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1

Functional magnetic resonance imaging (FMRI) of the human brain  

Microsoft Academic Search

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

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

1994-01-01

2

Functional magnetic resonance imaging (fMRI) and positron emission tomography measure local changes in brain  

E-print Network

, electroencephalography (EEG) and magnetoencephalography (MEG) measure instantaneously the current flows induced dipole EEG electroencephalography ERP event-related potential fMRI functional magnetic resonance imaging) and high-density electroencephalography (EEG) have enabled estimation of brain activity with a temporal

Udgaonkar, Jayant B.

3

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

Microsoft Academic Search

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

Jingqi Ao; Sunanda Mitra; Zheng Liu; Brian Nutter

2011-01-01

4

Application of independent component analysis for activation detection in functional magnetic resonance imaging (FMRI) data  

Microsoft Academic Search

In this extended summary, our aim is analyzing functional magnetic resonance imaging (fMRI) data by independent component analysis (ICA) in order to find regions of brain which were activated by neural activity in human brain. We employ the minimum description length (MDL) criterion to reduce the dimension of the data and estimate the number of components, which makes ICA work

Mahsa Akhbari; Emad Fatemizadeh

2009-01-01

5

Magnetic Resonance Imaging, vol. 19 pp 821-826: 2001 Comparing BOLD fMRI signal changes in the awake  

E-print Network

MRI in the conscious and anaesthetized state of the rat Key words: fMRI, rats, anaesthesia #12;Magnetic Resonance applied curarization and alpha-chloralose anaesthesia protocols, it was possible to compare quantitatively

De Schutter, Erik

6

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

7

Studying brain function with concurrent near-infrared spectroscopy (NIRS) and functional magnetic resonance imaging (fMRI)  

NASA Astrophysics Data System (ADS)

We present concurrent NIRS-fMRI measurements on a human subject during a finger tapping test. The optical data were collected with a frequency domain experimental apparatus (ISS, Inc., Champaign IL) comprising sixteen laser sources at 690 nm, sixteen laser sources at 830 nm and four photomultiplier tube detectors. The lasers were coupled to optical fibers that led the light onto the subject's head. A special optical helmet (fMRI-compatible) with a retractable and resilient set of optical fibers was devised to improve the coupling between the fibers and the scalp. The fMRI data were collected with a 3 Tesla Siemens Trio magnetic resonance scanner and a quadrature birdcage radiofrequency coil. The spatial and temporal comparison of the fMRI and NIRS signals associated with brain activation showed a very good agreement, confirming the role of NIRS as a reliable brain monitor for functional studies.

Sassaroli, A.; Tong, Y.; Frederick, B. B.; Renshaw, P. F.; Ehrenberg, B. L.; Fantini, S.

2005-04-01

8

A similarity retrieval method for functional magnetic resonance imaging (fMRI) statistical maps  

NASA Astrophysics Data System (ADS)

We propose a method for retrieving similar fMRI statistical images given a query fMRI statistical image. Our method thresholds the voxels within those images and extracts spatially distinct regions from the voxels that remain. Each region is defined by a feature vector that contains the region centroid, the region area, the average activation value for all the voxels within that region, the variance of those activation values, the average distance of each voxel within that region to the region's centroid, and the variance of the voxel's distance to the region's centroid. The similarity between two images is obtained by the summed minimum distance of their constituent feature vectors. Results on a dataset of fMRI statistical images from experiments involving distinct cognitive tasks are shown.

Tungaraza, R. F.; Guan, J.; Rolfe, S.; Atmosukarto, I.; Poliakov, A.; Kleinhans, N. M.; Aylward, E.; Ojemann, J.; Brinkley, J. F.; Shapiro, L. G.

2009-02-01

9

Multimodal neuroimaging integrating functional magnetic resonance Imaging and electroencephalography.  

E-print Network

??Functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) are two widely used neuroimaging modalities with complementary merits and limitations. FMRI has low temporal resolution but… (more)

Liu, Zhongming

2009-01-01

10

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

11

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

12

Abstract--Noise confounds present serious complications to functional magnetic resonance imaging (fMRI) analysis. The  

E-print Network

(fMRI) analysis. The amount of discernible signals within a single dataset of a subject is often to enable information coalescing. A distinct advantage of GMRF over standard fMRI group analysis in the case of binary labeling. We validate our technique on synthetic and real fMRI data and demonstrate GMRF

Hamarneh, Ghassan

13

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

PubMed

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

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

2012-12-01

14

Functional Magnetic Resonance Imaging  

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

15

Functional magnetic resonance imaging in pediatrics.  

PubMed

Functional magnetic resonance imaging (fMRI) allows non-invasive assessment of human brain function in vivo by detecting blood flow differences. In this review, we want to illustrate the background and different aspects of performing functional magnetic resonance imaging (fMRI) in the pediatric age group. An overview over current and future applications of fMRI will be given, and typical problems, pitfalls, and benefits of doing fMRI in the pediatric age group are discussed. We conclude that fMRI can successfully be applied in children and holds great promise for both research and clinical purposes. PMID:14598227

Wilke, M; Holland, S K; Myseros, J S; Schmithorst, V J; Ball, W S

2003-06-01

16

Articulatory/phonetic sequencing at the level of the anterior perisylvian cortex: a functional magnetic resonance imaging (fMRI) study.  

PubMed

Damage to the anterior peri-intrasylvian cortex of the dominant hemisphere may give rise to a fairly consistent syndrome of articulatory deficits in the absence of relevant paresis of orofacial or laryngeal muscles (apraxia of speech, aphemia, or phonetic disintegration). The available clinical data are ambiguous with respect to the relevant lesion site, indicating either dysfunction of the premotor aspect of the lower precentral gyrus or the anterior insula in the depth of the Sylvian fissure. In order to further specify the functional anatomic substratum of this syndrome, functional magnetic resonance imaging (fMRI) was performed during reiteration of syllables differing in their demands on articulatory/phonetic sequencing (CV versus CCCV versus CVCVCV). Horizontal tongue movements and a polysyllabic lexical item served as control conditions. Repetition of the CV and CCCV monosyllables elicited a rather bilateral symmetric hemodynamic response at the level of the anterior and posterior bank of the central sulcus (primary sensorimotor cortex), whereas a more limited area of neural activity arose within this domain during production of lexical and nonlexical polysyllables, significantly or exclusively lateralized toward the left hemisphere. There is neurophysiological evidence that primary sensorimotor cortex mediates the "fractionation" of movements. Assuming that the polysyllables considered are organized as coarticulated higher-order units, the observed restricted and lateralized cortical activation pattern, most presumably, reflects a mode of "nonindividualized" motor control posing fewer demands on "movement fractionation." These findings may explain the clinical observation of disproportionately worse repetition of trisyllabic items as compared to monosyllables in apraxia of speech. The various test materials failed to elicit significant activation of the anterior insula. If at all, only horizontal tongue movements yielded a hemodynamic reaction extending beyond the sensorimotor cortex to premotor areas. Since limbic projections target the inferior dorsolateral frontal lobe, the enlarged region of activation during horizontal tongue movements might reflect increased attentional requirements of this task. PMID:11049668

Riecker, A; Ackermann, H; Wildgruber, D; Meyer, J; Dogil, G; Haider, H; Grodd, W

2000-11-01

17

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

E-print Network

of functional magnetic resonance imaging (fMRI) signals that is capable of revealing connected brain systems to perform group-level analyses on datasets consisting of hundreds of scan sessions by combining the results fMRI; group ICA; bagging; clustering; bootstrap I. INTRODUCTION Functional magnetic resonance

Yuille, Alan L.

18

Low-dimensional embedding of fMRI datasets Xilin Shen and Franois G. Meyer  

E-print Network

Low-dimensional embedding of fMRI datasets Xilin Shen and François G. Meyer Department a functional magnetic resonance imaging (fMRI) dataset in a low-dimensional space. The embedding optimally magnetic resonance imaging (fMRI) datasets. FMRI provides a large scale (as compared to the scale

Meyer, Francois

19

Magnetic resonance imaging of brain function and neurochemistry  

Microsoft Academic Search

In the past decade, magnetic resonance imaging (MRI) research has been focused on the acquisition of physiological and biochemical information noninvasively. Probably the most notable accomplishment in this general effort has been the introduction of the MR approaches to map brain function. This capability, often referred to as functional magnetic resonance imaging, or fMRI, is based on the sensitivity of

KAMIL UGURBIL; DAE-SHIK KIM; TIM DUONG; XIAOPING HU; SEIJI OGAWA; ROLF GRUETTER; WEI CHEN; SEONG-GI KIM; XIAO-HUNG ZHU; ESSA YACOUB; PIERRE-FRANCOIS VAN DE MOORTELE; AMIR SHMUEL; JOSEF PFEUFFER; HELLMUT MERKLE; PETER ANDERSEN; GREGOR ADRIANY

2001-01-01

20

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

21

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

22

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

23

The economics of functional magnetic resonance imaging: clinical and research.  

PubMed

It is difficult to justify maintaining a clinical functional magnetic resonance imaging (fMRI) program based solely on revenue generation. The use of fMRI is, therefore, based mostly in patient care considerations, leading to better outcomes. The high costs of the top-of-the-line equipment, hardware, and software needed for state-of-the-art fMRI and the time commitment by multiple professionals are not adequately reimbursed at a representative rate by current payor schemes for the Current Procedure Terminology codes assigned. PMID:25441510

Yousem, David M

2014-11-01

24

Acoustic noise during functional magnetic resonance imaginga)  

PubMed Central

Functional magnetic resonance imaging (fMRI) enables sites of brain activation to be localized in human subjects. For studies of the auditory system, acoustic noise generated during fMRI can interfere with assessments of this activation by introducing uncontrolled extraneous sounds. As a first step toward reducing the noise during fMRI, this paper describes the temporal and spectral characteristics of the noise present under typical fMRI study conditions for two imagers with different static magnetic field strengths. Peak noise levels were 123 and 138 dB re 20 ?Pa in a 1.5-tesla (T) and a 3-T imager, respectively. The noise spectrum (calculated over a 10-ms window coinciding with the highest-amplitude noise) showed a prominent maximum at 1 kHz for the 1.5-T imager (115 dB SPL) and at 1.4 kHz for the 3-T imager (131 dB SPL). The frequency content and timing of the most intense noise components indicated that the noise was primarily attributable to the readout gradients in the imaging pulse sequence. The noise persisted above background levels for 300-500 ms after gradient activity ceased, indicating that resonating structures in the imager or noise reverberating in the imager room were also factors. The gradient noise waveform was highly repeatable. In addition, the coolant pump for the imager’s permanent magnet and the room air handling system were sources of ongoing noise lower in both level and frequency than gradient coil noise. Knowledge of the sources and characteristics of the noise enabled the examination of general approaches to noise control that could be applied to reduce the unwanted noise during fMRI sessions. PMID:11051496

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

2007-01-01

25

Investigation of BOLD fMRI Resonance Frequency Shifts and Quantitative Susceptibility Changes at 7 T  

PubMed Central

Although blood oxygenation level dependent (BOLD) functional magnetic resonance imaging (fMRI) experiments of brain activity generally rely on the magnitude of the signal, they also provide frequency information that can be derived from the phase of the signal. However, because of confounding effects of instrumental and physiological origin, BOLD related frequency information is difficult to extract and therefore rarely used. Here, we explored the use of high field (7 T) and dedicated signal processing methods to extract frequency information and use it to quantify and interpret blood oxygenation and blood volume changes. We found that optimized preprocessing improves detection of task-evoked and spontaneous changes in phase signals and resonance frequency shifts over large areas of the cortex with sensitivity comparable to that of magnitude signals. Moreover, our results suggest the feasibility of mapping BOLD quantitative susceptibility changes in at least part of the activated area and its largest draining veins. Comparison with magnitude data suggests that the observed susceptibility changes originate from neuronal activity through induced blood volume and oxygenation changes in pial and intracortical veins. Further, from frequency shifts and susceptibility values, we estimated that, relative to baseline, the fractional oxygen saturation in large vessels increased by 0.02–0.05 during stimulation, which is consistent to previously published estimates. Together, these findings demonstrate that valuable information can be derived from fMRI imaging of BOLD frequency shifts and quantitative susceptibility changes. PMID:23897623

Bianciardi, Marta; van Gelderen, Peter; Duyn, Jeff H.

2013-01-01

26

Investigation of BOLD fMRI resonance frequency shifts and quantitative susceptibility changes at 7 T.  

PubMed

Although blood oxygenation level dependent (BOLD) functional magnetic resonance imaging (fMRI) experiments of brain activity generally rely on the magnitude of the signal, they also provide frequency information that can be derived from the phase of the signal. However, because of confounding effects of instrumental and physiological origin, BOLD related frequency information is difficult to extract and therefore rarely used. Here, we explored the use of high field (7 T) and dedicated signal processing methods to extract frequency information and use it to quantify and interpret blood oxygenation and blood volume changes. We found that optimized preprocessing improves detection of task-evoked and spontaneous changes in phase signals and resonance frequency shifts over large areas of the cortex with sensitivity comparable to that of magnitude signals. Moreover, our results suggest the feasibility of mapping BOLD quantitative susceptibility changes in at least part of the activated area and its largest draining veins. Comparison with magnitude data suggests that the observed susceptibility changes originate from neuronal activity through induced blood volume and oxygenation changes in pial and intracortical veins. Further, from frequency shifts and susceptibility values, we estimated that, relative to baseline, the fractional oxygen saturation in large vessels increased by 0.02-0.05 during stimulation, which is consistent to previously published estimates. Together, these findings demonstrate that valuable information can be derived from fMRI imaging of BOLD frequency shifts and quantitative susceptibility changes. PMID:23897623

Bianciardi, Marta; van Gelderen, Peter; Duyn, Jeff H

2014-05-01

27

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

28

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

29

Classification of Functional Magnetic Resonance Imaging Data using Informative Pattern Features  

E-print Network

for analyzing functional magnetic resonance imaging (fMRI) data, statistical parametric map- ping, produces maps- monality of datasets with tens to hundreds of classes makes this problem even more acute. In this paper we (fMRI) is a tech- nique used in psychological experiments to measure the blood oxygenation level

Botvinick, Matthew

30

Functional magnetic resonance imaging at 0.2 Tesla  

Microsoft Academic Search

Functional magnetic resonance imaging of healthy human volunteers was carried out at 0.2 T, using proton-density weighted (TE = 24 ms) spin-echo imaging, in order to eliminate any contribution from the blood oxygenation-level dependent (BOLD) effect. The purpose of the study was to verify the existence of a proton-density change contribution to spin-echo functional magnetic resonance imaging (fMRI) data. Results

P. W Stroman; K. L Malisza; M Onu

2003-01-01

31

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

32

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

33

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

34

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,

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

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

Microsoft Academic Search

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

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

2004-01-01

37

Cross-Validation of Deformable Registration With Field Maps in Functional Magnetic Resonance Brain Imaging  

Microsoft Academic Search

The localization of brain functional activity with respect to brain anatomy requires registration between a functional image and a reference high-resolution anatomical image. The fast functional magnetic resonance brain images acquired via echo planar imaging (EPI) in functional magnetic resonance imaging (fMRI) suffer from local geometric distortions. After performing standard rigid or affine registration, local nonlinear distortions of up to

Ali Gholipour; Nasser Kehtarnavaz; Kaundinya Gopinath; Richard Briggs

2008-01-01

38

Electromyography as a Recording System for Eyeblink Conditioning with Functional Magnetic Resonance Imaging  

Microsoft Academic Search

This study was designed to develop a suitable method of recording eyeblink responses while con- ducting functional magnetic resonance imaging (fMRI). Given the complexity of this behavioral setup outside of the magnet, this study sought to adapt and further optimize an approach to eyeblink condition- ing that would be suitable for conducting event-re- lated fMRI experiments. This method involved the

M. G. Knuttinen; T. B. Parrish; C. Weiss; K. S. LaBar; D. R. Gitelman

2002-01-01

39

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.

