos; Olutola Jonah

2011-01-01

352

Molecular structure and motion in zero field magnetic resonance  

SciTech Connect

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

Jarvie, T.P.

1989-10-01

353

Nanodiamond graphitization: a magnetic resonance study.  

PubMed

We report on the first nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) study of the high-temperature nanodiamond-to-onion transformation. (1)H, (13)C NMR and EPR spectra of the initial nanodiamond samples and those annealed at 600, 700, 800 and 1800 ° C were measured. For the samples annealed at 600 to 800 ° C, our NMR data reveal the early stages of the surface modification, as well as a progressive increase in sp(2) carbon content with increased annealing temperature. Such quantitative experimental data were recorded for the first time. These findings correlate with EPR data on the sensitivity of the dangling bond EPR line width to air content, progressing with rising annealing temperature, that evidences consequent graphitization of the external layers of the diamond core. The sample annealed at 1800 ° C shows complete conversion of nanodiamond particles into carbon onions. PMID:23709490

Panich, A M; Shames, A I; Sergeev, N A; Olszewski, M; McDonough, J K; Mochalin, V N; Gogotsi, Y

2013-06-19

354

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

ERIC Educational Resources Information Center

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

Seedhouse, Steven J.; Hoffmann, Markus M.

2008-01-01

355

Review: Magnetic resonance imaging techniques in ophthalmology  

PubMed Central

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

Fagan, Andrew J.

2012-01-01

356

Magnetic resonance imaging of the cervix  

PubMed Central

Abstract Due to deficiencies of clinical staging, magnetic resonance (MR) imaging is being increasingly used in the pre-treatment work-up of cervical cancer. Lymph node status, as evaluated by advanced imaging modalities, is also being incorporated into management algorithms. Familiarity with MR imaging features will lead to more accurate staging of cervical cancer. Awareness of impact of staging on management will enable the radiologists to tailor the report to clinically and surgically relevant information. This article emphasizes the guidelines on the MR staging criteria, dependence of newer treatments on imaging staging and lymph node involvement, and MR imaging in post-treatment surveillance of cervical cancer.

Zand, Khashayar Rafat; Reinhold, Caroline; Abe, Hisashi; Maheshwari, Sharad; Mohamed, Ahmed; Upegui, Daniel

2007-01-01

357

Nuclear magnetic resonance in intermetallic compounds  

Microsoft Academic Search

The nuclear magnetic resonance absorption of aluminium and cobalt has been studied in the intermetallic compounds NiAl, CoAl, FeAl, Al2NiCo, Al2FeCo, Al2FeNi and CoTi. The intensity measurements indicate a high degree of order in all the compounds studied, particularly NiAl and CoAl. The relatively large values of intensity at compositions appreciably different from the equiatomic value for these two series

G. W. West

1964-01-01

358

Applications for breast magnetic resonance imaging.  

PubMed

This article reviews the relevant data on breast magnetic resonance imaging (MRI) use in screening, the short-term surgical outcomes and long-term cancer outcomes associated with the use of MRI in breast cancer staging, the use of MRI in occult primary breast cancer, as well as MRI to assess eligibility for accelerated partial breast irradiation and to evaluate tumor response after neoadjuvant chemotherapy. MRI for screening is supported in specific high-risk populations, namely, women with BRCA1 or BRCA2 mutations, a family history suggesting a hereditary breast cancer syndrome, or a history of chest wall radiation. PMID:24882343

Pilewskie, Melissa; Morrow, Monica

2014-07-01

359

Multiparametric magnetic resonance imaging of prostate cancer  

PubMed Central

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

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

2012-01-01

360

[Magnetic resonance imaging of craniofacial pathology].  

PubMed

Effectiveness of nuclear magnetic resonance imaging (MRI) was compared with that of the CT scan in several cases involving different lesions: intracranial, base of skull, facial sinuses, parapharyngeal spaces. MRI provided excellent contrast in soft tissues with good detection of tumors and their limits, the condition of neighboring tissues and any local or regional tumor extension. Vessels were also visualized. It was not influenced by dental artefacts, and allowed three-dimensional sections to be obtained simply without manipulation of patients. In contrast, bone structures were analyzed less clearly than by the CT scan. Marked progress in MRI technical features and results obtained can be expected in the very near future. PMID:3030179

Bourdinière, J; Le Clech, G; Varene, A; Lavalou, J F; Galand, A; Bahu, P

1986-01-01

361

Clinical Applications of Magnetic Resonance Imaging  

PubMed Central

Magnetic resonance imaging (MRI) is a relatively new diagnostic imaging technique that has substantially affected the diagnosis of a multitude of diseases. It has become the imaging modality of choice for a number of pathologic processes, especially in the central nervous system. The authors discuss the clinical applications of MRI, its current status in radiologic investigations, and radiographic features of some of the common diseases of the central nervous system. ImagesFigure 1Figures 2-3Figure 4Figures 5-6Figure 7Figure 8Figure 9Figure 10Figure 11Figures 12-13

Kumar, Alka; Montanera, Walter; Terbrugge, Karel G.; Willinsky, Robert; Fenton, Paul V.

1992-01-01

362

Nanoplatforms for magnetic resonance imaging of cancer  

PubMed Central

Summary The application of biomedical nanotechnology in magnetic resonance imaging (MRI) is expect to have a major impact leading to the development of new contrast drug candidates on the nanoscale (1–100 nm) that are able to react with specific biological targets at a molecular level. One of the major challenges in this regard is the construction of nanomaterials, especially used in molecular MRI diagnostics of cancer in vivo, specialized antitumor drug delivery or real-time evaluation of the efficacy of the implemented cancer treatment. In this paper, we tried to gain further insights into current trends of nanomedicine, with special focus on preclinical MRI studies in translation cancer research.

Cywinska, Monika A.; Grudzinski, Ireneusz P.; Cieszanowski, Andrzej; Bystrzejewski, Michal; Poplawska, Magdalena

2011-01-01

363

Image processing for magnetic-resonance elastography  

NASA Astrophysics Data System (ADS)

A newly developed magnetic resonance imaging technique can directly visualize propagating acoustic strain waves in tissue-like materials. By estimating the local wavelength of the acoustic wave pattern, quantitative values of shear modulus can be calculated and images generated that depict tissue elasticity or stiffness. Since tumors are significantly stiffer than normal tissue (the basis of their detection by palpation), this technique may have potential for 'palpation by imaging,' with possible application to the detection of tumors in breast, liver, kidney, and prostate. We describe the local wavelength estimation algorithm, study its properties, and show a variety of sample results.

Manduca, Armando; Muthupillai, Raja; Rossman, P. J.; Greenleaf, James F.; Ehman, Richard L.

1996-04-01

364

Magnetic resonance imaging of perianal fistulas.  

PubMed

Perianal fistulization is the result of a chronic inflammation of the perianal tissues. A wide spectrum of clinical manifestations, ranging from simple to complex fistulas, can be seen, the latter especially in patients with Crohn disease. Failure to detect secondary tracks and hidden abscesses may lead to therapeutic failure, such as insufficient response to medical treatment and relapse after surgery. Currently, magnetic resonance (MR) imaging is the preferred technique for evaluating perianal fistulas and associated complications. Initially used most often in the preoperative setting, MR imaging now also plays an important role in evaluating the response to medical therapy. PMID:24238135

Vanbeckevoort, Dirk; Bielen, Didier; Vanslembrouck, Ragna; Van Assche, Gert

2014-02-01

365

Cardiovascular magnetic resonance in systemic hypertension  

PubMed Central

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

2012-01-01

366

Magnetic resonance imaging of small bowel neoplasms  

PubMed Central

Abstract Magnetic resonance (MR) imaging is rapidly increasing clinical acceptance to evaluate the small bowel and can be the initial imaging method to investigate small bowel diseases. MR examinations may provide the first opportunity to detect and characterize tumours of the small bowel. Intra- and extraluminal MR findings, combined with contrast enhancement and functional information, help to make an accurate diagnosis and consequently characterize small bowel neoplasms. MR enteroclysis should be recommended for the initial investigation in patients suspected of having small bowel tumours. In this article, the MR findings of primary small bowel neoplasms are described and the MR findings for the differential diagnosis are discussed.

Casciani, Emanuele; Polettini, Elisabetta; Laghi, Francesca; Gualdi, Gianfranco

2013-01-01

367

Integrating and classifying parametric features from fMRI data for brain function characterization  

NASA Astrophysics Data System (ADS)

Recent advances in functional magnetic resonance imaging (fMRI) provide an unparalleled opportunity for measuring and characterizing brain function in humans. However, the typically small signal change is very noisy and susceptible to various artifacts, such as those caused by scanner drift, head motion, and cardio-respiratory effects. This paper presents an integrated and exploratory approach to characterize brain function from fMRI data by providing techniques for both functional segregation and integration without any prior knowledge of the experimental paradigm. We demonstrate that principal component analysis (PCA) can be used for temporal shape modeling and shape feature extraction, shedding lights from a different perspective for the application of PCA in fMRI analysis. Appropriate feature screening is also performed to eliminate the parameters corresponding to data noise or artifacts. The extracted and screened shape parameters are revealed to be effective and efficient representations of the true fMRI time series. We then propose a novel strategy which classifies the fMRI data into distinct activation regions based on the selected temporal shape features. Furthermore, we propose to infer functional connectivity of the identified patterns by the distance measures in this parametric shape feature space. Validation for accuracy, sensitivity, and efficiency of the method and comparison with existing fMRI analysis techniques are performed using both simulated and real fMRI data.

Wang, Yongmei Michelle; Zhou, Chunxiao

2006-03-01

368

Proton-nuclear magnetic resonance study of water solvent magnetic fluid's phase separation  

Microsoft Academic Search

We report proton-nuclear magnetic resonance experiments on a diluted water solvent magnetic fluid of colloidal volume fraction phi=0.30%. By sweeping the external magnetic field strength, H0, applied to the magnetic fluid around 4000 Oe, we found one major resonant field, HM, and two satellite resonant fields, HS1 and HS2, which correspond to resonant protons in three different coexisting phases. HS1

Susamu Taketomi; Shin-Hachiro Saito

2000-01-01

369

Metabolite specific proton magnetic resonance imaging  

SciTech Connect

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

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

1989-06-01

370

Magnetic resonance imaging of renal transplants.  

PubMed

Nineteen patients were examined to determine the clinical potential of magnetic resonance imaging (MRI) for evaluation of renal transplants. A 0.6-T cryogenic magnet and spin-echo technique with varying pulsing factors were used. T1-weighted images were best for differentiating the cortical and medullary parts of the transplanted kidney. Of the six living-related transplants with good renal function that were imaged, five demonstrated good corticomedullary differentiation (CMD) and one faint CMD. Three transplants with acute rejection were imaged, and all demonstrated a decrease in CMD and decrease in overall signal intensity compared with baseline. No CMD was seen in the three chronically rejecting transplants imaged. The appearance of cadaveric transplants and acute tubular necrosis was quite variable. All perinephric fluid collections were well depicted by MRI. Lymphoceles could be distinguished from hematomas. MRI may prove to be a useful adjunct in the evaluation of renal transplants and perinephric fluid collections. PMID:6388281

Geisinger, M A; Risius, B; Jordan, M L; Zelch, M G; Novick, A C; George, C R

1984-12-01

371

In vivo nuclear magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

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

Leblanc, A.

1986-05-01

372

Nuclear magnetic resonance imaging of liver hemangiomas  

SciTech Connect

Nine patients with cavernous hemangioma of the liver were examined by nuclear magnetic resonance imaging (MRI) with a 0.5 T superconductive magnet. Spin-echo technique was used with varying time to echo (TE) and repetition times (TR). Results were compared with /sup 99m/Tc red blood cell (RBC) scintigraphy, computed tomography (CT), echography, and arteriography. Four illustrated cases are reported. It was possible to establish a pattern for MRI characteristics of cavernous hemangiomas; rounded or smooth lobulated shape, marked increase in T1 and T2 values as compared with normal liver values. It is concluded that, although more experience is necessary to compare the specificity with that of ultrasound and CT, MRI proved to be very sensitive for the diagnosis of liver hemangioma, especially in the case of small ones which may be missed by /sup 99m/Tc-labeled RBC scintigraphy.

Sigal, R.; Lanir, A.; Atlan, H.; Naschitz, J.E.; Simon, J.S.; Enat, R.; Front, D.; Israel, O.; Chisin, R.; Krausz, Y.

