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1

The physics of functional magnetic resonance imaging (fMRI).  

PubMed

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 mm(3) 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. PMID:24006360

Buxton, Richard B

2013-09-01

2

A robust independent component analysis (ICA) model for functional magnetic resonance imaging (fMRI) data  

NASA Astrophysics Data System (ADS)

The coupling of carefully designed experiments with proper analysis of functional magnetic resonance imaging (fMRI) data provides us with a powerful as well as noninvasive tool to help us understand cognitive processes associated with specific brain regions and hence could be used to detect abnormalities induced by a diseased state. The hypothesisdriven General Linear Model (GLM) and the data-driven Independent Component Analysis (ICA) model are the two most commonly used models for fMRI data analysis. A hybrid ICA-GLM model combines the two models to take advantages of benefits from both models to achieve more accurate mapping of the stimulus-induced activated brain regions. We propose a modified hybrid ICA-GLM model with probabilistic ICA that includes a noise model. In this modified hybrid model, a probabilistic principle component analysis (PPCA)-based component number estimation is used in the ICA stage to extract the intrinsic number of original time courses. In addition, frequency matching is introduced into the time course selection stage, along with temporal correlation, F-test based model fitting estimation, and time course combination, to produce a more accurate design matrix for GLM. A standard fMRI dataset is used to compare the results of applying GLM and the proposed hybrid ICA-GLM in generating activation maps.

Ao, Jingqi; Mitra, Sunanda; Liu, Zheng; Nutter, Brian

2011-03-01

3

Whole-head rapid fMRI acquisition using echo-shifted magnetic resonance inverse imaging  

PubMed Central

The acquisition time of BOLD contrast functional MRI (fMRI) data with whole-brain coverage typically requires a sampling rate of one volume in 1 3 seconds. Although the volumetric sampling time of a few seconds is adequate for measuring the sluggish hemodynamic response (HDR) to neuronal activation, faster sampling of fMRI might allow for monitoring of rapid physiological fluctuations and detection of subtle neuronal activation timing information embedded in BOLD signals. Previous studies utilizing a highly accelerated volumetric MR inverse imaging (InI) technique have provided a sampling rate of one volume per 100 ms with 5 mm spatial resolution. Here, we propose a novel modification of this technique, the echo-shifted InI, which allows TE to be longer than TR, to measure BOLD fMRI at an even faster sampling rate of one volume per 25 ms with whole-brain coverage. Compared with conventional EPI, echo-shifted InI provided 80-fold speedup with similar spatial resolution and less than 2-fold temporal SNR loss. The capability of echo-shifted InI to detect HDR timing differences was tested empirically. At the group level (n=6), echo-spaced InI was able to detect statistically significant HDR timing differences of as low as 50 ms in visual stimulus presentation. At the level of individual subjects, significant differences in HDR timing were detected for 400 ms stimulus-onset differences. Our results also show that the temporal resolution of 25 ms is necessary for maintaining the temporal detecting capability at this level. With the capabilities of being able to distinguish the timing differences in the millisecond scale, echo-shifted InI could be a useful fMRI tool for obtaining temporal information at a time scale closer to that of neuronal dynamics. PMID:23563228

Chang, Wei-Tang; Nummenmaa, Aapo; Witzel, Thomas; Ahveninen, Jyrki; Huang, Samantha; Tsai, Kevin Wen-Kai; Chu, Ying-Hua; Polimeni, Jonathan R; Belliveau, John W.; Lin, Fa-Hsuan

2013-01-01

4

Functional Magnetic Resonance Imaging (fMRI) Neurofeedback: Implementations and Applications  

PubMed Central

Neurofeedback (NFB) allows subjects to learn how to volitionally influence the neuronal activation in the brain by employing real-time neural activity as feedback. NFB has already been performed with electroencephalography (EEG) since the 1970s. Functional MRI (fMRI), offering a higher spatial resolution, has further increased the spatial specificity. In this paper, we briefly outline the general principles behind NFB, the implementation of fMRI-NFB studies, the feasibility of fMRI-NFB, and the application of NFB as a supplementary therapy tool. PMID:24643368

DEWIPUTRI, Wan Ilma; AUER, Tibor

2013-01-01

5

Functional magnetic resonance imaging (fMRI) "brain reading": detecting and classifying distributed patterns of fMRI activity in human visual cortex.  

PubMed

Traditional (univariate) analysis of functional MRI (fMRI) data relies exclusively on the information contained in the time course of individual voxels. Multivariate analyses can take advantage of the information contained in activity patterns across space, from multiple voxels. Such analyses have the potential to greatly expand the amount of information extracted from fMRI data sets. In the present study, multivariate statistical pattern recognition methods, including linear discriminant analysis and support vector machines, were used to classify patterns of fMRI activation evoked by the visual presentation of various categories of objects. Classifiers were trained using data from voxels in predefined regions of interest during a subset of trials for each subject individually. Classification of subsequently collected fMRI data was attempted according to the similarity of activation patterns to prior training examples. Classification was done using only small amounts of data (20 s worth) at a time, so such a technique could, in principle, be used to extract information about a subject's percept on a near real-time basis. Classifiers trained on data acquired during one session were equally accurate in classifying data collected within the same session and across sessions separated by more than a week, in the same subject. Although the highest classification accuracies were obtained using patterns of activity including lower visual areas as input, classification accuracies well above chance were achieved using regions of interest restricted to higher-order object-selective visual areas. In contrast to typical fMRI data analysis, in which hours of data across many subjects are averaged to reveal slight differences in activation, the use of pattern recognition methods allows a subtle 10-way discrimination to be performed on an essentially trial-by-trial basis within individuals, demonstrating that fMRI data contain far more information than is typically appreciated. PMID:12814577

Cox, David D; Savoy, Robert L

2003-06-01

6

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

7

nAture methods | VOL.9 NO.6 | JUNE2012 | 597 Functional magnetic resonance imaging (fmri) based on  

E-print Network

in a simple, flexible and MRI-compatible way are desirable. Optical recording with an activity be recorded in a bulk fashion using single-photon excitation through an inexpensive optical fiber11. The MRI compatibility of optical fibers has been recently used to combine optogenetics and fMRI12,13. In this study, we

8

Magnetic Resonance  

Cancer.gov

Focus Group on Magnetic Resonance Spectroscopy (MRS) in Clinical Oncology(April 1999) To explore the technical requirements for MRS and the application of hydrogen and multinuclear spectroscopy for tumor response to therapy.

9

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

10

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

ERIC Educational Resources Information Center

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

Richards, Todd L.

2001-01-01

11

Decoding brain states using functional magnetic resonance imaging  

Microsoft Academic Search

Most leading research in basic and clinical neuroscience has been carried out by functional magnetic resonance imaging (fMRI),\\u000a which detects the blood oxygenation level dependent signals associated with neural activities. Among new fMRI applications,\\u000a brain decoding is an emerging research area, which infers mental states from fMRI signals. Brain decoding using fMRI includes\\u000a classification, identification, and reconstruction of brain states.

Dongha Lee; Changwon Jang; Hae-Jeong Park

2011-01-01

12

A Primer on Functional Magnetic Resonance Imaging  

Microsoft Academic Search

In this manuscript, basic principles of functional magnetic resonance imaging (fMRI) are reviewed. In the first section, two\\u000a intrinsic mechanisms of magnetic resonance image contrast related to the longitudinal and transverse components of relaxing\\u000a spins and their relaxation rates, T1 and T2, are described. In the second section, the biophysical mechanisms that alter the apparent transverse relaxation time, $$T_2^*$$, in

Gregory G. Brown; Joanna E. Perthen; Thomas T. Liu; Richard B. Buxton

2007-01-01

13

A Bayesian Time-Course Model for Functional Magnetic Resonance Imaging Data  

Microsoft Academic Search

Functional magnetic resonance imaging (fMRI) is a new technique for studying the workings of the active human brain. During an fMRI experiment, a sequence of magnetic resonance images is acquired while the subject performs specific behavioral tasks. Changes in the measured signal can be used to identify and characterize the brain activity resulting from task performance. The data obtained from

Christopher R. Genovese

2000-01-01

14

The Underpinnings of the BOLD Functional Magnetic Resonance Imaging Signal  

Microsoft Academic Search

The good coverage and high resolution afforded by functional mag-netic resonance imaging (fMRI) make it an excellent tool for the noninvasive imaging of the human brain. Equally interesting, how-ever, is the use of this technique in animal studies using high mag-netic fields. In the latter case, highly spatiotemporally resolved fMRI can reveal how widespread neural networks are organized, and ac-companying

Nikos K. Logothetis

2003-01-01

15

Magnetic resonance angiography  

MedlinePLUS

MRA; Angiography - magnetic resonance ... Kwong RY. Cardiovascular Magnetic Resonance Imaging. In: Bonow RO, Mann DL, Zipes DP, Libby P, eds. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine . 9th ...

16

Nuclear Magnetic Resonance  

NASA Astrophysics Data System (ADS)

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

Andrew, E. R.

2009-06-01

17

Modeling functional Magnetic Resonance Imaging (fMRI) experimental variables in the Ontology of Experimental Variables and Values (OoEVV).  

PubMed

Neuroimaging data is raw material for cognitive neuroscience experiments, leading to scientific knowledge about human neurological and psychological disease, language, perception, attention and ultimately, cognition. The structure of the variables used in the experimental design defines the structure of the data gathered in the experiments; this in turn structures the interpretative assertions that may be presented as experimental conclusions. Representing these assertions and the experimental data which support them in a computable way means that they could be used in logical reasoning environments, i.e. for automated meta-analyses, or linking hypotheses and results across different levels of neuroscientific experiments. Therefore, a crucial first step in being able to represent neuroimaging results in a clear, computable way is to develop representations for the scientific variables involved in neuroimaging experiments. These representations should be expressive, computable, valid, extensible, and easy-to-use. They should also leverage existing semantic standards to interoperate easily with other systems. We present an ontology design pattern called the Ontology of Experimental Variables and Values (OoEVV). This is designed to provide a lightweight framework to capture mathematical properties of data, with appropriate 'hooks' to permit linkage to other ontology-driven projects (such as the Ontology of Biomedical Investigations, OBI). We instantiate the OoEVV system with a small number of functional Magnetic Resonance Imaging datasets, to demonstrate the system's ability to describe the variables of a neuroimaging experiment. OoEVV is designed to be compatible with the XCEDE neuroimaging data standard for data collection terminology, and with the Cognitive Paradigm Ontology (CogPO) for specific reasoning elements of neuroimaging experimental designs. PMID:23684873

Burns, Gully A P C; Turner, Jessica A

2013-11-15

18

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

19

How fMRI Can Inform Cognitive Theories  

E-print Network

How can functional magnetic resonance imaging (fMRI) advance cognitive theory? Some have argued that fMRI can do little beyond localizing brain regions that carry out certain cognitive functions (and may not even be able ...

Kanwisher, Nancy

20

Magnetic resonance imaging and spectroscopy  

SciTech Connect

This book contains 17 selections. Some of the chapter titles are: Basic Principles of Magnetic Resonance Imaging;Evaluation of Demyelinating Diseases;Respiratory Gating in Magnetic Resonance Imaging;Magnetic Resonance Imaging of the Abdomen;Contrast Agents in Magnetic Resonance Imaging;and Economic Considerations in Magnetic Resonance Imaging.

Mettler, F.A.; Muroff, L.R.; Kulkarni, M.V.

1986-01-01

21

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

22

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

23

Pediatric functional magnetic resonance neuroimaging: tactics for encouraging task compliance  

Microsoft Academic Search

Background  Neuroimaging technology has afforded advances in our understanding of normal and pathological brain function and development\\u000a in children and adolescents. However, noncompliance involving the inability to remain in the magnetic resonance imaging (MRI)\\u000a scanner to complete tasks is one common and significant problem. Task noncompliance is an especially significant problem in\\u000a pediatric functional magnetic resonance imaging (fMRI) research because increases

Michael W Schlund; Michael F Cataldo; Greg J Siegle; Cecile D Ladouceur; Jennifer S Silk; Erika E Forbes; Ashley McFarland; Satish Iyengar; Ronald E Dahl; Neal D Ryan

2011-01-01

24

ANALYSIS OF FUNCTIONAL MAGNETIC RESONANCE IMAGING DATA USING SIGNAL PROCESSING TECHNIQUES  

E-print Network

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2 Clustered Components Analysis for fMRI . . . . . . . . . . . . . . . . . . . 3 2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 3 Supertemporal Resolution Analysis for fMRI Timeseries Data . . . . . . . 31 3.1 IntroductionANALYSIS OF FUNCTIONAL MAGNETIC RESONANCE IMAGING DATA USING SIGNAL PROCESSING TECHNIQUES A Thesis

25

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

E-print Network

.5-mm sampling, complicates the analysis of fMRI, as one must now consider activity variations within-resolution fMRI for depth analysis. These methods utilize white- matter segmentations coupled with deformableSurface-based analysis methods for high-resolution functional magnetic resonance imaging Rez Khan

Texas at Austin, University of

26

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

27

Simulation study of magnetic resonance imagingguided cortically constrained diffuse  

E-print Network

optical imaging and MRI has the potential to provide more quantitative estimates of the total oxygenation, as provided by optical absorption spectroscopy, than can be provided by fMRI.20 This potentialSimulation study of magnetic resonance imaging­guided cortically constrained diffuse optical

Boas, David

28

Nuclear magnetic resonance gyroscope  

SciTech Connect

A nuclear magnetic resonance gyro using two nuclear magnetic resonance gases, preferably xenon 129 and xenon 131, together with two alkaline metal vapors, preferably rubidium, potassium or cesium, one of the two alkaline metal vapors being pumped by light which has the wavelength of that alkaline metal vapor, and the other alkaline vapor being illuminated by light which has the wavelength of that other alkaline vapor.

Grover, B.C.

1984-02-07

29

Magnetic Resonance Imaging  

NSDL National Science Digital Library

This lesson ties the preceding lessons together and brings students back to the grand challenge question on MRI safety. During this lesson, students focus on the logistics of magnetic resonance imaging as well as the MRI hardware. Students can then integrate this knowledge with their acquired knowledge on magnetic fields to solve the challenge question.

VU Bioengineering RET Program, School of Engineering,

30

Nuclear magnetic resonance imaging.  

PubMed

NMR imaging is based on the ability to induce and monitor resonance of the magnetic moment of nuclei with an odd number of protons and/or neutrons in the presence of magnetic fields. By the use of magnetic fields whose strength varies with position, it is possible to define both the location and concentration of resonant nuclei, and, thereby, to create images that reflect their distribution in tissue. Hydrogen because it is the most sensitive of the stable nuclei to NMR and because it is also the most abundant nucleus in the body, is ideally suited for NMR imaging. PMID:7323305

Crooks, L; Herfkens, R; Kaufman, L; Hoenninger, J; Arakawa, M; McRee, R; Watts, J

1981-01-01

31

Cardiovascular Magnetic Resonance  

Microsoft Academic Search

\\u000a Cardiovascular magnetic resonance (CMR) creates images from atomic nuclei with uneven spin using radio waves in the presence\\u000a of a magnetic field. Full details of the physical principles can be found elsewhere [1]. For clinical purposes, MR is performed using hydrogen-1, which is abundant in water and fat. Radiofrequency waves excite\\u000a the area of interest to create tissue magnetization, which

Dudley J. Pennell

2001-01-01

32

Large-Scale, High-Resolution Neurophysiological Maps Underlying fMRI of Macaque Temporal Lobe  

E-print Network

Maps obtained by functional magnetic resonance imaging (fMRI) are thought to reflect the underlying spatial layout of neural activity. However, previous studies have not been able to directly compare fMRI maps to high-resolution ...

Issa, Elias

33

A client-server software application for statistical analysis of fMRI data  

E-print Network

Statistical analysis methods used for interrogating functional magnetic resonance imaging (fMRI) data are complex and continually evolving. There exist a scarcity of educational material for fMRI. Thus, an instructional ...

Choudhary, Vijay Singh, 1979-

2004-01-01

34

EXAMINING ASSOCIATIONS BETWEEN FMRI AND EEG DATA USING CANONICAL CORRELATION ANALYSIS  

E-print Network

EXAMINING ASSOCIATIONS BETWEEN FMRI AND EEG DATA USING CANONICAL CORRELATION ANALYSIS Nicolle Albuquerque, NM 87131 ABSTRACT Functional magnetic resonance imaging (fMRI) and electro- encephalography (EEG associations between these two modalities using canonical correlation analysis (CCA). Our multimodal canonical

Adali, Tulay

35

Brain Activation in Parkinson's Disease during a Functional Magnetic Resonance Imaging Set Shifting Task: Preliminary Findings  

E-print Network

Brain Activation in Parkinson's Disease during a Functional Magnetic Resonance Imaging Set Shifting with Parkinson's disease (PD) and age-matched controls using event-related functional magnetic resonance imaging (fMRI). Cognitive impairment is a common non-motor manifestation of Parkinson's disease (PD

Lichtarge, Olivier

36

Magnetic Resonance Online Texts  

NSDL National Science Digital Library

This well-organized and very thorough website was developed by the physicist Stanislav Sykora with the aim of providing free online texts, theses, and course materials on the subjects of magnetic resonance (MR), magnetic resonance imaging (MRI), nuclear-magnetic resonance (NMR) and other related topics. The amount of material on the site is impressive. At the top of the page are links to an "MR Blog", as well as to "MR Links" and the "Site Plan & SEARCH". The NMR/MRI Extras section on the right side of the page is particularly useful for visitors interested in all things about MR. Its links to "Events" provides an up-to-date list of symposia, conferences, and meetings, along with links to the events' sites. The "Societies" link offers at least 50 groups about MR, some of which are country-based, and others that are region- or application-based.

Sãâãâ½kora, Stanislav

37

Resonant and non-resonant magnetic scattering  

SciTech Connect

The tunability and the polarization of synchrotron radiation open upon new possibilities for the study of magnetism. Studies on magnetic materials performed at the National Synchrotron Light Source are reviewed, and thy fall into four areas: structure, evolution of magnetic order, separation of L and S, and resonance effects. In the vicinity of atomic absorption edges, the Faraday effect, magnetic circular dichroism, and resonant magnetic scattering are all related resonance effects which measure the spin polarized density of states. The production and analysis of polarized beams are discussed in the context of the study of magnetism with synchrotron radiation.

McWhan, D.B.; Hastings, J.B.; Kao, C.C.; Siddons, D.P.

1991-12-31

38

Resonant and non-resonant magnetic scattering  

SciTech Connect

The tunability and the polarization of synchrotron radiation open upon new possibilities for the study of magnetism. Studies on magnetic materials performed at the National Synchrotron Light Source are reviewed, and thy fall into four areas: structure, evolution of magnetic order, separation of L and S, and resonance effects. In the vicinity of atomic absorption edges, the Faraday effect, magnetic circular dichroism, and resonant magnetic scattering are all related resonance effects which measure the spin polarized density of states. The production and analysis of polarized beams are discussed in the context of the study of magnetism with synchrotron radiation.

McWhan, D.B.; Hastings, J.B.; Kao, C.C.; Siddons, D.P.

1991-01-01

39

UNIFIED ICA-SPM ANALYSIS OF FMRI EXPERIMENTS Implementation of an ICA graphical user interface for the SPM pipeline  

E-print Network

UNIFIED ICA-SPM ANALYSIS OF FMRI EXPERIMENTS Implementation of an ICA graphical user interface for exploratory analysis of functional magnetic resonance imaging (fMRI) data using independent component analysis Criterion (BIC), functional Magnetic Resonance Imaging (fMRI), General linear model (GLM), ica4spm

40

Magnetic resonance annual, 1988  

SciTech Connect

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

Kressel, H.Y.

1987-01-01

41

Magnetic Resonance Annual, 1985  

SciTech Connect

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

Kressel, H.Y.

1985-01-01

42

Task Repetition Can Affect Functional Magnetic Resonance Imaging-Based Measures of Language Lateralization and Lead to Pseudoincreases in Bilaterality  

Microsoft Academic Search

Summary: Repeated functional magnetic resonance imaging (fMRI) during learning and recovery can inform us about func- tional reorganization in the brain. We examined how, in the absence of reorganization, simple task repetition affects mea- sures of fMRI activation. We studied fMRI activation over 10 consecutive sessions of silent word generation in a healthy subject. Additionally, we performed functional transcranial Doppler

Hubertus Lohmann; Michael Deppe; Andreas Jansen; Wolfram Schwindt; Stefan Knecht

43

Task Repetition Can Affect Functional Magnetic Resonance Imaging-Based Measures of Language Lateralization and Lead to Pseudoincreases in Bilaterality  

Microsoft Academic Search

Repeated functional magnetic resonance imaging (fMRI) during learning and recovery can inform us about functional reorganization in the brain. We examined how, in the absence of reorganization, simple task repetition affects measures of fMRI activation. We studied fMRI activation over 10 consecutive sessions of silent word generation in a healthy subject. Additionally, we performed functional transcranial Doppler sonography (fTCD) to

Hubertus Lohmann; Michael Deppe; Andreas Jansen; Wolfram Schwindt; Stefan Knecht

2004-01-01

44

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. PMID:21435578

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

2013-01-01

45

Functional Magnetic Resonance in the Evaluation of Oesophageal Motility Disorders  

PubMed Central

Functional magnetic resonance imaging (fMRI) has been recently proposed for the evaluation of the esophagus. Our aim is to assess the role of fMRI as a technique to assess morphological and functional parameters of the esophagus in patients with esophageal motor disorders and in healthy controls. Subsequently, we assessed the diagnostic efficiency of fMRI in comparison to videofluoroscopic and manometric findings in the investigation of patients with esophageal motor disorders. Considering that fMRI was shown to offer valuable information on bolus transit and on the caliber of the esophagus, variations of these two parameters in the different types of esophageal motor alterations have been assessed. fMRI, compared to manometry and videofluoroscopy, showed that a deranged or absent peristalsis is significantly associated with slower transit time and with increased esophageal diameter. Although further studies are needed, fMRI represents a promising noninvasive technique for the integrated functional and morphological evaluation of esophageal motility disorders. PMID:21904543

Covotta, Francesco; Piretta, Luca; Badiali, Danilo; Laghi, Andrea; Biondi, Tommaso; Corazziari, Enrico S.; Panebianco, Valeria

2011-01-01

46

fMRI detection with spatial regularization  

E-print Network

Functional Magnetic Resonant Imaging (fMRI) is a non-invasive imaging technique used to study the brain. Neuroscientists have developed various algorithms to determine which voxels of the images are active. Most of these ...

Ou, Wanmei

2005-01-01

47

Combined fMRI and electrical microstimulation to determine functional connections in visual areas of the primate brain  

E-print Network

The use of functional magnetic resonance imaging (fMRI) to study the non-human primate brain has been developed over the past decade. Primate fMRI has many attractive features: it allows validation of previous homology ...

Ekstrom, Leeland Bruce

2009-01-01

48

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. PMID:23486058

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

2013-01-01

49

Direct magnetic resonance arthrography.  

PubMed

Magnetic resonance (MR) arthrography has gained increasing popularity as a diagnostic tool in the assessment of intra-articular derangements. Its role has been studied extensively in the shoulder, but it also has been explored in the hip, elbow, knee, wrist and ankle. This article reviews the current role of direct MR arthrography in several major joints, with consideration of pertinent anatomy, techniques and applications. PMID:15351900

Elentuck, Dmitry; Palmer, William E

2004-11-01

50

Pharmacological magnetic resonance imaging: a new application for functional MRI.  

PubMed

Various methods, including functional magnetic resonance imaging (fMRI), have recently been developed to allow investigators to study functional activity in the living brain. Such techniques are now being used to investigate regionally specific brain activity associated with the administration of CNS-active drugs. fMRI in particular is increasingly recognized as being a relatively non-invasive way to perform pharmacological investigations in experimental animals, healthy human volunteers, and individuals with CNS disease. This use of fMRI, dubbed 'pharmacological MRI' or 'phMRI', holds the promise of providing relatively straightforward pharmacodynamic assays and can be used to establish brain-penetrability parameters, or dose-ranging information for novel therapeutic compounds. PMID:10918638

Leslie, R A; James, M F

2000-08-01

51

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

PubMed Central

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 perform tasks related to the functional paradigm. The presence of ?B0 during data acquisition distorts reconstructed images and introduces extraneous fluctuations in the fMRI time series that decrease the BOLD contrast-to-noise ratio. Optimization of the fMRI data-processing pipeline to compensate for geometric distortions is of paramount importance to ensure high quality of fMRI data. To investigate ?B0 caused by subject movement, echo-planar imaging scans were collected with and without concurrent motion of a phantom arm. The phantom arm was constructed and moved by the experimenter to emulate forearm motions while subjects remained still and observed a visual stimulation paradigm. These data were then subjected to eight different combinations of preprocessing steps. The best preprocessing pipeline included navigator correction, a complex phase regressor, and spatial smoothing. The synergy between navigator correction and phase regression reduced geometric distortions better than either step in isolation, and preconditioned the data to make them more amenable to the benefits of spatial smoothing. The combination of these steps provided a 10% increase in t-statistics compared to only navigator correction and spatial smoothing, and reduced the noise and false activations in regions where no legitimate effects would occur. PMID:19695810

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

2009-01-01

52

Magnetic Resonance Imaging  

PubMed Central

Magnetic resonance imaging (MRI) is an important new imaging modality just arriving on the clinical scene in Canada. MRI uses no ionizing radiation; images are derived from the interaction of hydrogen nuclei, a powerful magnetic field, and radio waves. Images are displayed as tomographic slices, much like CT. Direct transverse, sagittal, coronal or oblique slices can be obtained. Unlike CT, the MRI image does not reflect varying tissue densities. In MRI, tissues are differentiated by variation in the amount of hydrogen they contain and by differences in the magnetic environment at a molecular level. All parts of the body can be examined with MRI, although the CNS is particularly well visualized. In addition to providing high resolution images, MRI has the potential for performing non-invasive angiography and biochemical analysis through spectroscopy. To date, there are no known harmful effects of MRI. ImagesFigure 1Figure 2Figure 3Figure 4Figure 5 PMID:21267205

Fache, J. Stephen

1986-01-01

53

Neurophysiological Architecture of Functional Magnetic Resonance Images of Human Brain  

Microsoft Academic Search

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 func- tional connections, defined

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

2005-01-01

54

Multimodal Magnetic Resonance Imaging for Brain Disorders: Advances and Perspectives  

Microsoft Academic Search

Modern brain imaging technologies play essential roles in our understanding of brain information processing and the mechanisms\\u000a of brain disorders. Magnetic Resonance Imaging (MRI) and Diffusion Tensor Imaging (DTI) can image the anatomy and structure\\u000a of the brain. In addition, functional MRI (fMRI) can identify active regions, patterns of functional connectivities and functional\\u000a networks during either tasks that are specifically

Tianzi Jiang; Yong Liu; Feng Shi; Ni Shu; Bing Liu; Jiefeng Jiang; Yuan Zhou

2008-01-01

55

Magnetic Resonance Facility (Fact Sheet)  

SciTech Connect

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

Not Available

2012-03-01

56

Functional magnetic resonance imaging in schizophrenia: initial methodology and evaluation of the motor cortex  

Microsoft Academic Search

The purpose of the present study was to evaluate the differential activation of the motor cortex during finger tapping in patients with schizophrenia using the newly available imaging method of functional magnetic resonance imaging (fMRI). Nine patients with DSMIII-R schizophrenia and 9 well-matched healthy volunteer subjects underwent fMRI examination on a conventional MR unit; activation of the primary motor cortex

Peter F. Buckley; Lee Friedman; Dee Wu; Song Lai; Herbert Y. Meltzer; E. Mark Haacke; David Miller; Jonathan S. Lewin

1997-01-01

57

Comparison between anisometropic and strabismic amblyopia using functional magnetic resonance imaging  

Microsoft Academic Search

AIMSTo assess calcarine activation with functional magnetic resonance imaging (fMRI) in patients with anisometropic and strabismic amblyopia.METHODS14 amblyopes (eight anisometropic and six strabismic) were studied with fMRI using stimuli of checkerboards of various checker sizes and temporal frequencies. While T2* weighted MRI were obtained every 3 seconds for 6 minutes, patients viewed the stimuli monocularly with either the amblyopic or

Mi Young Choi; Kyoung-Min Lee; Jeong-Min Hwang; Dong Gyu Choi; Dong Soo Lee; Ki Ho Park; Young Suk Yu

2001-01-01

58

Analysis of functional magnetic resonance imaging data using self-organizing mapping with spatial connectivity  

Microsoft Academic Search

Commonly used methods in analyzing functional magnetic resonance imaging (fMRI) data, such as the Student's t-test and cross-correlation analysis, are model-based approaches. Al- though these methods are easy to implement and are effective in analyzing data obtained with simple paradigms, they are not applicable in situations in which patterns of neuronal response are complicated and when fMRI response is unknown.

Shing-Chung Ngan; Xiaoping Hu

1999-01-01

59

Estimating the number of independent components for functional magnetic resonance imaging data  

Microsoft Academic Search

Multivariate analysis methods such as independent component analysis (ICA) have been applied to the analysis of functional magnetic resonance imaging (fMRI) data to study brain function. Because of the high dimensionality and high noise level of the fMRI data, order selection, i.e., estimation of the number of informative components, is critical to reduce over\\/underfitting in such methods. De- pendence among

Yi-Ou Li; Tulay Adali; Vince D. Calhoun

2007-01-01

60

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

61

nuclear magnetic resonance gyroscope  

SciTech Connect

A nuclear magnetic resonance gyroscope which derives angular rotation thereof from the phases of precessing nuclear moments utilizes a single-resonance cell situated in the center of a uniform DC magnetic field. The field is generated by current flow through a circular array of coils between parallel plates. It also utilizes a pump and read-out beam and associated electronics for signal processing and control. Encapsulated in the cell for sensing rotation are odd isotopes of Mercury Hg/sup 199/ and Hg/sup 201/. Unpolarized intensity modulated light from a pump lamp is directed by lenses to a linear polarizer, quarter wave plate combination producing circularly polarized light. The circularly polarized light is reflected by a mirror to the cell transverse to the field for optical pumping of the isotopes. Unpolarized light from a readout lamp is directed by lenses to another linear polarizer. The linearly polarized light is reflected by another mirror to the cell transverse to the field and orthogonal to the pump lamp light. The linear light after transversing the cell strikes an analyzer where it is converted to an intensity-modulated light. The modulated light is detected by a photodiode processed and utilized as feedback to control the field and pump lamp excitation and readout of angular displacement.

Karwacki, F. A.; Griffin, J.

1985-04-02

62

Motion Correction and the Use of Motion Covariates in Multiple-Subject fMRI Analysis  

E-print Network

Motion Correction and the Use of Motion Covariates in Multiple-Subject fMRI Analysis Tom Johnstone Brain Mapp 27:779­788, 2006. © 2006 Wiley-Liss, Inc. Key words: fMRI; motion correction; analysis; event and rapid event-related functional magnetic resonance imaging (fMRI) data. The purpose of motion correction

Wisconsin at Madison, University of

63

INDEPENDENT COMPONENT ANALYSIS APPLIED TO fMRI DATA: A GENERATIVE MODEL FOR  

E-print Network

INDEPENDENT COMPONENT ANALYSIS APPLIED TO fMRI DATA: A GENERATIVE MODEL FOR VALIDATING RESULTS V Magnetic Resonance Imaging (fMRI) data using independent component analysis (ICA). Our model assumes seconds following the electrical activity in the brain [1]. FMRI analysis approaches range from model

Adali, Tulay

64

A Sparse Spatial Linear Regression Model for fMRI Data Analysis  

E-print Network

A Sparse Spatial Linear Regression Model for fMRI Data Analysis Vangelis P. Oikonomou for the analysis of functional Magnetic Resonance Imaging (fMRI) data that simultaneously employs both spatial related to the activation of the neurons [1]. The fMRI data analysis consists of two basic stages

Blekas, Konstantinos

65

INDEPENDENT SUBSPACE ANALYSIS WITH PRIOR INFORMATION FOR FMRI DATA , Xi-Lin Li1  

E-print Network

INDEPENDENT SUBSPACE ANALYSIS WITH PRIOR INFORMATION FOR FMRI DATA Sai Ma1 , Xi-Lin Li1 , Nicolle M Terms-- fMRI, independent subspace analysis, in- dependent component analysis, semi-blind source magnetic resonance imaging (fMRI) analysis where the spatial net- works of activations are typically known

Adali, Tulay

66

STATISTICAL PARAMETRIC MAPPING OF FMRI DATA USING SPARSE DICTIONARY Kangjoo Lee1  

E-print Network

independency in ICA analysis for fMRI. Hence, we propose sparse learning algorithm, such as K for the statistical analysis of brain activity with functional magnetic resonance imaging (fMRI) [1, 2, 3] . It uses analysis of fMRI dataset. The common point in their approach is that the signals are decomposed

67

A Model-Based fMRI Analysis With Hierarchical Bayesian Parameter Estimation  

E-print Network

A Model-Based fMRI Analysis With Hierarchical Bayesian Parameter Estimation Woo-Young Ahn, Adam trend in decision neuroscience is the use of model-based functional magnetic resonance imaging (fMRI) using mathematical models of cognitive processes. How- ever, most previous model-based fMRI studies have

Busemeyer, Jerome R.