S�½kora, Stanislav

40

Simultaneous Electroencephalography and Functional Magnetic Resonance Imaging of General Anesthesia  

PubMed Central

It has been long appreciated that anesthetic drugs induce stereotyped changes in electroencephalogram (EEG), but the relationships between EEG and underlying brain function remain poorly understood. Functional imaging methods including positron emission tomography (PET) and functional magnetic resonance imaging (fMRI), have become important tools for studying how anesthetic drugs act in the human brain to induce the state of general anesthesia. To date, no investigation has combined functional MRI with EEG to study general anesthesia. We report here a paradigm for conducting combined fMRI and EEG studies of human subjects under general anesthesia. We discuss the several technical and safety problems that must be solved to undertake this type of multimodal functional imaging and show combined recordings from a human subject. Combined fMRI and EEG exploits simultaneously the high spatial resolution of fMRI and the high temporal resolution of EEG. In addition, combined fMRI and EEG offers a direct way to relate established EEG patterns induced by general anesthesia to changes neural activity in specific brain regions as measured by changes in fMRI blood oxygen level dependent (BOLD) signals. PMID:19351356

Purdon, Patrick L.; Pierce, Eric T.; Bonmassar, Giorgio; Walsh, John; Harrell, P. Grace; Kwo, Jean; Deschler, Daniel; Barlow, Margaret; Merhar, Rebecca C.; Lamus, Camilo; Mullaly, Catherine M.; Sullivan, Mary; Maginnis, Sharon; Skoniecki, Debra; Higgins, Helen-Anne; Brown, Emery N.

2009-01-01

41

Improved functional mapping of the human amygdala using a standard functional magnetic resonance imaging sequence with simple modifications  

Microsoft Academic Search

As the amygdala is involved in various aspects of emotional processing, its characterization using neuroimaging modalities, such as functional magnetic resonance imaging (fMRI), is of great interest. However, in fMRI, the amygdala region suffers from susceptibility artifacts that are composed of signal dropouts and image distortions. Various technically demanding approaches to reduce these artifacts have been proposed, and most require

Carmen Morawetz; Petra Holz; Claudia Lange; Jürgen Baudewig; Godehard Weniger; Eva Irle; Peter Dechent

2008-01-01

42

Magnetic Resonance Imaging and Magnetic Resonance Spectroscopy in Dementias  

PubMed Central

This article reviews recent studies of magnetic resonance imaging and magnetic resonance spectroscopy in dementia, including Alzheimer's disease, frontotemporal dementia, dementia with Lewy bodies, idiopathic Parkinson's disease, Huntington's disease, and vascular dementia. Magnetic resonance imaging and magnetic resonance spectroscopy can detect structural alteration and biochemical abnormalities in the brain of demented subjects and may help in the differential diagnosis and early detection of affected individuals, monitoring disease progression, and evaluation of therapeutic effect. PMID:11563438

Hsu, Yuan-Yu; Du, An-Tao; Schuff, Norbert; Weiner, Michael W.

2007-01-01

43

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

44

Magnetic resonance imaging  

SciTech Connect

The authors present a review of magnetic resonance imaging. Many topics are explored from instrumentation, spectroscopy, blood flow and sodium imaging to detailed clinical applications such as the differential diagnosis of multiple sclerosis or adrenal adenoma. The emphasis throughout is on descriptions of normal multiplanar anatomy and pathology as displayed by MRI.

Stark, D.D.; Bradley, W.G. Jr.

1988-01-01

45

Magnetic Resonance Spectroscopy (MRS)  

E-print Network

does not require any ionizing radiation. It provides a wealth of information (in vivo) on variousMagnetic Resonance Spectroscopy (MRS) and Its Application in Alzheimer's Disease PRAVAT K. MANDAL1 alterations and the pathophysiology of disease. This article provides a comprehensive description of the MRS

Mandal, Pravat K.

46

Clinical magnetic resonance imaging  

SciTech Connect

This book presents clinical applications of magnetic resonance imaging with a strong clinical orientation. Covers technique, instrumentation, and contrast agents. Describes MRI of the neck, brain, heart, spine, TMJ and orbit, chest abdomen, pelvis, and the joints. Also includes a high field atlas of the central nervous system.

Brady, T.J.; Edelman, R.R.

1988-01-01

47

Introduction Magnetic Resonance Imaging (MRI)  

E-print Network

Introduction Statistics Magnetic Resonance Imaging (MRI) Statistics in the UK Statistics at UCL and Beyond #12;Introduction Statistics Magnetic Resonance Imaging (MRI) Statistics in the UK Statistics Magnetic Resonance Imaging (MRI) Statistics in the UK Statistics at UCL Outline Why do Statistics? Some

Wirosoetisno, Djoko

48

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

PubMed Central

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

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

2010-01-01

49

Sources of signal fluctuations in functional magnetic resonance imaging at 7 Tesla  

Microsoft Academic Search

High-field magnetic resonance imaging (MRI) systems allow for critical improvements in image signal-to-noise ratio (SNR), potentially leading to higher sensitivity and spatial resolution for functional MRI (fMRI). 3D segmented echo volumar imaging (EVI) has recently been proposed for high- resolution fMRI at ultra-high fields. It provides higher image SNR than standard 2D echo planar imaging (EPI), but is also thought

Joao P. F. Jorge; P. Figueiredo; W. van der Zwaag; J. P. Marques

2011-01-01

50

A functional magnetic resonance imaging technique based on nulling extravascular gray matter signal  

Microsoft Academic Search

A new functional magnetic resonance imaging (fMRI) technique is proposed based on nulling the extravascular gray matter (GM) signal, using a spatially nonselective inversion pulse. The remaining MR signal provides cerebral blood volume (CBV) information from brain activation. A theoretical framework is provided to characterize the sources of GM-nulled (GMN) fMRI signal, effects of partial voluming of cerebrospinal fluid (CSF)

Yuji Shen; Risto A Kauppinen; Rishma Vidyasagar; Xavier Golay

2009-01-01

51

A functional magnetic resonance imaging study during sentence reading in Japanese dyslexic children  

Microsoft Academic Search

A functional magnetic resonance imaging (fMRI) study during Japanese ‘kana’ readings was performed on Japanese dyslexic children. Five dyslexic children (aged 9–12 years) and five healthy children (aged 9–11 years) were investigated. The fMRI examination was performed by getting these children to read sentences constructed from Japanese phonograms, ‘kana’, compared with staring at meaningless figures as a control task. All

Ayumi Seki; Tatsuya Koeda; Shuji Sugihara; Masayuki Kamba; Yoshiharu Hirata; Toshihide Ogawa; Kenzo Takeshita

2001-01-01

52

Functional Magnetic Resonance Imaging in a Low-Field Intraoperative Scanner  

Microsoft Academic Search

Background: Functional magnetic resonance imaging (fMRI) has been used for preoperative planning and intraoperative surgical navigation. However, most experience to date has been with preoperative images acquired on high-field echoplanar MRI units. We explored the feasibility of acquiring fMRI of the motor cortex with a dedicated low-field intraoperative MRI (iMRI). Methods: Five healthy volunteers were scanned with the 0.12-tesla PoleStar

Michael Schulder; Hooman Azmi; Bharat Biswal

2003-01-01

53

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

54

Experiences with functional magnetic resonance imaging at 1 tesla  

Microsoft Academic Search

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

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

1998-01-01

55

fMRI Supports the Sensorimotor Theory of Motor Resonance  

Microsoft Academic Search

The neural mechanisms mediating the activation of the motor system during action observation, also known as motor resonance, are of major interest to the field of motor control. It has been proposed that motor resonance develops in infants through Hebbian plasticity of pathways connecting sensory and motor regions that fire simultaneously during imitation or self movement observation. A fundamental problem

Claire Landmann; Sofia M. Landi; Scott T. Grafton; Valeria Della-Maggiore

2011-01-01

56

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

57

ICA-BASED SPARSE FEATURES RECOVERY FROM FMRI DATASETS Gael Varoquaux1,2  

E-print Network

ICA-BASED SPARSE FEATURES RECOVERY FROM FMRI DATASETS Ga¨el Varoquaux1,2 , Merlin Keller1,2 , Jean features from fMRI datasets. Specifically, we introduce a new thresholding procedure that controls Analysis (ICA) is increas- ingly used in the context of functional Magnetic Resonance Imaging (fMRI

Paris-Sud XI, Université de

58

Optimizing Design Efficiency of Free Recall Events for fMRI  

E-print Network

free recall latency distributions to generate simulated fMRI datasets and assessed design effi- ciencyU ncorrected Proof Optimizing Design Efficiency of Free Recall Events for fMRI Ilke Ã?ztekin, Nicole with func- tional magnetic resonance imaging (fMRI). We used both theo- retically and empirically derived

Badre, David

59

Nuclear Magnetic Resonance Gyroscope  

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

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

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

63

Nonlinear Dimension Reduction and Activation Detection for fMRI Dataset  

Microsoft Academic Search

Functional magnetic resonance imaging (fMRI) has been established as a powerful method for brain mapping. Different physical phenomena contribute to the dynamical changes in the fMRI signal, the task-related hemodynamic responses, non-task-related physiological rhythms, machine and motion artifacts, etc. In this paper, we propose a new approach for fMRI data analysis. Each fMRI time series is viewed as a point

Xilin Shen; Francois G. Meyer

2006-01-01

64

Proton Density-Weighted Functional Magnetic Resonance Imaging at 0.35 Tesla  

Microsoft Academic Search

Functional magnetic resonance imaging of healthy human volunteers was carried out at 0.35T MRI system, using proton-density weighted turbo spin-echo imaging. It aims at verifying the proton-density change contribution to spin-echo functional magnetic resonance imaging. And try to get better effect of fMRI studies at 0.35T MRI system. Results demonstrated that signal intensity changes in motor area of the brain

Ping. Yang; Jinxing. Wang; Yuesheng Chao; Guang Lu; Jinquan Shi

2008-01-01

65

Virtual magnetic resonance colonography  

PubMed Central

Colorectal cancer screening has vast potential. Beyond considerations for cost and diagnostic accuracy, the effectiveness of any colorectal screening strategy will be dependent on the degree of patient acceptance. Magnetic resonance (MR) colonography has been shown to be accurate regarding the detection of clinically relevant colonic polyps exceeding 10 mm in size, with reported sensitivity and specificity values exceeding 95%. To further increase patient acceptance, strategies for fecal tagging have recently been developed. By modulating the signal of fecal material to be identical to the signal characteristics of the enema applied to distend the colon, fecal tagging in conjunction with MR colonography obviates the need for bowel cleansing. The review will describe the techniques underlying MR colonography and describe early clinical experience with fecal tagging techniques. PMID:12746264

Debatin, J; Lauenstein, T

2003-01-01

66

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

67

Comparison of Filtering Methods for fMRI Datasets F. Kruggel, D. Y. von Cramon, and X. Descombes  

E-print Network

Comparison of Filtering Methods for fMRI Datasets F. Kruggel, D. Y. von Cramon, and X. Descombes August 31, 1998 When studying complex cognitive tasks using func- tional magnetic resonance imaging (fMRI is modulated onto foreground patches obtained from event-related fMRI experiments. Quantitative performance

Catholique de Louvain, Université

68

Naive random subspace ensemble with linear classifiers for real-time classification of fMRI data  

E-print Network

assigned by the classifier. We perform experiments on three fMRI datasets to demonstrate that naiveNaive random subspace ensemble with linear classifiers for real-time classification of fMRI data: Functional magnetic resonance imaging (fMRI) Online classification Naive labelling Classifier ensembles a b

Kuncheva, Ludmila I.

69

IEEE TRANSACTIONS ON MEDICAL IMAGING, VOL. 29, NO. 2, FEBRUARY 2010 531 Random Subspace Ensembles for fMRI Classification  

E-print Network

classifiers. RS was tested on three fMRI datasets from single-subject experiments: the Haxby et al. data for fMRI Classification Ludmila I. Kuncheva*, Member, IEEE, Juan J. Rodríguez, Member, IEEE, Catrin O through functional magnetic resonance imaging (fMRI) poses a serious challenge to pattern recognition

Kuncheva, Ludmila I.

70

Predicting cross-task behavioral variables from fMRI data using the k-support norm  

E-print Network

to predict real valued variables from brain fMRI data for cocaine addiction, in a principled model selection the use of the k-support norm for fMRI analysis and the generalizability of the I-RISA model of cocaine addiction. Keywords: Functional magnetic resonance Imaging (fMRI), Regular- ization, Sparse representations

Boyer, Edmond

71

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

72

Neuronal Clustering of Brain fMRI Images  

Microsoft Academic Search

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

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

2005-01-01

73

Cortical Activation in the Human Brain during Lateral Saccades Using EPISTAR Functional Magnetic Resonance Imaging  

Microsoft Academic Search

The location of the human cortical substrate underlying simple horizontal saccadic eye movements was investigated using echoplanar functional magnetic resonance imaging (fMRI) in young healthy volunteers. Echoplanar imaging with signal targeting and alternating radiofrequency (EPISTAR), a novel perfusion technique, measured signal intensity changes in one to four contiguous 10-mm slices centered to include both striate cortex and putative frontal eye

David G. Darby; Anna C. Nobre; Venkatesan Thangaraj; Robert Edelman; M-Marsel Mesulam; Steven Warach

1996-01-01

74

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

75

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

76

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

77

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

78

Recent developments in optimal experimental designs for functional magnetic resonance imaging  

PubMed Central

Functional magnetic resonance imaging (fMRI) is one of the leading brain mapping technologies for studying brain activity in response to mental stimuli. For neuroimaging studies utilizing this pioneering technology, there is a great demand of high-quality experimental designs that help to collect informative data to make precise and valid inference about brain functions. This paper provides a survey on recent developments in experimental designs for fMRI studies. We briefly introduce some analytical and computational tools for obtaining good designs based on a specified design selection criterion. Research results about some commonly considered designs such as blocked designs, and m-sequences are also discussed. Moreover, we present a recently proposed new type of fMRI designs that can be constructed using a certain type of Hadamard matrices. Under certain assumptions, these designs can be shown to be statistically optimal. Some future research directions in design of fMRI experiments are also discussed. PMID:25071884

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

2014-01-01

79

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

80

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

81

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

82

Interventional magnetic resonance imaging.  