1985-10-01

373

Epileptic Networks in Focal Cortical Dysplasia Revealed Using Electroencephalography-Functional Magnetic Resonance Imaging  

PubMed Central

Objective Surgical treatment of focal epilepsy in patients with focal cortical dysplasia (FCD) is most successful if all epileptogenic tissue is resected. This may not be evident on structural magnetic resonance imaging (MRI), so intracranial electroencephalography (icEEG) is needed to delineate the seizure onset zone (SOZ). EEG-functional MRI (fMRI) can reveal interictal discharge (IED)-related hemodynamic changes in the irritative zone (IZ). We assessed the value of EEG-fMRI in patients with FCD-associated focal epilepsy by examining the relationship between IED-related hemodynamic changes, icEEG findings, and postoperative outcome. Methods Twenty-three patients with FCD-associated focal epilepsy undergoing presurgical evaluation including icEEG underwent simultaneous EEG-fMRI at 3T. IED-related hemodynamic changes were modeled, and results were overlaid on coregistered T1-weighted MRI scans fused with computed tomography scans showing the intracranial electrodes. IED-related hemodynamic changes were compared with the SOZ on icEEG and postoperative outcome at 1 year. Results Twelve of 23 patients had IEDs during recording, and 11 of 12 had significant IED-related hemodynamic changes. The fMRI results were concordant with the SOZ in 5 of 11 patients, all of whom had a solitary SOZ on icEEG. Four of 5 had >50% reduction in seizure frequency following resective surgery. The remaining 6 of 11 patients had widespread or discordant regions of IED-related fMRI signal change. Five of 6 had either a poor surgical outcome (<50% reduction in seizure frequency) or widespread SOZ precluding surgery. Interpretation Comparison of EEG-fMRI with icEEG suggests that EEG-fMRI may provide useful additional information about the SOZ in FCD. Widely distributed discordant regions of IED-related hemodynamic change appear to be associated with a widespread SOZ and poor postsurgical outcome. ANN NEUROL 2011

Thornton, Rachel; Vulliemoz, Serge; Rodionov, Roman; Carmichael, David W; Chaudhary, Umair J; Diehl, Beate; Laufs, Helmut; Vollmar, Christian; McEvoy, Andrew W; Walker, Matthew C; Bartolomei, Fabrice; Guye, Maxime; Chauvel, Patrick; Duncan, John S; Lemieux, Louis

2011-01-01

374

Predicting Treatment Response in Social Anxiety Disorder From Functional Magnetic Resonance Imaging  

PubMed Central

Context Current behavioral measures poorly predict treatment outcome in social anxiety disorder (SAD). To our knowledge, this is the first study to examine neuroimaging-based treatment prediction in SAD. Objective To measure brain activation in patients with SAD as a biomarker to predict subsequent response to cognitive behavioral therapy (CBT). Design Functional magnetic resonance imaging (fMRI) data were collected prior to CBT intervention. Changes in clinical status were regressed on brain responses and tested for selectivity for social stimuli. Setting Patients were treated with protocol-based CBT at anxiety disorder programs at Boston University or Massachusetts General Hospital and underwent neuroimaging data collection at Massachusetts Institute of Technology. Patients Thirty-nine medication-free patients meeting DSM-IV criteria for the generalized subtype of SAD. Interventions Brain responses to angry vs neutral faces or emotional vs neutral scenes were examined with fMRI prior to initiation of CBT. Main Outcome Measures Whole-brain regression analyses with differential fMRI responses for angry vs neutral faces and changes in Liebowitz Social Anxiety Scale score as the treatment outcome measure. Results Pretreatment responses significantly predicted subsequent treatment outcome of patients selectively for social stimuli and particularly in regions of higher-order visual cortex. Combining the brain measures with information on clinical severity accounted for more than 40% of the variance in treatment response and substantially exceeded predictions based on clinical measures at baseline. Prediction success was unaffected by testing for potential confounding factors such as depression severity at baseline. Conclusions The results suggest that brain imaging can provide biomarkers that substantially improve predictions for the success of cognitive behavioral interventions and more generally suggest that such biomarkers may offer evidence-based, personalized medicine approaches for optimally selecting among treatment options for a patient.

Doehrmann, Oliver; Ghosh, Satrajit S.; Polli, Frida E.; Reynolds, Gretchen O.; Horn, Franziska; Keshavan, Anisha; Triantafyllou, Christina; Saygin, Zeynep M.; Whitfield-Gabrieli, Susan; Hofmann, Stefan G.; Pollack, Mark; Gabrieli, John D.

2013-01-01

375

Functional magnetic resonance imaging of sound pressure level encoding in the rat central auditory system.  

PubMed

Intensity is an important physical property of a sound wave and is customarily reported as sound pressure level (SPL). Invasive techniques such as electrical recordings, which typically examine one brain region at a time, have been used to study neuronal encoding of SPL throughout the central auditory system. Non-invasive functional magnetic resonance imaging (fMRI) with large field of view can simultaneously examine multiple auditory structures. We applied fMRI to measure the hemodynamic responses in the rat brain during sound stimulation at seven SPLs over a 72 dB range. This study used a sparse temporal sampling paradigm to reduce the adverse effects of scanner noise. Hemodynamic responses were measured from the central nucleus of the inferior colliculus (CIC), external cortex of the inferior colliculus (ECIC), lateral lemniscus (LL), medial geniculate body (MGB), and auditory cortex (AC). BOLD signal changes generally increase significantly (p<0.001) with SPL and the dependence is monotonic in CIC, ECIC, and LL. The ECIC has higher BOLD signal change than CIC and LL at high SPLs. The difference between BOLD signal changes at high and low SPLs is less in the MGB and AC. This suggests that the SPL dependences of the LL and IC are different from those in the MGB and AC and the SPL dependence of the CIC is different from that of the ECIC. These observations are likely related to earlier observations that neurons with firing rates that increase monotonically with SPL are dominant in the CIC, ECIC, and LL while non-monotonic neurons are dominant in the MGB and AC. Further, the IC's SPL dependence measured in this study is very similar to that measured in our earlier study using the continuous imaging method. Therefore, sparse temporal sampling may not be a prerequisite in auditory fMRI studies of the IC. PMID:23041525

Zhang, Jevin W; Lau, Condon; Cheng, Joe S; Xing, Kyle K; Zhou, Iris Y; Cheung, Matthew M; Wu, Ed X

2013-01-15

376

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

Microsoft Academic Search

This dissertation discusses the production of highly nonequilibrium nuclear spin polarization, referred to as hyperpolarization or hp, in the nuclear spin I = 9\\/2 noble gas isotope krypton-83 using spin exchange optical pumping (SEOP). This nonequilibrium polarization yields nuclear magnetic resonance (NMR) signals that are enhanced three or more orders of magnitude above those of thermally polarized krypton and enables

Zackary I. Cleveland

2008-01-01

377

Diffusion-weighted magnetic resonance imaging of the temporal bone  

Microsoft Academic Search

This paper summarizes the value of diffusion-weighted magnetic resonance imaging in the evaluation of temporal bone pathology.\\u000a It highlights the use of different types of diffusion-weighted magnetic resonance imaging in the different types of cholesteatoma,\\u000a prior to first stage surgery and prior to second look surgery. The value of diffusion-weighted magnetic resonance imaging\\u000a in the evaluation of pathology of the

B. De Foer; J. P. Vercruysse; M. Spaepen; T. Somers; M. Pouillon; E. Offeciers; J. W. Casselman

2010-01-01

378

Magnetic resonance studies of GaN-based LEDs  

Microsoft Academic Search

Electrically detected magnetic resonance (EDMR), electrically excited and optically detected magnetic resonance, photocurrent-detected magnetic resonance and the photo-quenching of EDMR are employed to study radiative and non-radiative recombination processes in single quantum well diodes. The effects of high current stress are studied in addition to recombination in unstressed devices. The signals are dominated by a broad line (g?2.01; ?B?13mT) which

William E Carlos; Shuji Nakamura

1998-01-01

379

Magnetic resonance elastography detected with a SQUID in microtesla magnetic fields  

Microsoft Academic Search

We have used a SQUID-based microtesla magnetic resonance imaging (MRI) system to perform magnetic resonance elastography (MRE) experiments in a measurement field of 132 microtesla. Magnetic resonance elastography is based on MRI and measures three-dimensional displacement and strain fields in a sample. With appropriate data processing this allows for a quantitative map of the physical response of a material to

Nathan Kelso; Kristie Koski; Jeffrey Reimer

2005-01-01

380

Functional magnetic resonance imaging of cognitive processing in young adults with Down syndrome.  

PubMed

The authors used functional magnetic resonance imaging (fMRI) to investigate neural activation during a semantic-classification/object-recognition task in 13 persons with Down syndrome and 12 typically developing control participants (age range ?=? 12-26 years). A comparison between groups suggested atypical patterns of brain activation for the individuals with Down syndrome. Correlation analyses between an index of visual spatial ability and brain activation depicted a positive relationship between (a) this index and brain activation in regions of the occipital and parietal lobes for the typically developing individuals and (b) the middle and dorsal frontal gyri in the individuals with Down syndrome. These findings supported the authors' hypothesis that persons with Down syndrome demonstrate atypical neural activation compared with typically developing individuals matched for chronological age. PMID:21905803

Jacola, Lisa M; Byars, Anna W; Chalfonte-Evans, Melinda; Schmithorst, Vincent J; Hickey, Fran; Patterson, Bonnie; Hotze, Stephanie; Vannest, Jennifer; Chiu, Chung-Yiu; Holland, Scott K; Schapiro, Mark B

2011-09-01

381

The impact of respiratory and cardiac effects on the phase and magnitude of resting-state fMRI signal  

NASA Astrophysics Data System (ADS)

Functional magnetic resonance imaging (fMRI) relies on detecting small changes in signal during brain activities, in presence of various noise, including those caused by respiration and cardiac pulsation. In the resting state, there is no explicit task event except the baseline neuroactivities of awakeness and other unknowns. However, the resting state is accompanied with the cardiac and respiration pulsations, which are the explicit non-neuronal physiological sources of fMRI signals. By recording the respiration and cardiac waveforms in synchrony with the fMRI scanning, we may estimate the physiological modulation artifacts in the fMRI dataset by the temporal correlations between the waveforms and the fMRI signal. In this work, we demonstrate that the respiration and cardiac modulation effects on the magnitude and phase components of the complex fMRI signal, including temporal correlation and time latency. In particular, our results show that: 1) the fMRI phase is slightly more modulated by the physiological modulations than its magnitude counterpart; 2) the fMRI signal (both magnitude and phase) shows 1 to 2s latency to respiration stimulus, and 0 to 1s latency to cardiac stimulus. For physiological artifact removal, we compare the band-stop filtering method with the RETROICOR method and find the former can remove the physiological modulations in a stable and consistent manner in frequency domain (stopping the signature frequencies irrespective of asynchrony.

Chen, Zikuan; Calhoun, Vince

2011-03-01

382

Antinociceptive activity of crotoxin in the central nervous system: a functional Magnetic Resonance Imaging study.  

PubMed

Crotoxin, the main neurotoxic component of the venom of South American rattlesnake (Crotalus durissus terrificus), is reported to have potent antinociceptive activity. Several authors have shown mainly in behavioral pain models that crotoxin induces antinociceptive effects, supposed to be mediated by actions on the central nervous system. The antinociceptive effects of crotoxin (45 ?g/kg ip) in rats were verified in this study by increased response latencies in a Hargreaves test and tail flick test. In addition, it was demonstrated that crotoxin does not lead to motor impairments during a rotarod test and open field test. The main objective, carried out by blood oxygen level dependent functional Magnetic Resonance Imaging (BOLD fMRI) in anesthetized rats, was to determine which specific brain structures are involved in these antinociceptive effects. Moreover, potential antihyperalgesic effects were investigated by inducing a local hyperalgesia on the left hind paw. Therefore, antinociceptive effects (right paw) and antihyperalgesic effects (left paw) of crotoxin were able to be differentiated. As a result, crotoxin exhibited dominant antihyperalgesic but also antinociceptive effects during pain stimulation. Reductions of BOLD signal already occurred in brain input structures but were most prominent in primary and secondary somatosensory cortices. In conclusion, BOLD fMRI in anesthetized rats proved to be a helpful tool in toxinology, particularly in unraveled mechanisms of modulating nociception in the central nervous system by (potential) analgesics like crotoxin. PMID:23916599

Wolz-Richter, S; Esser, K-H; Hess, A

2013-11-01

383

Real-time functional magnetic resonance imaging neurofeedback for treatment of Parkinson's disease.  