68

Spectral Analysis of fMRI Signal and Noise Chien-Chung Chen1  

E-print Network

63 Spectral Analysis of fMRI Signal and Noise Chien-Chung Chen1 and Christopher W. Tyler2 Summary easily reach 2%�4% in magnitude [2]. Thus, fMRI data analysis is highly susceptible to noise. The purpose We analyzed the noise in functional magnetic resonance imaging (fMRI) scans of the human brain during

Chen, Chein Chung

69

Magnetic resonance cell  

SciTech Connect

There is disclosed a nuclear magnetic alignment device for use in a nuclear magnetic resonance gyroscope and the like. One embodiment includes a container for gas having a layer of rubidium hydride on its inner surface. The container comprising a spherical portion and a tip portion, is rotationally symmetric about an axis of symmetry. Enclosed within the container is a nuclear moment gas having a nuclear electric quadrupole moment, such as xenon-131, and an optically pumpable substance, such as rubidium. A portion of the rubidium is a vapor. The remainder is a condensed pellet which is deposited in the tip of the container such that the pellet is also rotationally symmetric about the axis of symmetry of the container. A layer of rubidium hydride is deposited on the inner surface of the container. The device further includes means for orienting the symmetry axis of the container at an angle to an applied magnetic field such that the relaxation time constant of the aligned nuclear moment gas is substantially at a maximum.

Kwon, T.M.; Volk, C.H.

1984-05-01

70

Nuclear Magnetic Resonance and Magnetic Field Measurements  

NSDL National Science Digital Library

This laboratory is designed for students to become familiar with the principles and detection techniques of Nuclear Magnetic Resonance (NMR), examine the relationship between current and magnetic field in an electromagnet, and gain experience in the use of magnetic field measurement techniques.

2012-01-04

71

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

72

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

73

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

74

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

75

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

76

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. PMID:10466145

Howseman, A M; Bowtell, R W

1999-01-01

77

Physiological basis and image processing in functional magnetic resonance imaging: Neuronal and motor activity in brain  

PubMed Central

Functional magnetic resonance imaging (fMRI) is recently developing as imaging modality used for mapping hemodynamics of neuronal and motor event related tissue blood oxygen level dependence (BOLD) in terms of brain activation. Image processing is performed by segmentation and registration methods. Segmentation algorithms provide brain surface-based analysis, automated anatomical labeling of cortical fields in magnetic resonance data sets based on oxygen metabolic state. Registration algorithms provide geometric features using two or more imaging modalities to assure clinically useful neuronal and motor information of brain activation. This review article summarizes the physiological basis of fMRI signal, its origin, contrast enhancement, physical factors, anatomical labeling by segmentation, registration approaches with examples of visual and motor activity in brain. Latest developments are reviewed for clinical applications of fMRI along with other different neurophysiological and imaging modalities. PMID:15125779

Sharma, Rakesh; Sharma, Avdhesh

2004-01-01

78

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

79

INDEPENDENT COMPONENT ANALYSIS OF COMPLEX-VALUED FUNCTIONAL MAGNETIC RESONANCE IMAGING DATA  

E-print Network

information has a straightforward physiologic interpretation [2]. When performing an analysis of fMRI dataINDEPENDENT COMPONENT ANALYSIS OF COMPLEX-VALUED FUNCTIONAL MAGNETIC RESONANCE IMAGING DATA analysis (ICA) for separating complex- valued sources is needed for convolutive source

Adali, Tulay

80

Large Sample Group Independent Component Analysis of Functional Magnetic Resonance Imaging Using Anatomical  

E-print Network

from noise. The traditional approach to fMRI data analysis is explicitly model driven, usingLarge Sample Group Independent Component Analysis of Functional Magnetic Resonance Imaging Using, Los Angeles, CA Abstract Independent component analysis (ICA) is a popular method for the analysis

Yuille, Alan L.

81

Wavelets and statistical analysis of functional magnetic resonance images of the human brain  

E-print Network

Introduction 1.1 General motivations for wavelet analysis of fMRI data A wavelet is a little wave, or a briefWavelets and statistical analysis of functional magnetic resonance images of the human brain Ed for multiresolution analysis and decorrelation or `whitening' of nonstationary time series and spatial processes

Breakspear, Michael

82

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

83

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

84

Functional Magnetic Resonance Imaging Study of Human Olfaction and Normal Aging  

Microsoft Academic Search

Background. The function of human olfaction declines with advancing age. An important question centers on whether functional alterations to olfactory brain structures accompany age-related behavioral changes. In the present study, we tested the hypothesis that aged adults have intact though reduced activity in the central olfactory system using functional magnetic resonance imaging (fMRI). Methods. University of Pennsylvania Smell Identification Test

Jianli Wang; Paul J. Eslinger; Michael B. Smith; Qing X. Yang

2005-01-01

85

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

86

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

87

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

88

Magnetic resonance angiogram and imaging.  

PubMed

Reports from specialized medical tests may often reveal findings that are ambiguous. In this article, the significance of punctate signal changes and ischemia revealed by magnetic resonance scanning are discussed. PMID:15912911

Goodwin, L

2000-01-01

89

Nuclear magnetic resonance readable sensors  

E-print Network

The monitoring of physiological biomarkers is fundamental to the diagnosis and treatment of disease. We describe here the development of molecular sensors which can be read by magnetic resonance (MR) relaxometry. MR is an ...

Ling, Yibo

2010-01-01

90

Classification of whole brain fMRI activation patterns  

E-print Network

Functional magnetic resonance imaging (fMRI) is an imaging technology which is primarily used to perform brain activation studies by measuring neural activity in the brain. It is an interesting question whether patterns ...

Balc?, Serdar Kemal

2008-01-01

91

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

92

Magnetic resonance imaging in the evaluation of cognitive function.  

PubMed

Image quality of magnetic resonance imaging (MRI) scans of the brain currently approximate gross anatomy as would be viewed at autopsy. During the first decade of the 21st Century incredible advances in image processing and quantification have occurred permitting more refined methods for studying brain-behavior-cognitive functioning. The current presentation overviews the current status of MRI methods for routine clinical assessment of brain pathology, how these techniques identify neuropathology and how pathological findings are quantified. Diffusion tensor imaging (DTI), functional MRI (fMRI), and resting state fMRI are all reviewed, emphasizing how these techniques permit an examination of brain function and connectivity. General regional relationships of brain function associated with cognitive control will be highlighted. PMID:24920351

Bigler, Erin D

2014-10-01

93

A new scenario for negative functional magnetic resonance imaging signals: endogenous neurotransmission.  

PubMed

Functional magnetic resonance imaging (fMRI) has revolutionized investigations of brain functions. Increases in fMRI signals are usually correlated with neuronal activation, but diverse explanations have been proposed for negative fMRI responses, including decreases in neuronal activity, the vascular-steal effect, and large increases in oxygen consumption. These possible scenarios, although encompassing a wide range of potential neurovascular responses, cannot yet be used to interpret certain types of negative fMRI signals. Recent studies have found that intravenous injection of dopamine D(2) receptor (D2DR) agonist reduced the hemodynamic responses in the caudate-putamen (CPu); however, whether endogenous dopaminergic neurotransmission contributes to fMRI signals remains obscure. Since it has been suggested that the D2DR is involved in pain modulation, and the CPu shows equivocal fMRI signals during noxious stimulation, the present study established an animal model based on graded electrical stimulation to elicit different levels of nociception, and aimed to determine whether nociception-induced endogenous dopaminergic neurotransmission is sufficient to generate negative fMRI responses. Our results from cerebral blood volume (CBV)-weighted fMRI, Fos immunohistochemistry, and electrophysiological recording demonstrated a salient bilateral CBV decreases associated with heightened neuronal activity in the CPu induced by unilateral noxious electrical stimulation. In addition, preinjection of D2DR antagonist reduced the observed CBV decreases. Our findings reveal the role of the D2DR in regulating striatal vascular responses and suggest that endogenous neurotransmission-induced CBV decreases underlie negative fMRI signals. Hence, the influence of endogenous neurotransmission should be considered when interpreting fMRI data, especially in an area involved in strong vasoactive neurotransmission. PMID:19279240

Shih, Yen-Yu I; Chen, Chiao-Chi V; Shyu, Bai-Chuang; Lin, Zi-Jun; Chiang, Yun-Chen; Jaw, Fu-Shan; Chen, You-Yin; Chang, Chen

2009-03-11

94

Neuroelectrical decomposition of spontaneous brain activity measured with functional magnetic resonance imaging.  

PubMed

Spontaneous activity in the human brain occurs in complex spatiotemporal patterns that may reflect functionally specialized neural networks. Here, we propose a subspace analysis method to elucidate large-scale networks by the joint analysis of electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) data. The new approach is based on the notion that the neuroelectrical activity underlying the fMRI signal may have EEG spectral features that report on regional neuronal dynamics and interregional interactions. Applying this approach to resting healthy adults, we indeed found characteristic spectral signatures in the EEG correlates of spontaneous fMRI signals at individual brain regions as well as the temporal synchronization among widely distributed regions. These spectral signatures not only allowed us to parcel the brain into clusters that resembled the brain's established functional subdivision, but also offered important clues for disentangling the involvement of individual regions in fMRI network activity. PMID:23796947

Liu, Zhongming; de Zwart, Jacco A; Chang, Catie; Duan, Qi; van Gelderen, Peter; Duyn, Jeff H

2014-11-01

95

Graph-based inter-subject pattern analysis of fMRI data Sylvain Takerkart1,2,  

E-print Network

1 Graph-based inter-subject pattern analysis of fMRI data Sylvain Takerkart1,2, , Guillaume Auzias1 to brain activation patterns. Traditional univariate analysis methods of fMRI data process each voxel-subject variability present in functional magnetic resonance imaging (fMRI) data and to perform multivariate pattern

Paris-Sud XI, Université de

96

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

97

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

98

The emotional counting stroop paradigm: a functional magnetic resonance imaging probe of the anterior cingulate affective division  

Microsoft Academic Search

Background: The emotional counting Stroop (ecStroop) functional magnetic resonance imaging (fMRI) activation paradigm was designed to recruit the anterior cingulate affective division (ACad).Methods: Nine normal, healthy male and female subjects (mean age 24.2 years) reported via button press the number of neutral and negative words that appeared on a screen while reaction time and fMRI data were acquired.Results: We observed

Paul J. Whalen; George Bush; Richard J. McNally; Sabine Wilhelm; Sean C. McInerney; Michael A. Jenike; Scott L. Rauch

1998-01-01

99

Discussion on the choice of separated components in fMRI data analysis by spatial independent component analysis  

Microsoft Academic Search

By measuring the changes of magnetic resonance signals during a stimulation, the functional magnetic resonance imaging (fMRI) is able to localize the neural activation in the brain. In this report, we discuss the fMRI application of the spatial independent component analysis (spatial ICA), which maximizes statistical independence over spatial images. Included simulations show the possibility of the spatial ICA on

Huafu Chen; Dezhong Yao

2004-01-01

100

Overview of fMRI analysis  

Microsoft Academic Search

fMRI (functional magnetic resonance imaging) is a powerful non-invasive tool in the study of the function of the brain, used, for example, by psychologists, psychia- trists and neurologists. fMRI can give high quality visualization of the location of activity in the brain resulting from sensory stimulation or cognitive function. It therefore allows the study of how the healthy brain functions,

S M Smith

2004-01-01

101

vhf Pulsed Magnetic Resonance Duplexers  

Microsoft Academic Search

Coupling schemes for pulsed magnetic resonance spectrometers operating in the vhf region are discussed. Three such schemes are described in detail and their performances compared, using the 81Br nuclear quadrupole resonance signal at ?200 MHz in polycrystalline K2PtBr6. The first scheme employs a hybrid T, coaxial ring circuit with the transmitter, receiver, sample coil, and a dummy load in the

B. Michael Moores; Robin L. Armstrong

1971-01-01

102

[Magnetic resonance in biomedical research].  

PubMed

Magnetic resonances are spectroscopic methods by which some structural changes and metabolic processes in biological systems can be followed on the molecular level. There are two main types of magnetic resonance methods: nuclear magnetic resonance (NMR) and electron paramagnetic (spin) resonance (EPR or ESR). By NMR are followed the atomic nuclei with the magnetic moment; in biological systems these are usually 1H, 13C, 31P. By EPR are followed paramagnetic centres in biological systems; these are ions of the transition metal group (Fe3+, Cu2+, Mn2+), which appear as cofactors of the enzymes, or free radicals, which are intermediates in biochemical reactions. Instead of paramagnetic centres, which are native in biological systems, very often the molecules with a free radical are incorporated into the system--spin labels or spin probes. Centres with the magnetic moment serve as markers conveying the information about the metabolic processes in biological systems and about the changes in these processes in pathological conditions or under the influence of biologically active substances. In this work several typical applications of EPR and NMR in biomedical research are described showing a great variety of issues where magnetic resonances can be used. EPR experiments: Study of the microgeography of acetylcholinesterase active centre and the conformational changes of this centre under the influence of cholinergic substances. Changes in cell membrane fluidity under the influence of neurotoxins. Transport of cocarcinogens, forbolesters, through the cell membrane. Application of magnetic field gradient to the investigation of transport through the tissues. NMR experiments: Application of 1H-NMR to characterization of brain tumours in vitro and possible application of NMR tomography in vivo to diagnosis of tumours and other pathological conditions. Application of 31P-NMR for investigation of metabolic properties of skeletal muscles. PMID:2174235

Sentjurc, M

1990-06-01

103

Chapter 1 Magnetic Resonance Contributions to Other Sciences  

NASA Astrophysics Data System (ADS)

In 1947, I.I. Rabi invented the molecular beam magnetic resonance method for the important, but limited purpose, of measuring nuclear magnetic moments and five of us working in his laboratory immediately began such experiments. The first experiments with LiCl gave the expected single resonance for each nucleus, but we were surprised to discover six resonances for the proton in H2, which we soon showed was due to the magnetic effects of the other proton and the rotating charged molecule: from these measurements we could also obtain new information on molecular structure. We had another shock when we studied D2 and found the resonance curves were spread more widely for D2 than H2 even though the magnetic interactions should have been much smaller. We found we could explain this by assuming that the deuteron had an electric quadrupole moment and J. Schwinger pointed out that this would require the existence of a previously unsuspected electric tensor force between the neutron and the proton. With this, the resonance method was giving new fundamental information about nuclear forces. In 1944, Rabi and I pointed out that it should be possible by the Dirac theory and our past resonance experiments to calculate exactly the hyperfine interaction between the electron and the proton in the hydrogen atom and we had two graduate students, Nafe and Nelson do the experiment and they found a disagreement which led J. Schwinger to develop the first successful relativistic quantum field theory and QED. In 1964, Purcell, Bloch and others detected magnetic resonance transitions by the effect of the transition on the oscillator, called NMR, making possible measurements on liquids, solids and gases and giving information on chemical shifts and thermal relaxation times T1 and T2. I developed a magnetic resonance method for setting a limit to the EDM of a neutron in a beam and with others for neutrons stored in a suitably coated bottle. Magnetic resonance measurements provide high stability atomic clocks. Both the second and the meter are now defined in terms of atomic clocks. Lauterbuhr, Mansfield, Damadian and others developed the important methods of using inhomogeneous magnetic fields to localize the magnetic resonance in a tissue sample producing beautiful and valuable magnetic resonance images, MRI's, and fMRI's.

Ramsey, Norman F.

104

IEEE TRANSACTIONS ON MEDICAL IMAGING, VOL. 22, NO. 8, AUGUST 2003 933 Analysis of Event-Related fMRI Data  

E-print Network

IEEE TRANSACTIONS ON MEDICAL IMAGING, VOL. 22, NO. 8, AUGUST 2003 933 Analysis of Event-Related fMRI--We explore a new paradigm for the analysis of event- related functional magnetic resonance images (fMRI of this paper. The analysis of event-related fMRI data commonly relies on the as- sumption that the fMRI signal

Meyer, Francois

105

Magnetic Resonance Imaging of concrete  

E-print Network

1 Magnetic Resonance Imaging of concrete Dr Chris Burgoyne Department of Engineering University of Cambridge Assessment of Concrete Structures · How can we tell what is going on inside concrete? · We would like to know:- · Has the concrete hardened? · Is there corrosion? · Is there cracking? · Where

Burgoyne, Chris

106

Magnetic resonance imaging of atherosclerosis  

Microsoft Academic Search

Abundant data now link composition of the vascular wall, rather than the degree of luminal narrowing, with the risk for acute ischemic syndromes in the coronary, central nervous system, and peripheral arterial beds. Over the past few years, magnetic resonance angiography has evolved as a well-established method to determine the location and severity of advanced, lumen-encroaching atherosclerotic lesions. In addition,

T. Leiner; S. Gerretsen; R. Botnar; E. Lutgens; V. Cappendijk; E. Kooi; J. van Engelshoven

2005-01-01

107

Microcoil nuclear magnetic resonance spectroscopy  

Microsoft Academic Search

In comparison with most analytical chemistry techniques, nuclear magnetic resonance has an intrinsically low sensitivity, and many potential applications are therefore precluded by the limited available quantity of certain types of sample. In recent years, there has been a trend, both commercial and academic, towards miniaturization of the receiver coil in order to increase the mass sensitivity of NMR measurements.

A. G. Webb

2005-01-01

108

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. PMID:25009530

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

2014-01-01

109

International Society for Magnetic Resonance in Medicine  

MedlinePLUS

... Workshop & Educational Course Series ISMRM Workshop on Magnetic Resonance in Cancer: Challenges & Unmet Needs 06-09 November ... required) ALS Ice Bucket Challenge Videos Updated! Magnetic Resonance in Medicine 30th Anniversary (Password required) In Memoriam ...

110

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.

111

Studies in nonlinear optics and functional magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

There are two parts in this thesis. The first part will involve a study in the anomalous dispersion phase matched second-harmonic generation, and the second part will be a study in functional magnetic resonance imaging (fMRI) and a biophysical model of the human muscle. In part I, we report on a series of tricyanovinylaniline chromophores for use as dopants in poled poly(methyl methacrylate) waveguides for anomalous-dispersion phase- matched second-harmonic generation. Second-harmonic generation measurements as a function of mode index confirmed anomalous dispersion phase-matching efficiencies as large as 245%/Wcm2 over a propagation length of ~35 ?m. The waveguide coupling technique limited the interaction length. The photostability of the chromophores was measured directly and found to agree qualitatively with second-harmonic measurements over time and was found to be improved over previously reported materials. In part II, we designed a system that could record joint force and surface electromyography (EMG) simultaneously with fMRI data. I-Egh quality force and EMG data were obtained at the same time that excellent fMRI brain images were achieved. Using this system we determined the relationship between the fMRI-measured brain activation and the handgrip force, and between the fMRI-measured brain activation and the EMG of finger flexor muscles. We found that in the whole brain and in the majority of motor function-related cortical fields, the degree of muscle activation is directly proportional to the amplitude of the brain signal determined by the fMRI measurement. The similarity in the relationship between muscle output and fMRI signal in a number of brain areas suggests that multiple cortical fields are involved in controlling muscle force. The factors that may contribute to the fMRI signals are discussed. A biophysical twitch force model was developed to predict force response under electrical stimulation. Comparison between experimental and modeled force profiles, peak forces, and force duration shows excellent agreement between the model and the experimental data. It is concluded that the present model allows us to reproduce the main features of muscle activation under stimulation.

Dai, Tehui

112

Magnetic resonance imaging of oscillating electrical currents  

PubMed Central

Functional MRI has become an important tool of researchers and clinicians who seek to understand patterns of neuronal activation that accompany sensory and cognitive processes. However, the interpretation of fMRI images rests on assumptions about the relationship between neuronal firing and hemodynamic response that are not firmly grounded in rigorous theory or experimental evidence. Further, the blood-oxygen-level-dependent effect, which correlates an MRI observable to neuronal firing, evolves over a period that is 2 orders of magnitude longer than the underlying processes that are thought to cause it. Here, we instead demonstrate experiments to directly image oscillating currents by MRI. The approach rests on a resonant interaction between an applied rf field and an oscillating magnetic field in the sample and, as such, permits quantitative, frequency-selective measurements of current density without spatial or temporal cancellation. We apply this method in a current loop phantom, mapping its magnetic field and achieving a detection sensitivity near the threshold required for the detection of neuronal currents. Because the contrast mechanism is under spectroscopic control, we are able to demonstrate how ramped and phase-modulated spin-lock radiation can enhance the sensitivity and robustness of the experiment. We further demonstrate the combination of these methods with remote detection, a technique in which the encoding and detection of an MRI experiment are separated by sample flow or translation. We illustrate that remotely detected MRI permits the measurement of currents in small volumes of flowing water with high sensitivity and spatial resolution. PMID:20421504

Halpern-Manners, Nicholas W.; Bajaj, Vikram S.; Teisseyre, Thomas Z.; Pines, Alexander

2010-01-01

113

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

PubMed

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 bridging magnetic resonance (MR) signal and haemoglobin changes. We focused on capillary influences, which have been neglected in most previous fMRI studies and performed a combined fMRI and near-infrared spectroscopy (NIRS) study using a language task. Paradoxically, both the MR signal and deoxyHb content increased in Broca's area. On the other hand, fMRI activation in the auditory area near large veins correlated with a mirror-image decrease in deoxyHb and increase in oxygenated haemoglobin (oxyHb), in agreement with canonical BOLD theory. All fMRI signal changes correlated consistently with changes in oxyHb, the diamagnetism of which is insensitive to MR. We concluded that the discrepancy with the canonical BOLD theory is caused by the fact that the BOLD theory ignores the effect of the capillaries. Our theory explains the paradoxical phenomena of the oxyHb and deoxyHb contributions to the MR signal and gives a new insight into the precise haemodynamics of activation by analysing fMRI and NIRS data. PMID:11996059

Yamamoto, Toru; Kato, Toshinori

2002-04-01

114

Magnetic Resonance Connectome Automated Pipeline  

E-print Network

This manuscript presents a novel, tightly integrated pipeline for estimating a connectome, which is a comprehensive description of the neural circuits in the brain. The pipeline utilizes magnetic resonance imaging (MRI) data to produce a high-level estimate of the structural connectivity in the human brain. The Magnetic Resonance Connectome Automated Pipeline (MRCAP) is efficient and its modular construction allows researchers to modify algorithms to meet their specific requirements. The pipeline has been validated and over 200 connectomes have been processed and analyzed to date. This tool enables the prediction and assessment of various cognitive covariates, and this research is applicable to a variety of domains and applications. MRCAP will enable MR connectomes to be rapidly generated to ultimately help spur discoveries about the structure and function of the human brain.

Gray, William R; Vogelstein, Joshua T; Landman, Bennett A; Prince, Jerry L; Vogelstein, R Jacob

2011-01-01

115

Gadolinium magnetic resonance imaging dacryocystography.  

PubMed

A 1:100 solution of 48% gadopentolate in liquid tear solution was used in magnetic resonance dacryocystography to image the canaliculi, nasolacrimal sac, and nasolacrimal duct. It was administered as an eyedrop, one drop every minute for five minutes, immediately before scanning in six normal and five abnormal nasolacrimal outflow systems. In cases of nasolacrimal obstruction, the dilute gadolinium solution was injected through the canaliculus immediately before scanning. A three-inch surface coil enhanced the detail of soft-tissue structures such as the canaliculi and lacrimal sac. In the evaluation of complex tearing disorders such as congenital, neoplastic, postsurgical, and posttraumatic nasolacrimal obstruction, gadolinium lacrimal contrast adds useful information to magnetic resonance images of the lacrimal outflow system. Because of the expense of the test, we do not recommend it as a routine examination. PMID:8506908

Goldberg, R A; Heinz, G W; Chiu, L

1993-06-15

116

Adaptive functional magnetic resonance imaging  

E-print Network

Functional MRI (fMRI) detects the signal associated with neuronal activation, and has been widely used to map brain functions. Locations of neuronal activation are localized and distributed throughout the brain, however, ...

Yoo, Seung-Schik, 1970-

2000-01-01

117

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

118

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

119

Cortical reorganization in NT3-treated experimental spinal cord injury: Functional magnetic resonance imaging.  

PubMed

Functional magnetic resonance imaging (fMRI) studies were performed for visualizing ongoing brain plasticity in Neurotrophin-3 (NT3)-treated experimental spinal cord injury (SCI). In response to the electrical stimulation of the forepaw, the NT3-treated animals showed extensive activation of brain structures that included contralateral cortex, thalamus, caudate putamen, hippocampus, and periaqueductal gray. Quantitative analysis of the fMRI data indicated significant changes both in the volume and center of activations in NT3-treated animals relative to saline-treated controls. A strong activation in both ipsi- and contralateral periaqueductal gray and thalamus was observed in NT3-treated animals. These studies indicate ongoing brain reorganization in the SCI animals. The fMRI results also suggest that NT3 may influence nociceptive pathways. PMID:17112518

Ramu, Jaivijay; Bockhorst, Kurt H; Grill, Raymond J; Mogatadakala, Kishore V; Narayana, Ponnada A

2007-03-01

120

Testing the Diagnostic Value of Electrical Ear Canal Stimulation in Cochlear Implant Candidates by Functional Magnetic Resonance Imaging  

Microsoft Academic Search

Prior to cochlear implant (CI) surgery in children, the integrity of the auditory pathway is sometimes assessed by electrical ear canal stimulation (ECS). However, the evaluation of reactions as auditory is subjective. To test the prognostic value of ECS, functional magnetic resonance imaging (fMRI) was performed during ECS vicariously in 18 adult CI candidates. Activation of the primary auditory cortex

Katrin Neumann; Christine Preibisch; Joachim Spreer; Peter Raab; John Hamm; Harald A. Euler; Heinrich Lanfermann; Silke Helbig; Jan Kiefer

2008-01-01

121

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

122

Functional Magnetic Resonance Imaging of Story Listening in Adolescents and Young Adults with Down Syndrome: Evidence for Atypical Neurodevelopment  

ERIC Educational Resources Information Center

Background: Previous studies have documented differences in neural activation during language processing in individuals with Down syndrome (DS) in comparison with typically developing individuals matched for chronological age. This study used functional magnetic resonance imaging (fMRI) to compare activation during language processing in young…

Jacola, L. M.; Byars, A. W.; Hickey, F.; Vannest, J.; Holland, S. K.; Schapiro, M. B.

2014-01-01

123

Nuclear magnetic resonance imaging (MRI).  

PubMed

This article discusses the basic concepts of Magnetic Resonance Imaging (MRI) with the intention to introduce the subject to uninitiated. The MRI technique is a powerful noninvasive probe of the body's internal anatomy. In MRI, the images are produced not by X-rays, but through the use of non-ionizing radiowaves that stimulate transitions between spin states of nuclei in a magnetic field when passed through the body. The time required for the nucleus to return to equilibrium gives information about the environment of that nucleus. In this way tissue abnormalities can be determined in vivo. This article covers the basis of MRI phenomena, the concept of magnetic moment of the sample, NMR exalation and emission and the equipment necessary to observe these NMR properties. The primary agents used to increase tissue contrast in MRI are also mentioned. Finally the importance and prospects of this technique in Pakistan have been discussed. PMID:1753410

Khurshid, S J; Hussain, A M

1991-10-01

124

Correlates of alpha rhythm in functional magnetic resonance imaging and near infrared spectroscopy  

Microsoft Academic Search

We used simultaneous electroencephalogram-functional magnetic resonance imaging (EEG-fMRI) and EEG-near infrared spectroscopy (NIRS) to investigate whether changes of the posterior EEG alpha rhythm are correlated with changes in local cerebral blood oxygenation. Cross-correlation analysis of slowly fluctuating, spontaneous rhythms in the EEG and the fMRI signal revealed an inverse relationship between alpha activity and the fMRI-blood oxygen level dependent signal

Matthias Moosmann; Petra Ritter; Ina Krastel; Andrea Brink; Sebastian Thees; Felix Blankenburg; Birol Taskin; Hellmuth Obrig; Arno Villringer

2003-01-01

125

Functional magnetic resonance imaging of synesthesia: activation of V4\\/V8 by spoken words  

Microsoft Academic Search

In 'colored-hearing' synesthesia, individuals report color experiences when they hear spoken words. If the synesthetic color experience resembles that of normal color perception, one would predict activation of parts of the visual system specialized for such perception, namely the human 'color center', referred to as either V4 or V8. Using functional magnetic resonance imaging (fMRI), we here locate the region

L. J. Gregory; M. Brammer; S. C. R. Williams; D. M. Parslow; M. J. Morgan; R. G. Morris; E. T. Bullmore; S. Baron-Cohen; J. A. Gray; J. A. Nunn

2002-01-01

126

An Over-Complete Independent Component Analysis (ICA) Approach to Magnetic Resonance Image Analysis  

Microsoft Academic Search

This paper presents a new application of independent component analysis (ICA) in magnetic resonance (MR) image analysis. One of most successful applications for ICA-based approaches in MR imaging is functional MRI (fMRI) which basically deals with one-dimensional temporal signals. The ICA approach proposed in this paper is rather different and considers a set of MR images acquired by different pulse

Jing Wang; Chein-I Chang; Hsiang Ming Chen; Clayton Chi-Chang Chen; Jyh Wen Chai; Yen-Chieh Ouyang

2005-01-01

127

Comparison of data-driven analysis methods for identification of functional connectivity in fMRI  

E-print Network

Data-driven analysis methods, such as independent component analysis (ICA) and clustering, have found a fruitful application in the analysis of functional magnetic resonance imaging (fMRI) data for identifying functionally ...

Kim, Yongwook Bryce

2008-01-01

128

Optimized Design and Analysis of Sparse-Sampling fMRI Experiments  

E-print Network

Sparse-sampling is an important methodological advance in functional magnetic resonance imaging (fMRI), in which silent delays are introduced between MR volume acquisitions, allowing for the presentation of auditory stimuli ...

Perrachione, Tyler Kent

129

Solutions to various problems in reversible cooling fMRI studies  

E-print Network

Functional magnetic resonance imaging (fMRI) has been very useful in helping neuroscientists map the brain. One tool to investigate the interactions between brain regions is to disable a small region in the brain, and look ...

Khachaturian, Mark Haig, 1979-

2003-01-01

130

Real-time independent component analysis of fMRI time-series  

Microsoft Academic Search

Real-time functional magnetic resonance imaging (fMRI) enables one to monitor a subject's brain activity during an ongoing session. The availability of online information about brain activity is essential for developing and refining interactive fMRI paradigms in research and clinical trials and for neurofeedback applications. Data analysis for real-time fMRI has traditionally been based on hypothesis-driven processing methods. Off-line data analysis,

Fabrizio Esposito; Erich Seifritz; Elia Formisano; Renato Morrone; Tommaso Scarabino; Gioacchino Tedeschi; Sossio Cirillo; Rainer Goebel; Francesco Di Sallee

2003-01-01

131

Wavelet-based multifractal analysis of fMRI time series  

Microsoft Academic Search

Functional magnetic resonance imaging (fMRI) time series are investigated with a multifractal method based on the Wavelet Modulus Maxima (WTMM) method to extract local singularity (“fractal”) exponents. The spectrum of singularity exponents of each fMRI time series is quantified by spectral characteristics including its maximum and the corresponding dimension. We found that the range of Hölder exponents in voxels with

Yu Shimizu; Markus Barth; Christian Windischberger; Ewald Moser; Stefan Thurner

2004-01-01

132

fMRI studies of associative encoding in young and elderly controls and mild Alzheimer's disease  

E-print Network

PAPER fMRI studies of associative encoding in young and elderly controls and mild Alzheimer activation seen in normal aging and in mild Alzheimer's disease by functional magnetic resonance imaging (f with mild Alzheimer's disease were studied using fMRI during a face­name association encoding task. The f

Schacter, Daniel

133

Performance of blind source separation algorithms for fMRI analysis using a group ICA method  

Microsoft Academic Search

Independent component analysis (ICA) is a popular blind source separation technique that has proven to be promising for the analysis of functional magnetic resonance imaging (fMRI) data. A number of ICA approaches have been used for fMRI data analysis, and even more ICA algorithms exist; however, the impact of using different algorithms on the results is largely unexplored. In this

Nicolle Correa; Tülay Adal?; Vince D. Calhoun

2007-01-01

134

Physiological recordings: Basic concepts and implementation during functional magnetic resonance imaging  

PubMed Central

Combining human functional neuroimaging with other forms of psychophysiological measurement, including autonomic monitoring, provides an empirical basis for understanding brain–body interactions. This approach can be applied to characterize unwanted physiological noise, examine the neural control and representation of bodily processes relevant to health and morbidity, and index covert expression of affective and cognitive processes to enhance the interpretation of task-evoked regional brain activity. In recent years, human neuroimaging has been dominated by functional magnetic resonance imaging (fMRI) studies. The spatiotemporal information of fMRI regarding central neural activity is valuably complemented by parallel physiological monitoring, yet such studies still remain in the minority. This review article highlights fMRI studies that employed cardiac, vascular, respiratory, electrodermal, gastrointestinal and pupillary psychophysiological indices to address specific questions regarding interaction between brain and bodily state in the context of experience, cognition, emotion and behaviour. Physiological monitoring within the fMRI environment presents specific technical issues, most importantly related to safety. Mechanical and electrical hazards may present dangers to scanned subjects, operator and/or equipment. Furthermore, physiological monitoring may interfere with the quality of neuroimaging data, or itself be compromised by artefacts induced by the operation of the scanner. We review the sources of these potential problems and the current approaches and advice to enable the combination of fMRI and physiological monitoring in a safe and effective manner. PMID:19460445

Gray, Marcus A.; Minati, Ludovico; Harrison, Neil A.; Gianaros, Peter J.; Napadow, Vitaly; Critchley, Hugo D.