PubMed

The development of minimally invasive surgical and interventional techniques has created a need for more accurate and sensitive image guidance and monitoring. Magnetic resonance imaging, with its superior soft tissue discrimination and multiplanar facilities, seems the obvious choice for an ideal image-guidance tool. Until recently, the employment of MRI in this role has been prevented by the physical constraints of conventional, closed-configuration machines. The problem has now been overcome by the development of an open design allowing both horizontal and vertical access to the patient in the scanner so that procedures can be performed concurrent with image acquisition. This configuration, together with the use of fast gradient echo sequences which can scan at speeds close to real time, means that a wide range of interventional procedures can be performed with on-line image guidance and monitoring. In addition, the versatility of the open design means that patients can assume physiological positions to allow dynamic joint imaging to be performed. This opens up a whole new field in the understanding of joint pathophysiology. This review article discusses these recent technological developments and their clinical applications. In particular, the potential role in guidance of biopsies, monitoring of thermal ablation techniques and applications in endoscopic surgery is outlined. PMID:9534721

Lamb, G M; Gedroyc, W M

1997-11-01

83

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

84

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

Microsoft Academic Search

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

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

1998-01-01

85

Cortical motor areas in plantar response: an event-related functional magnetic resonance imaging study in normal subjects  

Microsoft Academic Search

The role of the cerebral cortices in normal plantar response was investigated with event-related functional magnetic resonance imaging (fMRI) at 3 Tesla in 12 right-handed normal subjects. During fMRI acquisition, the lateral (LS) and medial (MS) side of the left sole was mechanically stimulated every 16 s to evoke the plantar response under monitoring of the surface electromyogram. LS activated

Kenichi Oishi; Keiichiro Toma; Kayako Matsuo; Toshiharu Nakai; Kazuo Chihara; Hidenao Fukuyama

2003-01-01

86

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

87

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

88

Ethics in fMRI Studies  

Microsoft Academic Search

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

Daniela Seixas; Margarida Ayres Basto

2008-01-01

89

The fMRI Data Center  

NSDL National Science Digital Library

Maintained by Dartmouth College, the fMRI Data Center serves as a repository for the functional magnetic resonance imaging data for peer-reviewed, published studies. Intended to help the fMRI research community "speed the progress and the understanding of cognitive processes and the neural substrates that underlie them," the fMRI Data Center is in the process of making all datasets and associated material completely Web-accessible. Currently, the datasets (36 total, with more added every year) are available as free CDs, which the fMRI Data Center will ship directly to interested users. The fMRI Data Center enthusiastically urges researchers to submit peer-reviewed articles and underlying datasets, and may eventually accept any pertinent data.

90

Magnetic Resonance Force Microscope Development  

SciTech Connect

Our objectives were to develop the Magnetic Resonance Force Microscope (MRFM) into an instrument capable of scientific studies of buried structures in technologically and scientifically important electronic materials such as magnetic multilayer materials. This work resulted in the successful demonstration of MRFM-detected ferromagnetic resonance (FMR) as a microscopic characterization tool for thin magnetic films. Strong FMR spectra obtained from microscopic Co thin films (500 and 1000 angstroms thick and 40 x 200 microns in lateral extent) allowed us to observe variations in sample inhomogeneity and magnetic anisotropy field. We demonstrated lateral imaging in microscopic FMR for the first time using a novel approach employing a spatially selective local field generated by a small magnetically polarized spherical crystallite of yttrium iron garnet. These successful applications of the MRFM in materials studies provided the basis for our successful proposal to DOE/BES to employ the MRF M in studies of buried interfaces in magnetic materials.

Hammel, P.C.; Zhang, Z.; Suh, B.J.; Roukes, M.L.; Midzor, M.; Wigen, P.E.; Childress, J.R.

1999-06-03

91

Noble gas magnetic resonator  

DOEpatents

Precise measurements of a precessional rate of noble gas in a magnetic field is obtained by constraining the time averaged direction of the spins of a stimulating alkali gas to lie in a plane transverse to the magnetic field. In this way, the magnetic field of the alkali gas does not provide a net contribution to the precessional rate of the noble gas.

Walker, Thad Gilbert; Lancor, Brian Robert; Wyllie, Robert

2014-04-15

92

Methodological challenges and solutions in auditory functional magnetic resonance imaging  

PubMed Central

Functional magnetic resonance imaging (fMRI) studies involve substantial acoustic noise. This review covers the difficulties posed by such noise for auditory neuroscience, as well as a number of possible solutions that have emerged. Acoustic noise can affect the processing of auditory stimuli by making them inaudible or unintelligible, and can result in reduced sensitivity to auditory activation in auditory cortex. Equally importantly, acoustic noise may also lead to increased listening effort, meaning that even when auditory stimuli are perceived, neural processing may differ from when the same stimuli are presented in quiet. These and other challenges have motivated a number of approaches for collecting auditory fMRI data. Although using a continuous echoplanar imaging (EPI) sequence provides high quality imaging data, these data may also be contaminated by background acoustic noise. Traditional sparse imaging has the advantage of avoiding acoustic noise during stimulus presentation, but at a cost of reduced temporal resolution. Recently, three classes of techniques have been developed to circumvent these limitations. The first is Interleaved Silent Steady State (ISSS) imaging, a variation of sparse imaging that involves collecting multiple volumes following a silent period while maintaining steady-state longitudinal magnetization. The second involves active noise control to limit the impact of acoustic scanner noise. Finally, novel MRI sequences that reduce the amount of acoustic noise produced during fMRI make the use of continuous scanning a more practical option. Together these advances provide unprecedented opportunities for researchers to collect high-quality data of hemodynamic responses to auditory stimuli using fMRI. PMID:25191218

Peelle, Jonathan E.

2014-01-01

93

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.

94

Interventional Cardiovascular Magnetic Resonance Imaging  

PubMed Central

Cardiovascular magnetic resonance (CMR) combines excellent soft-tissue contrast, multiplanar views, and dynamic imaging of cardiac function without ionizing radiation exposure. Interventional cardiovascular magnetic resonance (iCMR) leverages these features to enhance conventional interventional procedures or to enable novel ones. Although still awaiting clinical deployment, this young field has tremendous potential. We survey promising clinical applications for iCMR. Next, we discuss the technologies that allow CMR-guided interventions and, finally, what still needs to be done to bring them to the clinic. PMID:19909937

Saikus, Christina E.; Lederman, Robert J.

2010-01-01

95

Magnetic resonance apparatus  

DOEpatents

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

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

1982-01-01

96

Magnetic resonance apparatus  

DOEpatents

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

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

1980-10-10

97

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

98

Bilingual and Monolingual Brains Compared: A Functional Magnetic Resonance Imaging Investigation of Syntactic Processing and a Possible \\  

Microsoft Academic Search

Does the brain of a bilingual process language differently from that of a monolingual? We compared how bilinguals and monolinguals recruit classic language brain areas in response to a language task and asked whether there is a ''neural signature'' of bilingualism. Highly proficient and early-exposed adult Spanish- English bilinguals and English monolinguals participated. During functional magnetic resonance imaging (fMRI), partic-

Ioulia Kovelman; Stephanie A. Baker; Laura-ann Petitto

2008-01-01

99

Imaging the pain of low back pain: functional magnetic resonance imaging in combination with monitoring subjective pain perception  

E-print Network

Imaging the pain of low back pain: functional magnetic resonance imaging in combination to generate predictor waveforms with which related brain activity can be identi®ed. Chronic low back pain-leg raising procedure is performed to exacerbate the back pain. In the normal volunteer, fMRI scans were done

Apkarian, A. Vania

100

An exploration of spatial similarities in temporal noise spectra in fMRI measurements  

Microsoft Academic Search

In this paper, we describe a method to evaluate similarities in estimated temporal noise spectra of functional Magnetic Resonance Imaging (fMRI) time series. Accurate noise spectra are needed for reliable activation detection in fMRI. Since these spectra are a-priori unknown, they have to be estimated from the fMRI data. A noise model can be estimated for each voxel separately, but

D. H. J. Poot; A. J. den Dekker

101

An exploration of spatial similarities in temporal noise spectra in fMRI measurements  

Microsoft Academic Search

In this paper, we describe a method to evaluate similarities in estimated temporal noise spectra of functional Magnetic Resonance Imaging (fMRI) time series. Accurate noise spectra are needed for reliable activation detection in fMRI. Since these spectra are a-priori unknown, they have to be estimated from the fMRI data. A noise model can be estimated for each voxel separately, but

D. H. J. Poot; J. Sijbers; A. J. den Dekker

2008-01-01

102

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

103

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

104

Resonant magnetic fields from inflation  

SciTech Connect

We propose a novel scenario to generate primordial magnetic fields during inflation induced by an oscillating coupling of the electromagnetic field to the inflaton. This resonant mechanism has two key advantages over previous proposals. First of all, it generates a narrow band of magnetic fields at any required wavelength, thereby allaying the usual problem of a strongly blue spectrum and its associated backreaction. Secondly, it avoids the need for a strong coupling as the coupling is oscillating rather than growing or decaying exponentially. Despite these major advantages, we find that the backreaction is still far too large during inflation if the generated magnetic fields are required to have a strength of O(10{sup ?15} Gauss) today on observationally interesting scales. We provide a more general no-go argument, proving that this problem will apply to any model in which the magnetic fields are generated on subhorizon scales and freeze after horizon crossing.

Byrnes, Christian T. [CERN, PH-TH Division, CH-1211, Genève 23 (Switzerland); Hollenstein, Lukas; Jain, Rajeev Kumar [Département de Physique Théorique and Center for Astroparticle Physics, Université de Genève, 24, Quai Ernest Ansermet, CH-1211 Genève 4 (Switzerland); Urban, Federico R., E-mail: cbyrnes@cern.ch, E-mail: lukas.hollenstein@unige.ch, E-mail: rajeev.jain@unige.ch, E-mail: urban@phas.ubc.ca [Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, B.C. V6T 1Z1 (Canada)

2012-03-01

105

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

106

Decoding visual brain states from fMRI using an ensemble of classifiers  

Microsoft Academic Search

Decoding perceptual or cognitive states based on brain activity measured using functional magnetic resonance imaging (fMRI) can be achieved using machine learning algorithms to train classifiers of specific stimuli. However, the high dimensionality and intrinsically low signal to noise ratio (SNR) of fMRI data poses great challenges to such techniques. The problem is aggravated in the case of multiple subject

Carlos Cabral; Margarida Silveira; Patricia Figueiredo

107

A wavelet-based statistical analysis of fMRI data  

Microsoft Academic Search

We propose a new method for statistical analysis of functional magnetic resonance imaging (fMRI) data. The discrete wavelet\\u000a transformation is employed as a tool for efficient and robust signal representation. We use structural magnetic resonance\\u000a imaging (MRI) and fMRI to empirically estimate the distribution of the wavelet coefficients of the data both across individuals\\u000a and spatial locations. An anatomical subvolume

Ivo D. Dinov; John W. Boscardin; Michael S. Mega; Elizabeth L. Sowell; Arthur W. Toga

2005-01-01

108

Quantitative nuclear magnetic resonance spectrometry  

Microsoft Academic Search

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

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

2002-01-01

109

Interventional cardiovascular magnetic resonance imaging  

PubMed Central

Magnetic resonance imaging (MRI) provides structural and functional cardiovascular information with excellent soft tissue contrast. Real-time MRI can guide transcatheter cardiovascular interventions in large animal models, and may prove superior to x-ray and adjunct modalities for peripheral vascular, structural heart and cardiac electrophysiology applications. We describe technical considerations, pre-clinical work and early clinical studies in this emerging field. PMID:17662914

Raman, Venkatesh K.; Lederman, Robert J.

2008-01-01

110

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

111

Linear coupling between functional magnetic resonance imaging and evoked potential amplitude in human somatosensory cortex  

Microsoft Academic Search

The interpretation of task-induced functional imaging of the brain is critically dependent on understanding the relationship between observed blood flow responses and the underlying neuronal changes. However, the exact nature of this neurovascular coupling relationship remains unknown. In particular, it is unclear whether blood oxygen level-dependent functional magnetic resonance imaging (BOLD fMRI) responses principally reflect neuronal synaptic activity. In order

O. J Arthurs; E. J Williams; T. A Carpenter; J. D Pickard; S. J Boniface

2000-01-01

112

Functional magnetic resonance imaging of the primary motor cortex in humans: response to increased functional demands  

Microsoft Academic Search

Functional magnetic resonance imaging (fMRI) studies have been performed on 20 right handed volunteers at 1.5 Tesla using\\u000a echo planar imaging (EPI) protocol. Index finger tapping invoked localized activation in the primary motor area. Consistent\\u000a and highly reproducible activation in the primary motor area was observed in six different sessions of a volunteer over a\\u000a period of one month. Increased

S. Khushu; S. S. Kumaran; R. P. Tripathi; A. Gupta; P. C. Jain; V. Jain

2001-01-01

113

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

Microsoft Academic Search

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

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

1997-01-01

114

Age related signal decrease in functional magnetic resonance imaging during motor stimulation in humans  

Microsoft Academic Search

Right handed healthy volunteers underwent functional magnetic resonance imaging (fMRI) examinations on a 1.5 Tesla MRI-scanner (Gyroscan ACS NT; Philips, Best, NL). Blood oxygen level dependent (BOLD) images were obtained using a three dimensional multi-shot echo planar imaging sequence employing a shifted echo technique (Principles of echo shifting with a train of observations). Finger tapping of the right hand was

Volker Hesselmann; Olivier Zaro Weber; Christoph Wedekind; Timo Krings; Oliver Schulte; Harald Kugel; Barbara Krug; Norfrid Klug; Klaus J. Lackner

2001-01-01

115

Functional Magnetic Resonance Imaging of Motor Activation in the Human Cervical Spinal Cord  

Microsoft Academic Search

Functional magnetic resonance imaging (fMRI) at 1.5 T of a 30-mm segment of the human spinal cord, centered at the seventh cervical cord segment, showed mean blood-oxygenation-dependent contrast changes in image intensity of 4.8% associated with a unilateral hand-closing task in normal human volunteers. The observed locale of activation in the ipsilateral intermediate and ventral gray matter of the cervical

Takashi Yoshizawa; Tadao Nose; Gregory J. Moore; Laurel O. Sillerud

1996-01-01

116

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

117

Physiological recordings: basic concepts and implementation during functional magnetic resonance imaging.  