PubMed

Self-regulation of brain activity in humans based on real-time feedback of functional magnetic resonance imaging (fMRI) signal is emerging as a potentially powerful, new technique. Here, we assessed whether patients with Parkinson's disease (PD) are able to alter local brain activity to improve motor function. Five patients learned to increase activity in the supplementary motor complex over two fMRI sessions using motor imagery. They attained as much activation in this target brain region as during a localizer procedure with overt movements. Concomitantly, they showed an improvement in motor speed (finger tapping) and clinical ratings of motor symptoms (37% improvement of the motor scale of the Unified Parkinson's Disease Rating Scale). Activation during neurofeedback was also observed in other cortical motor areas and the basal ganglia, including the subthalamic nucleus and globus pallidus, which are connected to the supplementary motor area (SMA) and crucial nodes in the pathophysiology of PD. A PD control group of five patients, matched for clinical severity and medication, underwent the same procedure but did not receive feedback about their SMA activity. This group attained no control of SMA activation and showed no motor improvement. These findings demonstrate that self-modulation of cortico-subcortical motor circuits can be achieved by PD patients through neurofeedback and may result in clinical benefits that are not attainable by motor imagery alone. PMID:22072682

Subramanian, Leena; Hindle, John V; Johnston, Stephen; Roberts, Mark V; Husain, Masud; Goebel, Rainer; Linden, David

2011-11-01

384

Auditory orienting and inhibition of return in schizophrenia: A functional magnetic resonance imaging study  

PubMed Central

Patients with schizophrenia (SP) exhibit deficits in both attentional reorienting and inhibition of return (IOR) during visual tasks. However, it is currently unknown whether these deficits are supramodal in nature and how these deficits relate to other domains of cognitive dysfunction. In addition, the neuronal correlates of this pathological orienting response have not been investigated in either the visual or auditory modality. Therefore, thirty SP and 30 healthy controls (HC) were evaluated with an extensive clinical protocol and functional magnetic resonance imaging (fMRI) during an auditory cuing paradigm. SP exhibited both increased costs and delayed IOR during auditory orienting, suggesting a prolonged interval for attentional disengagement from cued locations. Moreover, a delay in the development of IOR was associated with cognitive deficits on formal neuropsychological testing in the domains of attention/inhibition and working memory. Event-related fMRI showed the characteristic activation of a frontoparietal network (invalid trials > valid trials), but there were no differences in functional activation between patients and HC during either attentional reorienting or IOR. Current results suggest that orienting deficits are supramodal in nature in SP, and are related to higher-order cognitive deficits that directly interfere with day-to-day functioning.

Abbott, Christopher C.; Merideth, Flannery; Ruhl, David; Yang, Zhen; Clark, Vincent P.; Calhoun, Vince D.; Hanlon, Faith M.; Mayer, Andrew R.

2011-01-01

385

Quantitative functional magnetic resonance imaging of brain activity using bolus-tracking arterial spin labeling  

PubMed Central

Blood oxygen level dependent (BOLD) functional magnetic resonance imaging (fMRI) is the most widely used method for mapping neural activity in the brain. The interpretation of altered BOLD signals is problematic when cerebral blood flow (CBF) or cerebral blood volume change because of aging and/or neurodegenerative diseases. In this study, a recently developed quantitative arterial spin labeling (ASL) approach, bolus-tracking ASL (btASL), was applied to an fMRI experiment in the rat brain. The mean transit time (MTT), capillary transit time (CTT), relative cerebral blood volume of labeled water (rCBVlw), relative cerebral blood flow (rCBF), and perfusion coefficient in the forelimb region of the somatosensory cortex were quantified during neuronal activation and in the resting state. The average MTT and CTT were 1.939±0.175 and 1.606±0.106?secs, respectively, in the resting state. Both times decreased significantly to 1.616±0.207 and 1.305±0.201?secs, respectively, during activation. The rCBVlw, rCBF, and perfusion coefficient increased on average by a factor of 1.123±0.006, 1.353±0.078, and 1.479±0.148, respectively, during activation. In contrast to BOLD techniques, btASL yields physiologically relevant indices of the functional hyperemia that accompanies neuronal activation.

Kelly, Michael E; Blau, Christoph W; Griffin, Karen M; Gobbo, Oliviero L; Jones, James FX; Kerskens, Christian M

2010-01-01

386

Improving the spatial resolution of magnetic resonance inverse imaging via the blipped-CAIPI acquisition scheme.  

PubMed

Using simultaneous acquisition from multiple channels of a radio-frequency (RF) coil array, magnetic resonance inverse imaging (InI) achieves functional MRI acquisitions at a rate of 100ms per whole-brain volume. InI accelerates the scan by leaving out partition encoding steps and reconstructs images by solving under-determined inverse problems using RF coil sensitivity information. Hence, the correlated spatial information available in the coil array causes spatial blurring in the InI reconstruction. Here, we propose a method that employs gradient blips in the partition encoding direction during the acquisition to provide extra spatial encoding in order to better differentiate signals from different partitions. According to our simulations, this blipped-InI (bInI) method can increase the average spatial resolution by 15.1% (1.3mm) across the whole brain and from 32.6% (4.2mm) in subcortical regions, as compared to the InI method. In a visual fMRI experiment, we demonstrate that, compared to InI, the spatial distribution of bInI BOLD response is more consistent with that of a conventional echo-planar imaging (EPI) at the level of individual subjects. With the improved spatial resolution, especially in subcortical regions, bInI can be a useful fMRI tool for obtaining high spatiotemporal information for clinical and cognitive neuroscience studies. PMID:24374076

Chang, Wei-Tang; Setsompop, Kawin; Ahveninen, Jyrki; Belliveau, John W; Witzel, Thomas; Lin, Fa-Hsuan

2014-05-01

387

Functional Magnetic Resonance Imaging of Effects of a Nicotinic Agonist in Schizophrenia  

PubMed Central

3-(2,4-Dimethoxybenzylidene)-anabaseine (DMXB-A) is a partial agonist at ?7-nicotinic acetylcholine receptors and is now in early clinical development for treatment of deficits in neurocognition and sensory gating in schizophrenia. During its initial phase 2 test, functional magnetic resonance imaging (fMRI) studies were conducted to determine whether the drug had its intended effect on hippocampal inhibitory interneurons. Increased hemodynamic activity in the hippocampus in schizophrenia is found during many tasks, including smooth pursuit eye movements, and may reflect inhibitory dysfunction. Placebo and two doses of drug were administered in a random, double-blind crossover design. After the morning drug/placebo ingestion, subjects underwent fMRI while performing a smooth pursuit eye movement task. Data were analyzed from 16 nonsmoking patients, including 7 women and 9 men. The 150-mg dose of DMXB-A, compared with placebo, diminished the activity of the hippocampus during pursuit eye movements, but the 75-mg dose was ineffective. The effect at the 150-mg dose was negatively correlated with plasma drug levels. The findings are consistent with the previously established function of ?7-nicotinic receptors on inhibitory interneurons in the hippocampus and with genetic evidence for deficits in these receptors in schizophrenia. Imaging of drug response is useful in planning future clinical tests of this compound and other nicotinic agonists for schizophrenia.

Tregellas, Jason R; Olincy, Ann; Johnson, Lynn; Tanabe, Jody; Shatti, Shireen; Martin, Laura F; Singel, Debra; Du, Yiping P; Soti, Ferenc; Kem, William R; Freedman, Robert

2010-01-01

388

Functional magnetic resonance imaging of effects of a nicotinic agonist in schizophrenia.  

PubMed

3-(2,4-Dimethoxybenzylidene)-anabaseine (DMXB-A) is a partial agonist at alpha7-nicotinic acetylcholine receptors and is now in early clinical development for treatment of deficits in neurocognition and sensory gating in schizophrenia. During its initial phase 2 test, functional magnetic resonance imaging (fMRI) studies were conducted to determine whether the drug had its intended effect on hippocampal inhibitory interneurons. Increased hemodynamic activity in the hippocampus in schizophrenia is found during many tasks, including smooth pursuit eye movements, and may reflect inhibitory dysfunction. Placebo and two doses of drug were administered in a random, double-blind crossover design. After the morning drug/placebo ingestion, subjects underwent fMRI while performing a smooth pursuit eye movement task. Data were analyzed from 16 nonsmoking patients, including 7 women and 9 men. The 150-mg dose of DMXB-A, compared with placebo, diminished the activity of the hippocampus during pursuit eye movements, but the 75-mg dose was ineffective. The effect at the 150-mg dose was negatively correlated with plasma drug levels. The findings are consistent with the previously established function of alpha7-nicotinic receptors on inhibitory interneurons in the hippocampus and with genetic evidence for deficits in these receptors in schizophrenia. Imaging of drug response is useful in planning future clinical tests of this compound and other nicotinic agonists for schizophrenia. PMID:19956085

Tregellas, Jason R; Olincy, Ann; Johnson, Lynn; Tanabe, Jody; Shatti, Shireen; Martin, Laura F; Singel, Debra; Du, Yiping P; Soti, Ferenc; Kem, William R; Freedman, Robert

2010-03-01

389

Comparison of cerebral activity during teeth clenching and fist clenching: a functional magnetic resonance imaging study.  

PubMed

Using functional magnetic resonance imaging (fMRI), we compared the cerebral activity during bilateral light fist-clenching and light-teeth clenching to provide more information on the central processing mechanisms underlying awake bruxism. Fourteen subjects participated in our study. Statistical comparisons were used to identify brain regions with significant activation in the subtraction of light fist clenching and light teeth clenching activity minus baseline. Participants also evaluated the perceived effort of clenching for each task, using a visual analogue scale of 0-100, after fMRI was performed. Bilateral light fist-clenching significantly activated the bilateral sensorimotor cortex, while light teeth-clenching was significantly associated with activation of the bilateral sensorimotor cortex, supplementary motor area, dorsolateral prefrontal cortex, and posterior parietal cortex. The VAS scores for fist clenching and teeth clenching were not significantly different. As light teeth-clenching activates a more extensive cortical network compared with light fist-clenching, we suggest that the teeth clenching may induce a more complex cerebral activity compared with the performance of a hand motor task. The clinical significance of these findings remains unknown but could perhaps be related to the propensity to trigger awake bruxism. PMID:21083626

Iida, T; Kato, M; Komiyama, O; Suzuki, H; Asano, T; Kuroki, T; Kaneda, T; Svensson, P; Kawara, M

2010-12-01

390

Continuous functional magnetic resonance imaging reveals dynamic nonlinearities of "dose-response" curves for finger opposition.  

PubMed

Linear experimental designs have dominated the field of functional neuroimaging, but although successful at mapping regions of relative brain activation, the technique assumes that both cognition and brain activation are linear processes. To test these assumptions, we performed a continuous functional magnetic resonance imaging (MRI) experiment of finger opposition. Subjects performed a visually paced bimanual finger-tapping task. The frequency of finger tapping was continuously varied between 1 and 5 Hz, without any rest blocks. After continuous acquisition of fMRI images, the task-related brain regions were identified with independent components analysis (ICA). When the time courses of the task-related components were plotted against tapping frequency, nonlinear "dose- response" curves were obtained for most subjects. Nonlinearities appeared in both the static and dynamic sense, with hysteresis being prominent in several subjects. The ICA decomposition also demonstrated the spatial dynamics with different components active at different times. These results suggest that the brain response to tapping frequency does not scale linearly, and that it is history-dependent even after accounting for the hemodynamic response function. This implies that finger tapping, as measured with fMRI, is a nonstationary process. When analyzed with a conventional general linear model, a strong correlation to tapping frequency was identified, but the spatiotemporal dynamics were not apparent. PMID:10407059

Berns, G S; Song, A W; Mao, H

1999-07-15

391

Non-contrast-enhanced magnetic resonance angiography: techniques and applications.  

PubMed

Non-contrast-enhanced magnetic resonance angiography has gained renewed interest since the discovery of the association between gadolinium-based contrast agents and nephrogenic systemic fibrosis. The following article is an overview of the different magnetic resonance angiography sequences, the technical possibilities and new developments. Clinical options and recent advancements will be highlighted, and recommendations for non-contrast-enhanced magnetic resonance angiography techniques in different anatomical regions will be given. Furthermore, the authors seek to predict the future of non-contrast-enhanced magnetic resonance angiography, with special focus on patients at risk. PMID:22149527

Blankholm, Anne Dorte; Ringgaard, Steffen

2012-01-01

392

Measurement of acoustic streaming using magnetic resonance.  