2009-01-01

135

Complex ICA for fMRI analysis: performance of several approaches  

Microsoft Academic Search

Independent component analysis (ICA) for separating complex-valued sources is needed for convolutive source-separation in the frequency domain, or for performing source separation on complex-valued data, such as functional magnetic resonance imaging data. Functional magnetic resonance imaging (fMRI) is a technique that produces complex-valued data; however the vast majority of fMRI analyses utilize only magnitude images. We compare the performance of

V. D. Calhoun; T. Adali

2003-01-01

136

Principles of nuclear magnetic resonance  

SciTech Connect

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 T/sub 1/ and T/sub 2/, the spin-lattice and spin-spin relaxation time, and Fourier-tranform NMR spectroscopy.

Koutcher, J.A.; Burt, C.T.

1984-01-01

137

Pharmacological stress cardiovascular magnetic resonance.  

PubMed

Over the past decade, cardiovascular magnetic resonance (CMR) has evolved into a cardiac stress testing modality that can be used to diagnose myocardial ischemia using intravenous dobutamine or vasodilator perfusion agents such as adenosine or dipyridamole. Because CMR produces high-resolution tomographic images of the human heart in multiple imaging planes, it has become a highly attractive noninvasive testing modality for those suspected of having myocardial ischemia. The purpose of this article is to review the clinical, diagnostic, and prognostic utility of stress CMR testing for patients with (or suspected of having) coronary artery disease. PMID:21566427

Chotenimitkhun, Runyawan; Hundley, W Gregory

2011-05-01

138

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 PMID:8792545

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

1996-01-01

139

Introduction to Nuclear Magnetic Resonance  

NASA Technical Reports Server (NTRS)

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

Manatt, Stanley L.

1985-01-01

140

Nitinol in magnetic resonance imaging.  

PubMed

Surgical and interventional instruments as well as implants can cause significant magnetic resonance image (MRI) artifacts. The artifacts can be used to visualize instruments, cannulae, guide wires, catheters during interventional MRI and Nitinol devices have proven to be useful for MRI procedures. Diagnostic imaging is often compromised in the area of an implant. Complete vanishing of signals occurs in close proximity or inside implants. The paper presents a fundamental evaluation of MRI artifact of Nitinol devices such as Stents, Vena Cava Filter, heart defect closure devices, cannulae, guide wire, localizer, anastomosis device, etc. in a 1.0 Tesla magnetic field. The American Society for Testing Materials (ASTM) recommendations for selection of sequences and test setup were used but the results of this paper are not sufficient for FDA approval. PMID:16754135

Melzer; Michitsch; Konak; Schaefers; Bertsch, Th

2004-08-01

141

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. PMID:20544947

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

2011-01-01

142

Motion Estimation in Static Magnetic Resonance Elastography  

E-print Network

Elastography is the imaging of the biomechanical properties of a tissue to detect and diagnose abnormal pathologies in a variety of disease conditions. Static Magnetic Resonance Elastography (MRE) is a modality of elastography that uses Magnetic...

Popel, Elena

2009-12-09

143

Advances in mechanical detection of magnetic resonance  

PubMed Central

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

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

2008-01-01

144

Combining functional magnetic resonance imaging with transcranial electrical stimulation  

PubMed Central

Transcranial electrical stimulation (tES) is a neuromodulatory method with promising potential for basic research and as a therapeutic tool. The most explored type of tES is transcranial direct current stimulation (tDCS), but also transcranial alternating current stimulation (tACS) and transcranial random noise stimulation (tRNS) have been shown to affect cortical excitability, behavioral performance and brain activity. Although providing indirect measure of brain activity, functional magnetic resonance imaging (fMRI) can tell us more about the global effects of stimulation in the whole brain and what is more, on how it modulates functional interactions between brain regions, complementing what is known from electrophysiological methods such as measurement of motor evoked potentials. With this review, we aim to present the studies that have combined these techniques, the current approaches and discuss the results obtained so far. PMID:23935578

Saiote, Catarina; Turi, Zsolt; Paulus, Walter; Antal, Andrea

2013-01-01

145

Magnetic Resonance Imaging System Based on Earth's Magnetic Field  

Microsoft Academic Search

This article describes both the setup and the use of a system for magnetic resonance imaging (MRI) in the Earth's magnetic field. Phase instability caused by temporal fluctuations of Earth's field can be successfully improved by using a reference signal from a separate Earth's field nuclear magnetic resonance (NMR) spectrometer\\/magnetometer. In imaging, it is important to correctly determine the phase

Ales Mohoric; Gorazd Planinsic; Miha Kos; Andrej Duh; Janez Stepisnik

2004-01-01

146

Enhancement of magnetic resonance contrast effect using ionic magnetic clusters.  

PubMed

Precise diagnosis by magnetic resonance imaging (MRI) requires sensitive magnetic resonance probes to detect low concentrations of magnetic substances. Ionic magnetic clusters (IMCs) as versatile magnetic probes were successfully synthesized for enhancing the magnetic resonance (MR) contrast effect as well as ensuring high water solubility. IMCs with various sizes were prepared by assembly of MNCs using cationic cetyltrimethylammonium bromide (CTAB) and anionic sodium dodecyl sulfate (SDS). To synthesize IMCs in the aqueous phase, magnetic nanocrystals in an organic solvent were assembled with CTAB and SDS using the nanoemulsion method, to fabricate cationic magnetic clusters (CMCs) and anionic magnetic clusters (AMCs), respectively. IMCs demonstrated ultrasensitivity by MR imaging and sufficient magnetic mobility under an external magnetic field. PMID:18158155

Seo, Sung-Baek; Yang, Jaemoon; Lee, Tong-Il; Chung, Chan-Hwa; Song, Yong Jin; Suh, Jin-Suck; Yoon, Ho-Geun; Huh, Yong-Min; Haam, Seungjoo

2008-03-15

147

Magnetic resonance imaging of radiation optic neuropathy  

SciTech Connect

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

Zimmerman, C.F.; Schatz, N.J.; Glaser, J.S. (Univ. of Miami, FL (USA))

1990-10-15

148

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

149

Spiral parallel magnetic resonance imaging.  

PubMed

Spiral k-space scanning is a rapid magnetic resonance imaging (MRI) technique that can provide an order of magnitude reduction in scan time compared to conventional spin warp techniques. Parallel imaging is another method for reducing scan time that exploits spatially varying radiofrequency (RF) coil sensitivities to reduce the amount of data required to reconstruct an image. Combining spiral scanning with parallel imaging provide a scan time reduction factor that is the product of the reduction factors for each of the techniques and thus can permit very rapid imaging. Image reconstruction for spiral parallel MRI is more involved than for spin warp parallel MRI and is an area of active research. Two techniques for performing this image reconstruction are PILS, a simple image-domain method that relies on localized coil sensitivities, and BOSCO, a method that is based on successive convolution operations in k-space. PMID:17946823

Meyer, Craig H; Hu, Peng

2006-01-01

150

Modeling the macromolecular background in Nuclear Magnetic Resonance spectroscopic signals  

E-print Network

1 Modeling the macromolecular background in Nuclear Magnetic Resonance spectroscopic signals D- noising, nonparametric modeling, macromolecular back- ground. I. INTRODUCTION Nuclear Magnetic Resonance Engineering (ESAT-SCD), Leuven, Belgium Abstract--Metabolite quantitation of Nuclear Magnetic Resonance

151

21 CFR 892.1000 - Magnetic resonance diagnostic device.  

Code of Federal Regulations, 2013 CFR

... 2013-04-01 false Magnetic resonance diagnostic device. 892.1000 ...Diagnostic Devices § 892.1000 Magnetic resonance diagnostic device. (a) Identification. A magnetic resonance diagnostic device is intended...

2013-04-01

152

21 CFR 892.1000 - Magnetic resonance diagnostic device.  

Code of Federal Regulations, 2012 CFR

... 2012-04-01 false Magnetic resonance diagnostic device. 892.1000 ...Diagnostic Devices § 892.1000 Magnetic resonance diagnostic device. (a) Identification. A magnetic resonance diagnostic device is intended...

2012-04-01

153

21 CFR 892.1000 - Magnetic resonance diagnostic device.  

... 2014-04-01 false Magnetic resonance diagnostic device. 892.1000 ...Diagnostic Devices § 892.1000 Magnetic resonance diagnostic device. (a) Identification. A magnetic resonance diagnostic device is intended...

2014-04-01

154

Pictures of a thousand words: Investigating the neural mechanisms of reading with extremely rapid event-related fMRI  

Microsoft Academic Search

Reading is one of the most important skills human beings can acquire, but has proven difficult to study naturalistically using functional magnetic resonance imaging (fMRI). We introduce a novel Event-Related Reading (ERR) fMRI approach that enables reliable estimation of the neural correlates of single-word processing during reading of rapidly presented narrative text (200–300ms \\/word). Application to an fMRI experiment in

Tal Yarkoni; Nicole K. Speer; David A. Balota; Mark P. McAvoy; Jeffrey M. Zacks

2008-01-01

155

Distraction modulates connectivity of the cingulo-frontal cortex and the midbrain during pain—an fMRI analysis  

Microsoft Academic Search

Neuroimaging studies with positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) have delineated a human pain network in vivo. Despite the recognition of cerebral structures engaged in pain transmission, the cerebral mechanisms involved in pain modulation are still not well understood. Here, we investigated healthy volunteers using fMRI during experimental heat pain and distraction induced by a visual

Michael Valet; Till Sprenger; Henning Boecker; Frode Willoch; Ernst Rummeny; Bastian Conrad; Peter Erhard; Thomas R. Tolle

2004-01-01

156

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. PMID:18672071

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

2011-01-01

157

Task and task-free FMRI reproducibility comparison for motor network identification.  

PubMed

Test-retest reliability of individual functional magnetic resonance imaging (fMRI) results is of importance in clinical practice and longitudinal experiments. While several studies have investigated reliability of task-induced motor network activation, less is known about the reliability of the task-free motor network. Here, we investigate the reproducibility of task-free fMRI, and compare it to motor task activity. Sixteen healthy subjects participated in this study with a test-retest interval of seven weeks. The task-free motor network was assessed with a univariate, seed-voxel-based correlation analysis. Reproducibility was tested by means of intraclass correlation (ICC) values and ratio of overlap. Higher ICC values and a better overlap were found for task fMRI as compared to task-free fMRI. Furthermore, ratio of overlap improved for task fMRI at higher thresholds, while it decreased for task-free fMRI, suggesting a less focal spatial pattern of the motor network during resting state. However, for both techniques the most active voxels were located in the primary motor cortex. This indicates that, just like task fMRI, task-free fMRI can properly identify critical brain areas for motor task performance. Although both fMRI techniques are able to detect the motor network, resting-state fMRI is less reliable than task fMRI. PMID:22987751

Kristo, Gert; Rutten, Geert-Jan; Raemaekers, Mathijs; de Gelder, Bea; Rombouts, Serge A R B; Ramsey, Nick F

2014-01-01

158

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

159

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. PMID:22125419

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

2011-01-01

160

Naming of animals and tools: a functional magnetic resonance imaging study of categorical differences in the human brain areas commonly used for naming visually presented objects  

Microsoft Academic Search

To investigate the neural substrates for naming objects and their category-dependency, we performed functional magnetic resonance imaging (fMRI) with naming of animals and tools. Naming objects, irrespective of their category, activated left frontal to bilateral parietal regions and occipital to posterior temporal regions. Within these areas, naming animals caused more activation of the primary visual cortex bilaterally and the ventral

Tomohisa Okada; Shigeki Tanaka; Toshiharu Nakai; Sadahiko Nishizawa; Toshio Inui; Norihiro Sadato; Yoshiharu Yonekura; Junji Konishi

2000-01-01

161

Reducing Field Distortion in Magnetic Resonance Imaging  

NASA Technical Reports Server (NTRS)

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

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

2010-01-01

162

Chronic liver disease: evaluation by magnetic resonance  

SciTech Connect

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

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

1984-01-01

163

Gradient characterization in magnetic resonance imaging  

E-print Network

Special magnetic resonance (MR) scans, such as spiral imaging and echo-planar imaging, require speed and gradient accuracy while putting high demands on the MR gradient system that may cause gradient distortion. Additionally, ...

Cheng, Joseph Yitan

2007-01-01

164

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

165

Magnetic Resonance Imaging - Parts I and II.  

National Technical Information Service (NTIS)

This program provides the viewer with an introduction to magnetic resonance imaging (mri). Included is a discussion of the principle of nmr, its differences from computed tomography and other imaging modalities, its current and future applications, specia...

1994-01-01

166

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. PMID:19269527

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

2009-01-01

167

Simple Bridge for Pulsed Nuclear Magnetic Resonance  

Microsoft Academic Search

An asymmetrical rf bridge for pulsed magnetic resonance experiments is described. The balancing adjustments, which can be made quickly and easily, ensure a proper impedance match to transmitter and receiver. The bridge is particularly well suited for pure nuclear quadrupole resonance experiments.

K. R. Jeffrey; R. L. Armstrong

1967-01-01

168

Role of ongoing, intrinsic activity of neuronal populations for quantitative neuroimaging of functional magnetic resonance imaging-based networks.  

PubMed

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 (CMR(O2)). 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 ?CMR(O2) and through resting-state positron emission tomography/magnetic resonance spectroscopy measurements for average CMR(O2). PMID:22433047

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

2011-01-01

169

Reduced visual evoked responses in multiple sclerosis patients with optic neuritis: comparison of functional magnetic resonance imaging and visual evoked potentials.  

PubMed

The limited application of functional magnetic resonance imaging (fMRI) for investigations of multiple sclerosis (MS) patients has already shown that deficits of the motor, cognitive and visual systems may be identified by differences in the patterns of activation in response to a suitable stimulus. In MS patients with unilateral optic neuritis, the area of activation in the primary visual cortex, measured by fMRI techniques, is dramatically reduced in response to stimulation of the affected eye. The latency of the major positive component of the visual evoked potential (VEP) recorded upon stimulation of the affected eye is significantly increased in these patients, as compared to the unaffected eye and normal volunteers. We have found a correlation between the neural response measured using fMRI and the latency of the VEP. fMRI signal responses have the potential to provide more detailed topographic information relating to functional deficits in MS. PMID:10408715

Gareau, P J; Gati, J S; Menon, R S; Lee, D; Rice, G; Mitchell, J R; Mandelfino, P; Karlik, S J

1999-06-01

170

Ferromagnetic resonance in ?-Co magnetic composites.  

PubMed

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

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

2014-12-01

171

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

172

Functional magnetic resonance imaging of motor, sensory, and posterior parietal cortical areas during performance of sequential typing movements  

Microsoft Academic Search

We investigated the activation of sensory and motor areas involved in the production of typing movements using functional\\u000a magnetic resonance imaging (fMRI). Eleven experienced typists performed tasks, in which the spatial and temporal requirements\\u000a as well as the number of digits involved were varied. These included a simple uni-digit repetitive task, a uni-digit sequential\\u000a task, a dual-digit sequential task, a

A. M. Gordon; J.-H. Lee; D. Flament; K. Ugurbil; T. J. Ebner

1998-01-01

173

Functional magnetic resonance imaging of pain consciousness: Cortical networks of pain critically depend on what is implied by “pain”  

Microsoft Academic Search

Brain imaging studies, using primarily functional magnetic resonance imaging (fMRI), are reviewed. These studies are aimed\\u000a at developing imaging approaches that can be used in the clinical setting to investigate clinically relevant pain states.\\u000a To this end, our recent studies indicate that by taking advantage of the temporal variations in pain perception, we are able\\u000a to identify cortical regions that

A. Vania Apkarian

1999-01-01

174

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

175

Mental Rotation Studied by Functional Magnetic Resonance Imaging at High Field (4 Tesla): Performance and Cortical Activation  

Microsoft Academic Search

We studied the performance and cortical activation patterns during a mental rotation task (Shepard & Metzler, 1971) using functional magnetic resonance imaging (fMlU) at high field (4 Tesla). Twenty-four human subjects were imaged (fMRI group), whereas six additional subjects performed the task without being imaged (control group). All subjects were shown pairs of perspective drawings of 31, objects and asked

Georgios A. Tagaris; Seong-Gi Kim; John P. Strupp; Peter Andersen; Kamil U??urbil; Apostolos P. Georgopoulos

1997-01-01

176

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. PMID:22984396

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

2012-01-01

177

Coherence of magnetic resonators in a metamaterial  

SciTech Connect

The coherence of periodic magnetic resonators (MRs) under oblique incidence is studied using simulations. The correlated phase of interaction including both the retardation effect and relative phase difference between two MRs is defined, and it plays a key role in the MR interaction. The correlated phase is anisotropic, as is the coherence condition. The coherence condition is the same as the Wood's anomaly and verified by the Fano resonance. This study shows that the applications of the Fano resonance of periodic MRs will become widespread owing to achieving the Fano resonance simply by tuning the incident angle.

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

178

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

179

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

180

Magnetic resonance spectroscopy outcomes from a comprehensive magnetic resonance study of children with fetal alcohol spectrum disorders?  

PubMed Central

Magnetic resonance (MR) technology offers noninvasive methods for in vivo assessment of neuroabnormalities. A comprehensive neuropsychological/behavioral, MR imaging (MRI), MR spectroscopy (MRS) and functional MRI (fMRI) assessment was administered to children with fetal alcohol spectrum disorders (FASD) to determine whether global and/or focal abnormalities could be identified and to distinguish diagnostic subclassifications across the spectrum. The four study groups included (1) FAS/partial FAS; (2) static encephalopathy/alcohol exposed (SE/AE); (3) neurobehavioral disorder/alcohol exposed (ND/AE) as diagnosed with the FASD 4-Digit Code; and (4) healthy peers with no prenatal alcohol exposure. Results are presented in four separate reports: MRS (reported here) and neuropsychological/behavioral, MRI and fMRI outcomes (reported separately). MRS was used to compare neurometabolite concentrations [choline (Cho), n-acetyl-aspartate (NAA) and creatine (Cre)] in a white matter region and a hippocampal region between the four study groups. Choline concentration in the frontal/parietal white matter region, lateral to the midsection of the corpus callosum, was significantly lower in FAS/PFAS relative to all other study groups. Choline decreased significantly with decreasing frontal white matter volume and corpus callosum length. These outcomes suggest low choline concentrations may reflect white matter deficits among FAS/PFAS. Choline also decreased significantly with increasing severity of the 4-Digit FAS facial phenotype, increasing impairment in psychological performance and increasing alcohol exposure. NAA and Cre concentrations did not vary significantly. This study provides further evidence of the vulnerability of the cholinergic system in FASD. PMID:19342189

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

2014-01-01

181

Unified SPM–ICA for fMRI analysis  

Microsoft Academic Search

A widely used tool for functional magnetic resonance imaging (fMRI) data analysis, statistical parametric mapping (SPM), is based on the general linear model (GLM). SPM therefore requires a priori knowledge or specific assumptions about the time courses contributing to signal changes. In contradistinction, independent component analysis (ICA) is a data-driven method based on the assumption that the causes of responses

Dewen Hu; Lirong Yan; Yadong Liu; Zongtan Zhou; Karl J. Friston; Changlian Tan; Daxing Wu

2005-01-01

182

Decoding Cognitive States from fMRI Timeseries  

Microsoft Academic Search

Conventional analysis of functional magnetic resonance imaging (fMRI) data follows a regression-based approach, in which one identifies the neural correlates of a particu- lar cognitive function by correlating individual voxel time- courses with a known pattern of stimulus presentations. However, one can reverse the direction of analysis; rather than using knowledge of the stimulus pattern to infer brain activity, one

Catie Chang

183

Fully Bayesian spatio-temporal modeling of FMRI data  

Microsoft Academic Search

We present a fully Bayesian approach to modeling in functional magnetic resonance imaging (FMRI), incorporating spatio-temporal noise modeling and haemodynamic response function (HRF) modeling. A fully Bayesian approach allows for the uncertainties in the noise and signal modeling to be incorporated together to provide full posterior distributions of the HRF parameters. The noise modeling is achieved via a nonseparable space-time

Mark William Woolrich; Mark Jenkinson; J. Michael Brady; Stephen M. Smith

2004-01-01

184

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

185

SNR and functional sensitivity of BOLD and perfusion-based fMRI using arterial spin labeling with spiral SENSE at 3 T  

E-print Network

by low-frequency fluctuations, which were not dominant in the perfusion data due to signal processingSNR and functional sensitivity of BOLD and perfusion-based fMRI using arterial spin labeling-dependent (BOLD) functional magnetic resonance imaging (fMRI) studies using parallel imaging to reduce the readout

Liu, Thomas T.

186

Neural Correlates of Feigned Memory Impairment are Distinguishable from Answering Randomly and Answering Incorrectly: An fMRI and Behavioral Study  

ERIC Educational Resources Information Center

Previous functional magnetic resonance imaging (fMRI) studies have identified activation in the prefrontal-parietal-sub-cortical circuit during feigned memory impairment when comparing with truthful telling. Here, we used fMRI to determine whether neural activity can differentiate between answering correctly, answering randomly, answering…

Liang, Chun-Yu; Xu, Zhi-Yuan; Mei, Wei; Wang, Li-Li; Xue, Li; Lu, De Jian; Zhao, Hu

2012-01-01

187

Hosted by Yalin Wang Methods in Magnetic Resonance Imaging  

E-print Network

Hosted by Yalin Wang Methods in Magnetic Resonance Imaging Abstract: Magnetic Resonance Imaging of the Department of Radiology at Wayne State University, he joined Barrow Neurological Institute in 1999, where he Resonance Imaging and on the editorial boards of the journal Magnetic Resonance in Medicine. Dr. Pipe

Reisslein, Martin

188

Magnetic material arrangement in oriented termites: a magnetic resonance study  

NASA Astrophysics Data System (ADS)

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

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

2004-06-01

189

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

190

Magnetic resonance imaging by using nano-magnetic particles  

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

191

Nuclear magnetic resonance offers new insights into Pu 239  

E-print Network

- 1 - Nuclear magnetic resonance offers new insights into Pu 239 May 29, 2012 Nuclear magnetic signal of plutonium 239's unique nuclear magnetic resonance signature has been detected by scientists on the subject, "Observation of 239 Pu Nuclear Magnetic Resonance," was published in the May 18 issue of Science

192

Granular convection observed by magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

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.

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

1995-03-01

193

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

194

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. PMID:15987466

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

2005-01-01

195

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

196

Magnetic elliptical polarization of Schumann resonances  

NASA Technical Reports Server (NTRS)

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

Sentman, D. D.

1987-01-01

197

MAGNETIC RESONANCE IN CHEMISTRY Magn. Reson. Chem. 2006; 44: S206S212  

E-print Network

MAGNETIC RESONANCE IN CHEMISTRY Magn. Reson. Chem. 2006; 44: S206�S212 Published online in Wiley 16 March 2006 Sample concentrations can be measured by nuclear magnetic resonance (NMR) spectroscopy contains a resolved resonance; but can also be applied to spectral regions with overlapping resonances

Wider, Gerhard

198

A General Theory of Magnetic Resonance Absorption  

Microsoft Academic Search

A general expression for the frequency-dependent susceptibility of a magnetic system is derived by a quantum-statistical method based on the linear theory of irreversible process. This fundamental equation provides a physical ground for the so-called Fourier transform method for computing the resonance line contour. The auto-correlation function, or the relaxation function of the magnetic moment, that is the Fourier transform

Ryogo Kubo; Kazuhisa Tomita

1954-01-01

199

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

200

Magnetic resonance of ferrite nanoparticles  

Microsoft Academic Search

Ferromagnetic resonance (FMR) experiments at 9.26GHz on non-interacting maghemite (?-Fe2O3) nanoparticles of ferrofluids are performed as a function of temperature (3.5–300K) and particle diameter (4.8–10nm). The orientational mobility of the particles inside the fluid is employed to monitor the orientational distribution of the anisotropy axes by solidifying the MF matrix under the external field. On those textured suspensions, angular analysis

F. Gazeau; J. C Bacri; F. Gendron; R. Perzynski; Yu. L Raikher; V. I. Stepanov; E. Dubois

1998-01-01

201

Quantification and improvement of speech transmission performance using headphones in acoustic stimulated functional magnetic resonance imaging.  

PubMed

Functional magnetic resonance imaging (fMRI) has made a major contribution to the understanding of higher brain function, but fMRI with auditory stimulation, used in the planning of brain tumor surgery, is often inaccurate because there is a risk that the sounds used in the trial may not be correctly transmitted to the subjects due to acoustic noise. This prompted us to devise a method of digitizing sound transmission ability from the accuracy rate of 67 syllables, classified into three types. We evaluated this with and without acoustic noise during imaging. We also improved the structure of the headphones and compared their sound transmission ability with that of conventional headphones attached to an MRI device (a GE Signa HDxt 3.0 T). We calculated and compared the sound transmission ability of the conventional headphones with that of the improved model. The 95 percent upper confidence limit (UCL) was used as the threshold for accuracy rate of hearing for both headphone models. There was a statistically significant difference between the conventional model and the improved model during imaging (p < 0.01). The rate of accuracy of the improved model was 16 percent higher. 29 and 22 syllables were accurate at a 95% UCL in the improved model and the conventional model, respectively. This study revealed the evaluation system used in this study to be useful for correctly identifying syllables during fMRI. PMID:25327421

Yamamura, Ken Ichiro; Takatsu, Yasuo; Miyati, Tosiaki; Kimura, Tetsuya

2014-10-01

202

Computer-controlled stimulation for functional magnetic resonance imaging studies of the neonatal olfactory system  

PubMed Central

Aim Olfactory sensation is highly functional early in human neonatal life, with studies suggesting that odours can influence behaviour and infant–mother bonding. Due to its good spatial properties, blood oxygen level–dependent (BOLD) contrast functional magnetic resonance imaging (fMRI) has the potential to rapidly advance our understanding of the neural activity which underlies the development of olfactory perception in this key period. We aimed to design an ‘olfactometer’ specifically for use with neonatal subjects for fMRI studies of odour perception. Methods We describe a fully automated and programmable, fMRI compatible system capable of presenting odorant liquids. To prevent contamination of the system and minimize between-subject infective risk, the majority of the olfactometer is constructed from single-use, readily available clinical equipment. The system was used to present the odour of infant formula milk in a validation group of seven neonatal subjects at term equivalent postmenstrual age (median age 40 weeks). Results A safe, reliable and reproducible pattern of stimulation was delivered leading to well-localized positive BOLD functional responses in the piriform cortex, amygdala, thalamus, insular cortex and cerebellum. Conclusions The described system is therefore suitable for detailed studies of the ontology of olfactory sensation and perception during early human brain development. PMID:23789919

Arichi, T; Gordon-Williams, R; Allievi, A; Groves, AM; Burdet, E; Edwards, AD

2013-01-01

203

Magnetic resonance imaging of the child's brain  

Microsoft Academic Search

The most significant difference between magnetic resonance imaging (MRI) and computed tomography (CT) is that the former graphic representation of the cerebrospinal axis and its structures does not use ionizing radiation or the injection of contrast material. The physical principles of MRI and the very characteristic appearances of some pathological processes common in children require special study. Low-proton density areas

Beverly L. Hershey; Robert A. Zimmerman

1986-01-01

204

Nuclear magnetic resonance technology for medical studies  

Microsoft Academic Search

Nuclear magnetic resonance proton imaging provides anatomical definition of normal and abnormal tissues with a contrast and detection sensitivity superior to those of x-ray computed tomography in the human head and pelvis and parts of the cardiovascular and musculoskeletal systems. Recent improvements in technology should lead to advances in diagnostic imaging of the breast and regions of the abdomen. Selected-region

T. F. Budinger; P. C. Lauterbur

1984-01-01

205

Magnetic Resonance Connectome Automated Pipeline: An Overview  

Microsoft Academic Search

This article presents a novel, tightly integrated pipeline for estimating a connectome. The pipeline utilizes magnetic resonance (MR) imaging (MRI) data to produce a high-level estimate of the structural connectivity in the human brain. The MR connectome automated pipeline (MRCAP) is efficient, and its modular construction allows researchers to modify algorithms to meet their specific requirements. The pipeline has been

William R. Gray; John A. Bogovic; Joshua T. Vogelstein; Bennett A. Landman; Jerry L. Prince; R. Jacob Vogelstein

2012-01-01

206

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

207

Imaging Intelligence with Proton Magnetic Resonance Spectroscopy  

ERIC Educational Resources Information Center

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

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

2009-01-01

208

Nuclear magnetic resonance studies of biological molecules  

Microsoft Academic Search

A number of biological systems are investigated using a variety of nuclear magnetic resonance (NMR) techniques. The first two studies are applications of the technique to systems in solution. Proton NMR and lanthanide shift agents are used to determine the outside to inside ratio of lipids in large unilamellar vesicles produced by the method of reverse-phase evaporation. The observed ratio

1985-01-01

209

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

210

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

211

ORIGINAL ARTICLE Magnetic Resonance Imaging and Head  

E-print Network

, longitudinal HC data were examined from birth to age 3 years in 113 children with autism and 189 local controlORIGINAL ARTICLE Magnetic Resonance Imaging and Head Circumference Study of Brain Size in Autism the neuroanatomical basis of autism is not yet known, evidence suggests that brain enlarge- ment may be characteristic

Gerig, Guido

212

Magnetic Resonance Imaging of coarse sediment  

Microsoft Academic Search

Non-destructive observation methods for coarse sediments are usually limited to two dimensions, for instance in opened cores or at the surface. We report a trial of a promising new method for three-dimensional imaging of gravelly sediments: Magnetic Resonance Imaging (MRI). MRI maps contrasts in density and relaxation properties of protons, which are very different for sediment and water in the

Maarten G. Kleinhans; Cécile R. L. P. N. Jeukens; Chris J. G. Bakker; Roy M. Frings

2008-01-01

213

Techniques for Automatic Magnetic Resonance Image Classification  

Microsoft Academic Search

Designing and developing automatic techniques for magnetic resonance images (MR) for data analysis is very challenging. One popular and public available method, FAST (FMRIB Automatic Segmentation Tool) has been widely used for automatic brain tissue segmentation for this purpose. This paper investigates limitations of this software algorithm on implementation and further develops a new approach to automatic MR brain tissue

Hsian-Min Chen; Shih-Yu Chen; Jyh Wen Chai; Clayton Chi-Chang Chen; Chao-Cheng Wu; Yen-Chieh Ouyang; Ching Tsorng Tsai; Ching-Wen Yang; San-Kan Lee; Chein-I Chang

2010-01-01

214

Proton Magnetic Resonance Spectrum of Propane  

Microsoft Academic Search

Exact proton magnetic resonance eigenspectra of the spin Hamiltonian are calculated for a system containing one group of six identical protons and one group of two identical protons. The method of calculation considers each group of identical protons as a composite ``particle'' with fixed total spin, and does not require determination of the explicit form of the zero-order eigenfunctions. The

Donald R. Whitman; Lars Onsager; Martin Saunders; Hubert E. Dubb

1960-01-01

215

Small-Volume Nuclear Magnetic Resonance Spectroscopy  

Microsoft Academic Search

Nuclear magnetic resonance (NMR) spectroscopy is one of the most information-rich analytical techniques available. However, it is also inherently insensitive, and this drawback precludes the application of NMR spectroscopy to mass- and volume-limited samples. We review a particular approach to increase the sensitivity of NMR experiments, namely the use of miniaturized coils. When the size of the coil is reduced,