PubMed

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

2009-09-01

118

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

119

Bistable electron magnetic resonance in solids  

Microsoft Academic Search

This paper describes the phenomenon of Bistable Electron Magnetic Resonance, which manifests itself by a resonance line with a distorted shark fin-like shape. This effect requires only a fluctuating hyperfine interaction between electron spins and nuclear spins. It is demonstrated for shallow donors in semiconductors and conduction electrons in light metals. Bistability is an intrinsic property of electron magnetic resonance

Didier Gourier; Laurent Binet; Olivier Guillot-Noël

2004-01-01

120

Wide-range nuclear magnetic resonance detector  

NASA Technical Reports Server (NTRS)

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

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

1972-01-01

121

Integrated magnetic for LLC resonant converter  

Microsoft Academic Search

A new LLC resonant converter is proposed for front end DC\\/DC conversion in a distributed power system. This converter shows some potential benefits in this application. This paper proposes several integrated magnetic designs for LLC resonant converter. This converter has three magnetic components. With magnetic integration, first, a number of components can be reduced; secondly, flux ripple cancellation is achieved

Bo Yang; Rengang Chen; Fred C. Lee

2002-01-01

122

Low Dimensional Embedding of fMRI datasets  

Microsoft Academic Search

We propose a novel method to embed a functional magnetic resonance imaging (fMRI) dataset in a low-dimensional space. The embedding optimally preserves the local functional coupling between fMRI time series and provides a low-dimensional coordinate system for detecting activated voxels. To compute the embedding, we build a graph of functionally connected voxels. We use the commute time, instead of the

Xilin Shen; François G. Meyer

2007-01-01

123

Low-dimensional embedding of fMRI datasets  

Microsoft Academic Search

We propose a novel method to embed a functional magnetic resonance imaging (fMRI) dataset in a low-dimensional space. The embedding optimally preserves the local functional coupling between fMRI time series and provides a low-dimensional coordinate system for detecting activated voxels. To compute the embedding, we build a graph of functionally connected voxels. We use the commute time, instead of the

Xilin Shen; François G. Meyer

2008-01-01

124

Random Subspace Ensembles for fMRI Classification  

Microsoft Academic Search

Classification of brain images obtained through functional magnetic resonance imaging (fMRI) poses a serious challenge to pattern recognition and machine learning due to the extremely large feature-to-instance ratio. This calls for revision and adaptation of the current state-of-the-art classification methods. We investigate the suitability of the random subspace (RS) ensemble method for fMRI classification. RS samples from the original feature

Ludmila I. Kuncheva; Juan José Rodríguez Diez; Catrin O. Plumpton; David E. J. Linden; Stephen J. Johnston

2010-01-01

125

Robust Independent Component Analysis for fMRI  

Microsoft Academic Search

Summary. Independent component analysis (ICA) is an efiective exploratory tool for analyzing spatio-temporal data. It has been successfully applied in analyzing functional Magnetic Resonance Imaging (fMRI) data, to recover the interested source signals from difierent parts of the brain. Due to the high sensitivity of MR scanners, outliers are inevitable in acquiring fMRI datasets while they cause misleading efiects for

Ping Bai; Haipeng Shen; Young Truong

126

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

127

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

128

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

129

Naive random subspace ensemble with linear classifiers for real-time classification of fMRI data  

Microsoft Academic Search

Functional magnetic resonance imaging (fMRI) provides a spatially accurate measure of brain activity. Real-time classification allows the use of fMRI in neurofeedback experiments. With limited labelled data available, a fixed pre-trained classifier may be inaccurate. We propose that streaming fMRI data may be classified using a classifier ensemble which is updated through naive labelling. Naive labelling is a protocol where

Catrin O. Plumpton; Ludmila I. Kuncheva; Nikolaas N. Oosterhof; Stephen J. Johnston

130

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

131

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

132

Regression Models for Identifying Noise Sources in Magnetic Resonance Images  

PubMed Central

Stochastic noise, susceptibility artifacts, magnetic field and radiofrequency inhomogeneities, and other noise components in magnetic resonance images (MRIs) can introduce serious bias into any measurements made with those images. We formally introduce three regression models including a Rician regression model and two associated normal models to characterize stochastic noise in various magnetic resonance imaging modalities, including diffusion-weighted imaging (DWI) and functional MRI (fMRI). Estimation algorithms are introduced to maximize the likelihood function of the three regression models. We also develop a diagnostic procedure for systematically exploring MR images to identify noise components other than simple stochastic noise, and to detect discrepancies between the fitted regression models and MRI data. The diagnostic procedure includes goodness-of-fit statistics, measures of influence, and tools for graphical display. The goodness-of-fit statistics can assess the key assumptions of the three regression models, whereas measures of influence can isolate outliers caused by certain noise components, including motion artifacts. The tools for graphical display permit graphical visualization of the values for the goodness-of-fit statistic and influence measures. Finally, we conduct simulation studies to evaluate performance of these methods, and we analyze a real dataset to illustrate how our diagnostic procedure localizes subtle image artifacts by detecting intravoxel variability that is not captured by the regression models. PMID:19890478

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

2009-01-01

133

Emotional Memory in Early Steroid Abnormalities: An fMRI Study of Adolescents With Congenital Adrenal Hyperplasia  

Microsoft Academic Search

Hormonal imbalances during development may have long-lasting effects. Using functional magnetic resonance imaging (fMRI), we compared 14 youths with Congenital Adrenal Hyperplasia (CAH), a genetic disorder of hormonal dysfunction, with 22 healthy controls on memory encoding of emotional faces. Patients remembered fewer faces than controls, particularly fearful faces. FMRI data to successfully encoded fearful faces revealed that males with CAH

Luigi Mazzone; Sven C. Mueller; Francoise Maheu; Carol VanRyzin; Deborah P. Merke; Monique Ernst

2011-01-01

134

fMRI activation pattern recognition: A novel application of PCA in language network of pediatric localization related epilepsy  

Microsoft Academic Search

In this study, a novel application of Principal Component Analysis (PCA) is proposed to detect language activation map patterns. These activation patterns were obtained by processing functional Magnetic Resonance Imaging (fMRI) studies on both control and localization related epilepsy (LRE) patients as they performed an auditory word definition task. Most group statistical analyses of fMRI datasets look for ldquocommonalityrdquo under

Xiaozhen You; Magno Guillen; Byron Bernal; William D. Gaillard; Malek Adjouadi

2009-01-01

135

Combining independent component analysis and correlation analysis to probe interregional connectivity in fMRI task activation datasets  

Microsoft Academic Search

A new approach in studying interregional functional connectivity using functional magnetic resonance imaging (fMRI) is presented. Functional connectivity may be detected by means of cross correlating time course data from functionally related brain regions. These data exhibit high temporal coherence of low frequency fluctuations due to synchronized blood flow changes. In the past, this fMRI technique for studying functional connectivity

Konstantinos Arfanakis; Dietmar Cordes; Victor M Haughton; Chad H Moritz; Michelle A Quigley; Mary E Meyerand

2000-01-01

136

Analysis of fMRI Data by Blind Separation of Data in a Tiny Spatial Domain into Independent Temporal Component  

Microsoft Academic Search

Independent Component Analysis (ICA) is a promising tool for the analysis of functional magnetic resonance imaging (fMRI) time series. In these studies, mostly assumed is a spatially independent component map of fMRI data (spatial ICA). In this paper, we assume that the temporal courses of the signal and noises are independent within a Tiny spatial domain (temporal ICA). Then with

Huafu Chen; Dezhong Yao; Yan Zhuo; Lin Chen

2003-01-01

137

COmplex-Model-Based Estimation of thermal noise for fMRI data in the presence of artifacts  

E-print Network

COmplex-Model-Based Estimation of thermal noise for fMRI data in the presence of artifacts Yin Xua by fast-imaging acquisition in functional magnetic resonance imaging (fMRI) studies, it is very difficult of incidental phase fluctuations impairs the validity of currently available solutions based on complex datasets

Rowe, Daniel B.

138

Cadmium ferrite ionic magnetic fluid: Magnetic resonance investigation  

Microsoft Academic Search

In contrast to all magnetic resonance investigations previously performed using magnetic fluids (MFs) based on spinel ferrite nanoparticles, cadmium-ferrite-based MFs present an intense, relatively sharp resonance line near g=4, in addition to the typical, broad structure near g=2. The broad resonance structure is associated with larger cadmium-ferrite nanoparticles, whereas the sharp resonance line is associated with ultrasmall cadmium-ferrite nanoparticles. Transmission

O. Silva; E. C. D. Lima; P. C. Morais

2003-01-01

139

Cadmium ferrite ionic magnetic fluid: Magnetic resonance investigation  

Microsoft Academic Search

In contrast to all magnetic resonance investigations previously performed using magnetic fluids (MFs) based on spinel ferrite nanoparticles, cadmium–ferrite-based MFs present an intense, relatively sharp resonance line near g=4, in addition to the typical, broad structure near g=2. The broad resonance structure is associated with larger cadmium–ferrite nanoparticles, whereas the sharp resonance line is associated with ultrasmall cadmium–ferrite nanoparticles. Transmission

O. Silva; E. C. D. Lima; P. C. Morais

2003-01-01

140

Extension of dVCA model and its application in estimating fMRI components  

NASA Astrophysics Data System (ADS)

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

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

2010-03-01

141

Investigation of magnetic resonances for different split-ring resonator parameters and designs  

Microsoft Academic Search

We investigate the magnetic resonance of split-ring resonators (SRR) experimentally and numerically. The dependence of the geometrical parameters on the magnetic resonance frequency of SRR is studied. We further investigate the effect of lumped capacitors integrated to the SRR on the magnetic resonance frequency for tunable SRR designs. Different resonator structures are shown to exhibit magnetic resonances at various frequencies

Koray Aydin; Irfan Bulu; Kaan Guven; Maria Kafesaki; Costas M Soukoulis; Ekmel Ozbay

2005-01-01

142

A Java-based fMRI Processing Pipeline Evaluation System for Assessment of Univariate General Linear Model and Multivariate Canonical Variate Analysis-based Pipelines  

Microsoft Academic Search

As functional magnetic resonance imaging (fMRI) becomes widely used, the demands for evaluation of fMRI processing pipelines\\u000a and validation of fMRI analysis results is increasing rapidly. The current NPAIRS package, an IDL-based fMRI processing pipeline\\u000a evaluation framework, lacks system interoperability and the ability to evaluate general linear model (GLM)-based pipelines\\u000a using prediction metrics. Thus, it can not fully evaluate fMRI

Jing Zhang; Lichen Liang; Jon R. Anderson; Lael Gatewood; David A. Rottenberg; Stephen C. Strother

2008-01-01

143

Magnetic resonance sees lesions of multiple sclerosis  

SciTech Connect

The value of nuclear magnetic resonance imaging in the diagnosis and quantitation of the progression of multiple sclerosis is discussed. Magnetic resonance imaging generates images that reflect differential density and velocity of hydrogen nuclei between cerebral gray and white matter, as well as between white matter and pathological lesions of the disease.

Ziporyn, T.

1985-02-15

144

Chemical Principles Revisited. Proton Magnetic Resonance Spectroscopy.  

ERIC Educational Resources Information Center

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

McQuarrie, Donald A.

1988-01-01

145

Reliability measures of functional magnetic resonance imaging in a longitudinal evaluation of mild cognitive impairment.  

PubMed

As the aging population grows, it has become increasingly important to carefully characterize amnestic mild cognitive impairment (aMCI), a preclinical stage of Alzheimer's disease (AD). Functional magnetic resonance imaging (fMRI) is a valuable tool for monitoring disease progression in selectively vulnerable brain regions associated with AD neuropathology. However, the reliability of fMRI data in longitudinal studies of older adults with aMCI is largely unexplored. To address this, aMCI participants completed two visual working tasks, a Delayed-Recognition task and a One-Back task, on three separate scanning sessions over a three-month period. Test-retest reliability of the fMRI blood oxygen level dependent (BOLD) activity was assessed using an intraclass correlation (ICC) analysis approach. Results indicated that brain regions engaged during the task displayed greater reliability across sessions compared to regions that were not utilized by the task. During task-engagement, differential reliability scores were observed across the brain such that the frontal lobe, medial temporal lobe, and subcortical structures exhibited fair to moderate reliability (ICC=0.3-0.6), while temporal, parietal, and occipital regions exhibited moderate to good reliability (ICC=0.4-0.7). Additionally, reliability across brain regions was more stable when three fMRI sessions were used in the ICC calculation relative to two fMRI sessions. In conclusion, the fMRI BOLD signal is reliable across scanning sessions in this population and thus a useful tool for tracking longitudinal change in observational and interventional studies in aMCI. PMID:24018304

Zanto, Theodore P; Pa, Judy; Gazzaley, Adam

2014-01-01

146

Magnetic resonance imaging of glioblastoma using aptamer conjugated magnetic nanoparticles  

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

147

Magnetic resonance imaging of electrolysis.  

PubMed

This study explores the hypothesis that Magnetic Resonance Imaging (MRI) can image the process of electrolysis by detecting pH fronts. The study has relevance to real time control of cell ablation with electrolysis. To investigate the hypothesis we compare the following MR imaging sequences: T1 weighted, T2 weighted and Proton Density (PD), with optical images acquired using pH-sensitive dyes embedded in a physiological saline agar solution phantom treated with electrolysis and discrete measurements with a pH microprobe. We further demonstrate the biological relevance of our work using a bacterial E. Coli model, grown on the phantom. The results demonstrate the ability of MRI to image electrolysis produced pH changes in a physiological saline phantom and show that these changes correlate with cell death in the E. Coli model grown on the phantom. The results are promising and invite further experimental research. PMID:25659942

Meir, Arie; Hjouj, Mohammad; Rubinsky, Liel; Rubinsky, Boris

2015-01-01

148

Magnetic Resonance Imaging of Electrolysis.  

PubMed Central

This study explores the hypothesis that Magnetic Resonance Imaging (MRI) can image the process of electrolysis by detecting pH fronts. The study has relevance to real time control of cell ablation with electrolysis. To investigate the hypothesis we compare the following MR imaging sequences: T1 weighted, T2 weighted and Proton Density (PD), with optical images acquired using pH-sensitive dyes embedded in a physiological saline agar solution phantom treated with electrolysis and discrete measurements with a pH microprobe. We further demonstrate the biological relevance of our work using a bacterial E. Coli model, grown on the phantom. The results demonstrate the ability of MRI to image electrolysis produced pH changes in a physiological saline phantom and show that these changes correlate with cell death in the E. Coli model grown on the phantom. The results are promising and invite further experimental research. PMID:25659942

Meir, Arie; Hjouj, Mohammad; Rubinsky, Liel; Rubinsky, Boris

2015-01-01

149

[Cardiac magnetic resonance imaging (MRI)].  

PubMed

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

Vignaux, Olivier

2004-07-31

150

Magnetic resonance microscopy of embryos.  

PubMed

We demonstrate that magnetic resonance (MR) microscopy provides a mechanism to investigate normal and abnormal developmental anatomy in a non-destructive and distortion-free manner. Techniques for the fixation, embedding, perfusion and image acquisition of embryos between 3 and 30 mm crown rump length are described. We describe the perfusion of a contrast agent to enhance images of the developing embryonic vasculature. Data are acquired as three-dimensional isotropic arrays which permit images to be reformatted retrospectively in any plane. The data are available for archiving, distributing and for post-acquisition manipulations. MR microscopy is a fast technique for producing three-dimensional reconstructions and is free from registration and sectioning artifacts. PMID:9007215

Smith, B R; Linney, E; Huff, D S; Johnson, G A

1996-01-01

151

Magnetic resonance velocimetry: applications of magnetic resonance imaging in the measurement of fluid motion  

Microsoft Academic Search

Magnetic resonance velocimetry (MRV) is a non-invasive technique capable of measuring the three-component mean velocity field in complex three-dimensional geometries with either steady or periodic boundary conditions. The technique is based on the phenomenon of nuclear magnetic resonance (NMR) and works in conventional magnetic resonance imaging (MRI) magnets used for clinical imaging. Velocities can be measured along single lines, in

Christopher J. Elkins; Marcus T. Alley

2007-01-01

152

Magnetic resonance velocimetry: applications of magnetic resonance imaging in the measurement of fluid motion  

Microsoft Academic Search

Magnetic resonance velocimetry (MRV) is a non-invasive technique capable of measuring the three-component mean velocity field\\u000a in complex three-dimensional geometries with either steady or periodic boundary conditions. The technique is based on the\\u000a phenomenon of nuclear magnetic resonance (NMR) and works in conventional magnetic resonance imaging (MRI) magnets used for\\u000a clinical imaging. Velocities can be measured along single lines, in

Christopher J. Elkins; Marcus T. Alley

2007-01-01

153

Neural substrates of Hanja (Logogram) and Hangul (Phonogram) character readings by functional magnetic resonance imaging.  