PubMed

Magnetic resonance imaging (MRI) has been used to explore acoustic streaming caused in water under ultrasonic exposure conditions similar to those used for diagnostic applications. Streaming was established in an enclosed tube with acoustically transparent end windows, using a pulsed, weakly-focused transducer of acoustic frequency 3.5 MHz. Phase-detection MRI was used to image and quantify streaming profiles in the region of the acoustic focus. Acoustic powers in the range 0.4 mW to 100 mW were used. The sensitivity of the technique enabled streaming velocities down to 0. 1 mm s(-1) to be measured, generated by acoustic power less than 1 mW. In addition, acoustic streaming generated within open meshes with minimum pore dimensions of 3.0 mm and 2.0 mm was measured. The flow velocity in the coarser mesh reached 0.9 mm s(-1) at 95 mW total acoustic power. These observations demonstrate that acoustic streaming is probably a much more general phenomenon in diagnostic ultrasound (ultrasound) than previously recognised. The combination of magnetic resonance and ultrasound shows promise as a diagnostic method for the differentiation of cystic lesions in vivo, and for their characterisation, with sensitivity significantly greater than using ultrasound alone. PMID:10722922

Starritt, H C; Hoad, C L; Duck, F A; Nassiri, D K; Summers, I R; Vennart, W

2000-02-01

393

Magnetic Resonance Imaging Evaluation of Cardiac Masses  

PubMed Central

Background Cardiac tumors are extremely rare; however, when there is clinical suspicion, proper diagnostic evaluation is necessary to plan the most appropriate treatment. In this context, cardiovascular magnetic resonance imaging (CMRI) plays an important role, allowing a comprehensive characterization of such lesions. Objective To review cases referred to a CMRI Department for investigation of cardiac and paracardiac masses. To describe the positive case series with a brief review of the literature for each type of lesion and the role of cardiovascular magnetic resonance imaging in evaluation. Methods Between August 2008 and December 2011, all cases referred for CMRI with suspicion of tumor involving the heart were reviewed. Cases with positive histopathological diagnosis, clinical evolution or therapeutic response compatible with the clinical suspicion and imaging findings were selected. Results Among the 13 cases included in our study, eight (62%) had histopathological confirmation. We describe five benign tumors (myxomas, rhabdomyoma and fibromas), five malignancies (sarcoma, lymphoma, Richter syndrome involving the heart and metastatic disease) and three non-neoplastic lesions (pericardial cyst, intracardiac thrombus and infectious vegetation). Conclusion CMRI plays an important role in the evaluation of cardiac masses of non-neoplastic and neoplastic origin, contributing to a more accurate diagnosis in a noninvasive manner and assisting in treatment planning, allowing safe clinical follow-up with good reproducibility.

Braggion-Santos, Maria Fernanda; Koenigkam-Santos, Marcel; Teixeira, Sara Reis; Volpe, Gustavo Jardim; Trad, Henrique Simao; Schmidt, Andre

2013-01-01

394

Magnetic resonance imaging of adnexal masses.  

PubMed

Adnexal masses are common in women of all ages. A range of physiological and benign ovarian conditions that develop in women, especially in the reproductive age, and adnexal malignancies can be evaluated with magnetic resonance imaging (MRI). Management of women with adnexal masses is frequently guided by imaging findings; therefore, precise characterization of adnexal pathology should be performed whenever possible. Magnetic resonance imaging is useful in characterization of adnexal masses that are not completely evaluated by ultrasound because it can provide additional information on soft tissue composition of adnexal masses based on specific tissue relaxation times and allows multiplanar imaging at large field of view to define the origin and extent of pelvic pathology. The patients most likely to benefit from MRI are pregnant women and those who are premenopausal and have masses that have complex features on ultrasound but do not have raised cancer antigen 125 tumor marker levels. The overlap in imaging appearance among different cell type malignancies makes it difficult to predict exact histology based on MRI appearance; however, MRI has a high accuracy in differentiating benign from malignant masses. Teratomas, endometriomas, simple and hemorrhagic cysts, fibromas, exophytic or extrauterine fibroids, and hydrosalpinges can be diagnosed with high confidence. In this article, the authors review the histopathologic background and MRI features of adnexal masses and discuss the role of MRI in the differentiation of benign from malignant adnexal pathologies. PMID:17417086

Rajkotia, Kavita; Veeramani, Murugusundaram; Macura, Katarzyna J

2006-12-01

395

Metabolic tumor imaging using magnetic resonance spectroscopy.  

PubMed

The adaptability and the genomic plasticity of cancer cells, and the interaction between the tumor microenvironment and co-opted stromal cells, coupled with the ability of cancer cells to colonize distant organs, contribute to the frequent intractability of cancer. It is becoming increasingly evident that personalized molecular targeting is necessary for the successful treatment of this multifaceted and complex disease. Noninvasive imaging modalities such as magnetic resonance (MR), positron emission tomography (PET), and single-photon emission computed tomography (SPECT) are filling several important niches in this era of targeted molecular medicine, in applications that span from bench to bedside. In this review we focus on noninvasive magnetic resonance spectroscopy (MRS) and spectroscopic imaging (MRSI) and their roles in future personalized medicine in cancer. Diagnosis, the identification of the most effective treatment, monitoring treatment delivery, and response to treatment are some of the broad areas into which MRS techniques can be integrated to improve treatment outcomes. The development of novel probes for molecular imaging--in combination with a slew of functional imaging capabilities--makes MRS techniques, especially in combination with other imaging modalities, valuable in cancer drug discovery and basic cancer research. PMID:21362514

Glunde, Kristine; Bhujwalla, Zaver M

2011-02-01

396

Event-related single-shot volumetric functional magnetic resonance inverse imaging of visual processing.  

PubMed

Developments in multi-channel radio-frequency (RF) coil array technology have enabled functional magnetic resonance imaging (fMRI) with higher degrees of spatial and temporal resolution. While modest improvement in temporal acceleration has been achieved by increasing the number of RF coils, the maximum attainable acceleration in parallel MRI acquisition is intrinsically limited only by the amount of independent spatial information in the combined array channels. Since the geometric configuration of a large-n MRI head coil array is similar to that used in EEG electrode or MEG SQUID sensor arrays, the source localization algorithms used in MEG or EEG source imaging can be extended to also process MRI coil array data, resulting in greatly improved temporal resolution by minimizing k-space traversal during signal acquisition. Using a novel approach, we acquire multi-channel MRI head coil array data and then apply inverse reconstruction methods to obtain volumetric fMRI estimates of blood oxygenation level dependent (BOLD) contrast at unprecedented whole-brain acquisition rates of 100 ms. We call this combination of techniques magnetic resonance Inverse Imaging (InI), a method that provides estimates of dynamic spatially-resolved signal change that can be used to construct statistical maps of task-related brain activity. We demonstrate the sensitivity and inter-subject reliability of volumetric InI using an event-related design to probe the hemodynamic signal modulations in primary visual cortex. Robust results from both single subject and group analyses demonstrate the sensitivity and feasibility of using volumetric InI in high temporal resolution investigations of human brain function. PMID:18538587

Lin, Fa-Hsuan; Witzel, Thomas; Mandeville, Joseph B; Polimeni, Jonathan R; Zeffiro, Thomas A; Greve, Douglas N; Wiggins, Graham; Wald, Lawrence L; Belliveau, John W

2008-08-01

397

A Functional Magnetic Resonance Imaging Predictor of Treatment Response to Venlafaxine in Generalized Anxiety Disorder  

PubMed Central

Background Functional magnetic resonance imaging (fMRI) holds promise as a noninvasive means of identifying neural responses that can be used to predict treatment response before beginning a drug trial. Imaging paradigms employing facial expressions as presented stimuli have been shown to activate the amygdala and anterior cingulate cortex (ACC). Here, we sought to determine whether pretreatment amygdala and rostral ACC (rACC) reactivity to facial expressions could predict treatment outcomes in patients with generalized anxiety disorder (GAD). Methods Fifteen subjects (12 female subjects) with GAD participated in an open-label venlafaxine treatment trial. Functional magnetic resonance imaging responses to facial expressions of emotion collected before subjects began treatment were compared with changes in anxiety following 8 weeks of venlafaxine administration. In addition, the magnitude of fMRI responses of subjects with GAD were compared with that of 15 control subjects (12 female subjects) who did not have GAD and did not receive venlafaxine treatment. Results The magnitude of treatment response was predicted by greater pretreatment reactivity to fearful faces in rACC and lesser reactivity in the amygdala. These individual differences in pretreatment rACC and amygdala reactivity within the GAD group were observed despite the fact that 1) the overall magnitude of pretreatment rACC and amygdala reactivity did not differ between subjects with GAD and control subjects and 2) there was no main effect of treatment on rACC-amygdala reactivity in the GAD group. Conclusions These findings show that this pattern of rACC-amygdala responsivity could prove useful as a predictor of venlafaxine treatment response in patients with GAD.

Johnstone, Tom; Somerville, Leah H.; Nitschke, Jack B.; Polis, Sara; Alexander, Andrew L.; Davidson, Richard J.; Kalin, Ned H.

2008-01-01

398

Reciprocity and gyrotropism in magnetic resonance transduction  

NASA Astrophysics Data System (ADS)

We give formulas for transduction in magnetic resonance—i.e., the appearance of an emf due to Larmor precession of spins—based upon the modified Lorentz reciprocity principle for gyrotropic (also called “nonreciprocal”) media, i.e., in which a susceptibility tensor is carried to its transpose by reversal of an external static field [cf., R. F. Harrington and A. T. Villeneuve IRE Trans. Microwave Theory and Technique MTT6, 308 (1958)]. Prior applications of reciprocity to magnetic resonance, despite much success, have ignored the gyrotropism which necessarily arises due to nuclear and/or unpaired electronic spins. For detection with linearly polarized fields, oscillating at the Larmor frequency, the emf is written in terms of a volume integral containing a product of two factors which we define as the antenna patterns, i.e., (H1x±iH1y) , where, e.g., for a single transceive antenna, the H ’s are just the spatially dependent oscillatory magnetic field strengths, per the application of some reference current at the antenna terminals, with the negative sign obtaining for transmission, and the positive for reception. Similar expressions hold for separate transmit and receive antennas; expressions are also given for circular polarization of the fields. We then exhibit a receive-only array antenna of two elements for magnetic resonance imaging of protons, which, due an intensity artifact arising from stray reactive coupling of the elements, produces, despite its own bilateral symmetry, asymmetric proton NMR images of a symmetric cylindrical phantom containing aqueous saline solution [J. Tropp and T. Schirmer, J. Magn. Reson. 151, 146 (2001)]. Modification of this two-port antenna, to function in transmit-receive mode, allows us to demonstrate highly nonreciprocal behavior: that is, to record images (of cylindrical test phantoms containing aqueous saline solution) whose appearance dramatically changes, when the roles of transmission and reception are swapped between the two antenna ports—giving in one instance a signal intensity pattern whose form resembles an umbrella (i.e., with a central column of moderate intensity surmounted by a bright canopy), and in the other, a distorted oval with slight concavities at its horizontal extremes, whose outline suggests that of a cat’s eye. The relation between image patterns and drive scheme can be shown to reverse if the static polarizing field is reversed. Electromagnetic and circuit calculations, together with the modified reciprocity principle, allow us to reproduce these pattern changes in numerical simulations, closely and convincingly. Although the imaging experiments are performed at a static field of 3.0T , and consequently a Larmor frequency of 128MHz , the nonreciprocal effects are not related to the shortness of the wavelength in aqueous medium, but appear equally in simulations based in either the quasistatic or full electromagnetic regimes. Finally, we show that although antenna patterns for transmission and reception are swapped with reversal of the polarizing field, meaning that the receive pattern equals the transmit pattern with the field reversed, this in no way invalidates the familiar rotating wave model of spin dynamics in magnetic resonance.