Raluca M. Fratila; Aldrik H. Velders

2011-01-01

216

Proton Magnetic Resonance Spectroscopy of Hydrocephalic Infants  

Microsoft Academic Search

Objective: The authors present the first report evaluating neonates with chronic hydrocephalus using proton magnetic resonance spectroscopy (1H MRS). The goals of the study were (1) to determine absolute brain metabolite concentrations in premature infants and neonates with hydrocephalus and age-matched controls, (2) conduct an initial survey of potential biochemical abnormalities of the newborn hydrocephalic brain, and (3) determine whether

Sean A. McNatt; J. Gordon McComb; Marvin D. Nelson; Stefan Bluml

2007-01-01

217

Brain Morphometry Using Anatomical Magnetic Resonance Imaging  

ERIC Educational Resources Information Center

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

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

2008-01-01

218

Denoising fMRI Time-series Using Adaptive 3D Smoothing  

Microsoft Academic Search

An adaptive smoothing scheme to denoise functional magnetic resonance imaging (fMRI) time-series is introduced. The method relies on spatial smoothing of fMR images where the coefficients of the smoothing filter are determined on the basis of the correlation among the time- courses followed by the underlying voxels. The scheme is implemented on real fMRI data and is found to efficiently

Mohammed Yakoob Siyal; Syed Muhammad Monir

219

Variability of fMRI activation during a phonological and semantic language task in healthy subjects  

Microsoft Academic Search

Assessing inter-individual variability of functional activations is of practical importance in the use of functional magnetic resonance imaging (fMRI) in a clinical context. In this fMRI study we addressed this issue in 30 right-handed, healthy subjects using rhyme detection (phonologic) and semantic catego- rization tasks. Significant activations, found mainly in the left hemisphere, concerned the inferior frontal gyrus, the superior\\/middle

Mohamed L. Seghier; Alan J. Pegna; Jean-Marie Annoni; Ivan Zimine; Christoph M. Michel; Asaid Khateb

2004-01-01

220

Solving Incrementally the Fitting and Detection Problems in fMRI Time Series  

Microsoft Academic Search

\\u000a We tackle the problem of real-time statistical analysis of functional magnetic resonance imaging (fMRI) data. In a recent\\u000a paper, we proposed an incremental algorithm based on the extended Kalman filter (EKF) to fit fMRI time series in terms of\\u000a a general linear model with autoregressive errors (GLM-AR model). We here improve the technique using a new Kalman filter\\u000a variant specifically

Alexis Roche; Philippe Pinel; Stanislas Dehaene; Jean-baptiste Poline

2004-01-01

221

Analysis of activity in fMRI data using affinity propagation clustering  

Microsoft Academic Search

Clustering analysis is a promising data-driven method for the analysis of functional magnetic resonance imaging (fMRI) data. The huge computation load, however, makes it difficult for the practical use. We use affinity propagation clustering (APC), a new clustering algorithm especially for large data sets to detect brain functional activation from fMRI. It considers all data points as possible exemplars through

Jiang Zhang; Dahuan Li; Huafu Chen; Fang Fang

2011-01-01

222

Cognitive processing in Chinese literate and illiterate subjects: An fMRI study  

Microsoft Academic Search

Functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) were used to map brain activation during language tasks. While previous studies have compared performance between alphabetic literate and illiterate subjects, there have been no such data in Chinese-speaking individuals. In this study, we used fMRI to examine the effects of education on neural activation associated with silent word recognition

Geng Li; Raymond T. F. Cheung; Jia Hong Gao; Tatia M. C. Lee; Li Hai Tan; Peter T. Fox; Clifford R. Jack Jr.; Edward S. Yang

2006-01-01

223

fMRI Data Analysis With Nonstationary Noise Models: A Bayesian Approach  

Microsoft Academic Search

The assumption of noise stationarity in the functional magnetic resonance imaging (fMRI) data analysis may lead to the loss of crucial dynamic features of the data and thus result in inaccurate activation detection. In this paper, a Bayesian approach is proposed to analyze the fMRI data with two nonstationary noise models (the time-varying variance noise model and the fractional noise

Huaien Luo; Sadasivan Puthusserypady

2007-01-01

224

The nature and treatment of stuttering as revealed by fMRI  

Microsoft Academic Search

This article reviews some of our recent functional magnetic resonance imaging (fMRI) studies of stuttering. Using event-related fMRI experiments, we investigated brain activation during speech production. Results of three studies comparing persons who stutter (PWS) and persons who do not stutter (PWNS) are outlined. Their findings point to a region in the right frontal operculum (RFO) that was consistently implicated

Katrin Neumann; Harald A. Euler; Alexander Wolff von Gudenbergc; Anne-Lise Giraud; Heinrich Lanfermann; Volker Gall; Christine Preibisch

2003-01-01

225

Non-white noise in fMRI: Does modelling have an impact?  

Microsoft Academic Search

The sources of non-white noise in Blood Oxygenation Level Dependent (BOLD) functional magnetic resonance imaging (fMRI) are many. Familiar sources include low-frequency drift due to hardware imperfections, oscillatory noise due to respiration and cardiac pulsation and residual movement artefacts not accounted for by rigid body registration. These contributions give rise to temporal autocorrelation in the residuals of the fMRI signal

Torben E. Lund; Kristoffer H. Madsen; Karam Sidaros; Wen-Lin Luo; Thomas E. Nichols

2006-01-01

226

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

227

Understanding Others' Regret: A fMRI Study  

Microsoft Academic Search

Previous studies showed that the understanding of others' basic emotional experiences is based on a ''resonant'' mechanism, i.e., on the reactivation, in the observer's brain, of the cerebral areas associated with those experiences. The present study aimed to investigate whether the same neural mechanism is activated both when experiencing and attending complex, cognitively-generated, emotions. A gambling task and functional-Magnetic-Resonance-Imaging (fMRI)

Nicola Canessa; Matteo Motterlini; Cinzia Di Dio; Daniela Perani; Paola Scifo; Stefano F. Cappa; Giacomo Rizzolatti

2009-01-01

228

Introduction to magnetic resonance imaging  

SciTech Connect

The book is divided into ten chapters covering the history, physics, biologic effects, design of magnets, site selection, relaxation of tissues, MR of the central nervous system, MR of the body, spectroscopy, and the current status of MR imaging. The organization of the book serves as an introduction to MR. The images and drawings are positioned in the text so that the reader does not have to continually turn pages to refer to the numbered figures.

Morgan, C.J.; Hendee, W.R.

1984-01-01

229

Magnetic Resonance Imaging of Brain Function and Neurochemistry  

E-print Network

Magnetic Resonance Imaging of Brain Function and Neurochemistry KAMIL UGURBIL, DAE-SHIK KIM, TIM ANDERSEN, AND GREGOR ADRIANY Invited Paper In the past decade, magnetic resonance imaging (MRI) research approaches to map brain function. This capability, often referred to as functional magnetic resonance imaging

Duong, Timothy Q.

230

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. PMID:24755843

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

2014-01-01

231

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. PMID:19938211

BANDETTINI, PETER A.

2010-01-01

232

Low-frequency fluctuations in the cardiac rate as a source of variance in the resting-state fMRI BOLD signal  

Microsoft Academic Search

Heart rate fluctuations occur in the low-frequency range (<0.1 Hz) probed in functional magnetic resonance imaging (fMRI) studies of resting-state functional connectivity and most fMRI block paradigms and may be related to low-frequency blood-oxygenation-level-dependent (BOLD) signal fluctuations. To investigate this hypothesis, temporal correlations between cardiac rate and resting-state fMRI signal timecourses were assessed at 3 T. Resting-state BOLD fMRI and accompanying

Karin Shmueli; Peter van Gelderen; Jacco A. de Zwart; Silvina G. Horovitz; Masaki Fukunaga; J. Martijn Jansma; Jeff H. Duyn

2007-01-01

233

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

234

A hyperpolarized equilibrium for magnetic resonance  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

235

Infantile Sandhoff's disease: multivoxel magnetic resonance spectrosecopy findings.  

PubMed

Sandhoff's disease is a rare, genetic lysosomal storage disease leading to delayed myelination or demyelination. Although neuroimaging findings in this disease have been reported previously, magnetic resonance spectroscopy findings have not been reported. In this report, we present magnetic resonance imaging and magnetic resonance spectrscopy features of two cases with Sandhoff's disease. Magnetic resonance spectroscopy revealed findings indicating widespread demyelination in both cases and neuroaxonal loss and anaerobic metabolism in the second case. Magnetic resonance spectroscopy could provide useful information in the explanation of the clinical picture of cases with Sandhoff's disease. PMID:12886980

Alkan, Alpay; Kutlu, Ramazan; Yakinci, Cengiz; Sigirci, Ahmet; Aslan, Mehmet; Sarac, Kaya

2003-06-01

236

Resonantly Detecting Axion-Mediated Forces with Nuclear Magnetic Resonance  

NASA Astrophysics Data System (ADS)

We describe a method based on precision magnetometry that can extend the search for axion-mediated spin-dependent forces by several orders of magnitude. By combining techniques used in nuclear magnetic resonance and short-distance tests of gravity, our approach can substantially improve upon current experimental limits set by astrophysics, and probe deep into the theoretically interesting regime for the Peccei-Quinn (PQ) axion. Our method is sensitive to PQ axion decay constants between 109 and 1012 GeV or axion masses between 10-6 and 10-3 eV, independent of the cosmic axion abundance.

Arvanitaki, Asimina; Geraci, Andrew A.

2014-10-01

237

Resonantly detecting axion-mediated forces with nuclear magnetic resonance.  

PubMed

We describe a method based on precision magnetometry that can extend the search for axion-mediated spin-dependent forces by several orders of magnitude. By combining techniques used in nuclear magnetic resonance and short-distance tests of gravity, our approach can substantially improve upon current experimental limits set by astrophysics, and probe deep into the theoretically interesting regime for the Peccei-Quinn (PQ) axion. Our method is sensitive to PQ axion decay constants between 10^{9} and 10^{12}??GeV or axion masses between 10^{-6} and 10^{-3}??eV, independent of the cosmic axion abundance. PMID:25361250

Arvanitaki, Asimina; Geraci, Andrew A

2014-10-17

238

4 Nuclear Magnetic Resonance and MRI February 26, 2008  

E-print Network

that many nuclei have intrinsic angular momentum and magnetic moments ­ this is true of the ground states materials. The proton has a magnetic moment of µp = 1.409 � 10-26 joules per tesla, and the splitting4 Nuclear Magnetic Resonance and MRI February 26, 2008 The technique of nuclear magnetic resonance

Thouless, David

239

Integrated Cantilever Loop Probe for Magnetic Resonance Force Microscopy  

Microsoft Academic Search

The measurement of magnetic fields, especially at the nanoscale, has become an issue of considerable interest. Applications include quantum computing, data storage, and magnetic resonance imaging (MRI). At the interface between conventional atomic force microscopy and MRI lies magnetic resonance force microscopy. Radio frequency (RF) waves excite electrons in a sample, and a magnetic cantilever probe can image a slice

Douglas Lagally

2005-01-01

240

Principles of imaging by nuclear magnetic resonance  

SciTech Connect

Imaging by nuclear magnetic resonance (NMR) is a new modality for obtaining anatomic data. Magnetic field gradients are used to obtain spatial information. The advantages of NMR imaging include the ability to obtain images in multiple orientations (coronal, sagittal, and transverse), absence of ionizing radiation and the potential to obtain chemical information. NMR images of the central nervous system have been equal to those of TCT, and in some cases superior. The utility of NMR imaging is yet to be determined, although preliminary findings are encouraging.

Koutcher, J.A.; Burt, C.T.

1984-03-01

241

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

242

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. PMID:21691445

Skup, Martha

2010-01-01

243

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. PMID:22655113

Skup, Martha

2011-01-01

244

Diffusion tensor magnetic resonance image regularization  

Microsoft Academic Search

As multi-dimensional complex data become more common, new regularization schemes tailored to those data are needed. In this paper we present a scheme for regularising diffusion tensor magnetic resonance (DT-MR) data, and more generally multi-dimen- sional data defined by a direction map and one or several magnitude maps. The scheme is divided in two steps. First, a variational method is

Olivier Coulon; Daniel C. Alexander; Simon R. Arridge

2004-01-01

245

Magnetic Resonance Imaging Studies of Cigarette Smoking  

Microsoft Academic Search

This chapter reviews studies that have applied magnetic resonance imaging (MRI) toward a better understanding of the neurobiological\\u000a correlates and consequences of cigarette smoking and nicotine dependence. The findings demonstrate that smokers differ from\\u000a nonsmokers in regional brain structure and neurochemistry, as well as in activation in response to smoking-related stimuli\\u000a and during the execution of cognitive tasks. We also

Allen Azizian; John Monterosso; Joseph O'Neill; Edythe D. London

246

Magnetic resonance imaging of septic sacroiliitis  

Microsoft Academic Search

Five cases of septic sacroiliitis diagnosed by magnetic resonance imaging (MRI) are presented. Imaging was performed between\\u000a 2 and 14 days after onset of symptoms and consisted of varying combinations of coronal short tau inversion recovery (STIR),\\u000a axial T2-weighted spin echo (SE), and coronal and axial pre- and postcontrast T1-weighted SE scans. Abnormalities included\\u000a demonstration of sacroiliac joint effusions, bone

K. Sandrasegaran; A. Saifuddin; A. Coral; W. P. Butt

1994-01-01

247

Protocols in sports magnetic resonance imaging.  

PubMed

Magnetic resonance imaging, with its multiplanar imaging capability and superior soft-tissue contrast, has become the preferred method for imaging sports-related injuries. Advances in gradient technology, receiver coils, and imaging software have allowed the imaging of the injured athlete to take place quickly and at high resolution. Understanding the tissues being imaged, the underlying anatomy, and the capabilities of today's scanners is crucial to the design of intelligent and efficient protocols. PMID:12606866

Gold, Garry E; Hargreaves, Brian A; Beaulieu, Christopher F

2003-02-01

248

Magnetic Resonance Imaging of the Kidney  

Microsoft Academic Search

\\u000a This chapter describes the correct imaging technique for the magnetic resonance (MR) examination of the kidney, from the fundamental\\u000a morphologic sequences to the MR urography sequences up to diffusion sequences. The basic MR features of vascular and infectious\\u000a renal diseases and solid benign and malignant renal tumors up to the cystic renal tumors are described. The advanced applications\\u000a of the

Maria Assunta Cova; Marco Cavallaro; Paola Martingano; Maja Ukmar

249

Magnetic Resonance Imaging of Hepatocellular Carcinoma  

Microsoft Academic Search

In hepatocellular carcinomas (HCCs), T1 shortening occurs due to internal protein, fat, copper, iron, hypercellularity, or a combination thereof. T1-weighted magnetic resonance imaging (MRI) is obtained with a non-fat-suppressed phase shift [in- (4 ms) and opposed- (2 ms) phase] gradient-echo sequence. Internal fat deposition is often (36%) seen in well-differentiated HCCs between 1.1 and 1.5 cm in size. T2-weighted MRI

Masayuki Kanematsu; Hiroshi Kondo; Satoshi Goshima; Yusuke Tsuge; Haruo Watanabe

2008-01-01

250

Adaptive Fuzzy Segmentation of Magnetic Resonance Images  

Microsoft Academic Search

An algorithm is presented for the fuzzy segmentation of two and three-dimensionalmultispectral magnetic resonance (MR) images that have been corrupted by intensity inhomogeneities,also known as shading artifacts. The algorithm is an extension of the two-dimensionaladaptive fuzzy C-means algorithm (2-D AFCM) presented in previous work by the authors. Thisalgorithm models the intensity inhomogeneities as a gain field that causes image intensities

Dzung L. Pham; Jerry L. Prince

1999-01-01

251

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

252

Magnetic resonance imaging outcomes from a comprehensive magnetic resonance study of children with fetal alcohol spectrum disorders  

PubMed Central

Background Magnetic resonance (MR) technology offers non-invasive 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 abnormalities could be identified, and distinguish diagnostic subclassifications across the spectrum. The four study groups included: 1. FAS/Partial FAS; 2. Static Encephalopathy/Alcohol Exposed (SE/AE); 3. Neurobehavioral Disorder/Alcohol Exposed (ND/AE) as diagnosed with the FASD 4-Digit Code; and 4. healthy peers with no prenatal alcohol exposure. Presented here are the MRI assessments used to compare the sizes of brain regions between the four groups. The neuropsychological/behavioral, MRS, and fMRI outcomes are reported separately. Results Progressing across the four study groups from Controls to ND/AE to SE/AE to FAS/PFAS, the mean absolute size of the total brain, frontal lobe, caudate, putamen, hippocampus, cerebellar vermis, and corpus callosum length decreased incrementally and significantly. The FAS/PFAS group (the only group with the 4-Digit FAS facial phenotype) had disproportionately smaller frontal lobes relative to all other groups. The FAS/PFAS and SE/AE groups (the two groups with the most severe CNS dysfunction) had disproportionately smaller caudate regions relative to the ND/AE and Control groups. The prevalence of subjects in the FAS/PFAS, SE/AE, and ND/AE groups that had one or more brain regions, two or more standard deviations below the mean size observed in the Control group was78%, 58%, and 43%, respectively . Significant correlations were observed between size of brain regions and level of prenatal alcohol exposure, magnitude of FAS facial phenotype, and level of CNS dysfunction. Conclusions MRI provided further validation that ND/AE, SE/AE, and FAS/PFAS, as defined by the FASD 4-Digit Code, are three clinically distinct and increasingly more affected diagnostic subclassifications under the umbrella of FASD. Neurostructural abnormalities are present across the spectrum. MRI could importantly augment diagnosis of conditions under the umbrella of FASD, once population-based norms for structural development of the human brain are established. PMID:19572986

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

2011-01-01

253

Function Biomedical Informatics Research Network Recommendations for Prospective Multi-Center Functional Magnetic Resonance Imaging Studies  

PubMed Central

This report provides practical recommendations for the design and execution of Multi-Center functional Magnetic Resonance Imaging (MC-fMRI) studies based on the collective experience of the Function Biomedical Informatics Research Network (FBIRN). The paper was inspired by many requests from the fMRI community to FBIRN group members for advice on how to conduct MC-fMRI studies. The introduction briefly discusses the advantages and complexities of MC-fMRI studies. Prerequisites for MC-fMRI studies are addressed before delving into the practical aspects of carefully and efficiently setting up a MC-fMRI study. Practical multi-site aspects include: (1) establishing and verifying scan parameters including scanner types and magnetic fields, (2) establishing and monitoring of a scanner quality program, (3) developing task paradigms and scan session documentation, (4) establishing clinical and scanner training to ensure consistency over time, (5) developing means for uploading, storing, and monitoring of imaging and other data, (6) the use of a traveling fMRI expert and (7) collectively analyzing imaging data and disseminating results. We conclude that when MC-fMRI studies are organized well with careful attention to unification of hardware, software and procedural aspects, the process can be a highly effective means for accessing a desired participant demographics while accelerating scientific discovery. PMID:22314879

Glover, Gary H.; Mueller, Bryon A.; Turner, Jessica A.; van Erp, Theo G.M.; Liu, Thomas T.; Greve, Douglas N.; Voyvodic, James T.; Rasmussen, Jerod; Brown, Gregory G.; Keator, David B.; Calhoun, Vince D.; Lee, Hyo Jong; Ford, Judith M.; Mathalon, Daniel H.; Diaz, Michele; O'Leary, Daniel S.; Gadde, Syam; Preda, Adrian; Lim, Kelvin O.; Wible, Cynthia G.; Stern, Hal S.; Belger, Aysenil; McCarthy, Gregory; Ozyurt, Burak; Potkin, Steven G.

2011-01-01

254

Study on the regulatory effect of electro-acupuncture on Hegu point (LI4) in cerebral response with functional magnetic resonance imaging  

Microsoft Academic Search

Objective  To study, through blood oxygen level dependent functional magnetic resonance imaging (BOLD fMRI), the cerebral activated areas\\u000a evoked by electro-acupuncturing (EA) the right Hegu point (LI4) or non-acupoint points on the face, and through comparing\\u000a their similarities and differences, to speculate on the specific cerebral areas activated by stimulating LI4, for exploring\\u000a the mechanism of its effect in potential clinical

Wei Wang; Ling Liu; Xin Zhi; Jin-bai Huang; Ding-xi Liu; Hua Wang; Xiang-quan Kong; Hai-bo Xu

2007-01-01

255

Nuclear Magnetic Resonance: Portable and integrated Lead: P. Poulichet.  

E-print Network

Nuclear Magnetic Resonance: Portable and integrated Lead: P. Poulichet. Permanent members: L. Rousseau, A. Fakri. Associated researchers: C. Delabie, A. Exertier. Portable Nuclear Magnetic Resonance : our work in the field of nuclear magneto resonance is focused on the design and the realization

Baudoin, Geneviève

256

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

257

Measurement of AC magnetic field distribution using magnetic resonance imaging.  

PubMed

Electric currents are applied to body in numerous applications in medicine such as electrical impedance tomography, cardiac defibrillation, electrocautery, and physiotherapy. If the magnetic field within a region is measured, the currents generating these fields can be calculated using the curl operator. In this study, magnetic fields generated within a phantom by currents passing through an external wire is measured using a magnetic resonance imaging (MRI) system. A pulse sequence that is originally designed for mapping static magnetic field inhomogeneity is adapted. AC current in the form of a burst sine wave is applied synchronously with the pulse sequence. The frequency of the applied current is in the audio range with an amplitude of 175-mA rms. It is shown that each voxel value of sequential images obtained by the proposed pulse sequence is modulated similar to a single tone broadband frequency modulated (FM) waveform with the ac magnetic field strength determining the modulation index. An algorithm is developed to calculate the ac magnetic field intensity at each voxel using the frequency spectrum of the voxel signal. Experimental results show that the proposed algorithm can be used to calculate ac magnetic field distribution within a conducting sample that is placed in an MRI system. PMID:9368117

Ider, Y Z; Muftuler, L T

1997-10-01

258

Analysis of fMRI Data Using an Integrated Principal Component Analysis and Supervised Affinity Propagation Clustering Approach  

Microsoft Academic Search

Clustering analysis is a promising data-driven method for analyzing functional magnetic resonance imaging (fMRI) time series data. The huge computational load, however, creates practical difficulties for this technique. We present a novel approach, integrating principal component analysis (PCA) and su- pervised affinity propagation clustering (SAPC). In this method, fMRI data are initially processed by PCA to obtain a prelimi- nary

Jiang Zhang; Xianguo Tuo; Zhen Yuan; Wei Liao; Huafu Chen

2011-01-01

259

Modeling of regional dynamic CO2 reactivity in respiratory related brain areas using BOLD fMRI  

Microsoft Academic Search

The cerebrovascular bed is very sensitive to CO2 changes, particularly the areas responsible for generation and control of respiratory rhythm. We have used BOLD functional magnetic resonance imaging (fMRI) and externally induced CO2 challenges that stimulate respiration, to identify respiratory areas in-vivo in humans and to quantify the dynamic effects of CO2 on the BOLD fMRI signal (dynamic CO2 reactivity).

G. D. Mitsis; A. K. Harvey; S. Dirckx; S. D. Mayhew; R. Rogers; I. Tracey; R. G. Wise; K. Pattinson

2008-01-01

260

Effect of Acupuncture on the Brain in Children With Spastic Cerebral Palsy Using Functional Neuroimaging (fMRI)  

Microsoft Academic Search

We study the effect of acupuncture on brain activation patterns in children with cerebral palsy using functional magnetic resonance imaging (fMRI). fMRI of the whole brain was performed in 11 children with cerebral palsy and 10 healthy children during stimulation of a common acupoint in Traditional Medicine [Liv3 (Taichong)] on the left foot. We use both twisting and nontwisting methods

Yun Wu; Zhen Jin; Ke Li; Zhong-Li Lu; Virginia Wong; Tong-Li Han; Hua Zheng; Opher Caspi; Gang Liu; Ya-Wei Zeng; Li-Ping Zou

2008-01-01

261

The roles of changes in deoxyhemoglobin concentration and regional cerebral blood volume in the fMRI BOLD signal  

Microsoft Academic Search

To study the behavior of cerebral physiological parameters and to further the understanding of the functional magnetic resonance imaging (fMRI) blood-oxygen-level-dependent (BOLD) effect, multisource frequency-domain near-infrared and BOLD fMRI signals were recorded simultaneously during motor functional activation in humans. From the near-infrared data information was obtained on the changes in cerebral blood volume and oxygenation. To relate our observations to

Vlad Toronov; Scott Walker; Rajarsi Gupta; Jee H Choi; Enrico Gratton; Dennis Hueber; Andrew Webb

2003-01-01

262

A Multivariate Approach to Estimate Complexity of FMRI Time Series  

E-print Network

, multivariate entropy, fMRI data. 1 Introduction Traditionally, data analysis in fMRI (functional magnetic indispensable in thorough fMRI data analysis. Dhamala et al. (2002) used the correlation dimension to estimate that constrain the usefulness of this measure for the analysis of fMRI data. Here, we propose a new method

263

Pulsed Nuclear Magnetic Resonance: Spin Echoes MIT Department of Physics  

E-print Network

Pulsed Nuclear Magnetic Resonance: Spin Echoes MIT Department of Physics (Dated: February 5, 2014) In this experiment, the phenomenon of Nuclear Magnetic Resonance (NMR) is used to determine the magnetic moments-factor in atomic spectroscopy and is given by g = (µ/µN )/I, (2) and µN is the nuclear magneton, e /2mp

Seager, Sara

264

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

265

New magnetic resonance imaging methods in nephrology  

PubMed Central

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

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

2013-01-01

266

Cell tracking using magnetic resonance imaging  

PubMed Central

Cell tracking by in vivo magnetic resonance imaging (MRI) requires strategies of labelling the cells with MRI contrast agents. The principal routes to achieve efficient cell labelling for neurological applications are discussed with methodological advantages and caveats. Beyond temporo-spatial localization of labelled cells, the investigation of functional cell status is of great interest to allow studies of functional cell dynamics. The two major approaches to reach this goal, use of responsive contrast agents and generation of transgenic cell lines, are discussed. PMID:17690140

Hoehn, Mathias; Wiedermann, Dirk; Justicia, Carles; Ramos-Cabrer, Pedro; Kruttwig, Klaus; Farr, Tracy; Himmelreich, Uwe

2007-01-01

267

Magnetic resonance imaging features of breast leukemia.  

PubMed

Breast leukemia is extremely rare. Only 7 other reports describe its magnetic resonance (MR) imaging findings. This report describes a case of breast leukemia presenting as isolated intramammary leukemic relapse in the breasts after complete remission of acute myeloid leukemia. Dynamic contrast-enhanced MR imaging showed diffuse heterogeneous non-mass-like enhancement in one breast and a diffuse irregular heterogeneously enhancing mass in the other. Previous reports of MR imaging findings in breast leukemia have included only mass-like lesions; hence, the finding reported here is uncommon. PMID:24172785

Kim, Suk Jung

2013-12-25

268

Cardiomyopathies: focus on cardiovascular magnetic resonance  

PubMed Central

Cardiomyopathies (CMPs) are a group of often inherited diseases characterised by abnormalities and associated dysfunction of heart muscle. In the past decade, cardiovascular magnetic resonance (CMR) has emerged as a powerful tool in their assessment, providing data that are complementary to other aspects of clinical evaluation. Key advantages of CMR are three-dimensional visualisation of the heart and its relationship to thoracic structures; gold-standard quantification of cardiac volumes and function, which can safely be repeated over time (no ionising radiation is involved); and tissue characterisation to detect focal scar and fatty infiltration. This paper reviews the role of CMR in the clinical assessment of patients with CMPs. PMID:22723536

Quarta, G; Sado, D M; Moon, J C

2011-01-01

269

Magnetic resonance imaging of the hip.  

PubMed

Standard magnetic resonance imaging (MRI) as well as MR arthrography (MRA) have been important diagnostic tools to assess for a spectrum of clinical presentations related to the hip. MRA has allowed the radiologist to closely examine intracapsular structures such as the acetabular labrum. In this article, we provide a general review of soft tissue and osseous anatomy of hips, especially focusing on the MR appearances of the acetabular labrum and the osseous morphology of the greater trochanter and ischial tuberosity with their muscle and tendon attachments. In addition, current topics in recent literature will be discussed such as femoroacetabular impingement (FAI) and rotator cuff tears of the hip. PMID:18183574

Hong, Raymond J; Hughes, Tudor H; Gentili, Amilcare; Chung, Christine B

2008-03-01

270

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. PMID:22559053

2012-01-01

271

Magnetic levitation of metamaterial bodies enhanced with magnetostatic surface resonances  

NASA Astrophysics Data System (ADS)

We propose that macroscopic objects built from negative-permeability metamaterials may experience resonantly enhanced magnetic force in low-frequency magnetic fields. Resonant enhancement of the time-averaged force originates from magnetostatic surface resonances (MSRs), which are analogous to the electrostatic resonances of negative-permittivity particles, well known as surface plasmon resonances in optics. We generalize the classical problem of the MSR of a homogeneous object to include anisotropic metamaterials and consider the most extreme case of anisotropy, where the permeability is negative in one direction but positive in the others. It is shown that deeply subwavelength objects made of such indefinite (hyperbolic) media exhibit a pronounced magnetic dipole resonance that couples strongly to uniform or weakly inhomogeneous magnetic field and provides strong enhancement of the magnetic force, enabling applications such as enhanced magnetic levitation.

Urzhumov, Yaroslav; Chen, Wenchen; Bingham, Chris; Padilla, Willie; Smith, David R.

2012-02-01

272

Resonant microwave cavity for 8.512 GHz optically detected electron spin resonance with simultaneous nuclear magnetic resonance  

E-print Network

Resonant microwave cavity for 8.5­12 GHz optically detected electron spin resonance with simultaneous nuclear magnetic resonance J. S. Colton1,a and L. R. Wienkes2 1 Department of Physics online 16 March 2009 We present a newly developed microwave resonant cavity for use in optically detected

Hart, Gus

273

The Development of Event-Related fMRI Designs  

PubMed Central

The diversity of experimental designs that can be used with functional magnetic resonance imaging (fMRI) has played a key role in its widespread application to studies of human cognition. This flexibility is possible because the fMRI response to external stimuli is remarkably well approximated as the response of a linear time variant system. The experimental demonstration of this property provided the foundation for the development of event-related designs, in which the fMRI response is modeled as the linear summation of the hemodynamic response to discrete events. Building upon prior work from the fields of engineering, neuroscience, and statistics, researchers in the field have created a rich collection of event-related designs and developed a rigorous theoretical framework for characterizing and optimizing the performance of designs. Ongoing challenges include the optimization of designs in the presence of experimental constraints and the development of more time-efficient optimization algorithms. PMID:22037002

Liu, Thomas T.

2011-01-01

274

Fano resonance generated by magnetic scatterer in micro metal slit  

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

275

IMPROVING MAGNETIC RESONANCE RESOLUTION WITH SUPERVISED LEARNING  

PubMed Central

Despite ongoing improvements in magnetic resonance (MR) imaging (MRI), considerable clinical and, to a lesser extent, research data is acquired at lower resolutions. For example 1 mm isotropic acquisition of T1-weighted (T1-w) Magnetization Prepared Rapid Gradient Echo (MPRAGE) is standard practice, however T2-weighted (T2-w)—because of its longer relaxation times (and thus longer scan time)—is still routinely acquired with slice thicknesses of 2–5 mm and in-plane resolution of 2–3 mm. This creates obvious fundamental problems when trying to process T1-w and T2-w data in concert. We present an automated supervised learning algorithm to generate high resolution data. The framework is similar to the brain hallucination work of Rousseau, taking advantage of new developments in regression based image reconstruction. We present validation on phantom and real data, demonstrating the improvement over state-of-the-art super-resolution techniques.

Jog, Amod; Carass, Aaron; Prince, Jerry L.

2014-01-01

276

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

277

Infrared oculography—validation of a new method to monitor startle eyeblink amplitudes during fMRI  

Microsoft Academic Search

Amplitude modulation of the eyeblink component of the startle response is a commonly used index for the emotional state of an organism. The use of electromyography (EMG) to determine startle eyeblink amplitudes during functional magnetic resonance imaging (fMRI) is limited as interactions between strong switching magnetic fields, radio pulses and electrodes introduce large artefacts in EMG recordings. We demonstrate a

Silke Anders; Nikolaus Weiskopf; Dorothee Lule; Niels Birbaumer

2004-01-01

278

Science Drivers and Technical Challenges for Advanced Magnetic Resonance  

SciTech Connect

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

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

2013-03-07

279

[Lie detection and mind reading: is there a use for fMRI?: A critical survey and reflection].  