PubMed

The two basic scripts of the Korean writing system, Hanja (the logography of the traditional Korean character) and Hangul (the more newer Korean alphabet), have been used together since the 14th century. While Hanja character has its own morphemic base, Hangul being purely phonemic without morphemic base. These two, therefore, have substantially different outcomes as a language as well as different neural responses. Based on these linguistic differences between Hanja and Hangul, we have launched two studies; first was to find differences in cortical activation when it is stimulated by Hanja and Hangul reading to support the much discussed dual-route hypothesis of logographic and phonological routes in the brain by fMRI (Experiment 1). The second objective was to evaluate how Hanja and Hangul affect comprehension, therefore, recognition memory, specifically the effects of semantic transparency and morphemic clarity on memory consolidation and then related cortical activations, using functional magnetic resonance imaging (fMRI) (Experiment 2). The first fMRI experiment indicated relatively large areas of the brain are activated by Hanja reading compared to Hangul reading. The second experiment, the recognition memory study, revealed two findings, that is there is only a small difference in recognition memory for semantic transparency, while for the morphemic clarity was much larger between Hanja and Hangul. That is the morphemic clarity has significantly more effect than semantic transparency on recognition memory when studies by fMRI in correlation with behavioral study. PMID:25368497

Cho, Zang-Hee; Kim, Nambeom; Bae, Sungbong; Chi, Je-Geun; Park, Chan-Woong; Ogawa, Seiji; Kim, Young-Bo

2014-10-01

154

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

PubMed

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

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

2014-05-01

155

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

156

Level of sustained entorhinal activity at study correlates with subsequent cued-recall performance: A functional magnetic resonance imaging study with high acquisition rate  

Microsoft Academic Search

Functional magnetic resonance imaging (fMRI) with high acquisition rate was performed during the intentional memorizing of words to specify which medial temporal lobe structure is important in determining what words are subsequently remembered in a cued-recall test and to characterize the time course of activation in that structure. Functional images of six healthy young subjects were analyzed by two subject-

James B. Brewer; Zuo Zhao; Gary H. Glover; John D. E. Gabrieli

1999-01-01

157

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

ERIC Educational Resources Information Center

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

Blackman, Graham A.; Hall, Deborah A.

2011-01-01

158

[Magnetic resonance imaging of the breasts].  

PubMed

Not even magnetic resonance imaging is a perfect method for imaging of the breasts. Quality of the equipment, imaging parameters as well as the experience and competence of radiographers and radiologists have a significant effect on the final outcome of the study. Since interpretation of magnetic resonance imaging of the breasts is challenging, the radiologist should have access to a comprehensive medical history and previous images, including the reports. Feedback from the reports made and multidisciplinary postoperative meetings are important. Since magnetic resonance imaging is expensive and has low availability, it should be targeted at the correct patient groups. PMID:24340717

Hukkinen, Katja

2013-01-01

159

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

160

Magnetic resonance images in hanging.  

PubMed

Hanging is a devastating method of suicide and unfortunately is common in Japan. Although several CT findings of the head have been reported, there have not been any reports about magnetic resonance imaging (MRI) in hanging. We report here interesting MRI findings in a patient after hanging. A 39-year-old woman was transferred to our department after attempting suicide by hanging. Respiration had probably ceased for about three minutes but heart had not stopped when she was pulled down by her father. After her father performed cardiopulmonary resuscitation, she started to breathe immediately. She was treated conservatively in our intensive care unit for 14 days, her condition became stable. Ten days after admission, MRI demonstrated symmetrical hyperintensity on T1-weighted images and relative hyperintensity on T2 weighted images in bilateral lentiform nuclei and medial thalami. There have been several reports about characteristic MRI findings in the case of acute global cerebral ischaemia caused by severe hypoglycaemia or longstanding cardiopulmonary arrest. It was postulated that these specific findings reflected tissue degeneration, deposition of mineral substances, or lipid accumulation. These MRI findings suggest that severe acute global cerebral hypoperfusion also occurs in hanging in the same way as in long-standing cardiopulmonary arrest and that hanging has devastating sequelae. PMID:16458413

Matsuyama, Takeshi; Okuchi, Kazuo; Seki, Tadahiko; Higuchi, Takafumi; Ito, Shingo; Makita, Daisuke; Watanabe, Tomoo; Murao, Yoshinori

2006-05-01

161

Cocaine Decreases Cortical Cerebral Blood Flow But Does Not Obscure Regional Activation in Functional Magnetic Resonance Imaging in Human Subjects  

Microsoft Academic Search

The authors used functional magnetic resonance imaging (fMRI) to determine whether acute intravenous (IV) cocaine use would change global cerebral blood flow (CBF) or visual stimulation-induced functional activation. They used flow-sensitive alternating inversion recovery (FAIR) scan sequences to measure CBF and blood oxygen level-dependent (BOLD) sensitive T2* scan sequences during visual stimulation to measure neuronal activation before and after cocaine-and

Randy L. Gollub; Hans C. Breiter; Howard Kantor; David Kennedy; David Gastfriend; R. Thomas Mathew; Nikos Makris; Alex Guimaraes; Jonn Riorden; Terry Campbell; Mary Foley; Steve E. Hyman; Bruce Rosen; Robert Weisskoff

1998-01-01

162

“Calm Down Dear, It’s Only a Simulator.” An investigation into the effects of the fMRI environment on cognition.   

E-print Network

Functional Magnetic Resonance Imaging (fMRI) is a useful tool which permits the observation of the brain’s neuronal activity in a non-invasive, on-line manner. The usefulness of the technique has however been questioned ...

Black, Ashley Anne

2007-01-01

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

Parallel magnetic resonance imaging: characterization and comparison  

E-print Network

Magnetic Resonance Imaging (MRI) is now increasingly being used for fast imaging applications such as real-time cardiac imaging, functional brain imaging, contrast enhanced MRI, etc. Imaging speed in MRI is mainly limited by different imaging...

Rane, Swati Dnyandeo

2005-11-01

165

Magnetic Resonance Pulse Sequences for Fluorine-19  

E-print Network

. Magnetic resonance imaging (MRI) has the ability to noninvasively track the transplanted cells to ensure they are in the desired destination. Unlike other MRI contrast agents, fluorine-19 has the ability to provide unambiguous cell tracking for two reasons...

Terry, Robin

2014-07-11

166

Magnetic resonance imaging in cardiovascular disease   

E-print Network

Background Superparamagnetic particles of iron oxide (SPIO) are part of a novel and exciting class of ‘smart’ magnetic resonance imaging (MRI) contrast agents that are taken up by inflammatory cells. Ultrasmall SPIO ...

Richards, Jennifer Margaret Jane

2013-07-06

167

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

168

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, Jörg; Gerber, Thomas C.

2009-01-01

169

Optimization of Blocked Designs in fMRI Studies  

ERIC Educational Resources Information Center

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

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

2010-01-01

170

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

171

Toward fMRI Group Identification Based on Brain Lateralization  

Microsoft Academic Search

This research presents a novel application of Lateralization Index (LI) in support of a decision making process for the classification of subjects based on their brain activation patterns using Functional Magnetic Resonance Imaging (fMRI) datasets. The decision process considers the subject grouping based on additional spatial information provided by the LI behavior for each individual when calculated for specific Broca's

Magno R. Guillen; Malek Adjouadi; Xiaozhen You; Armando Barreto; Naphtali Rishe; William Gaillard

2009-01-01

172

Comparison of Filtering Methods for fMRI Datasets  

Microsoft Academic Search

When studying complex cognitive tasks using functional magnetic resonance imaging (fMRI) one often encounters weak signal responses. These weak responses are corrupted by noise and artifacts of various sources. Preprocessing of the raw data before the application of test statistics helps to extract the signal and can vastly improve signal detection. Artifact sources and algorithms to handle them are discussed.

F. Kruggel; D. Y. von Cramon; X. Descombes

1999-01-01

173

fMRI activation detection in wavelet signal subspace  

Microsoft Academic Search

A new method is proposed for activation detection in event-related functional magnetic resonance imaging (fMRI). The method is based on nonparametric analysis of selected resolution levels (a subspace) in translation invariant wavelet transform (TIWT) domain. Using a priori knowledge about the activation signal and trends, we analyze their power in different resolution levels in TIWT domain and select an optimal

Hamid Soltanian-Zadeh; Gholam-Ali Hossein-Zadeh; Babak A. Ardekani

2002-01-01

174

Magnetic resonance studies of lunar samples  

Microsoft Academic Search

Electron spin resonance searches at 9.5 gigahertz on several fines samples and portions of several rocks have yielded signals whose lineshapes and temperature dependences show that the samples are principally ferromagnetic in nature. Proton magnetic resonance searches at 60 megahertz of these samples have not revealed any signals ascribable to water or any other types of hydrogen in concentrations greater

Stanley L. Manatt; Daniel D. Elleman; Robert W. Vaughan; Sunney I. Chan; Fun-Dow Tsay; Wesley T. Huntress Jr.

1970-01-01

175

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

176

Mapping numerical processing, reading, and executive functions in the developing brain: an fMRI meta-analysis of 52 studies  

E-print Network

PAPER Mapping numerical processing, reading, and executive functions in the developing brain: an fMRI meta-analysis of 52 studies including 842 children Olivier Houde´,y1,2 Sandrine Rossi,y1 Ame´lie Lubin1 the first meta-analysis of functional magnetic resonance imaging (fMRI) data obtained over the past decade

Allman, John M.

177

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

178

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

179

HOSPITAL PHYSICS: Magnetic resonance imaging and spectroscopy  

Microsoft Academic Search

Nuclear Magnetic Resonance (NMR) was first described in the scientific literature 50 years ago when Bloch and Purcell, working independently, showed how certain nuclei placed in a magnetic field absorbed energy in the radiofrequency range and re-emitted this energy during their transition back to the relaxed state (Bloch 1946, Purcell 1946). This phenomenon has since revolutionized medical imaging with its

Caroline Andrews; Andrew Simmons; Steve Williams

1996-01-01

180

Resting-state FMRI confounds and cleanup  

PubMed Central

The goal of resting-state functional magnetic resonance imaging (FMRI) is to investigate the brain’s functional connections by using the temporal similarity between blood oxygenation level dependent (BOLD) signals in different regions of the brain “at rest” as an indicator of synchronous neural activity. Since this measure relies on the temporal correlation of FMRI signal changes between different parts of the brain, any non-neural activity-related process that affects the signals will influence the measure of functional connectivity, yielding spurious results. To understand the sources of these resting-state FMRI confounds, this article describes the origins of the BOLD signal in terms of MR physics and cerebral physiology. Potential confounds arising from motion, cardiac and respiratory cycles, arterial CO2 concentration, blood pressure/cerebral autoregulation, and vasomotion are discussed. Two classes of techniques to remove confounds from resting-state BOLD time series are reviewed: 1) those utilising external recordings of physiology and 2) data-based cleanup methods that only use the resting-state FMRI data itself. Further methods that remove noise from functional connectivity measures at a group level are also discussed. For successful interpretation of resting-state FMRI comparisons and results, noise cleanup is an often over-looked but essential step in the analysis pipeline. PMID:23571418

Murphy, Kevin; Birn, Rasmus M.; Bandettini, Peter A.

2013-01-01

181

Ferromagnetic resonance imaging of Co films using magnetic resonance force microscopy  

E-print Network

Ferromagnetic resonance imaging of Co films using magnetic resonance force microscopy B. J. Suh, P is similar to that used in magnetic force microscopy MFM ,4 where only the spin magnetization in the vicinity of microscopic ferromagnetic resonance FMR detected using the magnetic resonance force microscope MRFM

Hammel, P. Chris

182

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

183

Wave-Particle Resonance in Magnetized Plasma  

NASA Astrophysics Data System (ADS)

We report the first observation of the wave-particle resonance line in a magnetized and weakly collisional plasma. The linear resonance satisfies the relation ?-n?ci = k||?|| and has a width which is related to the wave-particle coherence time. Both the in-phase (real) and quadrature (imaginary) parts of the resonant response are directly determined by a phased-lock laser induced fluorescence diagnostic. The wave-particle coherence time obtained by fitting the resonance line shape to a one-dimensional Poisson-Fokker-Planck model does not agree with a simple model of ion collisionality.

Sarfaty, M.; de Souza-Machado, S.; Skiff, F.