Tropp, James

2006-12-01

399

Reciprocity and gyrotropism in magnetic resonance transduction  

SciTech Connect

We give formulas for transduction in magnetic resonance - i.e., the appearance of an emf due to Larmor precession of spins - based upon the modified Lorentz reciprocity principle for gyrotropic (also called 'nonreciprocal') media, i.e., in which a susceptibility tensor is carried to its transpose by reversal of an external static field [cf., R. F. Harrington and A. T. Villeneuve IRE Trans. Microwave Theory and Technique MTT6, 308 (1958)]. Prior applications of reciprocity to magnetic resonance, despite much success, have ignored the gyrotropism which necessarily arises due to nuclear and/or unpaired electronic spins. For detection with linearly polarized fields, oscillating at the Larmor frequency, the emf is written in terms of a volume integral containing a product of two factors which we define as the antenna patterns, i.e. (H{sub 1x}{+-}iH{sub 1y}), where, e.g., for a single transceive antenna, the H's are just the spatially dependent oscillatory magnetic field strengths, per the application of some reference current at the antenna terminals, with the negative sign obtaining for transmission, and the positive for reception. Similar expressions hold for separate transmit and receive antennas; expressions are also given for circular polarization of the fields. We then exhibit a receive-only array antenna of two elements for magnetic resonance imaging of protons, which, due an intensity artifact arising from stray reactive coupling of the elements, produces, despite its own bilateral symmetry, asymmetric proton NMR images of a symmetric cylindrical phantom containing aqueous saline solution [J. Tropp and T. Schirmer, J. Magn. Reson. 151, 146 (2001)]. Modification of this two-port antenna, to function in transmit-receive mode, allows us to demonstrate highly nonreciprocal behavior: that is, to record images (of cylindrical test phantoms containing aqueous saline solution) whose appearance dramatically changes, when the roles of transmission and reception are swapped between the two antenna ports--giving in one instance a signal intensity pattern whose form resembles an umbrella (i.e., with a central column of moderate intensity surmounted by a bright canopy), and in the other, a distorted oval with slight concavities at its horizontal extremes, whose outline suggests that of a cat's eye. The relation between image patterns and drive scheme can be shown to reverse if the static polarizing field is reversed. Electromagnetic and circuit calculations, together with the modified reciprocity principle, allow us to reproduce these pattern changes in numerical simulations, closely and convincingly. Although the imaging experiments are performed at a static field of 3.0 T, and consequently a Larmor frequency of 128 MHz, the nonreciprocal effects are not related to the shortness of the wavelength in aqueous medium, but appear equally in simulations based in either the quasistatic or full electromagnetic regimes. Finally, we show that although antenna patterns for transmission and reception are swapped with reversal of the polarizing field, meaning that the receive pattern equals the transmit pattern with the field reversed, this in no way invalidates the familiar rotating wave model of spin dynamics in magnetic resonance.

Tropp, James [General Electric Healthcare Technologies, 47697 Westinghouse Drive, Fremont, California 94539 (United States)

2006-12-15

400

Electron magnetic resonance of ferrofluids: Evidence for anisotropic resonance at 77 K in samples cooled in a magnetic field  

NASA Astrophysics Data System (ADS)

Evidence is presented from studies of electron magnetic resonance for the formation of linear chains in kerosene based Mn 0.1Fe 0.9Fe 2O 4 (MF1) ferrite ferrofluid cooled in a magnetic field. The resonance field at 77 K was found to depend on the field at which the sample was cooled. More interestingly, the samples cooled in a magnetic field exhibited anisotropy in a resonance field with 180° periodicity, giving evidence for frozen chains.

Sastry, M. D.; Babu, Y.; Goyal, P. S.; Mehta, R. V.; Upadhyay, R. V.; Srinivas, D.

1995-08-01

401

Proton Magnetic Resonance Imaging of Flowing Blood.  

NASA Astrophysics Data System (ADS)

A novel technique of making angiographic images non-invasively by NMR is introduced. In order to visualize the vascular structure, flowing blood must be labeled to achieve contrast against background static tissue. In this technique, a little surface coil is used as the labeling device in addition to a whole-body NMR imager. To label the flowing blood, a magnetic field gradient is applied along the long axis of a living subject. The labeling coil over a carotid artery in the neck is fed RF at the resonant frequency of the protons under the coil. Arterial flow moves blood protons from a field below resonance (at the heart), steadily passing through resonance (at the neck) to a field high above resonance (in the head); at the end of the event blood protons are inverted, or labeled by an adiabatic fast passage. Meanwhile, protons in stationary tissue feel only a constant field and remain unaffected. Blood retains this label as it flows downstream into the head and gives a negative signal, while protons in other tissue a positive signal. Two projection images of the head, with and without labeling, are obtained and subtracted digitally. The residue of the subtraction shows moving material only since signals arising from static material are identical and are cancelled in the subtraction process. Finally, the three dimensional vascular structure is presented in a projective format onto a two dimensional plane resembling an angiogram produced with dye injection and X-rays. Pulse sequences specially designed to image moving objects are presented and discussed. Experimental results on phantoms, volunteers and patients are demonstrated. Competing techniques by NMR are reviewed and compared.

Du, Leila Ning-Zhi

1987-09-01

402

Evaluation of a magnetic resonance-compatible dentoalveolar tactile stimulus device  

PubMed Central

Abstract Background Few methods exist to study central nervous system processes following dentoalveolar tactile stimulation using functional magnetic resonance imaging (fMRI), likely due to inherent technical difficulties. Our primary goal was to develop and perform feasibility testing of a novel device capable of delivering valid and reliable dentoalveolar stimuli at dental chair-side and during MRI. Details of a device designed to deliver dentoalveolar dynamic pressure stimuli are described. Device testing took place in three settings: a) laboratory testing to assess range of stimulus force intensities, b) dental chair-side to assess reliability, validity and discriminant ability in force-pain relationship; and c) MRI to evaluate magnetic compatibility and ability to evoke brain activation in painfree subjects similar to those described in the literature. Results A novel device capable of delivering valid and reliable dentoalveolar somatosensory stimulation was developed (ICC = 0.89, 0.78-1 [95% CI]). Psychophysical data analysis showed high discriminant ability in differentiating painfree controls from cases with chronic dentoalveolar pain related to deafferenting dental procedures (sensitivity = 100%, specificity = 86.7%, area under ROC curve = 0.99). FMRI results of dentoalveolar dynamic pressure pain in painfree subjects revealed activation of brain areas typically associated with acute pain processing including thalamus, primary/secondary somatosensory, insular and prefrontal cortex. Conclusions A novel psychophysical method to deliver dynamic dentoalveolar pressure stimulation was developed and validated, allowing non-invasive MRI-based exploration of central nervous system function in response to intraoral somatosensation. Background The organization of the trigeminal system is unique as it provides somatosensory innervation to the face, masticatory and oral structures, the majority of the intracranial contents [1] and to specialized structures (tongue, nasal mucosa, auricle, tympanic membrane, cornea and part of the conjunctiva) [2]. Somatic sensory information transmitted by the trigeminal nerve is crucial for normal orofacial function; however, the mechanisms of many chronic pain conditions affecting areas innervated by this sensory system are not well understood [3-5]. The clinical presentation of chronic intraoral pain in the area of a tooth or in a site formally occupied by a tooth with no clinical or radiological signs of pathology, referred to as atypical odontalgia (AO) [6,7], is one such chronic pain condition of particular interest to dentists that is difficult to diagnose and manage. Recent research suggests both peripheral and central nervous system mechanisms being involved in AO pathophysiology [8-10], but the majority of mechanism-based research of patients with AO has focused on the "peripheral aspect" [7]. Functional magnetic resonance imaging (fMRI) is an established research technique to study the central aspects of pain [11]. Of existing neuroimaging techniques, fMRI provides good spatial resolution of cortical and subcortical structures critical in the processing of nociception, acceptable temporal resolution, does not involve ionizing radiation, and can be performed using most MRI systems that already exist in research centers and the community. For these reasons, we sought to develop a protocol that allows us to use this tool to investigate the central mechanisms involved in the processes of intraoral pain arising from the dentoalveolar region. Using this device, our long-term objective is to improve our understanding of the underlying mechanisms of persistent dentoalveolar pain. In the past few years several studies used fMRI to investigate the human trigeminal system [12,13], with a limited subset focusing on intraoral stimulation - specifically on the dentoalveolar processes, such as lip, tongue and teeth stimulation [14] or only teeth [15-17]. Some reasons for scarce literature on this topic may be the technical challenges involved in delivering facial/intraoral stimulation inside a M

2010-01-01

403

Where in the brain is nonliteral language? A coordinate-based meta-analysis of functional magnetic resonance imaging studies.  

PubMed

An increasing number of studies have investigated non-literal language, including metaphors, idioms, metonymy, or irony, with functional magnetic resonance imaging (fMRI). However, key questions regarding its neuroanatomy remain controversial. In this work, we used coordinate-based activation-likelihood estimations to merge available fMRI data on non-literal language. A literature search identified 38 fMRI studies on non-literal language (24 metaphor studies, 14 non-salient stimuli studies, 7 idiom studies, 8 irony studies, and 1 metonymy study). Twenty-eight studies with direct comparisons of non-literal and literal studies were included in the main meta-analysis. Sub-analyses for metaphors, idioms, irony, salient metaphors, and non-salient metaphors as well as studies on sentence level were conducted. Studies reported 409 activation foci, of which 129 (32%) were in the right hemisphere. These meta-analyses indicate that a predominantly left lateralised network, including the left and right inferior frontal gyrus; the left, middle, and superior temporal gyrus; and medial prefrontal, superior frontal, cerebellar, parahippocampal, precentral, and inferior parietal regions, is important for non-literal expressions. PMID:22759997

Rapp, Alexander M; Mutschler, Dorothee E; Erb, Michael

2012-10-15

404

A desktop magnetic resonance imaging system.  

PubMed

Modern magnetic resonance imaging (MRI) systems consist of several complex, high cost subsystems. The cost and complexity of these systems often makes them impractical for use as routine laboratory instruments, limiting their use to hospitals and dedicated laboratories. However, advances in the consumer electronics industry have led to the widespread availability of inexpensive radio-frequency integrated circuits with exceptional abilities. We have developed a small, low-cost MR system derived from these new components. When combined with inexpensive desktop magnets, this type of MR scanner has the promise of becoming standard laboratory equipment for both research and education. This paper describes the development of a prototype desktop MR scanner utilizing a 0.21 T permanent magnet with an imaging region of approximately 2 cm diameter. The system uses commercially available components where possible and is programmed in LabVIEW software. Results from 3D data sets of resolution phantoms and fixed, newborn mice demonstrate the capability of this system to obtain useful images from a system constructed for approximately $13,500. PMID:11755094

Wright, Steven M; Brown, David G; Porter, Jay R; Spence, David C; Esparza, Emilio; Cole, David C; Huson, F Russell

2002-01-01

405

Permanent Magnet Structure for a Nuclear Magnetic Resonance Imager for Medical Diagnostics.  

National Technical Information Service (NTIS)

The present invention relates to the utilization of magnetic fields established by means of permanent magnets for use in medical diagnosis, particularly of the human body or torsi. Whole-body nuclear magnetic resonance diagnostics has been available in th...

H. A. Leupold E. Potenziani

1987-01-01

406

Convertible pneumatic actuator for magnetic resonance elastography of the brain  

Microsoft Academic Search

Here we present a novel pneumatic actuator design for brain magnetic resonance elastography (MRE). Magnetic resonance elastography is a phase contrast technique capable of tracing strain wave propagation and utilizing this information for the calculation of mechanical properties of materials and living tissues. In MRE experiments, the acoustic waves are generated in a synchronized way with respect to image acquisition,

Peter Latta; Marco L. H. Gruwel; Patricia Debergue; Brendon Matwiy; Uta N. Sboto-Frankenstein; Boguslaw Tomanek

2011-01-01

407

Shear Modulus Decomposition Algorithm in Magnetic Resonance Elastography  

Microsoft Academic Search

Magnetic resonance elastography (MRE) is an imaging modality capable of visualizing the elastic properties of an object using magnetic resonance imaging (MRI) measurements of transverse acoustic strain waves induced in the object by a harmonically oscillating mechanical vibration. Various algorithms have been designed to determine the mechanical properties of the object under the assumptions of linear elasticity, isotropic and local

Ohin Kwon; Hyun Soo Nam; Eung Je Woo; Jin Keun Seo; Kevin J. Glaser; Armando Manduca; Richard L. Ehman

2009-01-01

408

Gradient and RF Coil Issues in Magnetic Resonance Imaging  

Microsoft Academic Search

Techniques are presented for new analysis of coils in magnetic resonance imaging that should lead to faster and more accurate pictures of humans. Insertable planar, cylindrical or elliptical gradient coils offer the potential for significant performance increases in magnetic resonance imaging. Using variational methods to minimize inductance and thereby optimize switching speeds, we have analyzed coils with these three geometries.