PubMed

Great efforts have been made in recent years to use functional magnetic resonance imaging (fMRI) in the context of lie detection. In the present paper the pros and cons of such an approach are analyzed and critically discussed.Both epistemological and methodical considerations have shown that all attempts to derive mental states from fMRI findings ("reverse inference") are not valid. Consequently, fMRI scans cannot reveal a person's thoughts and whether (s)he is lying or telling the truth. PMID:20162411

Ruchsow, M; Hermle, L; Kober, M

2010-09-01

280

Methods for chemical exchange saturation transfer magnetic resonance imaging  

E-print Network

Chemical exchange saturation transfer (CEST) is a relatively new magnetic resonance imaging (MRI) acquisition technique that generates contrast dependent on tissue microenvironment, such as protein concentration and ...

Scheidegger, Rachel Nora

2013-01-01

281

Prospects for neutron probed magnetic resonance imaging  

SciTech Connect

The information gained from magnetic resonance imaging has provided useful insight into many insulators. Extending this technique to conductors requires an alternative means of spin manipulation besides electromagnetic radiation. A method to use neutron measurement of the Zeeman splitting to measure the relaxation time is described. The Zeeman splitting is observed by a neutron spectrometer as an incoherent signal with an energy transfer equal to the Zeeman energy. This energy scale is so small that fields in excess of 15 T are required to sufficiently separate this line from other incoherent processes. Once the Zeeman splitting is observed, a perturbation of the system is required to enable measurement of the nuclear spin relaxation time; the physical quantity measured in a Nuclear Magnetic Resonance experiment. The proposed perturbation is a pulsed field of 10 T. The relaxation of the Zeeman splitting back to the 15 T condition is then recorded as a function of time. The resultant data is the aforementioned measure of the relaxation time. With the ability to measure the relaxation times the image map can be created by rastering the sample with respect to the beam.

Granroth, Garrett E [ORNL

2009-01-01

282

Magnetic resonance imaging in acute mastoiditis  

PubMed Central

Background In cases of suspected mastoiditis, imaging is used to evaluate the extent of mastoid destruction and possible complications. The role of magnetic resonance imaging (MRI) in mastoiditis has not been systematically evaluated. Purpose To assess the diagnostic performance of MRI in patients with suspected acute mastoiditis. Material and Methods Twenty-three patients with suspected acute mastoiditis were included in this retrospective study (15 boys, 8 girls; mean age, 2 years 11 months). All patients were examined on a 1.5?T MRI system. The MRI examination included both enhanced and non-enhanced turbo spin echo (TSE), diffusion-weighted images, and venous time-of-flight magnetic resonance angiography (TOF MRA) for the evaluation of the venous sinuses. Surgical findings, as well as clinical and imaging follow-up were used as the standard of reference. The sensitivity and accuracy of MRI for mastoiditis and subperiosteal abscesses was calculated. Results Twenty (87%) of 23 patients had mastoiditis, and 12 (52%) of 23 patients had a subperiosteal abscess in addition to mastoiditis. Mastoiditis and subperiosteal abscesses were identified by MRI in all cases. Sensitivity for mastoiditis was 100%, specificity was 66%, and accuracy was 86%. Sensitivity for subperiosteal abscesses was 100% and accuracy was 100%. Conclusion Multiparametric MRI has high accuracy for mastoiditis and subperiosteal abscesses. PMID:24778805

Kitzler, Hagen H; Gudziol, Volker; Laniado, Michael; Hahn, Gabriele

2014-01-01

283

Volumetric segmentation of magnetic resonance images  

NASA Astrophysics Data System (ADS)

Current computer graphics techniques can generate 3-D views of the human anatomy from magnetic resonance images. These techniques require that the images first be segmented into the various tissue types. However, there has been no fully automated system that can perform this task on a single set of high-resolution 3-D magnetic resonance images. We present a fully automated segmentation algorithm based on the 3-D difference of Gaussians (DOG) filter. A novel method for the classification of regions found by the DOG filter, as well as a correction procedure that detects errors from the DOG filter, is presented. Regions are classified based on the mean gray level of the voxels within closed contours. In previous work, the user had to manually split falsely merged regions. Our automated correction algorithm detects such errors and splits the merged regions. Spatial information is also incorporated to help discriminate between tissues. Encouraging results were obtained with an average of less than five percent error in each image. Integral shading is used to obtain a 3-D rendering of the data set.

Lee, James D.; Rodriguez, Jeffrey J.

1994-09-01

284

Magnetic Resonance Microscopy of the Lung  

NASA Astrophysics Data System (ADS)

The lung presents both challenges and opportunities for study by magnetic resonance imaging (MRI). The technical challenges arise from respiratory and cardiac motion, limited signal from the tissues, and unique physical structure of the lung. These challenges are heightened in magnetic resonance microscopy (MRM) where the spatial resolution may be up to a million times higher than that of conventional MRI. The development of successful techniques for MRM of the lung present enormous opportunities for basic studies of lung structure and function, toxicology, environmental stress, and drug discovery by permitting investigators to study this most essential organ nondestructively in the live animal. Over the last 15 years, scientists at the Duke Center for In Vivo Microscopy have developed techniques for MRM in the live animal through an interdisciplinary program of biology, physics, chemistry, electrical engineering, and computer science. This talk will focus on the development of specialized radiofrequency coils for lung imaging, projection encoding methods to limit susceptibility losses, specialized support structures to control and monitor physiologic motion, and the most recent development of hyperpolarized gas imaging with ^3He and ^129Xe.

Johnson, G. Allan

1999-11-01

285

Magnetic resonance imaging. Application to family practice.  

PubMed Central

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

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

1999-01-01

286

Magnetic resonance imaging of pelvic bone tumors.  

PubMed

The aim of our study was to determine the value of magnetic resonance (MR) imaging in the diagnostic workup of pelvic bone tumors. We retrospectively evaluated the MR findings in 60 pelvic bone tumors. Owing to its high contrast resolution and multiplanar imaging capabilities, MR offers a clear depiction of cortical, medullar or soft tissue involvement, intratumoral necrosis, and relationship to neurovascular structures, and may be considered as the modality of choice for the staging of pelvic bone tumors. Since grading of bone tumors reaches a high accuracy on conventional radiography (CR), the value of MR imaging is rather complementary. Although the role of MR imaging in tissue characterization is mostly limited to recognition of tumoral components, accurate tissue characterization if often possible (e.g. in low-grade chondrosarcoma, eosinophilic granuloma, aneurysmal bone cyst, giant cell tumor, and chordoma). MR imaging in osteochondromas, metastases, and fibrous dysplasia remains of limited value since most of these lesions are well recognized on CR and/or CT. CR remains the first choice examination in diagnosis and grading of bone tumors, but MR imaging has significantly improved staging and tissue characterization in bone tumor imaging. The aim of our study is to determine the value of magnetic resonance (MR) imaging in the diagnostic workup of pelvic bone tumors, i.e. in staging, in differentiating benign from malignant tumors (grading), and in further characterization of tumors or tumoral components. PMID:8647781

De Beuckeleer, L H; De Schepper, A M; Ramon, F

1996-02-01

287

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

288

Purely electric and magnetic dipole resonances in metamaterial dielectric resonators through perturbation theory inspired geometries  

E-print Network

In this paper we describe a methodology for tailoring the design of metamaterial dielectric resonators, which represent a promising path toward low-loss metamaterials at optical frequencies. We first describe a procedure to decompose the far field scattered by subwavelength resonators in terms of multipolar field components, providing explicit expressions for the multipolar far fields. We apply this formulation to confirm that an isolated high-permittivity cube resonator possesses frequency separated electric and magnetic dipole resonances, as well as a magnetic quadrupole resonance in close proximity to the electric dipole resonance. We then introduce multiple dielectric gaps to the resonator geometry in a manner suggested by perturbation theory, and demonstrate the ability to overlap the electric and magnetic dipole resonances, thereby enabling directional scattering by satisfying the first Kerker condition. We further demonstrate the ability to push the quadrupole resonance away from the degenerate dipole ...

Campione, Salvatore; Warne, Larry K; Sinclair, Michael B

2014-01-01

289

Probing thalamic integrity in schizophrenia using concurrent transcranial magnetic stimulation and functional magnetic resonance imaging  

PubMed Central

Context Schizophrenia is a devastating illness with an indeterminate pathophysiology. Several lines of evidence implicate dysfunction in the thalamus, a key node in the distributed neural networks underlying perception, emotion, and cognition. Existing evidence of aberrant thalamic function is based on indirect measures of thalamic activity, but dysfunction has not yet been demonstrated with a causal method. Objective Test the hypothesis that direct physiological stimulation of cortex will produce an abnormal thalamic response in individuals with schizophrenia. Design We stimulated the precentral gyrus with single-pulse transcranial magnetic stimulation (spTMS) and measured the response to this pulse in synaptically-connected regions (thalamus, medial superior frontal cortex [mSFG], insula) using concurrent functional magnetic resonance imaging (fMRI). The mean hemodynamic response from these regions was fit with the sum of two gamma functions and response parameters were compared across groups. Setting Academic research laboratory. Participants Patients with schizophrenia and sex- and age- matched psychiatrically healthy subjects were recruited from the community. Main Outcome Measures Peak amplitude of the thalamic hemodynamic response to spTMS of precentral gyrus. Results spTMS-evoked responses did not differ between groups at the cortical stimulation site. Compared to healthy subjects, schizophrenia patients showed a reduced response to spTMS in the thalamus (P=1.86 × 10?9) and mSFG (P=.02). Similar results were observed in the insula. Sham TMS indicated that these results could not be attributed to indirect effects of TMS coil discharge. Functional connectivity analyses revealed weaker thalamus-mSFG and thalamus-insula connectivity in schizophrenia patients compared to control subjects. Conclusions Individuals with schizophrenia showed reduced thalamic activation in response to direct perturbation delivered to the cortex. These results extend prior work implicating the thalamus in the pathophysiology of schizophrenia and suggest that the thalamus contributes to the patterns of aberrant connectivity characteristic of this disease. PMID:22393203

Guller, Yelena; Ferrarelli, Fabio; Shackman, Alexander J.; Sarasso, Simone; Peterson, Michael J.; Langheim, Frederick J.; Meyerand, Mary E.; Tononi, Giulio; Postle, Bradley R.

2012-01-01

290

Toward brain correlates of natural behavior: fMRI during violent video games  

Microsoft Academic Search

Modern video games represent highly advanced virtual reality simulations and often contain virtual violence. In a significant amount of young males, playing video games is a quotidian activity, making it an almost natural behavior. Recordings of brain activation with functional magnetic resonance imaging (fMRI) during gameplay may reflect neuronal correlates of real-life behavior. We recorded 13 experienced gamers (18 -26

Klaus Mathiak; René Weber

2006-01-01

291

Ready…Go: Amplitude of the fMRI Signal Encodes Expectation of Cue Arrival Time  

Microsoft Academic Search

What happens when the brain awaits a signal of uncertain arrival time, as when a sprinter waits for the starting pistol? And what happens just after the starting pistol fires? Using functional magnetic resonance imaging (fMRI), we have discovered a novel correlate of temporal expectations in several brain regions, most prominently in the supplementary motor area (SMA). Contrary to expectations,

Xu Cui; Chess Stetson; P. Read Montague; David M. Eagleman

2009-01-01

292

A group model for stable multi-subject ICA on fMRI datasets  

Microsoft Academic Search

Spatial Independent Component Analysis (ICA) is an increasingly used data-driven method to analyze functional Magnetic Resonance Imaging (fMRI) data. To date, it has been used to extract sets of mutually correlated brain regions without prior information on the time course of these regions. Some of these sets of regions, interpreted as functional networks, have recently been used to provide markers

G. Varoquaux; S. Sadaghiani; P. Pinel; A. Kleinschmidt; J. B. Poline; B. Thirion

2010-01-01

293

Gender Differences in the Cognitive Control of Emotion: An fMRI Study  

ERIC Educational Resources Information Center

The interaction of emotion and cognition has become a topic of major interest. However, the influence of gender on the interplay between the two processes, along with its neural correlates have not been fully analysed so far. In this functional magnetic resonance imaging (fMRI) study we induced negative emotion using negative olfactory stimulation…

Koch, Kathrin; Pauly, Katharina; Kellermann, Thilo; Seiferth, Nina Y.; Reske, Martina; Backes, Volker; Stocker, Tony; Shah, N. Jon; Amunts, Katrin; Kircher, Tilo; Schneider, Frank; Habel, Ute

2007-01-01

294

The effects of reboxetine on emotional processing in healthy volunteers: an fMRI study  

Microsoft Academic Search

Recent neuropsychological studies in healthy volunteers suggest that antidepressants enhance the processing of positive emotional information. However, the neural substrates underpinning these changes have not been fully elucidated. The current study, therefore, used functional magnetic resonance imaging (fMRI) to map brain systems activated during successful categorization and subsequent recognition of self-referent positive and negative personality characteristics in healthy volunteers following

R Norbury; C E Mackay; P J Cowen; G M Goodwin; C J Harmer

2008-01-01

295

Differences in Processing of Taxonomic and Sequential Relations in Semantic Memory: An fMRI Investigation  

ERIC Educational Resources Information Center

Conceptual knowledge of our world is represented in semantic memory in terms of concepts and semantic relations between concepts. We used functional magnetic resonance imaging (fMRI) to examine the cortical regions underlying the processing of sequential and taxonomic relations. Participants were presented verbal cues and performed three tasks:…

Kuchinke, Lars; van der Meer, Elke; Krueger, Frank

2009-01-01

296

Perception of Biological Motion in Schizophrenia and Healthy Individuals: A Behavioral and fMRI Study  

Microsoft Academic Search

BackgroundAnomalous visual perception is a common feature of schizophrenia plausibly associated with impaired social cognition that, in turn, could affect social behavior. Past research suggests impairment in biological motion perception in schizophrenia. Behavioral and functional magnetic resonance imaging (fMRI) experiments were conducted to verify the existence of this impairment, to clarify its perceptual basis, and to identify accompanying neural concomitants

Jejoong Kim; Sohee Park; Randolph Blake

2011-01-01

297

Event-Related fMRI of Category Learning: Differences in Classification and Feedback Networks  

ERIC Educational Resources Information Center

Eighteen healthy young adults underwent event-related (ER) functional magnetic resonance imaging (fMRI) of the brain while performing a visual category learning task. The specific category learning task required subjects to extract the rules that guide classification of quasi-random patterns of dots into categories. Following each classification…

Little, Deborah M.; Shin, Silvia S.; Sisco, Shannon M.; Thulborn, Keith R.

2006-01-01

298

fMRI Studies of Stroop Tasks Reveal Unique Roles of Anterior and Posterior Brain Systems  

E-print Network

fMRI Studies of Stroop Tasks Reveal Unique Roles of Anterior and Posterior Brain Systems experiments using functional magnetic resonance imaging, we examined the effects of varying task of activation as attentional demands were increased for two Stroop tasks that differed in the task

Banich, Marie T.

299

Segregation of Somatosensory Activation in the Human Rolandic Cortex Using fMRI  

E-print Network

- vide functional magnetic resonance imaging (fMRI) evidence for the functional delineation on the fundus of the central sulcus, the position of area 3a, during the two tasks. Punctate tactile stimu of the digits, activated area 3a, the PreCG (areas 6 and 4), and the PoCG (areas 3b, 1, and 2). These activation

Corkin, Suzanne

300

Functional abnormalities in symptomatic concussed athletes: an fMRI study  

Microsoft Academic Search

Our aim was to quantify with functional magnetic resonance imaging (fMRI) changes in brain activity in concussed athletes and compare the results with those of normal control subjects. Regional brain activations associated with a working memory task were obtained from a group of concussed athletes (15 symptomatic, 1 asymptomatic) and eight matched control subjects, using blood oxygen level dependent (BOLD)

J.-K Chen; K. M Johnston; S Frey; M Petrides; K Worsley; A Ptito

2004-01-01

301

Spatio-temporal fMRI Analysis using Markov Random Fields  

Microsoft Academic Search

Functional magnetic resonance images (fMRI's) pro- vide high-resolution datasets which allow researchers to obtain accurate delineation and sensitive detection of activation areas involved in cognitive processes. To preserve the resolution of this noninvasive technique, refined methods are required in the analysis of the data. In this paper, we first discuss the widely used methods based on a statistical parameter map

Xavier Descombes; Frithjof Kruggel; D. Yves Von Cramon

1998-01-01

302

Motion correction and the use of motion covariates in multiple-subject fMRI analysis  

Microsoft Academic Search

The impact of using motion estimates as covariates of no interest was examined in general linear modeling (GLM) of both block design and rapid event-related functional magnetic resonance imaging (fMRI) data. The purpose of motion correction is to identify and eliminate artifacts caused by task- correlated motion while maximizing sensitivity to true activations. To optimize this process, a combina- tion

Tom Johnstone; Kathleen S. Ores Walsh; Larry L. Greischar; Andrew L. Alexander; Andrew S. Fox; Richard J. Davidson; Terrence R. Oakes

2006-01-01

303

A sparse Bayesian method for determination of flexible design matrix for fMRI data analysis  

Microsoft Academic Search

The construction of a design matrix is critical to the accurate detection of activation regions of the brain in functional magnetic resonance imaging (fMRI). The design matrix should be flexible to capture the unknown slowly varying drifts as well as robust enough to avoid overfitting. In this paper, a sparse Bayesian learning method is proposed to determine a suitable design

Huaien Luo; Sadasivan Puthusserypady

2005-01-01

304

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

305

Bayesian fMRI data analysis with sparse spatial basis function priors  

Microsoft Academic Search

In previous work we have described a spatially regularised General Linear Model (GLM) for the analysis of brain functional Magnetic Resonance Imaging (fMRI) data where Posterior Probability Maps (PPMs) are used to characterise regionally specific effects. The spatial regularisation is defined over regression coefficients via a Laplacian kernel matrix and embodies prior knowledge that evoked responses are spatially contiguous and

Guillaume Flandin; William D. Penny

2007-01-01

306

A role for fMRI in optimizing CNS drug development  

Microsoft Academic Search

Drug development today needs to balance agility, speed and risk in defining the probability of success for molecules, mechanisms and therapeutic concepts. New techniques in functional magnetic resonance imaging (fMRI) promise to be part of a sequence that could transform drug development for disorders of the central nervous system (CNS) by examining brain systems and their functional activation dynamically. The

David Borsook; Lino Becerra; Richard Hargreaves

2006-01-01

307

Generative Embedding for Model-Based Classification of fMRI Data  

Microsoft Academic Search

Decoding models, such as those underlying multivariate classification algorithms, have been increasingly used to infer cognitive or clinical brain states from measures of brain activity obtained by functional magnetic resonance imaging (fMRI). The practicality of current classifiers, however, is restricted by two major challenges. First, due to the high data dimensionality and low sample size, algorithms struggle to separate informative

Kay H. Brodersen; Thomas M. Schofield; Alexander P. Leff; Cheng Soon Ong; Ekaterina I. Lomakina; Joachim M. Buhmann; Klaas E. Stephan

2011-01-01

308

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

309

A Study of Combination fMRI and DTI in A Cognitive Task  

Microsoft Academic Search

Magnetic resonance diffusion tensor imaging (MR-DTI) as a noninvasive technique can investigate the cerebral white matter architecture based on the directional information of diffusion that is related to fiber tract. With the development of DTI technique in recent years, more and more studies of combining fMRI with DTI are used to explore the relationships between functional connectivity and its structural

Tingting Wang; Zifan Cai; Ni Tang; Jie Lu; Li Yao; Xiaojie Zhao

2007-01-01

310

The effect of social content on deductive reasoning: An fMRI study  

Microsoft Academic Search

Psychological studies of deductive reasoning have shown that subjects' performance is affected significantly by the content of the presented stimuli. Specifically, subjects find it easier to reason about contexts and situations with a social content. In the present study, the effect of content on brain activation was investigated with functional magnetic resonance imaging (fMRI) while subjects were solving two versions

Nicola Canessa; Alessandra Gorini; Stefano F. Cappa; Massimo Piattelli-Palmarini; Massimo Danna; Ferruccio Fazio; Daniela Perani

2005-01-01

311

Brain areas underlying visual mental imagery and visual perception: an fMRI study  

Microsoft Academic Search

We used functional magnetic resonance imaging (fMRI) to assess the maximal degree of shared neural processing in visual mental imagery and visual perception. Participants either visualized or saw faint drawings of simple objects, and then judged specific aspects of the drawings (which could only be evaluated properly if they used the correct stimulus). The results document that visual imagery and

Giorgio Ganis; William L Thompson; Stephen M Kosslyn

2004-01-01

312

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

313

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. PMID:24109446

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

2013-01-01

314

Development of a micro nuclear magnetic resonance system  

Microsoft Academic Search

Application of Nuclear Magnetic Resonance (NMR) to on-line\\/in-line control of industrial processes is currently limited by equipment costs and requirements for installation. A superconducting magnet generating strong fields is the most expensive part of a typical NMR instrument. In industrial environments, fringe magnetic fields make accommodation of NMR instruments difficult. However, a portable, low-cost and low-field magnetic resonance system can

Artem Goloshevsky

2004-01-01

315

Classifier ensembles for fMRI data analysis: an experiment  

Microsoft Academic Search

Functional magnetic resonance imaging (fMRI) is becoming a forefront brain–computer interface tool. To decipher brain patterns, fast, accurate and reliable classifier methods are needed. The support vector machine (SVM) classifier has been traditionally used. Here we argue that state-of-the-art methods from pattern recognition and machine learning, such as classifier ensembles, offer more accurate classification. This study compares 18 classification methods

Ludmila I. Kuncheva; Juan J. Rodríguez

2010-01-01

316

Unobtrusive integration of data management with fMRI analysis  

Microsoft Academic Search

This note describes a software utility, called X-batch which addresses two pressing issues typically faced by functional magnetic\\u000a resonance imaging (fMRI) neuroimaging laboratories (1) analysis automation and (2) data management. The first issue is addressed\\u000a by providing a simple batch mode processing tool for the popular SPM software package (http:\\/\\/www.fil.ion. ucl.ac.uk\\/spm\\/;\\u000a Welcome Department of Imaging Neuroscience, London, UK). The second

Andrew V. Poliakov; Xenia Hertzenberg; Eider B. Moore; David P. Corina; George A. Ojemann; James F. Brinkley

2007-01-01

317

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

318

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

319

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

320

Nuclear magnetic resonance studies of lens transparency  

SciTech Connect

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

Beaulieu, C.F.

1989-01-01

321

3D Magnetic Resonance Microscopy of Dehydrated Biological Specimens  

E-print Network

3D Magnetic Resonance Microscopy of Dehydrated Biological Specimens Dissertation zur Erlangung des and Mechatronics ­ 3D Magnetic Resonance Microscopy of Dehydrated Biological Specimens Daniel Mietchen Thesis Dehydration beyond a critical threshold poses a serious threat to most or- ganisms in their active state

Hammerton, James

322

A personal computer-based nuclear magnetic resonance spectrometer  

Microsoft Academic Search

Nuclear magnetic resonance (NMR) spectroscopy using personal computer-based hardware has the potential of enabling the application of NMR methods to fields where conventional state of the art equipment is either impractical or too costly. With such a strategy for data acquisition and processing, disciplines including civil engineering, agriculture, geology, archaeology, and others have the possibility of utilizing magnetic resonance techniques

Constantin Job; Robert M. Pearson; Michael F. Brown

1994-01-01

323

Supine magnetic resonance (MR) mammography in radiotherapy planning  

Microsoft Academic Search

Purpose: Radiotherapy of the breast is normally performed in a supine position, so conventional prone magnetic resonance (MR) mammography is unsuitable for radiotherapy planning purposes. No dedicated supine breast coil is yet available, limiting the application of magnetic resonance imaging (MRI) in this area. A technique has been developed on a 0.2T open scanner to produce breast images suitable for

Sadie Dunne; Amanda Gee

1999-01-01

324

DYNAMICAL RESONANCES AND SSF SINGULARITIES FOR A MAGNETIC SCHRODINGER OPERATOR  

E-print Network

DYNAMICAL RESONANCES AND SSF SINGULARITIES FOR A MAGNETIC SCHR¨ODINGER OPERATOR MAR´IA ANG Subject Classification: 35P25, 35J10, 47F05, 81Q10 Keywords: magnetic Schr¨odinger operators, resonances Schr¨odinger operator H which, from a physics point of view, is the quantum Hamiltonian of a 3D non

Boyer, Edmond

325

Algorithms for the Analysis of 3D Magnetic Resonance Angiography  

E-print Network

Algorithms for the Analysis of 3D Magnetic Resonance Angiography Images Xavier Tizon Centre Magnetic Resonance Angiography Images. Doctoral Thesis ISSN 1401-6230, ISBN 91-576-6700-4 Atherosclerosis- tries. Angiography refers to the group of imaging techniques used through the diagnosis, treatment

Paris-Sud XI, Université de

326

Multispectral analysis of magnetic resonance images.  

PubMed

Magnetic resonance (MR) imaging systems produce spatial distribution estimates of proton density, relaxation time, and flow, in a two dimensional matrix form that is analogous to that of the image data obtained from multispectral imaging satellites. Advanced NASA satellite image processing offers sophisticated multispectral analysis of MR images. Spin echo and inversion recovery pulse sequence images were entered in a digital format compatible with satellite images and accurately registered pixel by pixel. Signatures of each tissue class were automatically determined using both supervised and unsupervised classification. Overall tissue classification was obtained in the form of a theme map. In MR images of the brain, for example, the classes included CSF, gray matter, white matter, subcutaneous fat, muscle, and bone. These methods provide an efficient means of identifying subtle relationships in a multi-image MR study. PMID:3964938

Vannier, M W; Butterfield, R L; Jordan, D; Murphy, W A; Levitt, R G; Gado, M

1985-01-01

327

Magnetic resonance imaging of adolescent disc herniation.  

PubMed

Magnetic resonance imaging (MRI) was used to compare the appearance of the spine in 20 adolescents with proven symptomatic intervertebral disc herniations with that in 20 asymptomatic patients who acted as controls. Abnormality in the signal from the nucleus pulposus of one or more discs was present in all patients, while only four of the 20 controls had any abnormal signals. In all the patients the symptomatic disc produced an abnormal signal and in most a herniated fragment of the nucleus pulposus was identified. Fifteen of the 20 patients had multiple-disc abnormality: six had three abnormal discs and nine had two. This suggests there was an underlying diathesis in patients who later developed disc herniation. PMID:3680327

Gibson, M J; Szypryt, E P; Buckley, J H; Worthington, B S; Mulholland, R C

1987-11-01

328

Magnetic resonance imaging of placenta accreta  

PubMed Central

Placenta accreta (PA) is a severe pregnancy complication which occurs when the chorionic villi (CV) invade the myometrium abnormally. Optimal management requires accurate prenatal diagnosis. Ultrasonography (USG) and magnetic resonance imaging (MRI) are the modalities for prenatal diagnosis of PA, although USG remains the primary investigation of choice. MRI is a complementary technique and reserved for further characterization when USG is inconclusive or incomplete. Breath-hold T2-weighted half-Fourier rapid acquisition with relaxation enhancement (RARE) and balanced steady-state free precession imaging in the three orthogonal planes is the key MRI technique. Markedly heterogeneous placenta, thick intraplacental dark bands on half-Fourier acquisition single-shot turbo spin-echo (HASTE), and disorganized abnormal intraplacental vascularity are the cardinal MRI features of PA. MRI is less reliable in differentiating between different degrees of placental invasion, especially between accreta vera and increta. PMID:24604945

Varghese, Binoj; Singh, Navdeep; George, Regi A.N; Gilvaz, Sareena

2013-01-01

329

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. PMID:23696705

Graff-Radford, Jonathan; Kantarci, Kejal

2013-01-01

330

Magnetic resonance imaging of pancreatitis: An update  

PubMed Central

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

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

2014-01-01

331

Whole body postmortem magnetic resonance angiography.  

PubMed

  Computed tomography (CT) and magnetic resonance (MR) imaging have become important elements of forensic radiology. Whereas the feasibility and potential of CT angiography have long been explored, postmortem MR angiography (PMMRA) has so far been neglected. We tested the feasibility of PMMRA on four adult human cadavers. Technical quality of PMMRA was assessed relative to postmortem CT angiography (PMCTA), separately for each body region. Intra-aortic contrast volumes were calculated on PMCTA and PMMRA with segmentation software. The results showed that technical quality of PMMRA images was equal to PMCTA in 4/4 cases for the head, the heart, and the chest, and in 3/4 cases for the abdomen, and the pelvis. There was a mean decrease in intra-aortic contrast volume from PMCTA to PMMRA of 46%. PMMRA is technically feasible and allows combining the soft tissue detail provided by MR and the information afforded by angiography. PMID:22211886

Ruder, Thomas D; Hatch, Gary M; Ebert, Lars C; Flach, Patricia M; Ross, Steffen; Ampanozi, Garyfalia; Thali, Michael J

2012-05-01

332

Nuclear magnetic resonance imaging of the spine  

SciTech Connect

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

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

1984-01-01

333

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. PMID:22802828

Cywi?ska, Monika A.; Grudzi?ski, Ireneusz P.; Cieszanowski, Andrzej; Bystrzejewski, Micha?; Pop?awska, Magdalena

2011-01-01

334

Small-volume nuclear magnetic resonance spectroscopy.  

PubMed

Nuclear magnetic resonance (NMR) spectroscopy is one of the most information-rich analytical techniques available. However, it is also inherently insensitive, and this drawback precludes the application of NMR spectroscopy to mass- and volume-limited samples. We review a particular approach to increase the sensitivity of NMR experiments, namely the use of miniaturized coils. When the size of the coil is reduced, the sample volume can be brought down to the nanoliter range. We compare the main coil geometries (solenoidal, planar, and microslot/stripline) and discuss their applications to the analysis of mass-limited samples. We also provide an overview of the hyphenation of microcoil NMR spectroscopy to separation techniques and of the integration with lab-on-a-chip devices and microreactors. PMID:21391818

Fratila, Raluca M; Velders, Aldrik H

2011-01-01

335

Small-Volume Nuclear Magnetic Resonance Spectroscopy  

NASA Astrophysics Data System (ADS)

Nuclear magnetic resonance (NMR) spectroscopy is one of the most information-rich analytical techniques available. However, it is also inherently insensitive, and this drawback precludes the application of NMR spectroscopy to mass- and volume-limited samples. We review a particular approach to increase the sensitivity of NMR experiments, namely the use of miniaturized coils. When the size of the coil is reduced, the sample volume can be brought down to the nanoliter range. We compare the main coil geometries (solenoidal, planar, and microslot/stripline) and discuss their applications to the analysis of mass-limited samples. We also provide an overview of the hyphenation of microcoil NMR spectroscopy to separation techniques and of the integration with lab-on-a-chip devices and microreactors.

Fratila, Raluca M.; Velders, Aldrik H.

2011-07-01

336

Magnetic Resonance Microscopy of Mammalian Neurons  

PubMed Central

Magnetic resonance imaging (MRI) is now a leading diagnostic technique. As technology has improved, so has the spatial resolution achievable. In 1986 MR microscopy (MRM) was demonstrated with resolutions in the tens of microns, and is now an established subset of MRI with broad utility in biological and non-biological applications. To date, only large cells from plants or aquatic animals have been imaged with MRM limiting its applicability. Using newly developed microsurface coils and an improved slice preparation technique for correlative histology, we report here for the first time direct visualization of single neurons in the mammalian central nervous system (CNS) using native MR signal at a resolution of 4–8µm. Thus MRM has matured into a viable complementary cellular imaging technique in mammalian tissues. PMID:19286461

Flint, Jeremy J.; Lee, Choong H.; Hansen, Brian; Fey, Michael; Schmidig, Daniel; Bui, Jonathan D.; King, Michael A.; Vestergaard-Poulsen, Peter; Blackband, Stephen J.

2011-01-01

337

Chemical exchange magnetic resonance imaging (CHEMI)  

SciTech Connect

Systems investigated with NMR spectroscopy are sometimes heterogeneous with respect to chemical composition, rates of chemical exchange, and other properties influencing magnetic resonance parameters. A method was developed to spatially encode reaction kinetic information and produce NMR images sensitive to chemical exchange. A modified spin-echo pulse sequence was used to allow chemical shift-selective imaging and chemical exchange encoding. /sup 1/H and /sup 31/P images with microscopic resolution were obtained which yielded chemical exchange as a function of position. Chemical exchange images of the base-catalyzed proton exchange of acetylacetone and of the enzyme-catalyzed /sup 31/P transfer between PCr and ATP were obtained at 8.4 T in phantoms at 360 and 146 MHz, respectively. These images demonstrate a means of investigating kinetic heterogeneity and compartmentalization of reactions that are important in the study of both living and non-living systems.