1998-04-01

184

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

185

A functional magnetic resonance imaging study of listening comprehension of languages in human at 3 tesla-comprehension level and activation of the language areas  

Microsoft Academic Search

Passive listening comprehension of native and non-native language was investigated using high resolution functional magnetic resonance imaging (fMRI) at a static magnetic field strength of 3 tesla. Wernicke's area was activated by comprehensive and non-comprehensive languages indicating that this area is associated with common phonological processing of language. The task with comprehensive but non-native language activated Broca's area and angular

Toshiharu Nakai; Kayako Matsuo; Chikako Kato; Masako Matsuzawa; Tomohisa Okada; Gary H Glover; Tetsuo Moriya; Toshio Inui

1999-01-01

186

High-resolution mapping of iso-orientation columns by fMRI  

Microsoft Academic Search

Blood-oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) is an important tool for localizing brain functions in vivo . However, the ability of BOLD fMRI to map cortical columnar structures is highly controversial, as the ultimate functional specificity of BOLD remains unknown. Here we report a biphasic BOLD response to visual stimulation in the primary visual cortex of cats. In

Dae-Shik Kim; Timothy Q. Duong; Seong-Gi Kim

2000-01-01

187

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

Microsoft Academic Search

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

Roberto Cabeza; Lars Nyberg

2000-01-01

188

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

189

Coregistration of EEG and fMRI in a simple motor task  

Microsoft Academic Search

The purpose of this study was to waluate the adequacy of coregistration of movement-related cortical potentials (MRCPs) and functional magnetic resonance imaging (fMRI) data in the primary sensorimotor cortex. Data were acquired in four normal subjects during right and left simple index finger movements. In fMRI (single-slice, 1.5 Tesla, T2*-weighted FLASH sequence), contralateral primary motor (Ml) and primary sensory cortex

Christian Gerloff; Wolfgang Grodd; Rupert Kolb; Thomas Naegele; Uwe Klose; Karsten Voigt; Johannes Dichgans

1996-01-01

190

Modelling the neurovascular habituation effect on fMRI time series  

Microsoft Academic Search

In this paper, a novel non-stationary model of functional Magnetic Resonance Imaging (fMRI) time series is proposed. It allows us to account for some putative habituation effect arising in event-related fMRI paradigms that involves the so-called repetition-suppression phenomenon and induces decreasing magnitude responses over successive trials. Akin to , this model is defined over functionnally homogeneous regions-of-interest (ROIs) and embedded

Philippe Ciuciu; Stéphane Sockeel; Thomas Vincent; Jérôme Idier

2009-01-01

191

Tuning FCMP to Elicit Novel Time Course Signatures in fMRI Neural Activation Studies  

Microsoft Academic Search

Functional magnetic resonance imaging (fMRI) is a preferred imaging modality to infer in vivo organ function from blood flow intensities. FMRI analysis is complex due to the variety of hemodynamic response models and\\u000a the presence of noise. This complexity drives the use of exploratory data analysis (EDA) to elicit intrinsic data structure.\\u000a This work demonstrates the utility of a fuzzy

Mark D. Alexiuk; Nick J. Pizzi; Witold Pedrycz

2007-01-01

192

Parcellation of fMRI Datasets with ICA and PLS-A Data Driven Approach  

Microsoft Academic Search

Inter-subject parcellation of functional Magnetic Resonance Imaging (fMRI) data based on a standard General Linear Model (GLM)and spectral clustering was recently proposed as a means to alleviate the issues associated with spatial normalization in fMRI. However, for all its appeal, a GLM-based parcellation approach introduces its own biases, in the form of a priori knowledge about the shape of Hemodynamic

Yongnan Ji; Pierre-Yves Herve; Uwe Aickelin; Alain Pitiot

2010-01-01

193

Node merging in Kohonen's self-organizing mapping of fMRI data  

Microsoft Academic Search

In this paper, Kohonen’s self-organizing mapping (SOM) is used as a data-driven technique for analyzing functional magnetic resonance imaging (fMRI) data. Upon the completion of an SOM analysis, a cluster merging technique, based on examining the reproducibility of the fMRI data across epochs, is utilized to merge SOM nodes whose feature vectors are sufficiently similar to one another. The resulting

Shing-chung Ngan; Essa S. Yacoub; William F. Auffermann; Xiaoping Hu

2002-01-01

194

Detecting spatiotemporal nonlinear dynamics in resting state of human brain based on fMRI datasets  

Microsoft Academic Search

In this work, a nonlinear dynamics method, coupled map lattices, was applied to functional magnetic resonance imaging (fMRI) datasets to examine the spatiotemporal properties of resting state blood oxygen level-dependent (BOLD) fluctuations. Spatiotemporal Lyapunov Exponent (SPLE) was calculated to study the deterministic nonlinearity in resting state human brain of nine subjects based on fMRI datasets. The results show that there

Xiaoping Xie; Zhitong Cao; Xuchu Weng

2008-01-01

195

A new method for detecting brain activities from fMRI dataset  

Microsoft Academic Search

Functional magnetic resonance imaging (fMRI) is a promising method to determine the spatial distribution of brain activities evoked by a given stimuli in a noninvasive manner. In this paper, a two-dimensional delay multiple signal classification (MUSIC) algorithm is proposed as a new technique for the processing of the fMRI data derived from a successive single-shot echo-planar image, where a delay

Huafu Chen; Dezhong Yao; Lin Chen

2002-01-01

196

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

197

Planar Magnetic Metamaterial Slabs for Magnetic Resonance Imaging Applications  

NASA Astrophysics Data System (ADS)

A type of planar magnetic metamaterial is proposed with a square winding microstructure as a superlens for magnetic resonance imaging (MRI) applications. A direct magnetic field mapping measurement demonstrates that the radio-frequency magnetic field passing through the superlens is increased by as high as 46.9% at the position of about 3 cm behind the superlens. The resonance frequency of the fabricated slabs is found to be in good agreement with the target frequency (63.6 MHz) for a 1.5T MRI system. MRI experiments with the magnetic superlens show that the intensity of the image and the SNR (signal-to-noise ratio) are both enhanced, implying promising MRI applications of our planar magnetic superlens.

Li, Chun-Lai; Guo, Jie; Zhang, Peng; Yu, Quan-Qiang; Ma, Wei-Tao; Miao, Xi-Gen; Zhao, Zhi-Ya; Luan, Lin

2014-07-01

198

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

199

Magnetic resonance in multilayer Gd/Si/Co magnetic films  

SciTech Connect

The magnetic properties of multilayer Gd/Si/Co magnetic films are experimentally studied by electron magnetic resonance and analyzed theoretically. The introduction of a semiconductor silicon interlayer is found to substantially affect the magnetic interlayer coupling and the magnetic dynamics of the system. The interlayer coupling is shown to be ferromagnetic for the (Gd/Si){sub n} films and to be antiferromagnetic for the (Gd/Si/Co/Si){sub n} films. The temperature dependences of the exchange parameters and the gyromagnetic ratios are determined. Possible mechanisms responsible for the formation of the interlayer coupling are discussed.

Patrin, G. S. [Russian Academy of Sciences, Kirenskii Institute of Physics, Siberian Division (Russian Federation)], E-mail: patrin@iph.krasn.ru; Vas'kovskii, V. O.; Svalov, A. V. [Ural State University (Russian Federation); Eremin, E. V.; Panova, M. A.; Vasil'ev, V. N. [Russian Academy of Sciences, Kirenskii Institute of Physics, Siberian Division (Russian Federation)

2006-01-15

200

Magnetic resonance imaging of the body  

SciTech Connect

This text provides reference to magnetic resonance imaging (MRI) of the body. Beginning with explanatory chapters on the physics, instrumentation, and interpretation of MRI, it proceeds to the normal anatomy of the neck, thorax, abdomen, and pelvis. Other chapters cover magnetic resonance imaging of blood flow, the larynx, the lymph nodes, and the spine, as well as MRI in obstetrics. The text features detailed coverage of magnetic resonance imaging of numerous disorders and disease states, including neck disease, thoracic disease; breast disease; congenital and acquired heart disease; vascular disease; diseases of the liver, pancreas, and spleen; diseases of the kidney, adrenals, and retroperitoneum; diseases of the male and female pelvis; and musculoskeletal diseases. Chapters on the biological and environmental hazards of MRI, the current clinical status of MRI in comparison to other imaging modalities, and economic considerations are also included.

Higgins, C.B.; Hricak, H.

1987-01-01

201

Observation of 239Pu nuclear magnetic resonance.  

PubMed

In principle, the spin-½ plutonium-239 ((239)Pu) nucleus should be active in nuclear magnetic resonance spectroscopy. However, its signal has eluded detection for the past 50 years. Here, we report observation of a (239)Pu resonance from a solid sample of plutonium dioxide (PuO(2)) subjected to a wide scan of external magnetic field values (3 to 8 tesla) at a temperature of 4 kelvin. By mapping the external field dependence of the measured resonance frequency, we determined the nuclear gyromagnetic ratio (239)?(n)(PuO(2))/2? to be 2.856 ± 0.001 megahertz per tesla (MHz/T). Assuming a free-ion value for the Pu(4+) hyperfine coupling constant, we estimated a bare (239)?(n)/2? value of ~2.29 MHz/T, corresponding to a nuclear magnetic moment of ?(n) ? 0.15?(N) (where ?(N) is the nuclear magneton). PMID:22605773

Yasuoka, H; Koutroulakis, G; Chudo, H; Richmond, S; Veirs, D K; Smith, A I; Bauer, E D; Thompson, J D; Jarvinen, G D; Clark, D L

2012-05-18

202

Magnetic resonance lymphography in gynaecological malignancies  

PubMed Central

Abstract Following the submission of this article to Cancer Imaging, unfortunately the European manufacturer of ferumoxtran-10 (Guerbet) has withdrawn the product pending further phase III studies. This is secondary to the view of the Committee for Medicinal Products for Human Use that the phase III data did not provide adequate statistical demonstration of the product's efficacy. Magnetic resonance lymphography holds much promise for the non-invasive evaluation of lymph nodes. The technique utilizes ultrasmall superparamagnetic particles of iron oxide and has been shown to be highly sensitive and specific in the diagnosis of malignant lymph nodes. This article reviews the technique and the performance of magnetic resonance lymphography in studies to date; alternative newer methods of nodal assessment such as fluorodeoxyglucose-positron emission tomography/computed tomography and diffusion-weighted magnetic resonance imaging are also discussed, with emphasis on gynaecological malignancies. PMID:20233680

Narayanan, Priya; Rockall, Andrea

2010-01-01

203

Neuronal correlates of encoding and retrieval in episodic memory during a paired-word association learning task: a functional magnetic resonance imaging study  

Microsoft Academic Search

The investigation of memory function using functional magnetic resonance imaging (fMRI) is an expanding field of research.\\u000a The aim of this study was to demonstrate brain-activity patterns related to a word-pair association task employing a whole-brain\\u000a EPI sequence. Six right-handed, healthy male volunteers (mean age: 27.5 years) took part in the study. fMRI was performed\\u000a at a field strength of

F. M. Mottaghy; N. J. Shah; B. J. Krause; D. Schmidt; U. Halsband; L. Jäncke; H.-W. Müller-Gärtner

1999-01-01

204

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

205

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

206

Functional Magnetic Resonance Imaging for Imaging Neural Activity in the Human Brain: The Annual Progress  

PubMed Central

Functional magnetic resonance imaging (fMRI) is recently developed and applied to measure the hemodynamic response related to neural activity. The fMRI can not only noninvasively record brain signals without risks of ionising radiation inherent in other scanning methods, such as CT or PET scans, but also record signal from all regions of the brain, unlike EEG/MEG which are biased towards the cortical surface. This paper introduces the fundamental principles and summarizes the research progress of the last year for imaging neural activity in the human brain. Aims of functional analysis of neural activity from fMRI include biological findings, functional connectivity, vision and hearing research, emotional research, neurosurgical planning, pain management, and many others. Besides formulations and basic processing methods, models and strategies of processing technology are introduced, including general linear model, nonlinear model, generative model, spatial pattern analysis, statistical analysis, correlation analysis, and multimodal combination. This paper provides readers the most recent representative contributions in the area. PMID:22319550

Chen, Shengyong; Li, Xiaoli

2012-01-01

207

Magnetic Microparticle Aggregation For Viscosity Determination By Magnetic Resonance  

PubMed Central

Micron-sized magnetic particles were induced to aggregate when placed in homogeneous magnetic fields, like those of magnetic resonance (MR) imagers and relaxometers, and then spontaneously returned to their dispersed state when removed from the field. Associated with the aggregation and dispersion of the magnetic particles were time dependent increases and decreases in the spin-spin relaxation time (T2) of the water. Magnetic nanoparticles, with far smaller magnetic moments per particle, did not undergo magnetically induced aggregation, and exhibited time independent values of T2. The rate of T2 change associated with magnetic micro-particle aggregation was used to determine the viscosity of liquid samples, providing a method that can be of particular advantage for determining the viscosity of small volumes of potentially biohazardous samples of blood or blood plasma. PMID:18306403

Hong, Rui; Cima, Michael J.; Weissleder, Ralph; Josephson, Lee

2009-01-01

208

Analytic programming with FMRI data: a quick-start guide for statisticians using R.  

PubMed

Functional magnetic resonance imaging (fMRI) is a thriving field that plays an important role in medical imaging analysis, biological and neuroscience research and practice. This manuscript gives a didactic introduction to the statistical analysis of fMRI data using the R project, along with the relevant R code. The goal is to give statisticians who would like to pursue research in this area a quick tutorial for programming with fMRI data. References of relevant packages and papers are provided for those interested in more advanced analysis. PMID:24586801

Eloyan, Ani; Li, Shanshan; Muschelli, John; Pekar, Jim J; Mostofsky, Stewart H; Caffo, Brian S

2014-01-01

209

Analytic Programming with fMRI Data: A Quick-Start Guide for Statisticians Using R  

PubMed Central

Functional magnetic resonance imaging (fMRI) is a thriving field that plays an important role in medical imaging analysis, biological and neuroscience research and practice. This manuscript gives a didactic introduction to the statistical analysis of fMRI data using the R project, along with the relevant R code. The goal is to give statisticians who would like to pursue research in this area a quick tutorial for programming with fMRI data. References of relevant packages and papers are provided for those interested in more advanced analysis. PMID:24586801

Eloyan, Ani; Li, Shanshan; Muschelli, John; Pekar, Jim J.; Mostofsky, Stewart H.; Caffo, Brian S.

2014-01-01

210

Observation of ferromagnetic resonance in a microscopic sample using magnetic resonance force microscopy  

E-print Network

can be measured. Employing magnetic resonance force microscopy MRFM we have observed a strong FMRObservation of ferromagnetic resonance in a microscopic sample using magnetic resonance force resonance force microscopy MRFM . The large signal intensity in the resonance spectra suggests that MRFM

Hammel, P. Chris

211

Magnetic resonance imaging of the thorax  

SciTech Connect

Magnetic Resonance Imaging of the Thorax is an introductory text covering magnetic resources (MR) imaging of the heart, great vessels, mediastinum, hili, pulmonary nodules, pleura, and diaphragm. The book opens with a brief discussion of MR physics. This is followed by a larger section on normal mediastinal anatomy as viewed on axial, coronal, and sagittal MR images. This chapter suffers form several poor-quality images and inadequate labeling. The last section gives 13 cases for review and self-testing.

Sperber, M.; Kaiser, M.C.

1987-01-01

212

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

213

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

E-print Network

resonance imaging (fMRI) data. We focus on time series resampling by `wavestrapping' of wavelet coef cients Introduction 1.1 General motivations for wavelet analysis of fMRI data A wavelet is a little wave, or a brief for analysis of complex datasets. The rst orthonormal basis after Fourier was constructed by Alfred Haar around

Breakspear, Michael

214

Establishing the resting state default mode network derived from functional magnetic resonance imaging tasks as an endophenotype: A twins study.  

PubMed

The resting state default mode network (DMN) has been shown to characterize a number of neurological and psychiatric disorders. Evidence suggests an underlying genetic basis for this network and hence could serve as potential endophenotype for these disorders. Heritability is a defining criterion for endophenotypes. The DMN is measured either using a resting-state functional magnetic resonance imaging (fMRI) scan or by extracting resting state activity from task-based fMRI. The current study is the first to evaluate heritability of this task-derived resting activity. 250 healthy adult twins (79 monozygotic and 46 dizygotic same sex twin pairs) completed five cognitive and emotion processing fMRI tasks. Resting state DMN functional connectivity was derived from these five fMRI tasks. We validated this approach by comparing connectivity estimates from task-derived resting activity for all five fMRI tasks, with those obtained using a dedicated task-free resting state scan in an independent cohort of 27 healthy individuals. Structural equation modeling using the classic twin design was used to estimate the genetic and environmental contributions to variance for the resting-state DMN functional connectivity. About 9-41% of the variance in functional connectivity between the DMN nodes was attributed to genetic contribution with the greatest heritability found for functional connectivity between the posterior cingulate and right inferior parietal nodes (P<0.001). Our data provide new evidence that functional connectivity measures from the intrinsic DMN derived from task-based fMRI datasets are under genetic control and have the potential to serve as endophenotypes for genetically predisposed psychiatric and neurological disorders. PMID:24453120

Korgaonkar, Mayuresh S; Ram, Kaushik; Williams, Leanne M; Gatt, Justine M; Grieve, Stuart M

2014-08-01

215

Multivariate strategies in functional magnetic resonance imaging.  