Michael Alan Martens

1991-01-01

409

Graph theory based algorithm for magnetic resonance brain images segmentation  

Microsoft Academic Search

Image segmentation is often required as a preliminary and indispensable stage in the computer aided medical image process, particularly during the clinical analysis of magnetic resonance (MR) brain images. The segmentation of magnetic resonance image (MRI) is a challenging problem that has received an enormous amount of attention lately. In this paper, we propose a simple and effective segmentation method

Jianzhong Wang; Di Liu; Lili Dou; Baoxue Zhang; Jun Kong; Yinghua Lu

2008-01-01

410

The Nobel Prize in Medicine for Magnetic Resonance Imaging  

ERIC Educational Resources Information Center

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

Fry, Charles G.

2004-01-01

411

Computed tomography and magnetic resonance findings in lipoid pneumonia.  

PubMed Central

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

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

1991-01-01

412

Magnetic resonance imaging of fistula-in-ano  

Microsoft Academic Search

PURPOSE: Successful management of anal fistulas depends upon accurate assessment of the primary tract and any secondary extensions. Preoperative imaging has, to date, been disappointing. METHODS: A prospective study of 35 patients with a clinical diagnosis of fistula-in-ano was performed comparing magnetic resonance imaging with the independently documented operative findings. Magnetic resonance imaging was also compared with anal endosonography in

Peter J. Lunniss; Peter G. Barker; Abdul H. Sultan; Peter Armstrong; Rodney H. Reznek; Clive I. Bartram; Karen S. Cottam; Robin K. Phillips

1994-01-01

413

Rotational Resonance of Nonaxisymmetric Magnetic Braking in the KSTAR Tokamak  

NASA Astrophysics Data System (ADS)

One of the important rotational resonances in nonaxisymmetric neoclassical transport has been experimentally validated in the KSTAR tokamak by applying highly nonresonant n=1 magnetic perturbations to rapidly rotating plasmas. These so-called bounce-harmonic resonances are expected to occur in the presence of magnetic braking perturbations when the toroidal rotation is fast enough to resonate with periodic parallel motions of trapped particles. The predicted and observed resonant peak along with the toroidal rotation implies that the toroidal rotation in tokamaks can be controlled naturally in favorable conditions to stability, using nonaxisymmetric magnetic perturbations.

Park, J.-K.; Jeon, Y. M.; Menard, J. E.; Ko, W. H.; Lee, S. G.; Bae, Y. S.; Joung, M.; You, K.-I.; Lee, K.-D.; Logan, N.; Kim, K.; Ko, J. S.; Yoon, S. W.; Hahn, S. H.; Kim, J. H.; Kim, W. C.; Oh, Y.-K.; Kwak, J.-G.

2013-08-01

414

Rotational resonance of nonaxisymmetric magnetic braking in the KSTAR tokamak.  

PubMed

One of the important rotational resonances in nonaxisymmetric neoclassical transport has been experimentally validated in the KSTAR tokamak by applying highly nonresonant n=1 magnetic perturbations to rapidly rotating plasmas. These so-called bounce-harmonic resonances are expected to occur in the presence of magnetic braking perturbations when the toroidal rotation is fast enough to resonate with periodic parallel motions of trapped particles. The predicted and observed resonant peak along with the toroidal rotation implies that the toroidal rotation in tokamaks can be controlled naturally in favorable conditions to stability, using nonaxisymmetric magnetic perturbations. PMID:24033042

Park, J-K; Jeon, Y M; Menard, J E; Ko, W H; Lee, S G; Bae, Y S; Joung, M; You, K-I; Lee, K-D; Logan, N; Kim, K; Ko, J S; Yoon, S W; Hahn, S H; Kim, J H; Kim, W C; Oh, Y-K; Kwak, J-G

2013-08-30

415

[Magnetic resonance tomographic findings in cardiac tumors].  

PubMed

After ultrasound, magnetic resonance imaging (MRI) is the second noninvasive powerful method of examining the heart. The findings in 9 patients with cardiac tumors are reported, who were examined by means of MRI: There was little variance in the MRI signal behavior (with only one exception), although the tumor population examined was very heterogeneous. The MRI techniques used (T1-weighted spin echo, steady-state gradient echo) seem to allow no better tumor specification than ultrasound. Wince multiplanar reconstruction is possible with MRI, tumor size, localization, and the borders of the cardiac neoplasms can be depicted. The cine technique provides dynamic information. In addition, this method allows reliable discrimination between the flow effects and true space-occupying lesions. PMID:8480024

Guhl, L; Grawunder, H J; Arlart, I P

1993-03-01

416

Magnetic resonance spectroscopy of intact spermatozoa  

NASA Astrophysics Data System (ADS)

NMR and ESR techniques have been used to elucidate the cellular metabolism and maturation of goat spermatozoa. Due to electron transport chains in the mitochondrial part of the sperm, these cells reduce nitroxide spin labels such as TEMPO and the ESR signal intensity is a good measure of the reducing power of live cells. The use of 31P NMR helps in detecting changes in intracellular pH during metabolism as well as cellular capacity to generate ATP, while 13C NMR has been used to monitor metabolites generated by cells derived from different regions. The maturation of spermatozoa as it passes through the epididymal track has been characterized by magnetic resonance spectroscopy.

Govil, Girjesh; Phadke, Ratna S.; Srivastava, Sudha; Hegde, Umashashi C.; Fernandes, Elvyra J.

1992-12-01

417

Magnetic resonance spectroscopy in Alzheimer's disease  

PubMed Central

Aging is the primary risk factor for dementia. With increasing life expectancy and aging populations worldwide, dementia is becoming one of the significant public health problems of the century. The most common pathology underlying dementia in older adults is Alzheimer’s disease. Proton magnetic resonance spectroscopy (MRS) may provide a window into the biochemical changes associated with the loss of neuronal integrity and other neurodegenerative pathology that involve the brain before the manifestations of cognitive impairment in patients who are at risk for Alzheimer’s disease. This review focuses on proton MRS studies in normal aging, mild cognitive impairment, and dementia, and how proton MRS metabolite levels may be potential biomarkers for early diagnosis of dementia-related pathologic changes in the brain.

Graff-Radford, Jonathan; Kantarci, Kejal

2013-01-01

418

In vivo nuclear magnetic resonance imaging  

NASA Technical Reports Server (NTRS)

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

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

1984-01-01

419

[Ophthalmoplegic migraine: value of magnetic resonance].  

PubMed

Ophthalmoplegic migraine is a rare entity, usually starting in childhood, and characterized by recurrent episodes of migrainous headaches associated with an oculomotor cranial nerve palsy, most commonly affecting the third nerve. Its physiopathology remains unknown, but the most recent theory, that considers it as a neuropathy, has led to its inclusion in the last International Headache Classification into the group of neuralgias. Diagnosis is reliant on clinical grounds and the exclusion of other disorders. The characteristic finding of enlargement and enhancement with contrast of the cisternal portion of the oculomotor nerve, observed in Magnetic Resonance Imaging (MRI) has supported its diagnosis. We describe a clinically compatible case, supported by typical MRI images that progressed favourably following corticoids treatment. PMID:19423405

Vecino López, R; Rivero, J Casas; Alvarez-Linera Prado, J; Noval Martín, S

2009-07-01

420

Magnetic Resonance Imaging of the Knee  

PubMed Central

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

Hash, Thomas W.

2013-01-01

421

Cardiovascular magnetic resonance in carotid atherosclerotic disease  

PubMed Central

Atherosclerosis is a chronic, progressive, inflammatory disease affecting many vascular beds. Disease progression leads to acute cardiovascular events such as myocardial infarction, stroke and death. The diseased carotid alone is responsible for one third of the 700,000 new or recurrent strokes occurring yearly in the United States. Imaging plays an important role in the management of atherosclerosis, and cardiovascular magnetic resonance (CMR) of the carotid vessel wall is one promising modality in the evaluation of patients with carotid atherosclerotic disease. Advances in carotid vessel wall CMR allow comprehensive assessment of morphology inside the wall, contributing substantial disease-specific information beyond luminal stenosis. Although carotid vessel wall CMR has not been widely used to screen for carotid atherosclerotic disease, many trials support its potential for this indication. This review summarizes the current state of knowledge regarding carotid vessel wall CMR and its potential clinical application for management of carotid atherosclerotic disease.

2009-01-01

422

Magnetic Earth Ionosphere Resonant Frequencies (MEIRF) project  

NASA Technical Reports Server (NTRS)

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

Spaniol, Craig

1993-01-01

423

Cardiovascular magnetic resonance in pulmonary hypertension  

PubMed Central

Pulmonary hypertension represents a group of conditions characterized by higher than normal pulmonary artery pressures. Despite improved treatments, outcomes in many instances remain poor. In recent years, there has been growing interest in the use of Cardiovascular Magnetic Resonance (CMR) in patients with pulmonary hypertension. This technique offers certain advantages over other imaging modalities since it is well suited to the assessment of the right ventricle and the proximal pulmonary arteries. Reflecting the relatively sparse evidence supporting its use, CMR is not routinely recommended for patients with pulmonary hypertension. However, it is particularly useful in patient with pulmonary arterial hypertension associated with congenital heart disease. Furthermore, it has proven informative in a number of ways; illustrating how right ventricular remodeling is favorably reversed by drug therapies and providing explicit confirmation of the importance of the right ventricle to clinical outcome. This review will discuss these aspects and practical considerations before speculating on future applications.

2012-01-01

424

Magnetic resonance imaging in pediatric stroke.  

PubMed

Pediatric stroke is a term that can be used to encompass everything from hypoxic-ischemic injury to the fetal central nervous system, and especially the premature neonate, to bland versus hemorrhagic infarction from arterial or venous causes in the infant and older child. Pediatric stroke is a chronically underrecognized and therefore underdiagnosed problem that may have significant economic implications. The risk factors for stroke in children are numerous and differ from those in adults. However, with adequate workup, the etiology can be identified in about 75% of cases. Cardiac disorders and hemoglobinopathy are the most common causes of ischemic infarction in children, whereas various congenital anomalies of the blood vessels or defects in coagulation or platelet function often are found in children with parenchymal hemorrhage. Magnetic resonance imaging provides a noninvasive method of investigating childhood stroke, aiding in both better diagnosis and management of this problem. PMID:11847499

Hunter, Jill Vanessa

2002-02-01

425

Magnetic resonance elastography of the brain.  

PubMed

The purpose of this study was to obtain normative data using magnetic resonance elastography (MRE) (a) to obtain estimates of the shear modulus of human cerebral tissue in vivo and (b) to assess a possible age dependence of the shear modulus of cerebral tissue in healthy adult volunteers. MR elastography studies were performed on tissue-simulating gelatin phantoms and 25 healthy adult volunteers. The data were analyzed using spatiotemporal filters and a local frequency estimating algorithm. Statistical analysis was performed using a paired t-test. The mean shear stiffness of cerebral white matter was 13.6 kPa (95% CI 12.3 to 14.8 kPa); while that of gray matter was lower at 5.22 kPa (95% CI 4.76 to 5.66 kPa). The difference was statistically significant (p<0.0001). PMID:17913514

Kruse, Scott A; Rose, Gregory H; Glaser, Kevin J; Manduca, Armando; Felmlee, Joel P; Jack, Clifford R; Ehman, Richard L

2008-01-01

426

Oxygenation-sensitive cardiovascular magnetic resonance  

PubMed Central

Oxygenation-sensitive cardiovascular magnetic resonance (CMR) is a non-contrast technique that allows the non-invasive assessment of myocardial oxygenation. It capitalizes on the fact that deoxygenated hemoglobin in blood can act as an intrinsic contrast agent, changing proton signals in a fashion that can be imaged to reflect the level of blood oxygenation. Increases in O2 saturation increase the BOLD imaging signal (T2 or T2*), whereas decreases diminish it. This review presents the basic concepts and limitations of the BOLD technique, and summarizes the preclinical and clinical studies in the assessment of myocardial oxygenation with a focus on recent advances. Finally, it provides future directions and a brief look at emerging techniques of this evolving CMR field.

2013-01-01

427

Economic costs of nuclear magnetic resonance imaging.  