McFarland, E.W.; Neuringer, L.J.; Kushmerick, M.J.

1988-09-01

338

Cranial magnetic resonance imaging findings in kwashiorkor.  

PubMed

Protein energy malnutrition (PEM) is an important public health problem in the developing countries, although it is becoming uncommon in South West Nigeria. Cerebral changes have been associated with severe PEM. This study evaluated the neurological changes using Magnetic Resonance Imaging (MRI) in Ibadan south west Nigeria. The 5 children evaluated had a median age of 16 months and all the children had brain changes compatible with cerebral atrophy. In addition two of the children had periventricular white matter changes, while one these two had mega cisterna magna in addition. Though this study did not re-evaluate the brains of these children after nutritional rehabilitation, it is possible that changes are reversible as demonstrated in earlier studies. PMID:20128668

Atalabi, Omolola Mojisola; Lagunju, Ikeoluwa Abiola; Tongo, Olukemi Oluwatoyin; Akinyinka, Olusegun Olusina

2010-01-01

339

Myocardial tissue characterization with magnetic resonance imaging.  

PubMed

The availability of an accurate, noninvasive method using cardiac magnetic resonance imaging (MRI) to distinguish microscopic myocardial tissue changes at a macroscopic scale is well established. High-resolution in vivo monitoring of different pathologic tissue changes in the heart is a useful clinical tool for assessing the nature and extent of cardiac pathology. Cardiac MRI utilizes myocardial signal characteristics based on relaxation parameters such as T1, T2, and T2 star values. Identifying changes in relaxation time enables the detection of distinctive myocardial diseases such as cardiomyopathies and ischemic myocardial injury. The presented state-of-the-art review paper serves the purpose of introducing and summarizing MRI capability of tissue characterization in present clinical practice. PMID:24394716

Sharma, Vishal; Binukrishnan, Sukumaran; Schoepf, U Joseph; Ruzsics, Balazs

2014-11-01

340

Two-dimensional nuclear magnetic resonance petrophysics.  

PubMed

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

Sun, Boqin; Dunn, Keh-Jim

2005-02-01

341

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

342

Functional magnetic resonance imaging during emotion recognition in social anxiety disorder: an activation likelihood meta-analysis  

PubMed Central

Background: Social anxiety disorder (SAD) is characterized by abnormal fear and anxiety in social situations. Functional magnetic resonance imaging (fMRI) is a brain imaging technique that can be used to demonstrate neural activation to emotionally salient stimuli. However, no attempt has yet been made to statistically collate fMRI studies of brain activation, using the activation likelihood-estimate (ALE) technique, in response to emotion recognition tasks in individuals with SAD. Methods: A systematic search of fMRI studies of neural responses to socially emotive cues in SAD was undertaken. ALE meta-analysis, a voxel-based meta-analytic technique, was used to estimate the most significant activations during emotional recognition. Results: Seven studies were eligible for inclusion in the meta-analysis, constituting a total of 91 subjects with SAD, and 93 healthy controls. The most significant areas of activation during emotional vs. neutral stimuli in individuals with SAD compared to controls were: bilateral amygdala, left medial temporal lobe encompassing the entorhinal cortex, left medial aspect of the inferior temporal lobe encompassing perirhinal cortex and parahippocampus, right anterior cingulate, right globus pallidus, and distal tip of right postcentral gyrus. Conclusion: The results are consistent with neuroanatomic models of the role of the amygdala in fear conditioning, and the importance of the limbic circuitry in mediating anxiety symptoms. PMID:23335892

Hattingh, Coenraad J.; Ipser, J.; Tromp, S. A.; Syal, S.; Lochner, C.; Brooks, S. J.; Stein, D. J.

2012-01-01

343

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

344

Investigation of high-resolution functional magnetic resonance imaging by means of surface and array radiofrequency coils at 7 T.  

PubMed

In this investigation, high-resolution, 1x1x1-mm(3) functional magnetic resonance imaging (fMRI) at 7 T is performed using a multichannel array head coil and a surface coil approach. Scan geometry was optimized for each coil separately to exploit the strengths of both coils. Acquisitions with the surface coil focused on partial brain coverage, while whole-brain coverage fMRI experiments were performed with the array head coil. BOLD sensitivity in the occipital lobe was found to be higher with the surface coil than with the head array, suggesting that restriction of signal detection to the area of interest may be beneficial for localized activation studies. Performing independent component analysis (ICA) decomposition of the fMRI data, we consistently detected BOLD signal changes and resting state networks. In the surface coil data, a small negative BOLD response could be detected in these resting state network areas. Also in the data acquired with the surface coil, two distinct components of the positive BOLD signal were consistently observed. These two components were tentatively assigned to tissue and venous signal changes. PMID:19261421

van der Zwaag, Wietske; Marques, José P; Hergt, Martin; Gruetter, Rolf

2009-10-01

345

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

346

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. PMID:21331311

Price, Anthony N.; Cheung, King K.; Cleary, Jon O; Campbell, Adrienne E; Riegler, Johannes; Lythgoe, Mark F

2010-01-01

347

Could magnetic resonance provide in vivo histology?  

PubMed Central

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

Dominietto, Marco; Rudin, Markus

2014-01-01

348

Selectivity in multiple quantum nuclear magnetic resonance  

SciTech Connect

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

Warren, W.S.

1980-11-01

349

Multivoxel magnetic resonance spectroscopy in a rhizomelic chondrodysplasia punctata case.  

PubMed

A case of a 5-day-old newborn with rhizomelic chondrodysplasia punctata was investigated with multivoxel magnetic resonance spectroscopy, including chemical shift imaging maps, which disclosed a decrease in the choline peak and the choline signal intensity, respectively, in the right cerebral hemisphere. This is the second report of multivoxel magnetic resonance spectroscopy examination of the brain associated with rhizomelic chondrodysplasia punctata in the literature. Multivoxel magnetic resonance spectroscopy with chemical shift imaging maps has the advantage of obtaining more information in a short period of time, which shortens the duration of anesthesia and its associated risks and complications. We suggest that future efforts be directed to evaluating such patients with multivoxel magnetic resonance spectroscopy instead of single-voxel magnetic resonance spectroscopy. PMID:16225820

Sigirci, Ahmet; Alkan, Alpay; Kutlu, Ramazan; Gülcan, Hande

2005-08-01

350

Thoracic magnetic resonance imaging: pulmonary thromboembolism.  

PubMed

Ongoing technical developments have substantially improved the potential of magnetic resonance imaging (MRI) in the assessment of the pulmonary circulation. These developments includes improved magnet and hardware design, new k-space sampling techniques (ie, parallel imaging), and alternative contrast materials. With these techniques, not only can pulmonary vessels be visualized by MR angiography with high spatial resolution but also the perfusion of the lungs and its changes in relation to pulmonary thromboembolism (PE) can be assessed. Considering venous thromboembolism as a systemic disease, MR venography might be added for the diagnosis of underlying deep venous thrombosis. A unique advantage of MRI over other imaging tests is its potential to evaluate changes in cardiac function as a result of obstruction of the pulmonary circulation, which may have a significant impact on patient monitoring and treatment. Finally, MRI does not involve radiation, which is advantageous, especially in young patients. Over the years, a number of studies have shown promising results not only for MR angiography but also for MRI of lung perfusion and for MR venography. This review article summarizes and discusses the current evidence on pulmonary MRI for patients with suspected PE. PMID:23545949

Fink, Christian; Henzler, Thomas; Shirinova, Aysel; Apfaltrer, Paul; Wasser, Klaus

2013-05-01

351

Cardiac imaging using gated magnetic resonance  

SciTech Connect

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

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

1984-01-01

352

Multiple-mouse Neuroanatomical Magnetic Resonance Imaging  

PubMed Central

The field of mouse phenotyping with magnetic resonance imaging (MRI) is rapidly growing, motivated by the need for improved tools for characterizing and evaluating mouse models of human disease. MRI is an excellent modality for investigating genetically altered animals. It is capable of whole brain coverage, can be used in vivo, and provides multiple contrast mechanisms for investigating different aspects of neuranatomy and physiology. The advent of high-field scanners along with the ability to scan multiple mice simultaneously allows for rapid phenotyping of novel mutations. Effective mouse MRI studies require attention to many aspects of experiment design. In this article, we will describe general methods to acquire quality images for mouse phenotyping using a system that images mice concurrently in shielded transmit/receive radio frequency (RF) coils in a common magnet (Bock et al., 2003). We focus particularly on anatomical phenotyping, an important and accessible application that has shown a high potential for impact in many mouse models at our imaging centre. Before we can provide the detailed steps to acquire such images, there are important practical considerations for both in vivo brain imaging (Dazai et al., 2004) and ex vivo brain imaging (Spring et al., 2007) that should be noted. These are discussed below. PMID:21829155

Cahill, Lindsay S.; Henkelman, R. Mark

2011-01-01

353

Designing Magnetic Resonance Imaging Curriculum for Undergraduates  

NSDL National Science Digital Library

A new hands-on curriculum developed at Vanderbilt University focuses on teaching medical imaging, specifically magnetic resonance imaging(MRI). This material was designed to engage students in real world applications of biomedical engineering through challenge based activities. These activities include homework, quizzes, and hands-on experiments. The materials for each activity are easy to find and can be purchased for under $25. The curriculum begins with a Grand Challenge that presents a medical case in order to interest the students. The challenge questions allow the students to play the role of the patient, technician, and physician. The material was organized in five modules: Electromagnetic Fields and Magnetic Moments, Spin Behavior: Excitation and Relaxation, Spatial Encoding and Detecting Signals, Image Reconstruction, and Image Characteristics. In addition, there are expert interviews that provide the students with multiple perspectives on the information. The material was tested in the summer of 2007 on five students in order to gain feedback, correct errors, and gauge student understanding. Testing showed that the curriculum had a positive impact on student interest in biomedical imaging and resulted in several improvements and additions to the curriculum. During the academic year, the materials will be field-tested at the undergraduate and high school level. Additionally, the materials are being adapted for high school level implementation.

2009-10-29

354

Controlling interactions between highly magnetic atoms with Feshbach resonances.  

PubMed

This paper reviews current experimental and theoretical progress in the study of dipolar quantum gases of ground and meta-stable atoms with a large magnetic moment. We emphasize the anisotropic nature of Feshbach resonances due to coupling to fast-rotating resonant molecular states in ultracold s-wave collisions between magnetic atoms in external magnetic fields. The dramatic differences in the distribution of resonances of magnetic (7)S3 chromium and magnetic lanthanide atoms with a submerged 4f shell and non-zero electron angular momentum is analyzed. We focus on dysprosium and erbium as important experimental advances have been recently made to cool and create quantum-degenerate gases for these atoms. Finally, we describe progress in locating resonances in collisions of meta-stable magnetic atoms in electronic P-states with ground-state atoms, where an interplay between collisional anisotropies and spin-orbit coupling exists. PMID:25221938

Kotochigova, Svetlana

2014-09-01

355

Controlling interactions between highly-magnetic atoms with Feshbach resonances  

E-print Network

This paper reviews current experimental and theoretical progress in the study of dipolar quantum gases of ground and meta-stable atoms with a large magnetic moment. We emphasize the anisotropic nature of Feshbach resonances due to coupling to fast-rotating resonant molecular states in ultracold s-wave collisions between magnetic atoms in external magnetic fields. The dramatic differences in the distribution of resonances of magnetic $^7$S$_3$ chromium and magnetic lanthanide atoms with a submerged 4f shell and non-zero electron angular momentum is analyzed. We focus on Dysprosium and Erbium as important experimental advances have been recently made to cool and create quantum-degenerate gases for these atoms. Finally, we describe progress in locating resonances in collisions of meta-stable magnetic atoms in electronic P states with ground-state atoms, where an interplay between collisional anisotropies and spin-orbit coupling exists.

Kotochigova, Svetlana

2014-01-01

356

Controlling interactions between highly magnetic atoms with Feshbach resonances  

NASA Astrophysics Data System (ADS)

This paper reviews current experimental and theoretical progress in the study of dipolar quantum gases of ground and meta-stable atoms with a large magnetic moment. We emphasize the anisotropic nature of Feshbach resonances due to coupling to fast-rotating resonant molecular states in ultracold s-wave collisions between magnetic atoms in external magnetic fields. The dramatic differences in the distribution of resonances of magnetic 7S3 chromium and magnetic lanthanide atoms with a submerged 4f shell and non-zero electron angular momentum is analyzed. We focus on dysprosium and erbium as important experimental advances have been recently made to cool and create quantum-degenerate gases for these atoms. Finally, we describe progress in locating resonances in collisions of meta-stable magnetic atoms in electronic P-states with ground-state atoms, where an interplay between collisional anisotropies and spin–orbit coupling exists.

Kotochigova, Svetlana

2014-09-01

357

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

358

Model-based fMRI of Category Learning 1 Running head: Model-based fMRI of Category Learning  

E-print Network

resonance imaging (fMRI) analysis technModel-based fMRI of Category Learning 1 Running head: Model-based fMRI of Category Learning Revealed by Model-based fMRI Tyler Davis1 , Bradley C. Love2 , Alison R. Preston2-4 1 Imaging Research

Davis, Tyler

359

Assessment of brain activity during memory encoding in a narcolepsy patient on and off modafinil using normative fMRI data  

Microsoft Academic Search

We present behavioral and functional magnetic resonance imaging (fMRI) findings of a 20-year-old female with narcolepsy who completed a standardized fMRI-adapted face memory task both ‘off’ and ‘on’ modafinil compared to a normative sample (N?=?38). The patient showed poor recognition performance off modafinil (z =??2.03) but intact performance on modafinil (z?=?0.78). fMRI results showed atypical activation during memory encoding off

Mark D. Allen; Dawson W. Hedges; Thomas J. Farrer; Michael J. Larson

2012-01-01

360

Assessment of brain activity during memory encoding in a narcolepsy patient on and off modafinil using normative fMRI data  

Microsoft Academic Search

We present behavioral and functional magnetic resonance imaging (fMRI) findings of a 20-year-old female with narcolepsy who completed a standardized fMRI-adapted face memory task both ‘off’ and ‘on’ modafinil compared to a normative sample (N?=?38). The patient showed poor recognition performance off modafinil (z =??2.03) but intact performance on modafinil (z?=?0.78). fMRI results showed atypical activation during memory encoding off

Mark D. Allen; Dawson W. Hedges; Thomas J. Farrer; Michael J. Larson

2011-01-01

361

Giant magnetic modulation of a planar, hybrid metamolecule resonance  

NASA Astrophysics Data System (ADS)

Coupling magnetic elements to metamaterial structures creates hybrid metamolecules with new opportunities. Here we report on the magnetic control of a metamolecule resonance, by utilizing the interaction between a single split ring resonator (SRR) and a magnetic thin film of permalloy. To suppress eddy current shielding, the permalloy films are patterned into arrays of 30-500 ?m diameter discs. Strong hybridized resonances were observed at the anticrossing between the split ring resonance and the ferromagnetic resonance (FMR) of the permalloy. In particular, it is possible to achieve 40 dB modulation of the electric (symmetric) mode of the SRR on sweeping the applied magnetic field through the SRR/FMR anticrossing. The results open the way to the design of planar metamaterials, with potential applications in nonlinear metamaterials, tunable metamaterials and spintronics.

Gregory, Simon A.; Stenning, Gavin B. G.; Bowden, Graham J.; Zheludev, Nikolay I.; de Groot, Peter A. J.

2014-06-01

362

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

363

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. PMID:24905072

Callan, Daniel; Mills, Lloyd; Nott, Connie; England, Robert; England, Shaun

2014-01-01

364

A functional Magnetic Resonance Imaging study of neurohemodynamic abnormalities during emotion processing in subjects at high risk for schizophrenia  

PubMed Central

Background: Emotion processing abnormalities are considered among the core deficits in schizophrenia. Subjects at high risk (HR) for schizophrenia also show these deficits. Structural neuroimaging studies examining unaffected relatives at high risk for schizophrenia have demonstrated neuroanatomical abnormalities involving neo-cortical and sub-cortical brain regions related to emotion processing. The brain functional correlates of emotion processing in these HR subjects in the context of ecologically valid, real-life dynamic images using functional Magnetic Resonance Imaging (fMRI) has not been examined previously. Aim: To examine the neurohemodynamic abnormalities during emotion processing in unaffected subjects at high risk for schizophrenia in comparison with age-, sex-, handedness- and education-matched healthy controls, using fMRI. Materials and Methods: HR subjects for schizophrenia (n=17) and matched healthy controls (n=16) were examined. The emotion processing of fearful facial expression was examined using a culturally appropriate and valid tool for Indian subjects. The fMRI was performed in a 1.5-T scanner during an implicit emotion processing paradigm. The fMRI analyses were performed using the Statistical Parametric Mapping 2 (SPM2) software. Results: HR subjects had significantly reduced brain activations in left insula, left medial frontal gyrus, left inferior frontal gyrus, right cingulate gyrus, right precentral gyrus and right inferior parietal lobule. Hypothesis-driven region-of-interest analysis revealed hypoactivation of right amygdala in HR subjects. Conclusions: Study findings suggest that neurohemodynamic abnormalities involving limbic and frontal cortices could be potential indicators for increased vulnerability toward schizophrenia. The clinical utility of these novel findings in predicting the development of psychosis needs to be evaluated. PMID:21267363

Venkatasubramanian, Ganesan; Puthumana, Dawn Thomas K.; Jayakumar, Peruvumba N.; Gangadhar, B. N.

2010-01-01

365

Quantifying Mixing using Magnetic Resonance Imaging  

PubMed Central

Mixing is a unit operation that combines two or more components into a homogeneous mixture. This work involves mixing two viscous liquid streams using an in-line static mixer. The mixer is a split-and-recombine design that employs shear and extensional flow to increase the interfacial contact between the components. A prototype split-and-recombine (SAR) mixer was constructed by aligning a series of thin laser-cut Poly (methyl methacrylate) (PMMA) plates held in place in a PVC pipe. Mixing in this device is illustrated in the photograph in Fig. 1. Red dye was added to a portion of the test fluid and used as the minor component being mixed into the major (undyed) component. At the inlet of the mixer, the injected layer of tracer fluid is split into two layers as it flows through the mixing section. On each subsequent mixing section, the number of horizontal layers is duplicated. Ultimately, the single stream of dye is uniformly dispersed throughout the cross section of the device. Using a non-Newtonian test fluid of 0.2% Carbopol and a doped tracer fluid of similar composition, mixing in the unit is visualized using magnetic resonance imaging (MRI). MRI is a very powerful experimental probe of molecular chemical and physical environment as well as sample structure on the length scales from microns to centimeters. This sensitivity has resulted in broad application of these techniques to characterize physical, chemical and/or biological properties of materials ranging from humans to foods to porous media 1, 2. The equipment and conditions used here are suitable for imaging liquids containing substantial amounts of NMR mobile 1H such as ordinary water and organic liquids including oils. Traditionally MRI has utilized super conducting magnets which are not suitable for industrial environments and not portable within a laboratory (Fig. 2). Recent advances in magnet technology have permitted the construction of large volume industrially compatible magnets suitable for imaging process flows. Here, MRI provides spatially resolved component concentrations at different axial locations during the mixing process. This work documents real-time mixing of highly viscous fluids via distributive mixing with an application to personal care products. PMID:22314707

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

2012-01-01

366

Quantifying mixing using magnetic resonance imaging.  

PubMed

Mixing is a unit operation that combines two or more components into a homogeneous mixture. This work involves mixing two viscous liquid streams using an in-line static mixer. The mixer is a split-and-recombine design that employs shear and extensional flow to increase the interfacial contact between the components. A prototype split-and-recombine (SAR) mixer was constructed by aligning a series of thin laser-cut Poly (methyl methacrylate) (PMMA) plates held in place in a PVC pipe. Mixing in this device is illustrated in the photograph in Fig. 1. Red dye was added to a portion of the test fluid and used as the minor component being mixed into the major (undyed) component. At the inlet of the mixer, the injected layer of tracer fluid is split into two layers as it flows through the mixing section. On each subsequent mixing section, the number of horizontal layers is duplicated. Ultimately, the single stream of dye is uniformly dispersed throughout the cross section of the device. Using a non-Newtonian test fluid of 0.2% Carbopol and a doped tracer fluid of similar composition, mixing in the unit is visualized using magnetic resonance imaging (MRI). MRI is a very powerful experimental probe of molecular chemical and physical environment as well as sample structure on the length scales from microns to centimeters. This sensitivity has resulted in broad application of these techniques to characterize physical, chemical and/or biological properties of materials ranging from humans to foods to porous media (1, 2). The equipment and conditions used here are suitable for imaging liquids containing substantial amounts of NMR mobile (1)H such as ordinary water and organic liquids including oils. Traditionally MRI has utilized super conducting magnets which are not suitable for industrial environments and not portable within a laboratory (Fig. 2). Recent advances in magnet technology have permitted the construction of large volume industrially compatible magnets suitable for imaging process flows. Here, MRI provides spatially resolved component concentrations at different axial locations during the mixing process. This work documents real-time mixing of highly viscous fluids via distributive mixing with an application to personal care products. PMID:22314707

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

2012-01-01

367

NMR-0Fessler, Univ. of Michigan Nuclear Magnetic Resonance Imaging  

E-print Network

. A spin's magnetic moment experiences a torque, causing precession. B 0 M > 0 (Anti-Parallel) Higher surrounding a nuclei perturb the local magnetic field: Beff(r) = B0(1-(r)), where (r) depends on localNMR-0Fessler, Univ. of Michigan Nuclear Magnetic Resonance Imaging Jeffrey A. Fessler EECS

Fessler, Jeffrey A.

368

Microscopic magnetic resonance elastography (?MRE) applications  

NASA Astrophysics Data System (ADS)

Microscopic magnetic resonance elastography (?MRE) is a phase contrast based imaging technique that is capable of mapping the acoustic shear waves resulting from low amplitude cyclic displacement in tissue-like materials. This new technique has proven successful in imaging gel phantoms mimicking soft biological tissues with shear moduli ranging from 0.7 to 40 kPa. The 4-dimensional (4D) spatial-temporal shear wave vector can be measured, which in turn can be used to identify material properties with high spatial resolution. Experiments were conducted using 5 and 10 mm RF saddle coils in the 10 mm vertical imaging bore of an 11.74 Tesla magnet. The field-of-view ranged from 4 to 14 mm, with in plane resolution up to 34 ?m x 34 ?m and slice thickness up to 100 ?m using shear wave excitation of 550 to 580 Hz. In this study, the capability and constraints of ?MRE are investigated. The constraints include the range of measured shear moduli, excitation frequency, and minimum physical sample volume. Applications investigated include: 1) late-stage frog oocytes with typical diameter from 1 to 1.5 mm; and 2) tissue engineered constructs at different growth stages. Mesenchymal stem cells (MSCs) extracted from bone marrow can serve as progenitor cells that differentiate into specific types of tissues such as bone, adipose tissue, cartilage and muscle. ?MRE can monitor the growth of such tissues and evaluate their mechanical properties. Also, a silicon-based tissue phantom material (CF-11-2188, Nusil Technologies) is tested in order to address challenges associated with excitation frequency and the dispersive nature of the media.

Othman, Shadi F.; Xu, Huihui; Royston, Thomas J.; Magin, Richard L.

2005-04-01

369

Magnetic resonance imaging and ultrasound in hepatosplenic schistosomiasis mansoni.  

PubMed

We report the findings of abdominal ultrasound and magnetic resonance imaging observed in a patient with advanced schistosomiasis mansoni. A 25-year-old man with hepatosplenic schistosomiasis and variceal bleeding confirmed by upper endoscopy was submitted to abdominal ultrasound and magnetic resonance imaging. During surgery for portal hypertension, a liver biopsy was taken and the diagnosis of Symmers' fibrosis was confirmed. magnetic resonance imaging scans gave more precise information about the gallbladder, periportal thickening and abdominal venous system than did the ultrasound. PMID:15334268

Lambertucci, José Roberto; Silva, Luciana Cristina dos Santos; Andrade, Luciene Mota; de Queiroz, Leonardo Campos; Pinto-Silva, Rogério Augusto

2004-01-01

370

Pancoast tumor: the role of magnetic resonance imaging.  

PubMed

We report imaging techniques in the definition of the therapeutic planning of a 65-year-old man with a diagnosis of Pancoast tumor. Computed Tomography has a pivotal role in the assessment of nodes involvement and distant metastasis. Magnetic Resonance allows a detailed study of locoregional extension for its high soft tissue resolution. We particularly highlight the actual importance of Magnetic Resonance Neurography, Diffusion-Weighted Imaging, and Magnetic Resonance Angiography techniques in the assessment of the superior sulcus vascular and nervous structures involvement. Their integrity has been showed in our patient with a complete surgical excision of the lesion. PMID:23607032

Manenti, Guglielmo; Raguso, Mario; D'Onofrio, Silvia; Altobelli, Simone; Scarano, Angela Lia; Vasili, Erald; Simonetti, Giovanni

2013-01-01

371

Pancoast Tumor: The Role of Magnetic Resonance Imaging  

PubMed Central

We report imaging techniques in the definition of the therapeutic planning of a 65-year-old man with a diagnosis of Pancoast tumor. Computed Tomography has a pivotal role in the assessment of nodes involvement and distant metastasis. Magnetic Resonance allows a detailed study of locoregional extension for its high soft tissue resolution. We particularly highlight the actual importance of Magnetic Resonance Neurography, Diffusion-Weighted Imaging, and Magnetic Resonance Angiography techniques in the assessment of the superior sulcus vascular and nervous structures involvement. Their integrity has been showed in our patient with a complete surgical excision of the lesion. PMID:23607032

Manenti, Guglielmo; Raguso, Mario; D'Onofrio, Silvia; Altobelli, Simone; Scarano, Angela Lia; Vasili, Erald; Simonetti, Giovanni

2013-01-01

372

Correlation between the Effects of Acupuncture at Taichong (LR3) and Functional Brain Areas: A Resting-State Functional Magnetic Resonance Imaging Study Using True versus Sham Acupuncture  

PubMed Central

Functional magnetic resonance imaging (fMRI) has been shown to detect the specificity of acupuncture points, as proved by numerous studies. In this study, resting-state fMRI was used to observe brain areas activated by acupuncture at the Taichong (LR3) acupoint. A total of 15 healthy subjects received brain resting-state fMRI before acupuncture and after sham and true acupuncture, respectively, at LR3. Image data processing was performed using Data Processing Assistant for Resting-State fMRI and REST software. The combination of amplitude of low-frequency fluctuation (ALFF) and regional homogeneity (ReHo) was used to analyze the changes in brain function during sham and true acupuncture. Acupuncture at LR3 can specifically activate or deactivate brain areas related to vision, movement, sensation, emotion, and analgesia. The specific alterations in the anterior cingulate gyrus, thalamus, and cerebellar posterior lobe have a crucial effect and provide a valuable reference. Sham acupuncture has a certain effect on psychological processes and does not affect brain areas related to function. PMID:24963329

Qu, Shanshan; Zhang, Jiping; Chen, Junqi; Zhang, Shaoqun; Li, Zhipeng; Chen, Jiarong; Ouyang, Huailiang; Huang, Yong; Tang, Chunzhi

2014-01-01

373

Magnetic resonance imaging of the clavicular ossification.  

PubMed

Assessment of the degree of ossification of the medial clavicular epiphyseal cartilage is of vital importance in forensic age diagnostics of living individuals aged more than 18 years. To date, reference studies on the assessment of clavicular ossification using imaging procedures only relate to conventional radiography and computed tomography (CT). In this study, magnetic resonance (MR) scans of 54 sternoclavicular joints of bodies aged between 6 and 40 years were evaluated prospectively. All of the examined medial clavicular epiphyseal cartilages permitted an assessment of the degree of ossification. Stage 2 was first observed at the age of 15.0 years, the earliest age at which stage 3 was observed was 16.9 years, and stage 4 was first observed at the age of 23.8 years. The observed age intervals of the respective degrees of ossification correspond to the known data from X-ray and CT scan examinations. The achieved results should be examined with a larger number of cases. A modified examination protocol is required for the MR examination of the medial clavicular epiphyseal cartilage for the purpose of forensic age diagnostics of living individuals. PMID:17437121

Schmidt, Sven; Mühler, Matthias; Schmeling, Andreas; Reisinger, Walter; Schulz, Ronald

2007-07-01

374

Statistical normalization techniques for magnetic resonance imaging???  

PubMed Central

While computed tomography and other imaging techniques are measured in absolute units with physical meaning, magnetic resonance images are expressed in arbitrary units that are difficult to interpret and differ between study visits and subjects. Much work in the image processing literature on intensity normalization has focused on histogram matching and other histogram mapping techniques, with little emphasis on normalizing images to have biologically interpretable units. Furthermore, there are no formalized principles or goals for the crucial comparability of image intensities within and across subjects. To address this, we propose a set of criteria necessary for the normalization of images. We further propose simple and robust biologically motivated normalization techniques for multisequence brain imaging that have the same interpretation across acquisitions and satisfy the proposed criteria. We compare the performance of different normalization methods in thousands of images of patients with Alzheimer's disease, hundreds of patients with multiple sclerosis, and hundreds of healthy subjects obtained in several different studies at dozens of imaging centers. PMID:25379412

Shinohara, Russell T.; Sweeney, Elizabeth M.; Goldsmith, Jeff; Shiee, Navid; Mateen, Farrah J.; Calabresi, Peter A.; Jarso, Samson; Pham, Dzung L.; Reich, Daniel S.; Crainiceanu, Ciprian M.

2014-01-01

375

Moderne Entwicklung der NMR (Nuclear Magnetic Resonance)  

NASA Astrophysics Data System (ADS)

Die NMR-Spektroskopie kann sich altersmäßig nicht mit den Annalen der Physik messen; sie entstand vor rd. 45 Jahren. Ihre Entwicklung wurde und wird durch unterschiedliche Erfahrungen, Erkenntnisse und Techniken bestimmt; sie zeigt, daß auch heute noch die Fortschritte von Spezialgebieten Impulse aus weiten Bereichen der Physik, der Naturwissenschaften und Technik beziehen. In entsprechender Weise machen Spezialzeitschriften das Erscheinen allgemeiner Fachzeitschriften nicht überflüssig. Diese Zusammenhänge sollen an einigen Beispielen der NMR demonstriert werden.Translated AbstractModern Development of NMR (Nuclear Magnetic Resonance)The age of NMR-spectroscopy is not comparable with that of the Annalen der Physik; NMR was established only about 45 years ago. Its development was promoted by different experience, knowledge and techniques; it shows that also in these days the progress of a special topic depends on stimulations by other parts of physics, of natural and technical science. In an analogous way general scientific journals are not made superfluous by the existence of special papers. These relations are demonstrated with some examples in NMR.

Lösche, Artur

376

Scatter-based magnetic resonance elastography  

NASA Astrophysics Data System (ADS)

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

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

2009-04-01

377

Magnetic resonance in quantum spin chains  

NASA Astrophysics Data System (ADS)

The present understanding of quantum spin chains is reviewed from the magnetic resonance point of view. This includes both the ideal one-dimensional properties in the spin sector as well as the complex interplay with orbital, charge, and lattice degrees of freedom which govern the ground state. In copper-phosphates we observe an extremely extended paramagnetic regime governed by strong antiferromagnetic correlations with record values of the ratio kBTN/J < 6×10-4, which compares the ordering temperature of a Néel state to the magnitude of the exchange J between neighbouring spins. A detailed quantitative discussion of NMR and ESR relaxation within this paramagnetic regime elucidates the relevant exchange interactions in typical bonding geometries of most common quantum-spin-chain systems like KCuF3, CuGeO3, NaxV2O5, and LiCuVO4. Concerning the ground state, paramount topics of modern solid-state physics arise among these examples as there are multiferroicity, charge order, metal-insulator transition, and spin dimerization as well as phase separation.

Krug von Nidda, H.-A.; Büttgen, N.; Loidl, A.

2009-12-01

378

Hybrid sparse regularization for magnetic resonance spectroscopy.  