PubMed

We discuss aspects of multivariate fMRI modeling, including the statistical evaluation of multivariate models and means for dimensional reduction. In a case study we analyze linear and non-linear dimensional reduction tools in the context of a 'mind reading' predictive multivariate fMRI model. PMID:17223190

Hansen, Lars Kai

2007-08-01

216

Functional atlas of emotional faces processing: a voxel-based meta-analysis of 105 functional magnetic resonance imaging studies  

PubMed Central

Background Most of our social interactions involve perception of emotional information from the faces of other people. Furthermore, such emotional processes are thought to be aberrant in a range of clinical disorders, including psychosis and depression. However, the exact neurofunctional maps underlying emotional facial processing are not well defined. Methods Two independent researchers conducted separate comprehensive PubMed (1990 to May 2008) searches to find all functional magnetic resonance imaging (fMRI) studies using a variant of the emotional faces paradigm in healthy participants. The search terms were: “fMRI AND happy faces,” “fMRI AND sad faces,” “fMRI AND fearful faces,” “fMRI AND angry faces,” “fMRI AND disgusted faces” and “fMRI AND neutral faces.” We extracted spatial coordinates and inserted them in an electronic database. We performed activation likelihood estimation analysis for voxel-based meta-analyses. Results Of the originally identified studies, 105 met our inclusion criteria. The overall database consisted of 1785 brain coordinates that yielded an overall sample of 1600 healthy participants. Quantitative voxel-based meta-analysis of brain activation provided neurofunctional maps for 1) main effect of human faces; 2) main effect of emotional valence; and 3) modulatory effect of age, sex, explicit versus implicit processing and magnetic field strength. Processing of emotional faces was associated with increased activation in a number of visual, limbic, temporoparietal and prefrontal areas; the putamen; and the cerebellum. Happy, fearful and sad faces specifically activated the amygdala, whereas angry or disgusted faces had no effect on this brain region. Furthermore, amygdala sensitivity was greater for fearful than for happy or sad faces. Insular activation was selectively reported during processing of disgusted and angry faces. However, insular sensitivity was greater for disgusted than for angry faces. Conversely, neural response in the visual cortex and cerebellum was observable across all emotional conditions. Limitations Although the activation likelihood estimation approach is currently one of the most powerful and reliable meta-analytical methods in neuroimaging research, it is insensitive to effect sizes. Conclusion Our study has detailed neurofunctional maps to use as normative references in future fMRI studies of emotional facial processing in psychiatric populations. We found selective differences between neural networks underlying the basic emotions in limbic and insular brain regions. PMID:19949718

Fusar-Poli, Paolo; Placentino, Anna; Carletti, Francesco; Landi, Paola; Allen, Paul; Surguladze, Simon; Benedetti, Francesco; Abbamonte, Marta; Gasparotti, Roberto; Barale, Francesco; Perez, Jorge; McGuire, Philip; Politi, Pierluigi

2009-01-01

217

Nuclear Magnetic Resonance Technology for Medical Studies.  

ERIC Educational Resources Information Center

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

Budinger, Thomas F.; Lauterbur, Paul C.

1984-01-01

218

Myocardial tissue tagging with cardiovascular magnetic resonance  

Microsoft Academic Search

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

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

2009-01-01

219

STROBOSCOPIC ARTICULOGRAPHY USING FAST MAGNETIC RESONANCE IMAGING  

Microsoft Academic Search

A method to display dynamic aspects of vocal tract configuration during speech production by means of fast magnetic resonance imaging (MRI) is presented. Data acquisition during repetitive movement relies on a stroboscopy-like procedure. The time res- olution achieved is 120 images per second in a selected plane. As compared to other techniques of kinematic measurements of speech motor processes, this

K. Mathiak; U. Klose; H. Ackermann; I. Hertrich; W.-E. Kincses; W. Grodd

220

Magnetic resonance images of chronic patellar tendinitis  

Microsoft Academic Search

Chronic patellar tendinitis can be a frustrating diagnostic and therapeutic problem. This report evaluates seven tendons in five patients with chronic patellar tendinitis. The etiologies included “jumper's knee” and Osgood-Schlatter disease. In all cases magnetic resonance images (MRI) showed thickening of the tendon. Some of the tendons had focal areas of thickening which helped establish the etiology. All cases had

David Bodne; Stephen F. Quinn; William T. Murray; Thomas Bolton; Steven Rudd; Kirk Lewis; Peter Daines; John Bishop; Courtney Cochran

1988-01-01

221

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

222

Magnetic Resonance Imaging in Lewy Body Dementias  

Microsoft Academic Search

Dementia with Lewy bodies (DLB) and Parkinson’s disease dementia (PDD) share common clinical, neuropsychological and pathological features. In clinical diagnosis, distinguishing between these conditions and other dementia subtypes such as Alzheimer’s disease (AD) can be difficult. Despite the development of consensus diagnostic criteria, sensitivity for diagnosis remains low, especially outside specialist centres. Neuroimaging techniques using magnetic resonance (MR) can assess

Rosie Watson; Andrew M. Blamire; John T. O’Brien

2009-01-01

223

Analytical Methods for Characterizing Magnetic Resonance Probes  

PubMed Central

SUMMARY The efficiency of Gd(III) contrast agents in magnetic resonance image enhancement is governed by a set of tunable structural parameters. Understanding and measuring these parameters requires specific analytical techniques. This Feature describes strategies to optimize each of the critical Gd(III) relaxation parameters for molecular imaging applications and the methods employed for their evaluation. PMID:22624599

Manus, Lisa M.; Strauch, Renee C.; Hung, Andy H.; Eckermann, Amanda L.; Meade, Thomas J.

2012-01-01

224

Magnetic resonance imaging in prostate cancer  

Microsoft Academic Search

With the recently published National Institute of Clinical Excellence guidelines, it is now generally accepted that magnetic resonance imaging (MRI) is the imaging method of choice for staging prostate cancer in patients for whom radical treatment is being considered. MRI offers the single most accurate assessment of local disease and regional metastatic spread. As well as detecting extraprostatic extension, this

S D Heenan

2004-01-01

225

Magnetic Resonance Imaging in Endodontic Treatment Prediction  

Microsoft Academic Search

The necessary condition for successful endodontic treatment is the precise mapping of the shape of dental cavities. The aim of this work has been an elaboration and verification of the possibility of using three-dimensional (3D) spin echo magnetic resonance imaging (MRI) techniques in dentistry. Six extracted molar teeth were used for measurements without additional preparation and after endodontic preparation. MRI

Marta Tanasiewicz

2010-01-01

226

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

227

An improved nuclear magnetic resonance spectrometer  

NASA Technical Reports Server (NTRS)

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

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

1967-01-01

228

Sample spinner for nuclear magnetic resonance spectrometer  

SciTech Connect

A sample spinner for a nuclear magnetic resonance spectrometer having improved operating characteristics is described comprising a rotor supported at both ends by support gas bearings and positioned by a thrust gas bearing. Improved support gas bearings are also described which result in a spinner exhibiting long-term stable operation characteristics.

Stejskal, E.O.

1984-05-01

229

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

230

Functional Magnetic Resonance Imaging of Pain Consciousness  

E-print Network

reflex sympathetic dystrophy (RSD) and chronic back pain. The review emphasizes that differentFunctional Magnetic Resonance Imaging of Pain Consciousness: Cortical Networks of Pain Critically Depend on What is Implied by "Pain" A. Vania Apkarian, PhD Address SUNY Health Science Center, Department

Apkarian, A. Vania

231

Quantum electrodynamic equations for magnetic resonance- and optical spectroscopic transitions  

E-print Network

Quantum electrodynamic equations for magnetic resonance- and optical spectroscopic transitions have been for the first time obtained. New phenomena - stochastic electrical and magnetic spin wave resonances are predicted to be the effects of EM-field quantization.

D. Yearchuck; Y. Yerchak; A. Alexandrov

2009-03-02

232

Multidimensionally Encoded Magnetic Resonance Imaging  

E-print Network

algorithm. As an alternative to linear SEMs, nonlinear SEMs have been used to improve the dynamic range-dimensional spatial bases created by linear spa- tial encoding magnetic fields (SEMs). Recently, imaging strat- egies and linear SEMs can be used jointly to further improve the image reconstruction performance. Here, we propose

233

Magnetic Layer in Neutron Wave Resonator  

NASA Astrophysics Data System (ADS)

Expressions for the neutron density and the neutron reflection amplitude are given in the case of a non-collinear magnetic layer inside of the neutron wave resonator subject to a static or a rotating magnetic fields. It is shown that the enhancement of the spin-flip reflection intensity and density of neutrons in opposite to initial spin state are enhanced in second and third degree relatively of enhancement of neutron density in the initial spin state, correspondently. Conditions are defined for high sensitive measurements of the magnetic layer parameters.

Nikitenko, Yu. V.

234

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

235

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

236

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

237

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

238

Magnetic resonance properties of some lunar material.  

PubMed

Paramagnetic resonance spectra of Apollo 11 fines and rocks were measured at 9 and 35 gigahertz and at 4 degrees , 80 degrees , and 300 degrees K. At both frequencies the material has an intense absorption at g = 2, with a line width of approximately 950 gauss. Fe ions with strong exchange interactions produce this resonance. A comparison of the resonance absorption due to Fe(3+) showed that the energy of the crystal field interaction was approximately 0.1 per centimeter. Mn(2+) was identified in several samples, and an absorption at g = 1.89 was tentatively attributed to Ti(3+). The nuclear magnetic resonance spectra of (27)Al had a distribution of asymmetry parameters eta ranging from 0.25 to 0.75 and had nuclear quadrupole coupling constants e(2)qQ/h of approximately 3 megahertz. PMID:17781555

Weeks, R A; Chatelain, A; Kolopus, J L; Kline, D; Castle, J G

1970-01-30

239

Slow fluctuations in eye position and resting-state functional magnetic resonance imaging brain activity during visual fixation  

PubMed Central

The neuronal circuitry that supports voluntary changes in eye position in tasks that require attention-driven oculo-motor control is well known. However, less is known about the neuronal basis for eye control during visual fixation. This, together with the fact that visual fixation is one of the most commonly used baseline conditions in resting-state functional magnetic resonance imaging (fMRI) studies, prompted us to conduct a study in which we employed resting-state fMRI and concurrent recordings of eye gaze to investigate the relationship between spontaneous changes in eye position during passive visual fixation and intrinsic brain activity. As a control experiment, we recorded fMRI brain activity related to cued voluntary vertical and horizontal changes in eye position in a block-related task-evoked fMRI experiment. Our results for the voluntarily performed changes in eye position elicited brain activity in the bilateral occipitotemporal cortex, supplementary motor cortex and frontal eye fields. In contrast, we show that slow fluctuations in eye position during passive visual fixation are linked to intrinsic brain activity, foremost in midline cortical brain regions located in the posteromedial parietal cortex and the medial prefrontal cortex, brain regions that act as core cortical hubs in the brain's default mode network. Our results suggest that subconscious and sustained changes in behavior are tied to intrinsic brain activity on a moment-by-moment basis. PMID:25302817

Fransson, Peter; Flodin, Pär; Seimyr, Gustaf Öqvist; Pansell, Tony

2014-01-01

240

Quantitative fMRI and oxidative neuroenergetics  

PubMed Central

The discovery of functional magnetic resonance imaging (fMRI) has greatly impacted neuroscience. The blood oxygenation level-dependent (BOLD) signal, using deoxyhemoglobin as an endogenous paramagnetic contrast agent, exposes regions of interest in task-based and resting-state paradigms. However the BOLD contrast is at best a partial measure of neuronal activity, because the functional maps obtained by differencing or correlations ignore the total neuronal activity in the baseline state. Here we describe how studies of brain energy metabolism at Yale, especially with 13C magnetic resonance spectroscopy and related techniques, contributed to development of quantitative functional brain imaging with fMRI by providing a reliable measurement of baseline energy. This narrative takes us on a journey, from molecules to mind, with illuminating insights about neuronal-glial activities in relation to energy demand of synaptic activity. These results, along with key contributions from laboratories worldwide, comprise the energetic basis for quantitative interpretation of fMRI data. PMID:22542993

Hyder, Fahmeed; Rothman, Douglas L.

2012-01-01

241

Magnetic Earth Ionosphere Resonant Frequencies  

NASA Technical Reports Server (NTRS)

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

Spaniol, Craig

1994-01-01

242

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

243

Independent Component Analysis of Instantaneous Power-Based fMRI  

PubMed Central

In functional magnetic resonance imaging (fMRI) studies using spatial independent component analysis (sICA) method, a model of “latent variables” is often employed, which is based on the assumption that fMRI data are linear mixtures of statistically independent signals. However, actual fMRI signals are nonlinear and do not automatically meet with the requirement of sICA. To provide a better solution to this problem, we proposed a novel approach termed instantaneous power based fMRI (ip-fMRI) for regularization of fMRI data. Given that the instantaneous power of fMRI signals is a scalar value, it should be a linear mixture that naturally satisfies the “latent variables” model. Based on our simulated data, the curves of accuracy and resulting receiver-operating characteristic curves indicate that the proposed approach is superior to the traditional fMRI in terms of accuracy and specificity by using sICA. Experimental results from human subjects have shown that spatial components of a hand movement task-induced activation reveal a brain network more specific to motor function by ip-fMRI than that by the traditional fMRI. We conclude that ICA decomposition of ip-fMRI may be used to localize energy signal changes in the brain and may have a potential to be applied to detection of brain activity. PMID:24738008

Liu, Yijun; Lu, Guangming

2014-01-01

244

Independent component analysis of instantaneous power-based fMRI.  

PubMed

In functional magnetic resonance imaging (fMRI) studies using spatial independent component analysis (sICA) method, a model of "latent variables" is often employed, which is based on the assumption that fMRI data are linear mixtures of statistically independent signals. However, actual fMRI signals are nonlinear and do not automatically meet with the requirement of sICA. To provide a better solution to this problem, we proposed a novel approach termed instantaneous power based fMRI (ip-fMRI) for regularization of fMRI data. Given that the instantaneous power of fMRI signals is a scalar value, it should be a linear mixture that naturally satisfies the "latent variables" model. Based on our simulated data, the curves of accuracy and resulting receiver-operating characteristic curves indicate that the proposed approach is superior to the traditional fMRI in terms of accuracy and specificity by using sICA. Experimental results from human subjects have shown that spatial components of a hand movement task-induced activation reveal a brain network more specific to motor function by ip-fMRI than that by the traditional fMRI. We conclude that ICA decomposition of ip-fMRI may be used to localize energy signal changes in the brain and may have a potential to be applied to detection of brain activity. PMID:24738008

Zhong, Yuan; Zheng, Gang; Liu, Yijun; Lu, Guangming

2014-01-01

245

Magnetic resonance studies of lunar samples.  