PubMed

The costs of nuclear magnetic resonance (NMR) imaging have been carefully accounted during its early use at one institution. Capital requirements total $2,250,000 ($750,000 for construction and $1,500,000 for equipment). The annual operational costs are estimated at $907,000. At the current estimated patient procedure volume of 1,500 per year, an economic break-even point analysis indicates a required charge of $775 per patient procedure. This compares with the current break-even point charge for computed tomography of $342. If patient throughout can be increased to 12 procedures per day, the NMR break-even point charge would be reduced to $402. PMID:6707263

Evens, R G

1984-04-01

428

Cardiovascular magnetic resonance: deeper insights through bioengineering.  

PubMed

Heart disease is the main cause of morbidity and mortality worldwide, with coronary artery disease, diabetes, and obesity being major contributing factors. Cardiovascular magnetic resonance (CMR) can provide a wealth of quantitative information on the performance of the heart, without risk to the patient. Quantitative analyses of these data can substantially augment the diagnostic quality of CMR examinations and can lead to more effective characterization of disease and quantification of treatment benefit. This review provides an overview of the current state of the art in CMR with particular regard to the quantification of motion, both microscopic and macroscopic, and the application of bioengineering analysis for the evaluation of cardiac mechanics. We discuss the current clinical practice and the likely advances in the next 5-10 years, as well as the ways in which clinical examinations can be augmented by bioengineering analysis of strain, compliance, and stress. PMID:23662778

Young, A A; Prince, J L

2013-01-01

429

Morphometric magnetic resonance imaging in psychiatry.  

PubMed

Although advances in the clinical criteria of various axis I psychiatric disorders are continually being made, there is still considerable overlap in the clinical features, and diagnosis is often challenging. As a result, there has been substantial interest in using morphometric magnetic resonance imaging to better characterize these diseases and inform diagnosis. Region of interest and voxel-based morphometry studies are reviewed herein to examine the extent to which these goals are being met across various psychiatric disorders. It is concluded based on the studies reviewed that specific patterns of regional loss, although present in certain axis I disorders, are not, as yet, diagnostically useful. However, advances in outcome and treatment monitoring show considerably more promise for rapid application in psychiatry. PMID:19363434

Fleck, David E; Nandagopal, Jayasree; Cerullo, Michael A; Eliassen, James C; DelBello, Melissa P; Adler, Caleb M; Strakowski, Stephen M

2008-04-01

430

Nuclear magnetic resonance imaging of atherosclerotic disease  

SciTech Connect

Nuclear magnetic resonance (NMR) images of 93 patients undergoing studies of the abdomen and pelvis were studied for evidence of lesions of the aorta and the iliac and femoral arteries; atherosclerotic lesions were present in 13 of them. The lesions consisted of eccentric and concentric mural thickening with luminal narrowing and discrete plaques protruding into the vessel lumen. This appearance was distinctly different from the morphology of the internal vessel surface and uniformly thin vessel wall in normal patients and volunteers under the age of 30 years. Intraluminal flow signals observed in atherosclerotic and nonatherosclerotic subjects could be distinguished from mural lesions because of their lack of contiguity with the vessel wall and variation in appearance on multiple images obtained with the first and second spin echo. This initial experience suggests a potential role for NMR in the noninvasive imaging of atherosclerotic lesions. The natural contrast between flowing blood and the vessel wall indicates a distinct advantage of NMR for vascular imaging.

Herfkens, R.J.; Higgins, C.B.; Hricak, H.; Lipton, M.J.; Crooks, L.E.; Sheldon, P.E.; Kaufman, L.

1983-07-01

431

Magnetic Resonance Elastography of the Brain  

PubMed Central

The purpose of this study was to obtain normative data using magnetic resonance elastography (MRE) to: [a] obtain estimates of the shear modulus of human cerebral tissue in vivo, and [b] assess a possible age dependence of the shear modulus of cerebral tissue in healthy adult volunteers. MR elastography studies were performed on tissue-simulating gelatin phantoms and 25 healthy adult volunteers. The data were analyzed using spatio-temporal filters and a local frequency estimating algorithm. Statistical analysis was performed using a paired t-test. The mean shear stiffness of cerebral white matter was 13.6 kPa (95% CI 12.3 to 14.8 kPa); while that of gray matter was lower at 5.22 kPa (95% CI 4.76 to 5.66 kPa). The difference was statistically significant (p < 0.0001).

Kruse, Scott A.; Rose, Gregory H.; Glaser, Kevin J.; Manduca, Armando; Felmlee, Joel P.; Jack, Clifford R.; Ehman, Richard L.

2008-01-01

432

Interactive Course on Magnetic Resonance Imagining  

NSDL National Science Digital Library

As the health care professions continue to attract talented individuals, online resources have become an attractive way to learn new skills and supplement classroom learning. This website offers interested parties a step-by-step, interactive course on magnetic resonance imaging (MRI). It's worth noting that the site has received several awards from organizations such as the Radiological Society of North America. The course is divided into 16 sections, including Cardiac MRI, Image Formation, and Functional MRI. Each section contains a table of contents and a detailed list of learning objectives. As a whole, the site is a great way to get acquainted with this important medical tool and it is a resource that educators will want to share with friends and colleagues. [KMG

2013-01-01

433

Magnetic resonance imaging after exposure to microgravity  

NASA Technical Reports Server (NTRS)

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

Leblanc, Adrian

1993-01-01

434

Magnetic resonance spectroscopy in common dementias.  

PubMed

Neurodegenerative dementias are characterized by elevated myoinositol and decreased N-acetylaspartate (NAA) levels. The increase in myoinositol seems to precede decreasing NAA levels in Alzheimer's diseases. NAA/myo-inositol ratio in the posterior cingulate gyri decreases with increasing burden of Alzheimer's disease pathologic conditions. Proton magnetic resonance spectroscopy ((1)H MRS) is sensitive to the pathophysiologic processes associated with the risk of dementia in patients with mild cognitive impairment. Although significant progress has been made in improving the acquisition and analysis techniques in (1)H MRS, translation of these technical developments to clinical practice have not been effective because of the lack of standardization for multisite applications and normative data and an insufficient understanding of the pathologic basis of (1)H MRS metabolite changes. PMID:23928196

Kantarci, Kejal

2013-08-01

435

Magnetic penetration depth measurements with the microstrip resonator technique  

Microsoft Academic Search

The microstrip resonator technique is a convenient way to sensitively measure the temperature dependence of the magnetic penetration depth ?(T) in superconducting thin films. Because the method relies on measuring the resonant frequency of a high-Q transmission line resonator at microwave frequencies, one can very precisely measure small changes in ?(T). This technique is applied to studying the low-temperature dependence

S. M. Anlage; B. W. Langley; H. J. Snortland; C. B. Eom; T. H. Geballe; M. R. Beasley

1990-01-01

436

Dipole Resonances in a Homogeneous Plasma in a Magnetic Field  

Microsoft Academic Search

Radar observations recently made from a satellite orbiting above the ionosphere provide evidence for resonances of a plasma in a magnetic field which may be excited and detected by a dipole. The plasma may be said to be resonant, for a particular mode and frequency, if the group velocity is zero. These resonances are studied theoretically on the assumption that

Peter A. Sturrock

1965-01-01

437

Nuclear magnetic resonance technology in acupoint catgut embedding therapy for the treatment of menopausal panic disorder: its applications  

NASA Astrophysics Data System (ADS)

Nuclear Magnetic Resonance (NMR) is a diagnostic method which is non-invasive and non-ionizing irradiative to the human body. It not only suits structural, but also functional imaging. The NMR technique develops rapidly in its application in life science, which has become the hotspot in recent years. Menopausal panic disorder (MPD) is a typical psychosomatic disease during climacteric period, which may affect physical and mental health. Looking for a convenient, effective, and safe method, which is free of toxic-side effects to control the disease, is a modern medical issue. Based on reviewing the etiology and pathogenesis of MPD according to dual traditional Chinese medicine (TCM) and western medicine, further analyzed the advantages and principles for selecting acupoint prescription by tonifying kidney and benefiting marrow therapy for acupoint catgut-embedding to this disease. The application of Nuclear Magnetic Resonance Spectroscopy (NMRS) and Magnetic Resonance Imaging (MRI) technologies in mechanism research on acupoint catgut embedding for the treatment of MPD was discussed. It's pointed out that this intervention method is safe and effective to treat MPD. Breakthrough will be achieved from the research of the selection of acupoint prescription and therapeutic mechanism of acupoint catgut embedding for the treatment of menopausal panic disorder by utilizing the Functional Nuclear Magnetic Resonance Imaging (fMRI) and Metabonomics technologies.

Chen, Gui-zhen; Zhang, Sha-sha; Xu, Yun-xiang; Wang, Xiao-yun

2011-11-01

438

Cardiovascular Magnetic Resonance Imaging in Experimental Models  

PubMed Central

Cardiovascular magnetic resonance (CMR) imaging is the modality of choice for clinical studies of the heart and vasculature, offering detailed images of both structure and function with high temporal resolution. Small animals are increasingly used for genetic and translational research, in conjunction with models of common pathologies such as myocardial infarction. In all cases, effective methods for characterising a wide range of functional and anatomical parameters are crucial for robust studies. CMR is the gold-standard for the non-invasive examination of these models, although physiological differences, such as rapid heart rate, make this a greater challenge than conventional clinical imaging. However, with the help of specialised magnetic resonance (MR) systems, novel gating strategies and optimised pulse sequences, high-quality images can be obtained in these animals despite their small size. In this review, we provide an overview of the principal CMR techniques for small animals for example cine, angiography and perfusion imaging, which can provide measures such as ejection fraction, vessel anatomy and local blood flow, respectively. In combination with MR contrast agents, regional dysfunction in the heart can also be identified and assessed. We also discuss optimal methods for analysing CMR data, particularly the use of semi-automated tools for parameter measurement to reduce analysis time. Finally, we describe current and emerging methods for imaging the developing heart, aiding characterisation of congenital cardiovascular defects. Advanced small animal CMR now offers an unparalleled range of cardiovascular assessments. Employing these methods should allow new insights into the structural, functional and molecular basis of the cardiovascular system.

Price, Anthony N.; Cheung, King K.; Cleary, Jon O; Campbell, Adrienne E; Riegler, Johannes; Lythgoe, Mark F

2010-01-01

439

Magnetic Resonance Studies of Energy Storage Materials  

NASA Astrophysics Data System (ADS)

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

Vazquez Reina, Rafael

440

Magnetic resonance characterization of silicon nanowires  

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

441

A Java-based fMRI processing pipeline evaluation system for assessment of univariate general linear model and multivariate canonical variate analysis-based pipelines.  

PubMed

As functional magnetic resonance imaging (fMRI) becomes widely used, the demands for evaluation of fMRI processing pipelines and validation of fMRI analysis results is increasing rapidly. The current NPAIRS package, an IDL-based fMRI processing pipeline evaluation framework, lacks system interoperability and the ability to evaluate general linear model (GLM)-based pipelines using prediction metrics. Thus, it can not fully evaluate fMRI analytical software modules such as FSL.FEAT and NPAIRS.GLM. In order to overcome these limitations, a Java-based fMRI processing pipeline evaluation system was developed. It integrated YALE (a machine learning environment) into Fiswidgets (a fMRI software environment) to obtain system interoperability and applied an algorithm to measure GLM prediction accuracy. The results demonstrated that the system can evaluate fMRI processing pipelines with univariate GLM and multivariate canonical variates analysis (CVA)-based models on real fMRI data based on prediction accuracy (classification accuracy) and statistical parametric image (SPI) reproducibility. In addition, a preliminary study was performed where four fMRI processing pipelines with GLM and CVA modules such as FSL.FEAT and NPAIRS.CVA were evaluated with the system. The results indicated that (1) the system can compare different fMRI processing pipelines with heterogeneous models (NPAIRS.GLM, NPAIRS.CVA and FSL.FEAT) and rank their performance by automatic performance scoring, and (2) the rank of pipeline performance is highly dependent on the preprocessing operations. These results suggest that the system will be of value for the comparison, validation, standardization and optimization of functional neuroimaging software packages and fMRI processing pipelines. PMID:18506642

Zhang, Jing; Liang, Lichen; Anderson, Jon R; Gatewood, Lael; Rottenberg, David A; Strother, Stephen C

2008-01-01

442

The electrically detected magnetic resonance microscope: Combining conductive atomic force microscopy with electrically detected magnetic resonance  

NASA Astrophysics Data System (ADS)

We present the design and implementation of a scanning probe microscope, which combines electrically detected magnetic resonance (EDMR) and (photo-)conductive atomic force microscopy ((p)cAFM). The integration of a 3-loop 2-gap X-band microwave resonator into an AFM allows the use of conductive AFM tips as a movable contact for EDMR experiments. The optical readout of the AFM cantilever is based on an infrared laser to avoid disturbances of current measurements by absorption of straylight of the detection laser. Using amorphous silicon thin film samples with varying defect densities, the capability to detect a spatial EDMR contrast is demonstrated. Resonant current changes as low as 20 fA can be detected, allowing the method to realize a spin sensitivity of 8 × 10^6spins/?Hz at room temperature.