PubMed

Magnetic resonance spectroscopy imaging (MRSI) is a powerful non-invasive tool for characterising markers of biological processes. This technique extends conventional MRI by providing an additional dimension of spectral information describing the abnormal presence or concentration of metabolites of interest. Unfortunately, in vivo MRSI suffers from poor signal-to-noise ratio limiting its clinical use for treatment purposes. This is due to the combination of a weak MR signal and low metabolite concentrations, in addition to the acquisition noise. We propose a new method that handles this challenge by efficiently denoising MRSI signals without constraining the spectral or spatial profiles. The proposed denoising approach is based on wavelet transforms and exploits the sparsity of the MRSI signals both in the spatial and frequency domains. A fast proximal optimization algorithm is then used to recover the optimal solution. Experiments on synthetic and real MRSI data showed that the proposed scheme achieves superior noise suppression (SNR increase up to 60%). In addition, this method is computationally efficient and preserves data features better than existing methods. PMID:24111297

Laruelo, Andrea; Chaari, Lotfi; Batatia, Hadj; Ken, Soleakhena; Rowland, Ben; Laprie, Anne; Tourneret, Jean-Yves

2013-01-01

379

Brain magnetic resonance in hepatic encephalopathy.  

PubMed

The term hepatic encephalopathy (HE) covers a wide spectrum of neuropsychiatric abnormalities caused by portal-systemic shunting. The diagnosis requires demonstration of liver dysfunction or portal-systemic shunts and exclusion of other neurologic disorders. Most patients with this condition have liver dysfunction caused by cirrhosis, but it also occurs in patients with acute liver failure and less commonly, in patients with portal-systemic shunts that are not associated with hepatocellular disease. Various magnetic resonance (MR) techniques have improved our knowledge about the pathophysiology of HE. Proton MR spectroscopy and T1-weighted imaging can detect and quantify accumulations of brain products that are normally metabolized or eliminated such as glutamine and manganese. Other MR techniques such as T2-weighted and diffusion-weighted imaging can identify white matter abnormalities resulting from disturbances in cell volume homeostasis secondary to brain hyperammonemia. Partial or complete recovery of these abnormalities has been observed with normalization of liver function or after successful liver transplantation. MR studies have undoubtedly improved our understanding of the mechanisms involved in the pathogenesis of HE, and some findings can be considered biomarkers for monitoring the effects of therapeutic measures focused on correcting this condition. PMID:24745889

Alonso, Juli; Córdoba, Juan; Rovira, Alex

2014-04-01

380

Magnetic resonance imaging of cranial radiation lesions  

SciTech Connect

Fifty-six patients who previously received therapeutic cranial irradiation (CRT) were imaged by a 1.5 Magnetic Resonance (MR) System 0.1-11 years following CRT. Abnormal MR findings within the treatment volume unrelated to tumor, prior to surgery, or coexisting conditions were reviewed for an association with CRT. Twenty-four patients had MR abnormalities considered to be attributable to CRT. These were scored as mild (Grade I) in 6, moderate (Grade II) in 9, and severe (Grade III) in 9. Eight of these 24 patients with CRT findings on MR had CT abnormalities that correlated with the MR. Six lesions seen on computed tomography (CT) were Grade III abnormalities; all were judged as being visualized better by MR. Eight patients had significant neurologic dysfunction attributable to their CRT lesions, and 7 of these had Grade III lesions. Whereas the clinical significance of mild or moderate CRT effects seen on MR is uncertain, Grade III (severe) MR lesions correlate well with important clinical findings.

Curran, W.J.; Hecht-Leavitt, C.; Schut, L.; Zimmerman, R.A.; Nelson, D.F.

1987-07-01

381

Nuclear magnetic resonance imaging of the kidney  

SciTech Connect

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

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

1983-02-01

382

[Magnetic resonance angiography of the renal arteries].  

PubMed

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

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

1999-09-01

383

Small animal imaging with magnetic resonance microscopy.  

PubMed

Small animal magnetic resonance microscopy (MRM) has evolved significantly from testing the boundaries of imaging physics to its expanding use today as a tool in noninvasive biomedical investigations. MRM now increasingly provides functional information about living animals, with images of the beating heart, breathing lung, and functioning brain. Unlike clinical MRI, where the focus is on diagnosis, MRM is used to reveal fundamental biology or to noninvasively measure subtle changes in the structure or function of organs during disease progression or in response to experimental therapies. High-resolution anatomical imaging reveals increasingly exquisite detail in healthy animals and subtle architectural aberrations that occur in genetically altered models. Resolution of 100 mum in all dimensions is now routinely attained in living animals, and (10 mum)(3) is feasible in fixed specimens. Such images almost rival conventional histology while allowing the object to be viewed interactively in any plane. In this review we describe the state of the art in MRM for scientists who may be unfamiliar with this modality but who want to apply its capabilities to their research. We include a brief review of MR concepts and methods of animal handling and support, before covering a range of MRM applications-including the heart, lung, and brain-and the emerging field of MR histology. The ability of MRM to provide a detailed functional and anatomical picture in rats and mice, and to track this picture over time, makes it a promising platform with broad applications in biomedical research. PMID:18172332

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

2008-01-01

384

Magnetic Resonance Imaging at Ultrahigh Fields  

PubMed Central

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

Ugurbil, Kamil

2014-01-01

385

Magnetic resonance imaging: present and future applications  

PubMed Central

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

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

1985-01-01

386

Rare Infraglottic Lesions in Magnetic Resonance Imaging  

PubMed Central

Summary Background Primary pathological laryngeal lesions occur rarely in infraglottic space. Modern possibilities of diagnostic imaging of infraglottic space include computed tomography (CT) and magnetic resonance (MR). Diagnostic imaging was performed in potential lesions in this area: inflammatory process – cicatrical pemphigoid, benign neoplastic process – chondroma, malignant neoplastic – squamous cell carcinoma. The aim of the paper is to present clinical and radiographical characteristics of selected lesions located in infraglottic space in MRI examination. Material/Methods Three patients examined at the Department of Radiology and Diagnostic Imaging of University Hospital No. 1 in Lodz (SPZOZ USK nr 1) from 2010–2011 with a pathological mass in infraglottic space. Standard imaging protocol for MRI of the neck was used in all patients: field of 1.5 T, slice thickness 3 mm, the distance between the scans 10–20%, FOV – 3 mm, sequences: T1 (TR/TE 455/9, 7 ms, T2 (TR/TE 5300/67 ms), T1 + Gd-DTPA (contrast agent Gd-DTPA at 0.2 mmol/kg). Conclusions 1. It is possible to determine characteristic signal pattern for rare lesions of the infraglottic space in MRI. 2. MRI is a valuable complementary modality for the diagnostics and differentiation of lesions in infraglottic space, the evaluation of their advancement and treatment planning.

Blasiak-Kolacinska, Nina; Pietruszewska, Wioletta; Grzelak, Piotr; Razniewski, Marek; Stefanczyk, Ludomir; Majos, Agata

2014-01-01

387

Sensitive magnetic force detection with a carbon nanotube resonator  

NASA Astrophysics Data System (ADS)

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

Willick, Kyle; Haapamaki, Chris; Baugh, Jonathan

2014-03-01

388

[Magnetic resonance imaging and magnetic resonance spectroscopy methods for measuring intra- and extra-cellular pH: clinical implications].  

PubMed

We review the different methods for measuring pH by magnetic resonance imaging and magnetic resonance spectroscopy and discuss their potential diagnostic repercussions. We begin with a brief description of intra- and extra-cellular pH regulation in physiological and pathological conditions. Then we present the main 31P or 1H magnetic resonance spectroscopy procedures, which are based on the dependence of the pH on the chemical displacements of the intrinsic intracellular inorganic phosphate or of the H2 proton of imidazole in extrinsic indicators. Finally, we describe the procedures that use magnetic resonance imaging, whose main tool is the dependence of the pH (i) on the relaxivity of certain paramagnetic contrast agents, or (ii) on the processes of magnetic transference between diamagnetic molecules (DIACEST) or paramagnetic molecules (PARACEST) and the free water in the tissues. We briefly illustrate the potential clinical applications of these new procedures. PMID:19100206

Ballesteros, P; Pérez-Mayoral, E; Benito, M; Cerdán, S

2008-01-01

389

MAGNETIC RESONANCE IN CHEMISTRY Magn. Reson. Chem. 2007; 45: 937941  

E-print Network

of Chemistry, Lewis & Clark College, 0615 SW Palatine Hill Road, Portland, OR 97219, USA Received 25 June 2007 & Clark College, 0615 SW Palatine Hill Road, Portland, OR 97219, USA. E-mail: loening@lclark.edu resonance

Loening, Niko

390

Practical magnetic resonance imaging evaluation of peripheral nerves in children: magnetic resonance neurography.  

PubMed

Magnetic resonance (MR) imaging is an excellent tool for the evaluation of peripheral nerves in children not only because of its excellent soft tissue contrast resolution but also because it is noninvasive and does not use ionizing radiation. In nonconclusive cases, MR neurography can be complementary to physical examination and electromyography in identifying a specific affected nerve and the site of the lesion. This article reviews the MR imaging technique used in the evaluation of peripheral nerves (ie, MR neurography), its major indications, and the common pathologic conditions encountered in the pediatric population. PMID:23830792

Cortes, Cesar; Ramos, Yanerys; Restrepo, Ricardo; Restrepo, Jose Andres; Grossman, John A I; Lee, Edward Y

2013-07-01

391

Resonant Magnetic X-ray Diffraction.  

National Technical Information Service (NTIS)

Traditionally, the technique of choice for the study at an atomic level of detail of magnetic structures, correlations and excitations has been magnetic neutron scattering. Reviews of the neutron probe in the study of magnetism have been presented by Ross...

S. Longridge, S. W. Lovesey

2000-01-01

392

Current status of magnetic resonance spectroscopy - basic and clinical aspects  

Microsoft Academic Search

Magnetic resonance (MR) spectroscopy is a well-established method of chemical analysis in which the magnetic moment and radio-frequency emission characteristics of each atom and molecule are subjected to a high-intensity magnetic field. This method is now established as a noninvasive way of studying metabolism in vivo. With the development of wide-bore, high field (1.5 tesla or above) magnets, studies of

Chan

1985-01-01

393

Linear electro-optic effect for nuclear magnetic resonance coil  

NASA Astrophysics Data System (ADS)

An electrooptic transduction is here used to perform a low invasive characterization of the magnetic field in the context of magnetic resonance imaging. A resonant coil is coupled to a passive electrooptic crystal and the electromotive force of the magnetic field sensor is converted into a polarization state modulation of a laser probe beam. The optical conversion is demonstrated and lead to a fiber remote measurement of the magnetic field. The setup sensitivity and dynamics are finally dramatically enhanced using a LiNbO3 integrated waveguide. The minimum detectable field is as low as 60 fT.Hz-1/2 and the dynamics exceeds 100 dB.

Ayde, R.; Gaborit, Gwenaël.; Dahdah, Jean; Duvillaret, Lionel; Sablong, Raphaël.; Perrier, Anne-Laure; Beuf, Olivier

2014-05-01

394

Target-specific contrast agents for magnetic resonance microscopy  

E-print Network

High-resolution ex vivo magnetic resonance microscopy (MRM) can be used to delineate prominent architectonic features in the human brain, but increased contrast is required to visualize more subtle distinctions. The goal ...

Hepler Blackwell, Megan Leticia

2007-01-01

395

Designing and characterizing hyperpolarizable silicon nanoparticles for magnetic resonance imaging  

E-print Network

Magnetic Resonance Imaging (MRI) is one of the most powerful noninvasive tools for diagnosing human disease, but its utility is limited because current contrast agents are ineffective when imaging air-tissue interfaces, ...

Anahtar, Melis Nuray

2008-01-01

396

Analysis of the laser magnetic resonance spectrum of HO2  

Microsoft Academic Search

An analysis of the previously detected laser magnetic resonance spectrum of HOt is carried out by (i) assigning MJ quantum numbers to each observed Zeeman line, (ii) determining the quantum numbers (N'K\\

J. T. HOUGEN; K. M. EVENSON; CAKLETON J. HOWA; C HOWARD

1975-01-01

397

Magnetic resonance imaging for the assessment of liver function.  

E-print Network

??This thesis presents dynamic hepatocyte-specific contrast-enhanced magnetic resonance imaging (DHCE-MRI) as a new method for total and segmental liver function assessment. The method is based… (more)

Nilsson, Henrik

2011-01-01

398

Improvements in magnetic resonance imaging excitation pulse design  

E-print Network

This thesis focuses on the design of magnetic resonance imaging (MRI) radio-frequency (RF) excitation pulses, and its primary contributions are made through connections with the novel multiple-system single-output (MSSO) ...

Zelinski, Adam Charles

2008-01-01

399

Detection of brain metabolites in magnetic resonance spectroscopy  

E-print Network

While magnetic resonance imaging (MRI) derives its signal from protons in water, additional and potentially important biochemical compounds are detectable in vivo within the proton spectrum. The detection and mapping of ...

Kok, Trina

2009-01-01

400

Nuclear magnetic resonance data of CF3I  

NASA Astrophysics Data System (ADS)

This document is part of Part 1 `Aliphatic Compounds' of Subvolume D 'Chemical Shifts and Coupling Constants for Carbon-13' of Landolt-Börnstein III/35 'Nuclear Magnetic Resonance Data', Group III 'Condensed Matter'.

Kalinowski, H.-O.; Kumar, M.; Gupta, V.; Gupta, R.

401

Model-based reconstruction of magnetic resonance spectroscopic imaging  

E-print Network

Magnetic resonance imaging (MRI) is a medical imaging technique that is used to obtain images of soft tissue throughout the body. Since its development in the 1970s, MRI has gained tremendous importance in clinical practice ...

Chatnuntawech, Itthi

2013-01-01

402

Design algorithms for parallel transmission in magnetic resonance imaging  

E-print Network

The focus of this dissertation is on the algorithm design, implementation, and validation of parallel transmission technology in Magnetic Resonance Imaging (MRI). Novel algorithms are proposed which yield excellent excitation ...

Setsompop, Kawin

2008-01-01

403

Magnetic resonance imaging contrast agents for chemical sensing  

E-print Network

Magnetic resonance imaging (MRI) is frequently used for examining the human body. MRI contrast agents currently used in the clinic assist physicians in locating problematic areas, but other tools are needed to interrogate ...

Liu, Vincent Hok

2014-01-01

404

Fast magnetic resonance spectroscopic imaging using RF coil arrays  

E-print Network

Conventional Magnetic Resonance Spectroscopic Imaging (MRSI) suffers from both low signal-to-noise (SNR), as well as long acquisition times. The development of high-fidelity gradient coils has opened opportunities for fast ...

Gagoski, Borjan Aleksandar

2006-01-01

405

Magnetic resonance spectroscopic imaging using parallel transmission at 7T  

E-print Network

Conventional magnetic resonance spectroscopic imaging (MRSI), also known as phase-encoded (PE) chemical shift imaging (CSI), suffers from both low signal-to-noise ratio (SNR) of the brain metabolites, as well as inflexible ...

Gagoski, Borjan Aleksandar

2011-01-01

406

Imaging agents for in vivo magnetic resonance and scintigraphic imaging  

DOEpatents

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

Engelstad, Barry L. (Orinda, CA); Raymond, Kenneth N. (Berkeley, CA); Huberty, John P. (Corte Madera, CA); White, David L. (Oakland, CA)

1991-01-01

407

Posttraumatic Stress Disorder and fMRI Activation Patterns of Traumatic Memory in Patients with Borderline Personality Disorder  

Microsoft Academic Search

Background: Early traumatization and additional post- traumatic stress disorder are frequent in patients with borderline personality disorder (BPD). The purpose of this study was to investigate neural correlates of traumatic memory in BPD with and without posttraumatic stress disorder (PTSD) using functional magnetic resonance imaging (fMRI). Methods: We studied 12 traumatized female patients BPD, 6 of them with and 6

Martin Driessen; Thomas Beblo; Markus Mertens; Martina Piefke; Nina Rullkoetter; Anamaria Silva-Saavedra; Luise Reddemann; Harald Rau; Hans J. Markowitsch; Hella Wulff; Wolfgang Lange; Friedrich G. Woermann

2003-01-01

408

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

409

Exploring Possible Neural Mechanisms of Intelligence Differences Using Processing Speed and Working Memory Tasks: An fMRI Study  

ERIC Educational Resources Information Center

To explore the possible neural foundations of individual differences in intelligence test scores, we examined the associations between Raven's Matrices scores and two tasks that were administered in a functional magnetic resonance imaging (fMRI) setting. The two tasks were an n-back working memory (N = 37) task and inspection time (N = 47). The…

Waiter, Gordon D.; Deary, Ian J.; Staff, Roger T.; Murray, Alison D.; Fox, Helen C.; Starr, John M.; Whalley, Lawrence J.

2009-01-01

410

Attentional Bias to Food Images Associated With Elevated Weight and Future Weight Gain: An fMRI Study  

Microsoft Academic Search

Behavioral studies reveal that obese vs. lean individuals show attentional bias to food stimuli. Yet research has not investigated this relation using objective brain imaging or tested whether attentional bias to food stimuli predicts future weight gain, which are important aims given the prominence of food cues in the environment. We used functional magnetic resonance imaging (fMRI) to examine attentional

Sonja Yokum; Janet Ng; Eric Stice

2011-01-01

411

Cortical capacity constraints for visual working memory: dissociation of fMRI load effects in a fronto-parietal network  

Microsoft Academic Search

Working memory (WM) capacity limitations and their neurophysiological correlates are of special relevance for the understanding of higher cognitive functions. Evidence from behavioral studies suggests that restricted attentional resources contribute to these capacity limitations. In an event-related functional magnetic resonance imaging (fMRI) study, we probed the capacity of the human visual WM system for up to four complex nonnatural objects

David E. J. Linden; Robert A. Bittner; Lars Muckli; James A. Waltz; Nikolaus Kriegeskorte; Rainer Goebel; Wolf Singer; Matthias H. J. Munk

2003-01-01

412

Human attachment security is mediated by the amygdala: Evidence from combined fMRI and psychophysiological measures  

Microsoft Academic Search

The neural basis of human attachment security remains unexamined. Using event-related functional magnetic resonance imaging (fMRI) and simultaneous recordings of skin conductance levels, we measured neural and autonomic responses in healthy adult individuals during a semantic conceptual priming task measuring human attachment security \\

Erwin Lemche; Vincent P. Giampietro; Simon A. Surguladze; Edson J. Amaro; Christopher M. Andrew; Steven C. R. Williams; Michael J. Brammer; Natalia Lawrence; Markus A. Maier; Tamara A. Russell; Andrew Simmons; Christine Ecker; Peter Joraschky; Mary L. Phillips

2006-01-01

413

Raloxifene Treatment Enhances Brain Activation during Recognition of Familiar Items: a Pharmacological fMRI Study in Healthy Elderly Males  

Microsoft Academic Search

Raloxifene is a selective estrogen receptor modulator that may delay the onset of mild cognitive impairment in elderly women. Effects of raloxifene treatment on mental performance in males remain to be investigated. In a previous functional magnetic resonance imaging (fMRI) study, we showed that raloxifene treatment enhanced brain activation in elderly males during encoding of new information (faces) into memory.

Rutger Goekoop; Frederik Barkhof; Erik J J Duschek; Coen Netelenbos; Dirk L Knol; Philip Scheltens; Serge ARB Rombouts

2006-01-01

414

Analysis of fMRI Data Using Improved Self-Organizing Mapping and Spatio-Temporal Metric Hierarchical Clustering  

Microsoft Academic Search

The self-organizing mapping (SOM) and hierarchical clustering (HC) methods are integrated to detect brain functional activation; functional magnetic resonance imaging (fMRI) data are first processed by SOM to obtain a primary merged neural nodes image, and then by HC to obtain further brain activation patterns. The conventional Euclidean distance metric was replaced by the correlation distance metric in SOM to

Wei Liao; Huafu Chen; Qin Yang; Xu Lei

2008-01-01

415

Human Amygdala Activation during Conditioned Fear Acquisition and Extinction: a Mixed-Trial fMRI Study  

Microsoft Academic Search

Echoplanar functional magnetic resonance imaging (fMRI) was used in normal human subjects to investigate the role of the amygdala in conditioned fear acquisition and extinction. A simple discrimination procedure was employed in which activation to a visual cue predicting shock (CS+) was compared with activation to another cue presented alone (CS?). CS+ and CS? trial types were intermixed in a

Kevin S. LaBar; J. Christopher Gatenby; John C. Gore; Joseph E. LeDoux; Elizabeth A. Phelps

1998-01-01

416

Nuclear magnetic resonance study of methane adsorbed on porous silicon  

E-print Network

NUCLEAR MAGNETIC RESONANCE STUDY OF METHANE ADSORBED ON POROUS SILICON A Thesis by FENG I I Submitted to the Office of Graduate Studies of Texas ARM University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE... May 1992 Major Subject: Physics NUCLEAR MAGNETIC RESONANCE STUDY OF METHANE ADSORBED ON POROUS SILICON A Thesis by FENG LI Approved as to style and content by: . P. Kirk (Chair of Committee) i G. Agnolet (Member) J. H. Ross, r (Member) M...

Li, Feng

2012-06-07

417

Testing a prototype of the neutron magnetic resonance stabilization system  

NASA Astrophysics Data System (ADS)

The design of a multichannel system of stabilization of the magnetic resonance of ultracold neutrons in a multichamber spectrometer developed in the search for the electric dipole moment (EDM) of the neutron is briefly described. The results of tests on a prototype of this system are presented, which show the possibility of ensuring the stability of resonance lines that is equivalent to a magnetic field variation not exceeding ˜30 fT over a 100-s period of EDM measurements.

Aleksandrov, E. B.; Balabas, M. V.; Borisov, Yu. V.; Dmitriev, S. P.; Dovator, N. A.; Ivanov, A. I.; Krasnoshekova, I. A.; Kulyasov, V. N.; Marchenkov, V. V.; Pazgalev, A. S.; Serebrov, A. P.; Solovei, V. A.; Shmelev, G. E.

2007-01-01

418

Perfluoro-crown ethers in fluorine magnetic resonance spectroscopy  

SciTech Connect

This patent describes a method for obtaining a {sup 19}F-fluorine magnetic resonance spectrum from body cavities, organs or tissue by administering to a mammal a fluorine-containing agent in a diagnostically effective amount to provide a fluorine magnetic resonance spectrum from such cavities, organs or tissues, the improvement comprising using as the fluorine-containing agent an aqueous isotonic emulsion of perfluoro 15-crown-5 ether.

Schweighardt, F.K.; Rubertone, J.A.

1991-11-26

419

Magnetic Resonance and Susceptibility of Several Ilmenite Powders.  

National Technical Information Service (NTIS)

Magnetic susceptibility, paramagnetic resonance, and antiferromagnetic resonance were measured in MnTiO3, FeTiO3, CoTiO3, and NiTiO3. Neel temperatures TN of 65, 56, 37, and 23 plus or minus 2K, respectively, were measured. The molar susceptibilities appe...

J. J. Stickler, S. Kern, A. Wold, G. S. Heller

1967-01-01

420

Radiative Detection of Pulsed Nuclear Magnetic Resonance.  

NASA Astrophysics Data System (ADS)

The problem investigated is nuclear magnetic resonance (NMR) as used in conjunction with nuclear orientation (NO) studies of nuclei at low temperatures. Both theoretical and practical aspects are covered. Chapter 1 consists of a historical review, and a survey of concepts in NMR, NO and the combined subject NMRNO. This includes NMR in ferromagnets and ferromagnetic polarization, as a preamble to the experimental Chapter 5, where an experiment is described using ('60)Co nuclei in the ferromagnetic host nickel. Sections 1.4.3. and 1.4.4. are used to obtain the anisotropy as a function of inverse temperature, as shown in figure 5.1.. Single passage and pulsed NMRNO is reviewed in section 1.5., and pulsed NMRNO is carried out on ('60)Co in polycrystalline nickel, a host which had not previously been used with success by Barclay (1969). From a theoretical point of view, section 1.3.6(B) shows that when the quadrupole interactions of the nuclei are ignored, the quantum mechanical solution for the time dependence of the spin magnetization is identical with that from a classical treatment. Consequently, Chapter 2 has a brief review of three dimensional rotation matrices, used in sections 2.4. to 2.8. inclusive, and from which the analytic expressions are obtained for general pulse sequences, using the Fourier transform discussed in section 2.3.3.. These expressions assume that the linewidth of the distribution of nuclei is negligible compared with the enhanced RF field which the nuclei experience. Although, after correcting for experimental resolution, the exact lineshape function obtained in an experiment for a particular sample should be used, possibly including satellite lines, this is a system-dependent calculation, and is not amenable to analytic solution. For a more general calculation, we have used a Gaussian linefunction, as described in section 2.3., and we have furthermore used the dimensionless variables of section 2.3.2.. An interesting adjunct to two pulse NMRNO (section 2.5.) is the Shirley two pulse equivalent of section 2.5.3., which shows explicitly how the multipole effects may be observed. Since the Jaynes and Bloom papers are landmarks in the development of signal calculations in pulsed NMR, Chapter 3 describes their method in detail, and shows that the results obtained are consistent for one to five pulses, with those obtained in Chapter 2. In Chapter 4, a computer program which had been developed to calculate broad line pulsed NMRNO signals, and checked against the analytic expressions, yields and signals S(,k) for k = 1 to 4. Other more general features, such as mixed multipole signals, asymptotic signals for multiple pulse, and the general detection angle are also discussed. In Chapter 5, as previously mentioned, experiments on the ('60)Co in Ni systems are described, and also, we estimate the thermal link time for the salt-coldfinger -sample, both theoretically and experimentally. General results obtained experimentally for ('60)Co Fe were a thermal link time of order 9 sec. at 68.6 MHz, which is the resonant frequency for the ('60)Co Ni system, and a nominal 10 mK. The ratio, R, for the effective RF field B(,1) to the linewidth obtained was 0.14, significantly lower than the value, R = 0.45, obtained at 165 MHz in similar studies on ('60)Co Fe (Foster, 1979). Consequently, a 90(DEGREES) pulse corresponding to 6 (mu)sec for ('60)Co Ni was much longer than the 0.8 (mu)sec for ('60)Co Fe. From the theoretical point of view, the appearance of subechoes, and their subsequent experimental observation for ('60)Co Fe, together with their time shifts, made the calculations well worth while. Chapter 6 concludes the thesis, and presents some possibilities for further work, some of which has already been initiated.

Cooke, Peter

421

Breathhold unenhanced and gadolinium-enhanced magnetic resonance tomography and magnetic resonance cholangiography in hilar cholangiocarcinoma.  

PubMed

We assessed the imaging characteristics of hilar cholangiocarcinoma in magnetic resonance imaging (MRI) and magnetic resonance cholangiography (MRC). Breathhold MRI (T2-weighted turbo spin echo sequences, unenhanced T1-weighted gradient echo sequences, and gadolinium-enhanced fat-suppressed gradient echo sequences) and breathhold MRC (fat-suppressed two-dimensional projection images) performed in 12 patients with histologically confirmed hilar cholangiocarcinoma were retrospectively reviewed for morphological tumor characteristics and contrast enhancement patterns. MRC demonstrated a significant bile duct stenosis with intrahepatic bile duct dilatation in all cases except in one patient who received an endoprothesis prior to imaging. Hilar cholangiocarcinoma was diagnosed by MRC only in one patient and MRI and MRC in 11. Mass lesions were seen in nine patients and circumferential tumor growth in three, including the patient diagnosed by MRC only. The tumor appeared hypointense relative to liver parenchyma in 10 of 11 patients in unenhanced T1-weighted images. T2-weighted sequences showed isointense or only slightly hyperintense signal in 5 of 11 patients, 3 of whom demonstrated desmoplastic reactions by histology. The other 6 patients revealed strongly hyperintense signal intensities. Contrast enhancement was increased compared to liver in 5 of 11 patients and decreased in 6 of 11 patients. MRI with MRC seem to be a sensitive tools in the detection of hilar cholangiocarcinomas. The variable imaging characteristics are most probably related to the inhomogeneous histological appearance of this tumor entity. PMID:11459293

Altehoefer, C; Ghanem, N; Furtwängler, A; Schneider, B; Langer, M

2001-06-01

422

Magnetic Resonance Imaging in Postprostatectomy Radiotherapy Planning  

SciTech Connect

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

Sefrova, Jana, E-mail: sefrova@post.cz [Department of Oncology and Radiotherapy, University Hospital Hradec Kralove, Hradec Kralove (Czech Republic); Odrazka, Karel [Department of Clinical and Radiation Oncology, Multiscan and Pardubice Regional Hospital, Pardubice (Czech Republic); First and Third Faculty of Medicine, Charles University in Prague, Prague (Czech Republic); Paluska, Petr [Department of Oncology and Radiotherapy, University Hospital Hradec Kralove, Hradec Kralove (Czech Republic); Belobradek, Zdenek [Department of Radiology, University Hospital Hradec Kralove, Hradec Kralove (Czech Republic); Brodak, Milos [Department of Urology, University Hospital Hradec Kralove, Hradec Kralove (Czech Republic); Dolezel, Martin [Department of Clinical and Radiation Oncology, Multiscan and Pardubice Regional Hospital, Pardubice (Czech Republic); First and Third Faculty of Medicine, Charles University in Prague, Prague (Czech Republic); Prosvic, Petr [Department of Urology, Regional Hospital Nachod, Nachod (Czech Republic); Macingova, Zuzana; Vosmik, Milan [Department of Oncology and Radiotherapy, University Hospital Hradec Kralove, Hradec Kralove (Czech Republic); Hoffmann, Petr [Department of Radiology, University Hospital Hradec Kralove, Hradec Kralove (Czech Republic); Louda, Miroslav [Department of Urology, University Hospital Hradec Kralove, Hradec Kralove (Czech Republic); Nejedla, Anna [Department of Oncology and Radiotherapy, University Hospital Hradec Kralove, Hradec Kralove (Czech Republic)

2012-02-01

423

Magnetic resonance imaging evaluation of myocardial perfusion.  

PubMed

Noninvasive qualitative/quantitative assessment of myocardial perfusion is considered to be fundamental in the management of known and suspected coronary artery disease patients, as shown by the widespread utilization of thallium-201- and technetium-99m-labeled agents in myocardial single-photon emission computed tomography (SPECT) scintigraphy for diagnostic as well as prognostic purposes. Recently, the availability of subsecond ultrafast magnetic resonance imaging (MRI) sequences (FLASH, TurboFLASH, EPI) has provided new avenues for assessing myocardial perfusion by MRI in conjunction with contrast-agent bolus administration (contrast-enhanced first-pass MRI). MRI contrast agents can be classified into relaxation agents (T1 "positive") and susceptibility agents (T2 star [T2*] "negative"). All the commercially available MRI contrast agents used in clinical practice are relaxation agents employing the T1 shortening effect of metal ions like gadolinium (paramagnetism), thus producing a tissue signal-intensity increase on T1-weighted images (positive enhancement). On the other hand, T2* agents induce mainly susceptibility effects, i.e., rapid dephasing of spins with resultant signal loss on T2*-sensitive sequences (negative enhancement). Unfortunately, both relaxation and susceptibility agents are, by definition, "extracellular" contrast media, as they rapidly diffuse into the interstitial space, thus hampering the simple application of indicator-dilution kinetics for myocardial perfusion assessment. Blood pool agents are therefore needed to obtain predictable relations between the concentration of contrast medium in the myocardium and the change in signal intensity. In addition, newer MRI techniques for tissue perfusion quantitation have been recently reported, based on blood-sensitive sequences, thus without intravenous contrast administration. PMID:9662231

Passariello, R; De Santis, M

1998-06-18

424

Magnetoliposomes as magnetic resonance imaging contrast agents.  

PubMed

Among the wide variety in iron oxide nanoparticles which are routinely used as magnetic resonance imaging (MRI) contrast agents, magnetoliposomes (MLs) take up a special place. In the present work, the two main types (large and small MLs) are defined and their specific features are commented. For both types of MLs, the flexibility of the lipid coating allows for efficient functionalization, enabling bimodal imaging (e.g., MRI and fluorescence) or the use of MLs as theranostics. These features are especially true for large MLs, where several magnetite cores are encapsulated within a single large liposome, which were found to be highly efficient theranostic agents. By carefully fine-tuning the number of magnetite cores and attaching Gd(3+) -complexes onto the liposomal surface, the large MLs can be efficiently optimized for dynamic MRI. A special type of MLs, biogenic MLs, can also be efficiently used in this regard, with potential applications in cancer treatment and imaging. Small MLs, where the lipid bilayer is immediately attached onto a solid magnetite core, give a very high r2 /r1 ratio. The flexibility of the lipid bilayer allows the incorporation of poly(ethylene glycol)-lipid conjugates to increase blood circulation times and be used as bone marrow contrast agents. Cationic lipids can also be incorporated, leading to high cell uptake and associated strong contrast generation in MRI of implanted cells. Unique for these small MLs is the high resistance the particles exhibit against intracellular degradation compared with dextran- or citrate-coated particles. Additionally, intracellular clustering of the iron oxide cores enhances negative contrast generation and enables longer tracking of labeled cells in time. WIREs Nanomed Nanobiotechnol 2011 3 197-211 DOI: 10.1002/wnan.122 For further resources related to this article, please visit the WIREs website. PMID:25363747

Soenen, Stefaan J; Vande Velde, Greetje; Ketkar-Atre, Ashwini; Himmelreich, Uwe; De Cuyper, Marcel

2011-03-01

425

Tools for cardiovascular magnetic resonance imaging.  