Klein, Konrad; Hauer, Benedikt; Stoib, Benedikt; Trautwein, Markus; Matich, Sonja; Huebl, Hans; Astakhov, Oleksandr; Finger, Friedhelm; Bittl, Robert; Stutzmann, Martin; Brandt, Martin S.

2013-10-01

443

Spin-echo fMRI in humans using high spatial resolutions and high magnetic fields  

Microsoft Academic Search

The Hahn spin-echo (HSE)-based BOLD effect at high magnetic fields is expected to provide functional images that originate exclusively from the microvasculature. The blood contribution that dominates HSE BOLD contrast at low magnetic fields (e.g., 1.5 T), and degrades specificity, is highly attenuated at high fields because the apparent T2 of venous blood in an HSE experiment decreases quadratically with

Essa Yacoub; Timothy Q. Duong; Pierre-Francois Van De Moortele; Martin Lindquist; Gregor Adriany; Seong-Gi Kim; Xiaoping Hu

2003-01-01

444

A Tool for Classifying Individuals with Chronic Back Pain: Using Multivariate Pattern Analysis with Functional Magnetic Resonance Imaging Data  

PubMed Central

Chronic pain is one of the most prevalent health problems in the world today, yet neurological markers, critical to diagnosis of chronic pain, are still largely unknown. The ability to objectively identify individuals with chronic pain using functional magnetic resonance imaging (fMRI) data is important for the advancement of diagnosis, treatment, and theoretical knowledge of brain processes associated with chronic pain. The purpose of our research is to investigate specific neurological markers that could be used to diagnose individuals experiencing chronic pain by using multivariate pattern analysis with fMRI data. We hypothesize that individuals with chronic pain have different patterns of brain activity in response to induced pain. This pattern can be used to classify the presence or absence of chronic pain. The fMRI experiment consisted of alternating 14 seconds of painful electric stimulation (applied to the lower back) with 14 seconds of rest. We analyzed contrast fMRI images in stimulation versus rest in pain-related brain regions to distinguish between the groups of participants: 1) chronic pain and 2) normal controls. We employed supervised machine learning techniques, specifically sparse logistic regression, to train a classifier based on these contrast images using a leave-one-out cross-validation procedure. We correctly classified 92.3% of the chronic pain group (N?=?13) and 92.3% of the normal control group (N?=?13) by recognizing multivariate patterns of activity in the somatosensory and inferior parietal cortex. This technique demonstrates that differences in the pattern of brain activity to induced pain can be used as a neurological marker to distinguish between individuals with and without chronic pain. Medical, legal and business professionals have recognized the importance of this research topic and of developing objective measures of chronic pain. This method of data analysis was very successful in correctly classifying each of the two groups.

Callan, Daniel; Mills, Lloyd; Nott, Connie; England, Robert; England, Shaun

2014-01-01

445

A tool for classifying individuals with chronic back pain: using multivariate pattern analysis with functional magnetic resonance imaging data.  

PubMed

Chronic pain is one of the most prevalent health problems in the world today, yet neurological markers, critical to diagnosis of chronic pain, are still largely unknown. The ability to objectively identify individuals with chronic pain using functional magnetic resonance imaging (fMRI) data is important for the advancement of diagnosis, treatment, and theoretical knowledge of brain processes associated with chronic pain. The purpose of our research is to investigate specific neurological markers that could be used to diagnose individuals experiencing chronic pain by using multivariate pattern analysis with fMRI data. We hypothesize that individuals with chronic pain have different patterns of brain activity in response to induced pain. This pattern can be used to classify the presence or absence of chronic pain. The fMRI experiment consisted of alternating 14 seconds of painful electric stimulation (applied to the lower back) with 14 seconds of rest. We analyzed contrast fMRI images in stimulation versus rest in pain-related brain regions to distinguish between the groups of participants: 1) chronic pain and 2) normal controls. We employed supervised machine learning techniques, specifically sparse logistic regression, to train a classifier based on these contrast images using a leave-one-out cross-validation procedure. We correctly classified 92.3% of the chronic pain group (N?=?13) and 92.3% of the normal control group (N?=?13) by recognizing multivariate patterns of activity in the somatosensory and inferior parietal cortex. This technique demonstrates that differences in the pattern of brain activity to induced pain can be used as a neurological marker to distinguish between individuals with and without chronic pain. Medical, legal and business professionals have recognized the importance of this research topic and of developing objective measures of chronic pain. This method of data analysis was very successful in correctly classifying each of the two groups. PMID:24905072

Callan, Daniel; Mills, Lloyd; Nott, Connie; England, Robert; England, Shaun

2014-01-01

446

Multi-dimensionally encoded magnetic resonance imaging  

PubMed Central

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

Lin, Fa-Hsuan

2013-01-01

447

Microrobotic navigable entities for Magnetic Resonance Targeting.  

PubMed

Magnetic Resonance Targeting (MRT) uses MRI for gathering tracking data to determine the position of microscale entities with the goal of guiding them towards a specific target in the body accessible through the vascular network. At full capabilities, a MRT platform designed to treat a human would consist of a clinical MRI scanner running special algorithms and upgraded to provide propulsion gradient up to approximately 400mT/m to enable entities as small as a few tens of micrometers in diameter and containing magnetic nanoparticles (MNP) to be steered at vessel bifurcations based on tracking information. Indeed, using a clinical MRI system, we showed that such single entity with a diameter as small as 15microm is detectable in gradient-echo scans. Among many potential interventions, targeted cancer therapy is a good initial application for such new microrobotic approach since secondary toxicity for the patient could be reduced while increasing therapeutic efficacy using lower dosages. Although many types of such entities are needed to provide a larger set of tools, here, only three initial types designed with different functionalities and for different types of cancer are briefly described. Initially designed for targeted chemo-embolization of liver tumors, the first type known as Therapeutic Magnetic Micro-Carriers (TMMC) consists in its present form of approximately 50 microm PLGA microparticles containing therapeutics and approximately 180 nm FeCo MNP. For the second type, MNP are not only used for propulsion and tracking, but also actuation based on a local elevation of the temperature. In its simplest form, it consists of approxiamtely 20 nm MNP embedded in a thermo-sensitive hydrogel known as PNIPA, allowing additional functionalities such as computer triggered drug release and targeted hyperthermia. The third type initially considered to target colorectal tumors, consists of 1-2 microm MR-trackable and controllable MC-1 Magnetotactic Bacteria (MTB) with propelling thrust force provided by two flagella bundles per cell exceeding 4 pN. PMID:21097003

Martel, Sylvain

2010-01-01

448

Computer simulation of magnetic resonance spectra employing homotopy.  

PubMed

Multidimensional homotopy provides an efficient method for accurately tracing energy levels and hence transitions in the presence of energy level anticrossings and looping transitions. Herein we describe the application and implementation of homotopy to the analysis of continuous wave electron paramagnetic resonance spectra. The method can also be applied to electron nuclear double resonance, electron spin echo envelope modulation, solid-state nuclear magnetic resonance, and nuclear quadrupole resonance spectra. PMID:9799683

Gates, K E; Griffin, M; Hanson, G R; Burrage, K

1998-11-01

449

Neurochemistry of Drug Action: Insights from Proton Magnetic Resonance Spectroscopic Imaging And Their Relevance to Addiction  

PubMed Central

Proton magnetic resonance spectroscopy (1H MRS) is a non-invasive imaging technique that permits measurement of particular compounds or metabolites within the tissue of interest. In the brain, 1H MRS provides a snapshot of the neurochemical environment within a defined volume of interest. A search of the literature demonstrates the widespread utility of this technique for characterizing tumors, tracking the progress of neurodegenerative disease, and for understanding the neurobiological basis of psychiatric disorders. As of relatively recently, 1H MRS has found its way into substance abuse research, and it is beginning to become recognized as a valuable complement in the brain imaging toolbox that also contains positron emission tomography (PET), single photon emission computed tomography (SPECT), and functional magnetic resonance imaging (fMRI). Drug abuse studies employing 1H MRS have identified a number biochemical changes in the brain. The most consistent alterations across drug class were reductions in N-acetylaspartate and elevations in myo-inositol, while changes in choline, creatine, and amino acid transmitters also were abundant. Together, the studies discussed herein provide evidence that drugs of abuse may have a profound impact on neuronal health, energy metabolism and maintenance, inflammatory processes, cell membrane turnover, and neurotransmission, and these biochemical changes may underlie the neuropathology within brain tissue that subsequently gives rise to the cognitive and behavioral impairments associated with drug addiction.

Licata, Stephanie C.; Renshaw, Perry F.

2011-01-01

450

[Application of pharmaco functional magnetic resonance imaging (phMRI) in the research of affective disorders].  

PubMed

Many common psychiatric disorders such as depression and anxiety disorders are associated with dysfunction in the monoamine neurotransmission in the central nervous system. However, the investigation of these pathophysiological processes in the human living brain is difficult. In case of functional magnetic resonance imaging (fMRI), a non-invasive method for the examination of brain activity, the activity-inducing stimulus is generally a cognitive psychological test, while during pharmacological magnetic resonance imaging (phMRI) the activation is triggered by a specific pharmacon. In the present work we review the available scientific literature related to this method using literature search in PubMed. Through application of a selective pharmacon like the selective serotonine reuptake inhibitors (SSRIs) citalopram or escitalopram in a challenge phMRI study, the serotonergic neurotransmitter system can be examined specifically, the functioning brain areas involved in its effect become observable.. With modulation phMRI we can monitor the long-term effect of an antidepressant or we can examine the immediate effect of a single dose of the medication on congitive psychological functions like emotional processing. Thus, the application of phMRI methods may help deepen our understanding of serotonergic function in the living human brain as well as of diseases related to serotonergic neurotransmitter system dysfunction. PMID:24978048

Edes, Andrea Edit; Gonda, Xenia; Bagdy, Gyorgy; Juhasz, Gabriella

2014-06-01

451

Source Monitoring 15 Years Later: What Have We Learned from fMRI about the Neural Mechanisms of Source Memory?  

ERIC Educational Resources Information Center

Focusing primarily on functional magnetic resonance imaging (fMRI), this article reviews evidence regarding the roles of subregions of the medial temporal lobes, prefrontal cortex, posterior representational areas, and parietal cortex in source memory. In addition to evidence from standard episodic memory tasks assessing accuracy for neutral…

Mitchell, Karen J.; Johnson, Marcia K.

2009-01-01

452

FMRI Brain Activation in a Finnish Family with Specific Language Impairment Compared with a Normal Control Group  

ERIC Educational Resources Information Center

The aim of the present study was to investigate differences in brain activation in a family with SLI as compared to intact individuals with normally developed language during processing of language stimuli. Functional magnetic resonance imaging (fMRI) was used to monitor changes in neuronal activation in temporal and frontal lobe areas in 5…

Hugdahl, Kenneth; Gundersen, Hilde; Brekke, Cecilie; Thomsen, Tormod; Rimol, Lars Morten; Ersland, Lars; Niemi, Jussi

2004-01-01

453

Enhanced Sympathetic Arousal in Response to fMRI Scanning Correlates with Task Induced Activations and Deactivations  

Microsoft Academic Search

It has been repeatedly shown that functional magnetic resonance imaging (fMRI) triggers distress and neuroendocrine response systems. Prior studies have revealed that sympathetic arousal increases, particularly at the beginning of the examination. Against this background it appears likely that those stress reactions during the scanning procedure may influence task performance and neural correlates. However, the question how sympathetic arousal elicited

Markus Muehlhan; Ulrike Lueken; Jens Siegert; Hans-Ulrich Wittchen; Michael N. Smolka; Clemens Kirschbaum

2013-01-01