PubMed

In less than fifteen years, as a non-invasive imaging option, cardiovascular MR has grown from a being a mere curiosity to becoming a widely used clinical tool for evaluating cardiovascular disease. Cardiovascular magnetic resonance imaging (CMRI) is now routinely used to study myocardial structure, cardiac function, macro vascular blood flow, myocardial perfusion, and myocardial viability. For someone entering the field of cardiac MR, this rapid pace of development in the field of CMRI might make it difficult to identify a cohesive starting point. In this brief review, we have attempted to summarize the key cardiovascular imaging techniques that have found widespread clinical acceptance. In particular, we describe the essential cardiac and respiratory gating techniques that form the backbone of all cardiovascular imaging methods. It is followed by four sections that discuss: (I) the gradient echo techniques that are used to assess ventricular function; (II) black-blood turbo spin echo (SE) methods used for morphologic assessment of the heart; (III) phase-contrast based techniques for the assessment of blood flow; and (IV) CMR methods for the assessment of myocardial ischemia and viability. In each section, we briefly summarize technical considerations relevant to the clinical use of these techniques, followed by practical information for its clinical implementation. In each of those four areas, CMRI is considered either as the benchmark imaging modality against which the diagnostic performance of other imaging modalities are compared against, or provides a complementary capability to existing imaging techniques. We have deliberately avoided including cutting-edge CMR imaging techniques practiced at few academic centers, and restricted our discussion to methods that are widely used and are likely to be available in a clinical setting. Our hope is that this review would propel an interested reader toward more comprehensive reviews in the literature. PMID:24834409

Krishnamurthy, Ramkumar; Cheong, Benjamin; Muthupillai, Raja

2014-04-01

426

Magnetic Resonance Imaging-guided Vascular Interventions  

PubMed Central

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

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

2007-01-01

427

Small Animal Imaging with Magnetic Resonance Microscopy  

PubMed Central

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

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

2009-01-01

428

Ferromagnetic resonance in $\\epsilon$-Co magnetic composites  

E-print Network

We investigate the electromagnetic properties of assemblies of nanoscale $\\epsilon$-cobalt crystals with size range between 5 nm to 35 nm, embedded in a polystyrene (PS) matrix, at microwave (1-12 GHz) frequencies. We investigate the samples by transmission electron microscopy (TEM) imaging, demonstrating that the particles aggregate and form chains and clusters. By using a broadband coaxial-line method, we extract the magnetic permeability in the frequency range from 1 to 12 GHz, and we study the shift of the ferromagnetic resonance with respect to an externally applied magnetic field. We find that the zero-magnetic field ferromagnetic resonant peak shifts towards higher frequencies at finite magnetic fields, and the magnitude of complex permeability is reduced. At fields larger than 2.5 kOe the resonant frequency changes linearly with the applied magnetic field, demonstrating the transition to a state in which the nanoparticles become dynamically decoupled. In this regime, the particles inside clusters can ...

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

2014-01-01

429

Understanding the Pathophysiology of Alzheimer's Disease and Mild Cognitive Impairment: A Mini Review on fMRI and ERP Studies  

PubMed Central

The prevalence of Alzheimer's disease (AD) is predicted to increase rapidly in the coming decade, highlighting the importance of early detection and intervention in patients with AD and mild cognitive impairment (MCI). Recently, remarkable advances have been made in the application of neuroimaging techniques in investigations of AD and MCI. Among the various neuroimaging techniques, functional magnetic resonance imaging (fMRI) has many potential advantages, noninvasively detecting alterations in brain function that may be present very early in the course of AD and MCI. In this paper, we first review task-related and resting-state fMRI studies on AD and MCI. We then present our recent fMRI studies with additional event-related potential (ERP) experiments during a motion perception task in MCI. Our results indicate that fMRI, especially when combined with ERP recording, can be useful for detecting spatiotemporal functional changes in AD and MCI patients. PMID:21773027

Yamasaki, Takao; Muranaka, Hiroyuki; Kaseda, Yumiko; Mimori, Yasuyo; Tobimatsu, Shozo

2012-01-01

430

Resonant Spin Wave Excitation by Terahertz Magnetic Near-field Enhanced with Split Ring Resonator  

E-print Network

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

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

2014-01-01

431

Electron paramagnetic resonance of nitroxide-doped magnetic fluids  

NASA Astrophysics Data System (ADS)

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

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

2002-11-01

432

Stochastic Resonance in a simple model of magnetic reversals  

E-print Network

We discuss the effect of stochastic resonance in a simple model of magnetic reversals. The model exhibits statistically stationary solutions and bimodal distribution of the large scale magnetic field. We observe a non trivial amplification of stochastic resonance induced by turbulent fluctuations, i.e. the amplitude of the external periodic perturbation needed for stochastic resonance to occur is much smaller than the one estimated by the equilibrium probability distribution of the unperturbed system. We argue that similar amplifications can be observed in many physical systems where turbulent fluctuations are needed to maintain large scale equilibria.

Roberto Benzi; Jean-Francois Pinton

2011-04-22

433

Predicting EEG single trial responses with simultaneous fMRI and relevance vector machine regression.  

PubMed

The combination of electroencephalography (EEG) and functional Magnetic Resonance Imaging (fMRI) has been proposed as a tool to study brain dynamics with both high temporal and high spatial resolution. Integration through EEG-fMRI trial-by-trial coupling has been proposed as a method to combine the different data sets and achieve temporal expansion of the fMRI data (Eichele et al., 2005). To fully benefit of this type of analysis simultaneous EEG-fMRI acquisitions are necessary (Debener et al., 2006). Here we address the issue of predicting the signal in one modality using information from the other modality. We use multivariate Relevance Vector Machine (RVM) regression to "learn" the relation between fMRI activation patterns and simultaneously acquired EEG responses in the context of a complex cognitive task entailing an auditory cue, visual mental imagery and a control visual target. We show that multivariate regression is a valuable approach for predicting evoked and induced oscillatory EEG responses from fMRI time series. Prediction of EEG from fMRI is largely influenced by the overall filtering effects of the hemodynamic response function. However, a detailed analysis of the auditory evoked responses shows that there is a small but significant contribution of single trial modulations that can be exploited for linking spatially-distributed patterns of fMRI activation to specific components of the simultaneously-recorded EEG signal. PMID:20691274

De Martino, Federico; de Borst, Aline W; Valente, Giancarlo; Goebel, Rainer; Formisano, Elia

2011-05-15

434

Paradigm-free mapping with morphological component analysis: getting most out of fMRI data  

NASA Astrophysics Data System (ADS)

Functional magnetic resonance imaging (fMRI) is a non-invasive imaging technique that maps the brain's response to neuronal activity based on the blood oxygenation level dependent (BOLD) effect. This work proposes a novel method for fMRI data analysis that enables the decomposition of the fMRI signal in its sources based on morphological descriptors. Beyond traditional fMRI hypothesis-based or blind data-driven exploratory approaches, this method allows the detection of BOLD responses without prior timing information. It is based on the deconvolution of the neuronal-related haemodynamic component of the fMRI signal with paradigm free mapping and also furnishes estimates of the movement-related effects, instrumental drifts and physiological fluctuations. Our algorithm is based on an overcomplete representation of the fMRI voxel time series with an additive linear model that is recovered by means of a L1-norm regularized least-squares estimators and an adapted block coordinate relaxation procedure. The performance of the technique is evaluated with simulated data and real experimental data acquired at 3T.

Caballero Gaudes, César; Van De Ville, Dimitri; Petridou, Natalia; Lazeyras, François; Gowland, Penny

2011-09-01

435

Multi-area integrated E/MEG and fMRI modeling  

NASA Astrophysics Data System (ADS)

Functional magnetic resonance imaging (fMRI) has complementary spatiotemporal resolution compared to Electroencephalography (EEG) as well as Magnetoencephalography (MEG). Thus, their integrated analysis should improve the overall resolution. To integrate analysis of E/MEG and fMRI, we extend our previously proposed integrated E/MEG and fMRI neural mass model to a multi-area model by defining two types of connections: the Short-Range Connections (SRCs) between minicolumns within the areas and Long-Range Connections (LRCs) between inter-areas minicolumns. The nonlinear input/output relationship in the proposed model is derived from the state space representation of the multi-area model. The E/MEG signals are originated from the overall synaptic activities of the pyramidal cells of all minicolumns and can be calculated using the lead field matrix (i.e., forward electromagnetic model). The fMRI signal is extracted from the proposed integrated model by calculating the overall neural activities in the areas and using it as the input of the extended balloon model (EBM). Using the simulation results, the capabilities of the proposed model to generate E/MEG and fMRI signals is shown. In addition, changes in the dynamics of the model to variations of its parameters were evaluated and lead us to the appropriate ranges for the parameters. In conclusion, this work proposes an effective method to integrate E/MEG and fMRI for the more effective use of these techniques in functional neuroimaging.

Babajani-Feremi, Abbas; Bowyer, Susan; Moran, John; Elisevich, Kost; Podell, Kenneth; Soltanian-Zadeh, Hamid

2009-02-01

436

Empirical Examination of the Potential Adverse Psychological Effects Associated with Pediatric fMRI Scanning  

PubMed Central

Abstract Background Over the past decade, the number of functional magnetic resonance imaging (fMRI) studies has increased dramatically. As MRI scans may be anxiety provoking, performing them in a research setting, particularly with children already prone to anxiety, raises questions about ethics as well as methodological feasibility. It is essential to address these questions before expanding the use of this technique to clinical settings, or more widely in the context of pediatric psychopharmacology and biological psychiatry research. The current study investigates the psychological reactions of anxious and non-anxious children and non-anxious adults to an fMRI scan. Methods Eighty-seven anxious children, 140 non-anxious children, and 98 non-anxious adults rated their emotional reactions to an fMRI scan. Results Results indicated that anxious and non-anxious children reported no greater anxiety after fMRI scanning than did adults. In addition, no age-related differences in distress were observed. These data demonstrate that anxious children, healthy children, and healthy adults have similar emotional reactions to fMRI scanning. Conclusions The observed findings suggest that the potential for fMRI to produce anxiety should not impede its widespread use in clinical research, psychopharmacology, and biological psychiatry. PMID:23738869

Wakschlag, Naomi; Britton, Jennifer C.; Jarcho, Johanna; Ernst, Monique; Pine, Daniel S.

2013-01-01

437

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

SciTech Connect

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

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

2008-03-27

438

Unsaturated hydraulic conductivity from nuclear magnetic resonance measurements  

Microsoft Academic Search

Gravity-driven drainage of water from a column of glass beads of uniform size is studied using nuclear magnetic resonance (NMR). The evolution of proton magnetization and its spin-spin relaxation time is measured as a function of drainage time at different locations within the column. On the basis of these measurements a model for calculating water relative permeability directly from relaxation

M. A. Ioannidis; I. Chatzis; C. Lemaire; R. Perunarkilli

2006-01-01

439

Remote auscultatory patient monitoring during magnetic resonance imaging  

Microsoft Academic Search

A system for patient monitoring during magnetic resonance imaging (MRI) is described. The system is based on remote auscultation of heart sounds and respiratory sounds using specially developed pickup heads that are positioned on the precordium or at the nostrils and connected to microphones via polymer tubing. The microphones operate in a differential mode outside the strong magnetic field to

S. Henneberg; B. Hök; L. Wiklund; G. Sjödin

1991-01-01

440

Artificial magnetic metamaterial design by using spiral resonators  

Microsoft Academic Search

A metallic planar particle, that will be called spiral resonator (SR), is introduced as a useful artificial atom for artificial magnetic media design and fabrication. A simple theoretical model which provides the most relevant properties and parameters of the SR is presented. The model is validated by both electromagnetic simulation and experiments. The applications of SR's include artificial negative magnetic

Juan D. Baena; Ricardo Marqués; Francisco Medina; Jesús Martel

2004-01-01

441

A Quantum Mechanical Review of Magnetic Resonance Imaging  

E-print Network

In this paper, we review the quantum mechanics of magnetic resonance imaging (MRI). We traverse its hierarchy of scales from the spin and orbital angular momentum of subatomic particles to the ensemble magnetization of tissue. And we review a number of modalities used in the assessment of acute ischemic stroke and traumatic brain injury.

Odaibo, Stephen G

2012-01-01

442

Tagged magnetic resonance imaging of the heart: a survey  

Microsoft Academic Search

Magnetic resonance imaging (MRI) of the heart with magnetization tagging provides a potentially useful new way to assess car-diac mechanical function, through revealing the local motion of otherwise indistinguishable portions of the heart wall. While still an evolving area, tagged cardiac MRI is already able to provide novel quantitative information on cardiac function. Exploiting this potential requires developing tailored methods

Leon Axel; Albert Montillo; Daniel Kim

2005-01-01

443

Magnetic resonance angiography of dialysis access shunts: Initial results  

Microsoft Academic Search

The objective of this study was the feasibility of imaging hemodialysis fistulae with magnetic resonance angiography (MRA). MRA was performed in eight Brescia-Cimino fistulae and seven goretex loop grafts, five of which were stenosed and 10 normal. We compared two MRA methods: a 2D magnetization prepared turbo field echo (MPTFE) and a 3D phase contrast (PC) sequence. Digital subtraction angiography

Geert J. Waldman; Peter M. T. Pattynama; Peter C. Chang; Cornelis Verburgh; Johan H. C. Reiber; Albert de Roos

1996-01-01

444

Resonant Magnetic Field Sensors Based On MEMS Technology  

Microsoft Academic Search

Microelectromechanical systems (MEMS) technology allows the integration of magnetic field sensors with electronic components, which presents important advantages such as small size, light weight, minimum power consumption, low cost, better sensitivity and high resolution. We present a discussion and review of resonant magnetic field sensors based on MEMS technology. In practice, these sensors exploit the Lorentz force in order to

Agustín L. Herrera-May; Luz A. Aguilera-Cortés; Pedro J. García-Ramírez; Elías Manjarrez

2009-01-01

445

Neural Correlates of Recognition Memory in Children with Febrile Seizures: Evidence from Functional Magnetic Resonance Imaging  

PubMed Central

Febrile seizures (FS) are assumed to not have adverse long-term effects on cognitive development. Nevertheless, FS are often associated with hippocampal sclerosis which can imply episodic memory deficits. This interrelation has hardly been studied so far. In the current study 13 children who had suffered from FS during infancy and 14 control children (7 to 9-years-old) were examined for episodic and semantic memory with standardized neuropsychological tests. Furthermore, using functional magnetic resonance imaging (fMRI) we studied neuronal activation while the children performed a continuous recognition memory task. The analysis of the behavioral data of the neuropsychological tests and the recognition memory experiment did not reveal any between-group differences in memory performance. Consistent with other studies fMRI revealed repetition enhancement effects for both groups in a variety of brain regions (e.g., right middle frontal gyrus, left parahippocampal gyrus) and a repetition suppression effect in the right superior temporal gyrus. Different neural activation patterns between both groups were obtained selectively within the right supramarginal gyrus (BA 40). In the control group correct rejections of new items were associated with stronger activation than correctly identified old items (HITs) whereas in the FS group no difference occurred. On the background that the right supramarginal gyrus is assumed to mediate a top-down process to internally direct attention toward recollected information, the results could indicate that control children used strategic recollection in order to reject new items (recall-to-reject). In contrast, the missing effect in the FS group could reflect a lack of strategy use, possibly due to impaired recollective processing. This study demonstrates that FS, even with mainly benign courses, can be accompanied by selective modifications in the neural structures underlying recognition memory. PMID:22347857

Kipp, Kerstin H.; Opitz, Bertram; Becker, Martina; Hofmann, Juliane; Krick, Christoph; Gortner, Ludwig; Mecklinger, Axel

2012-01-01

446

Saccular stimulation of the human cortex: a functional magnetic resonance imaging study.  

PubMed

Recent imaging studies have reported the projection of semicircular canal signals onto wide regions of the cerebral cortex but little is known about otolith projections onto the cerebral cortex. We used functional magnetic resonance imaging (fMRI) to investigate the activation of the cortex by loud clicks that selectively stimulate the sacculus. Twelve normal volunteers were presented with auditory stimuli via an earphone containing a piezo electric element. High-intensity [maximum volume of 120 dB (SPL)] or low-intensity [maximum volume of 110 dB (SPL)] clicks were delivered at a frequency of 1 Hz and lasted 1 ms. We first checked that the high-intensity, but not low-intensity, clicks stimulated the sacculus by determining the vestibular evoked myogenic potentials. We then analyzed two task conditions (high- and low-intensity clicks) in a boxcar paradigm. We obtained gradient echo echo-planar images by using a 1.5 T MRI system. We analyzed the fMRI time series data with SPM2. High-intensity clicks activated wide areas of the cortex, namely, the frontal lobe (prefrontal cortex, premotor cortex, and frontal eye fields), parietal lobe (the region around the intraparietal sulcus, temporo-parietal junction, and paracentral lobule), and cingulate cortex. These areas are similar to those reported in previous imaging studies that analyzed the cortical responses to the activation of the semicircular canals. Thus, semicircular canal and otolith/saccular signals may be processed in similar regions of the human cortex. PMID:17662530

Miyamoto, Tamaki; Fukushima, Kikuro; Takada, Toshihisa; de Waele, Catherine; Vidal, Pierre-Paul

2007-08-01

447

Recent developments of functional magnetic resonance imaging research for drug development in Alzheimer's disease.  

PubMed

The objective of this review is to evaluate recent advances in functional magnetic resonance imaging (fMRI) research in Alzheimer's disease for the development of therapeutic agents. The basic building block underpinning cognition is a brain network. The measured brain activity serves as an integrator of the various components, from genes to structural integrity, that impact the function of networks underpinning cognition. Specific networks can be interrogated using cognitive paradigms such as a learning task or a working memory task. In addition, recent advances in our understanding of neural networks allow one to investigate the function of a brain network by investigating the inherent coherency of the brain networks that can be measured during resting state. The coherent resting state networks allow testing in cognitively impaired patients that may not be possible with the use of cognitive paradigms. In particular the default mode network (DMN) includes the medial temporal lobe and posterior cingulate, two key regions that support episodic memory function and are impaired in the earliest stages of Alzheimer's disease (AD). By investigating the effects of a prospective drug compound on this network, it could illuminate the specificity of the compound with a network supporting memory function. This could provide valuable information on the methods of action at physiological and behaviourally relevant levels. Utilizing fMRI opens up new areas of research and a new approach for drug development, as it is an integrative tool to investigate entire networks within the brain. The network based approach provides a new independent method from previous ones to translate preclinical knowledge into the clinical domain. PMID:21777651

Hampel, Harald; Prvulovic, David; Teipel, Stefan J; Bokde, Arun L W

2011-12-01

448

Central Pain Processing in Chronic Chemotherapy-Induced Peripheral Neuropathy: A Functional Magnetic Resonance Imaging Study  

PubMed Central

Life expectancy in multiple myeloma has significantly increased. However, a high incidence of chemotherapy induced peripheral neuropathy (CIPN) can negatively influence quality of life during this period. This study applied functional magnetic resonance imaging (fMRI) to compare areas associated with central pain processing in patients with multiple myeloma who had chemotherapy induced peripheral neuropathy (MM-CIPN) with those from healthy volunteers (HV). Twenty-four participants (n?=?12 MM-CIPN, n?=?12 HV) underwent Blood Oxygen Level-Dependent (BOLD) fMRI at 3T whilst noxious heat-pain stimuli were applied to the foot and then thigh. Patients with MM-CIPN demonstrated greater activation during painful stimulation in the precuneus compared to HV (p?=?0.014, FWE-corrected). Patients with MM-CIPN exhibited hypo-activation of the right superior frontal gyrus compared to HV (p?=?0.031, FWE-corrected). Significant positive correlation existed between the total neuropathy score (reduced version) and activation in the frontal operculum (close to insular cortex) during foot stimulation in patients with MM-CIPN (p?=?0.03, FWE-corrected; adjusted R2?=?0.87). Painful stimuli delivered to MM-CIPN patients evoke differential activation of distinct cortical regions, reflecting a unique pattern of central pain processing compared with healthy volunteers. This characteristic activation pattern associated with pain furthers the understanding of the pathophysiology of painful chemotherapy induced peripheral neuropathy. Functional MRI provides a tool for monitoring cerebral changes during anti-cancer and analgesic treatment. PMID:24821182

Boland, Elaine G.; Selvarajah, Dinesh; Hunter, Mike; Ezaydi, Yousef; Tesfaye, Solomon; Ahmedzai, Sam H.; Snowden, John A.; Wilkinson, Iain D.

2014-01-01

449

Automatic selection of resting-state networks with functional magnetic resonance imaging  

PubMed Central

Functional magnetic resonance imaging (fMRI) during a resting-state condition can reveal the co-activation of specific brain regions in distributed networks, called resting-state networks, which are selected by independent component analysis (ICA) of the fMRI data. One of the major difficulties with component analysis is the automatic selection of the ICA features related to brain activity. In this study we describe a method designed to automatically select networks of potential functional relevance, specifically, those regions known to be involved in motor function, visual processing, executive functioning, auditory processing, memory, and the default-mode network. To do this, image analysis was based on probabilistic ICA as implemented in FSL software. After decomposition, the optimal number of components was selected by applying a novel algorithm which takes into account, for each component, Pearson's median coefficient of skewness of the spatial maps generated by FSL, followed by clustering, segmentation, and spectral analysis. To evaluate the performance of the approach, we investigated the resting-state networks in 25 subjects. For each subject, three resting-state scans were obtained with a Siemens Allegra 3 T scanner (NYU data set). Comparison of the visually and the automatically identified neuronal networks showed that the algorithm had high accuracy (first scan: 95%, second scan: 95%, third scan: 93%) and precision (90%, 90%, 84%). The reproducibility of the networks for visual and automatic selection was very close: it was highly consistent in each subject for the default-mode network (?92%) and the occipital network, which includes the medial visual cortical areas (?94%), and consistent for the attention network (?80%), the right and/or left lateralized frontoparietal attention networks, and the temporal-motor network (?80%). The automatic selection method may be used to detect neural networks and reduce subjectivity in ICA component assessment. PMID:23730268

Storti, Silvia Francesca; Formaggio, Emanuela; Nordio, Roberta; Manganotti, Paolo; Fiaschi, Antonio; Bertoldo, Alessandra; Toffolo, Gianna Maria

2013-01-01

450

Pharmacologic magnetic resonance imaging (phMRI): imaging drug action in the brain.  

PubMed

The technique of functional magnetic resonance (fMRI), using various cognitive, motor and sensory stimuli has led to a revolution in the ability to map brain function. Drugs can also be used as stimuli to elicit an hemodynamic change. Stimulation with a pharmaceutical has a number of very different consequences compared to user controllable stimuli, most importantly in the time course of stimulus and response that is not, in general, controllable by the experimenter. Therefore, this type of experiment has been termed pharmacologic MRI (phMRI). The use of a drug stimulus leads to a number of interesting possibilities compared to conventional fMRI. Using receptor specific ligands one can characterize brain circuitry specific to neurotransmitter systems. The possibility exists to measure parameters reflecting neurotransmitter release and binding associated with the pharmacokinetics and/or the pharmacodynamics of drugs. There is also the ability to measure up- and down-regulation of receptors in specific disease states. phMRI can be characterized as a molecular imaging technique using the natural hemodynamic transduction related to neuro-receptor stimulus. This provides a coupling mechanism with very high sensitivity that can rival positron emission tomography (PET) in some circumstances. The large numbers of molecules available, that do not require a radio-label, means that phMRI becomes a very useful tool for performing drug discovery. Data and arguments will be presented to show that phMRI can provide information on neuro-receptor signaling and function that complements the static picture generated by PET studies of receptor numbers and occupancies. PMID:22495143

Jenkins, Bruce G

2012-08-15

451

Haptic fMRI: combining functional neuroimaging with haptics for studying the brain's motor control representation.  

PubMed

A challenging problem in motor control neuroimaging studies is the inability to perform complex human motor tasks given the Magnetic Resonance Imaging (MRI) scanner's disruptive magnetic fields and confined workspace. In this paper, we propose a novel experimental platform that combines Functional MRI (fMRI) neuroimaging, haptic virtual simulation environments, and an fMRI-compatible haptic device for real-time haptic interaction across the scanner workspace (above torso ? .65×.40×.20m(3)). We implement this Haptic fMRI platform with a novel haptic device, the Haptic fMRI Interface (HFI), and demonstrate its suitability for motor neuroimaging studies. HFI has three degrees-of-freedom (DOF), uses electromagnetic motors to enable high-fidelity haptic rendering (>350Hz), integrates radio frequency (RF) shields to prevent electromagnetic interference with fMRI (temporal SNR >100), and is kinematically designed to minimize currents induced by the MRI scanner's magnetic field during motor displacement (<2cm). HFI possesses uniform inertial and force transmission properties across the workspace, and has low friction (.05-.30N). HFI's RF noise levels, in addition, are within a 3 Tesla fMRI scanner's baseline noise variation (?.85±.1%). Finally, HFI is haptically transparent and does not interfere with human motor tasks (tested for .4m reaches). By allowing fMRI experiments involving complex three-dimensional manipulation with haptic interaction, Haptic fMRI enables-for the first time-non-invasive neuroscience experiments involving interactive motor tasks, object manipulation, tactile perception, and visuo-motor integration. PMID:24110643

Menon, Samir; Brantner, Gerald; Aholt, Chris; Kay, Kendrick; Khatib, Oussama

2013-01-01

452

Visualization of Rabi oscillations in a magnetic resonance  

E-print Network

A visualization scheme for dynamics of a qudit polarization vector in a time-dependent magnetic field is presented by solving equations for a density matrix in Hermitian basis. This is realized by means of mapping solution for the polarization vector on the three-dimensional spherical curve (vector hodograph). The obtained results obviously display the interference of precessional and nutational effects on the polarization vector in a magnetic resonance. The study can find the practical applications in a magnetic resonance and 3D visualization of computational data.

E. A. Ivanchenko

2013-11-11

453

fMRI analysis software tools: an evaluation framework  

NASA Astrophysics Data System (ADS)

Performance comparison of functional Magnetic Resonance Imaging (fMRI) software tools is a very difficult task. In this paper, a framework for comparison of fMRI analysis results obtained with different software packages is proposed. An objective evaluation is possible only after pre-processing steps that normalize input data in a standard domain. Segmentation and registration algorithms are implemented in order to classify voxels belonging to brain or not, and to find the non rigid transformation that best aligns the volume under inspection with a standard one. Through the definitions of intersection and union of fuzzy logic an index was defined which quantify information overlap between Statistical Parametrical Maps (SPMs). Direct comparison between fMRI results can only highlight differences. In order to assess the best result, an index that represents the goodness of the activation detection is required. The transformation of the activation map in a standard domain allows the use of a functional Atlas for labeling the active voxels. For each functional area the Activation Weighted Index (AWI) that identifies the mean activation level of whole area was defined. By means of this brief, but comprehensive description, it is easy to find a metric for the objective evaluation of a fMRI analysis tools. Trough the first evaluation method the situations where the SPMs are inconsistent were identified. The result of AWI analysis suggest which tool has higher sensitivity and specificity. The proposed method seems a valid evaluation tool when applied to an adequate number of patients.

Pedoia, Valentina; Colli, Vittoria; Strocchi, Sabina; Vite, Cristina; Binaghi, Elisabetta; Conte, Leopoldo

2011-03-01

454

Spin microscope based on optically detected magnetic resonance  

DOEpatents

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

Berman, Gennady P. (Los Alamos, NM); Chernobrod, Boris M. (Los Alamos, NM)

2009-10-27

455

Spin microscope based on optically detected magnetic resonance  

DOEpatents

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

Berman, Gennady P. (Los Alamos, NM); Chernobrod, Boris M. (Los Alamos, NM)

2009-11-10

456

Spin microscope based on optically detected magnetic resonance  

DOEpatents

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

Berman, Gennady P. (Los Alamos, NM); Chernobrod, Boris M. (Los Alamos, NM)

2007-12-11

457

Nuclear magnetic resonance spectroscopy with single spin sensitivity  

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

458

One-pot synthesis of magnetic nanoclusters enabling atherosclerosis-targeted magnetic resonance imaging  

PubMed Central

In this study, dextran-encrusted magnetic nanoclusters (DMNCs) were synthesized using a one-pot solution phase method for detection of atherosclerosis by magnetic resonance imaging. Pyrenyl dextran was used as a surfactant because of its electron-stabilizing effect and its amphiphilic nature, rendering the DMNCs stable and water-dispersible. The DMNCs were 65.6±4.3 nm, had a narrow size distribution, and were superparamagnetic with a high magnetization value of 60.1 emu/g. Further, they showed biocompatibility and high cellular uptake efficiency, as indicated by a strong interaction between dextran and macrophages. In vivo magnetic resonance imaging demonstrated the ability of DMNCs to act as an efficient magnetic resonance imaging contrast agent capable of targeted detection of atherosclerosis. In view of these findings, it is concluded that DMNCs can be used as magnetic resonance imaging contrast agents to detect inflammatory disease. PMID:24904209

Kukreja, Aastha; Lim, Eun-Kyung; Kang, Byunghoon; Choi, Yuna; Lee, Taeksu; Suh, Jin-Suck; Huh, Yong-Min; Haam, Seungjoo

2014-01-01

459

Magnetic Resonance Imaging of Surgical Implants Made from Weak Magnetic Materials  

NASA Astrophysics Data System (ADS)

Materials with high magnetic susceptibility cause local inhomogeneities in the main field of the magnetic resonance (MR) tomograph. These inhomogeneities lead to loss of phase coherence, and thus to a rapid loss of signal in the image. In our research we investigated inhomogeneous field of magnetic implants such as magnetic fibers, designed for inner suture during surgery. The magnetic field inhomogeneities were studied at low magnetic planar phantom, which was made from four thin strips of magnetic tape, arranged grid-wise. We optimized the properties of imaging sequences with the aim to find the best setup for magnetic fiber visualization. These fibers can be potentially exploited in surgery for internal stitches. Stitches can be visualized by the magnetic resonance imaging (MRI) method after surgery. This study shows that the imaging of magnetic implants is possible by using the low field MRI systems, without the use of complicated post processing techniques (e.g., IDEAL).

Gogola, D.; Kraf?ík, A.; Štrbák, O.; Frollo, I.

2013-08-01

460

Effects of Acute Nicotine Abstinence on Cue-elicited Ventral Striatum\\/Nucleus Accumbens Activation in Female Cigarette Smokers: A Functional Magnetic Resonance Imaging Study  

Microsoft Academic Search

To achieve greater understanding of the brain mechanisms underlying nicotine craving in female smokers, we examined the influence\\u000a of nicotine non-abstinence vs. acute nicotine abstinence on cue-elicited activation of the ventral striatum. Eight female\\u000a smokers underwent an event-related functional magnetic resonance imaging (fMRI) paradigm presenting randomized sequences of\\u000a smoking-related and non-smoking related pictures. Participants were asked to indicate by a

Sean P. David; Marcus R. Munafò; Heidi Johansen-Berg; James MacKillop; Lawrence H. Sweet; Ronald A. Cohen; Raymond Niaura; Robert D. Rogers; Paul M. Matthews; Robert T. Walton

2007-01-01

461

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

NASA Astrophysics Data System (ADS)

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

Herrera, Sheryl Lyn

462

Tactile-associated fMRI recruitment of the cervical cord in healthy subjects.  

PubMed

Using spinal cord functional magnetic resonance imaging (fMRI), 12 right-handed healthy subjects were scanned during a tactile stimulation of the palm of the right hand. The task-related mean signal change was computed for all activated voxels within the cervical cord, and separately, in the four cord quadrants (right and left anterior, right and left posterior) from C5 to C8. The frequency of fMRI activity at each cord level was obtained by assigning a score of 25% at each active quadrant and by averaging the percentage of active quadrants at each level of all subjects. The difference in the occurrence of fMRI activity (a) in right versus left, and anterior versus posterior cord, and (b) among the different cord levels, was evaluated using a random effect logistic regression model, with the frequency of fMRI activity as the dependent variable and the subject as the grouping factor. The task-related mean signal change of all activated voxels of the cord was 3.2% (SD = 0.8%). During the tactile stimulation, subjects showed a higher occurrence of fMRI cord activity in the right than in the left cervical cord (odds ratio = 2.25, 95% confidence interval = 1.31-3.87, P = 0.003). A significant heterogeneity in frequency