PubMed

Electron spin resonance searches at 9.5 gigahertz on several fines samples and portions of several rocks have yielded signals whose lineshapes and temperature dependences show that the samples are principally ferromagnetic in nature. Proton magnetic resonance searches at 60 megahertz of these samples have not revealed any signals ascribable to water or any other types of hydrogen in concentrations greater than 0.0001 percent by weight contained in narrow lines (5 oersteds wide or less) and 0.01 percent by weight in wide lines (as wide as 100 oersteds). PMID:17781557

Manatt, S L; Elleman, D D; Vaughan, R W; Chan, S I; Tsay, F D; Huntress, W T

1970-01-30

246

Cadmium ferrite ionic magnetic fluid: Magnetic resonance investigation  

NASA Astrophysics Data System (ADS)

In contrast to all magnetic resonance investigations previously performed using magnetic fluids (MFs) based on spinel ferrite nanoparticles, cadmium-ferrite-based MFs present an intense, relatively sharp resonance line near g=4, in addition to the typical, broad structure near g=2. The broad resonance structure is associated with larger cadmium-ferrite nanoparticles, whereas the sharp resonance line is associated with ultrasmall cadmium-ferrite nanoparticles. Transmission electron microscopy (TEM) data confirm the bimodal particle size distribution in the sample investigated. The temperature T dependence of the resonance field HR is almost linear, for both high-field (HF) and low-field (LF) resonance lines, in the range of 100-300 K. In support of the identification of the HF line (around g=2) and LF line (around g=4) with larger and smaller Cd-ferrite nanoparticles, respectively, the slope of the HR versus T curve is lower for the HF line (1.3 G/K) compared to the LF line (1.69 G/K), whereas the intercept constant of the HF line (3050 G) is higher than the intercept constant of the LF line (1130 G).

Silva, O.; Lima, E. C. D.; Morais, P. C.

2003-05-01

247

Magnetic resonance of calcified tissues  

NASA Astrophysics Data System (ADS)

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

Wehrli, Felix W.

2013-04-01

248

Journal of Magnetism and Magnetic Materials 286 (2005) 324328 Light-free magnetic resonance force microscopy for studies of  

E-print Network

Journal of Magnetism and Magnetic Materials 286 (2005) 324­328 Light-free magnetic resonance force for Physical Sciences, College Park, MD, USA Available online 4 November 2004 Abstract Magnetic resonance force microscopy is a scanned probe technique capable of three-dimensional magnetic resonance imaging. Its

249

Foundations of Advanced Magnetic Resonance Imaging  

PubMed Central

Summary: During the past decade, major breakthroughs in magnetic resonance imaging (MRI) quality were made by means of quantum leaps in scanner hardware and pulse sequences. Some advanced MRI techniques have truly revolutionized the detection of disease states and MRI can now—within a few minutes—acquire important quantitative information noninvasively from an individual in any plane or volume at comparatively high resolution. This article provides an overview of the most common advanced MRI methods including diffusion MRI, perfusion MRI, functional MRI, and the strengths and weaknesses of MRI at high magnetic field strengths. PMID:15897944

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

2005-01-01

250

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

251

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

252

Granger Causality Analysis implementation on MATLAB: a graphic user interface toolkit for fMRI data processing  

Microsoft Academic Search

A lot of functional magnetic resonance imaging (fMRI) studies have indicated that Granger causality analysis (GCA) is a suitable method to reveal causal effect among brain regions. Based on another MATLAB GUI toolkit, Resting State fMRI Data Analysis Toolkit (REST), we implemented GCA on MATLAB as a graphical user interface (GUI) toolkit. This toolkit, namely REST-GCA, could output both the

Zhen-Xiang Zang; Chao-Gan Yan; Zhang-Ye Dong; Jian Huang; Yu-Feng Zang

253

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

Microsoft Academic Search

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

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

2011-01-01

254

Proton magnetic resonance spectroscopy in multiple sclerosis  

SciTech Connect

Regional in vivo proton magnetic resonance spectroscopy provides quantitative data on selected chemical constituents of brain. We imaged 16 volunteers with clinically definite multiple sclerosis on a 1.5 tesla magnetic resonance scanner to define plaque-containing volumes of interest, and obtained localized water-suppressed proton spectra using a stimulated echo sequence. Twenty-five of 40 plaque-containing regions provided spectra of adequate quality. Of these, 8 spectra from 6 subjects were consistent with the presence of cholesterol or fatty acids; the remainder were similar to those obtained from white matter of normal volunteers. This early experience with regional proton spectroscopy suggests that individual plaques are distinct. These differences likely reflect dynamic stages of the evolution of the demyelinative process not previously accessible to in vivo investigation.

Wolinsky, J.S.; Narayana, P.A.; Fenstermacher, M.J. (Univ. of Texas Health Science Center, Houston (USA))

1990-11-01

255

Contrast testing for magnetic resonance imaging.  

PubMed

A test phantom for evaluating magnetic resonance image contrast was constructed using separate chambers filled with manganese chloride (MnCl2) solutions of different concentrations. The concentrations were chosen so that the relaxation times produced were distributed over the range appropriate for human tissues in brain imaging. Specific solutions had relaxation properties similar to those of white matter, gray matter, and brain tumors. The region surrounding the chambers was filled with a sodium chloride solution with conductivity similar to that of brain tissue so that radiofrequency signal absorption would be appropriate. When magnetic resonance relaxation response curves were obtained with the phantom, relaxation contrast and latitude could be compared for different imaging pulse sequences. Contrast responses for gradient echo sequences differed considerably when the flip angle was changed. PMID:2720266

Anderson, D W; Yamanashi, W S; Stanley, D W; Wohler, J B

1989-01-01

256

Magnetic resonance spectroscopy in myocardial disease.  

PubMed

31-phosphorous ((31)P) magnetic resonance spectroscopy (MRS) is a technique that allows the noninvasive characterization of the biochemical and metabolic state of the myocardium in vivo. MRS is a pure form of molecular imaging using magnetic resonance signals from nuclei with nuclear spin to assess cardiac metabolism without the need for external radioactive tracers. (31)P MRS provides information on the underlying metabolic abnormalities that are fundamental to common conditions including ischemic heart disease, cardiomyopathy, hypertrophy and valvular disease. (31)P MRS could potentially also have a role to play in assessing response to therapy as well as the effectiveness of metabolic modulating agents. However, the use of MRS is currently limited to research due to its poor reproducibility, low spatial and temporal resolution, and long acquisition times. With technical advances in both the spectrometers and postprocessing, MRS is likely to play a role in the future of multimodal noninvasive cardiac assessment. PMID:20136613

Beadle, Roger; Frenneaux, Michael

2010-02-01

257

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

258

Diagnostic Magnetic Resonance Imaging of the Breast  

PubMed Central

Contrast enhanced breast magnetic resonance imaging is a modality that is frequently used into the breast radiologist’s daily clinical practice. MRI examination should have optimal technical proficiency in order to attain diagnostic quality avoiding false positive and negative diagnoses. Furthermore, due to increasing usage fields of the examinations uniting with high sensitivity phenomenon, excessive usage and excision/interventional procedures are inevitable. Therefore, we hope to highlight the appropriate usage of the MRI technique and it’s clinical applications.

Kilic, Fahrettin; Ogul, Hayri; Bayraktutan, Ummugulsum; Gumus, Hatice; Unal, Ozlem; Kantarci, Mecit; Yilmaz, M. Halit

2012-01-01

259

Neurosurgical uses for intraprocedural magnetic resonance imaging.  

PubMed

Neurosurgical procedures demand precision, and efforts to create accurate neurosurgical navigation have been central to the profession through its history. Magnetic resonance image (MRI)-guided navigation offers the possibility of real-time, image-based stereotactic information for the neurosurgeon, which makes possible a number of diagnostic and therapeutic procedures. This article will review both current options for intraoperative MRI operative suite arrangements and the current therapeutic/diagnostic uses of intraoperative MRI. PMID:16924171

Mutchnick, Ian S; Moriarty, Thomas M

2005-10-01

260

Musculoskeletal magnetic resonance imaging: importance of radiography  

Microsoft Academic Search

ObjectiveTo determine the usefulness of radiography for interpretation of musculoskeletal (MSK) magnetic resonance imaging (MRI) studies.Designs and patientsIn a 1-year period, 1,030 MSK MRI studies were performed in 1,002 patients in our institution. For each study, the interpreting radiologist completed a questionnaire regarding the availability and utility of radiographs, radiological reports and clinical information for the interpretation of the MRI

Mihra S. Taljanovic; Tim B. Hunter; Kimberly A. Fitzpatrick; Elizabeth A. Krupinski; Thomas L. Pope

2003-01-01

261

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

262

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

263

Functional magnetic resonance imaging of swine brain during change in thiopental anesthesia into EEG burst-suppression level — A preliminary study  

Microsoft Academic Search

Deepening anesthesia produces well known changes in electroencephalogram (EEG) and evoked potentials, differing in pathological\\u000a and normal brain. Yet, it is not known how the T2*-weighted signal changes in the healthy brain during deepening anesthesia.\\u000a We studied the effect of thiopental bolus on functional magnetic resonance imaging (fMRI) in the healthy brain using porcine\\u000a model. In five pigs (2–3 months,

Minna J. MÄkiranta; Jukka P. T. Jauhiainen; Jarkko T. Oikarinen; Kalervo Suominen; Osmo Tervonen; Seppo Alahuhta; Ville JÄntti

2002-01-01

264

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

Microsoft Academic Search

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

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

2007-01-01

265

Functional Magnetic Resonance Imaging Is More Reliable than Somatosensory Evoked Potential or Mapping for the Detection of the Primary Motor Cortex in Proximity to a Tumor  

Microsoft Academic Search

The accurate localization of the primary motor cortex (M1) is critical for the preservation of motor function during resection of brain tumors in and around the M1. The goal of the present study was to determine which technique provided the most accurate localization of M1. The accuracy of preoperative functional magnetic resonance imaging (fMRI), intraoperative somatosensory evoked potential (SEP) and

N. Shinoura; R. Yamada; Y. Suzuki; T. Kodama; K. Sekiguchi; M. Takahashi; K. Yagi

2007-01-01

266

Fluctuating magnetic field induced resonant activation.  

PubMed

In this paper, we have studied the properties of a Brownian particle at stationary state in the presence of a fluctuating magnetic field. Time dependence of the field makes the system thermodynamically open. As a signature of that the steady state distribution function becomes function of damping strength, intensity of fluctuations and constant parts of the applied magnetic field. It also depends on the correlation time of the fluctuating magnetic field. Our another observation is that the random magnetic field can induce the resonant activation phenomenon. Here correlation time is increased under the fixed variance of the fluctuating field. But if the correlation time (?) increases under the fixed field strength then the mean first passage time rapidly grows at low ? and it almost converges at other limit. This is sharp contrast to the usual colored noise driven open system case where the mean first passage time diverges exponentially. We have also observed that a giant enhancement of barrier crossing rate occurs particularly at large strength of constant parts of the applied magnetic field even for very weak fluctuating magnetic field. Finally, break down of the Arrhenius result and disappearance of the Kramers' turn over phenomenon may occur in the presence of a fluctuating magnetic field. PMID:25494726

Mondal, Shrabani; Das, Sudip; Baura, Alendu; Bag, Bidhan Chandra

2014-12-14

267

Fluctuating magnetic field induced resonant activation  

NASA Astrophysics Data System (ADS)

In this paper, we have studied the properties of a Brownian particle at stationary state in the presence of a fluctuating magnetic field. Time dependence of the field makes the system thermodynamically open. As a signature of that the steady state distribution function becomes function of damping strength, intensity of fluctuations and constant parts of the applied magnetic field. It also depends on the correlation time of the fluctuating magnetic field. Our another observation is that the random magnetic field can induce the resonant activation phenomenon. Here correlation time is increased under the fixed variance of the fluctuating field. But if the correlation time (?) increases under the fixed field strength then the mean first passage time rapidly grows at low ? and it almost converges at other limit. This is sharp contrast to the usual colored noise driven open system case where the mean first passage time diverges exponentially. We have also observed that a giant enhancement of barrier crossing rate occurs particularly at large strength of constant parts of the applied magnetic field even for very weak fluctuating magnetic field. Finally, break down of the Arrhenius result and disappearance of the Kramers' turn over phenomenon may occur in the presence of a fluctuating magnetic field.

Mondal, Shrabani; Das, Sudip; Baura, Alendu; Bag, Bidhan Chandra

2014-12-01

268

Magnetic resonance imaging of prosthetic heart valves.  

PubMed

To evaluate the safety of magnetic resonance (MR) imaging of prosthetic heart valves, nine different synthetic and tissue valves were studied ex vivo. Deflection was measured in 0.35-tesla (T) and 1.5-T superconducting magnets and at the edge of the bore of a 2.35-T electromagnet in field gradients of 5, 1.1, and 6.3 mT/cm, respectively. No valve deflected in the 0.35-T magnet; six synthetic valves deflected 0.25 degrees-3 degrees in the 1.5-T magnet; all valves deflected 1 degree-27 degrees at the edge of the 2.35-T magnet. Each valve was then submerged in a vial of water and the temperature was measured immediately before and after each of two spin-echo imaging sequences in the two superconducting magnets. No significant temperature rise followed exposure in either magnet. Image distortion varied from negligible to severe in both imagers; magnitude of distortion paralleled magnitude of deflection. These data suggest that patients with present-day prosthetic heart valves can be safely imaged in present-day MR imagers and that prosthesis-induced artifacts will not interfere with interpretation in most instances. PMID:3969474

Soulen, R L; Budinger, T F; Higgins, C B

1985-03-01

269

[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

270

Superconducting Magnet Safety Nuclear Magnetic Resonance (NMR) facilities present unique hazards not found in most  

E-print Network

Superconducting Magnet Safety Nuclear Magnetic Resonance (NMR) facilities present unique hazards not found in most laboratory environments. The NMR facilities maintain superconducting magnets which have associated with installation and operation. Temperature, structural support and magnetic field isolation

Maroncelli, Mark

271

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

272

Compact low field magnetic resonance imaging magnet: Design and optimization  

NASA Astrophysics Data System (ADS)

Magnetic resonance imaging (MRI) is performed with a very large instrument that allows the patient to be inserted into a region of uniform magnetic field. The field is generated either by an electromagnet (resistive or superconductive) or by a permanent magnet. Electromagnets are designed as air cored solenoids of cylindrical symmetry, with an inner bore of 80-100 cm in diameter. In clinical analysis of peripheral regions of the body (legs, arms, foot, knee, etc.) it would be better to adopt much less expensive magnets leaving the most expensive instruments to applications that require the insertion of the patient in the magnet (head, thorax, abdomen, etc.). These "dedicated" apparati could be smaller and based on resistive magnets that are manufactured and operated at very low cost, particularly if they utilize an iron yoke to reduce power requirements. In order to obtain good field uniformity without the use of a set of shimming coils, we propose both particular construction of a dedicated magnet, using four independently controlled pairs of coils, and an optimization-based strategy for computing, a posteriori, the optimal current values. The optimization phase could be viewed as a low-cost shimming procedure for obtaining the desired magnetic field configuration. Some experimental measurements, confirming the effectiveness of the proposed approach (construction and optimization), have also been reported. In particular, it has been shown that the adoption of the proposed optimization based strategy has allowed the achievement of good uniformity of the magnetic field in about one fourth of the magnet length and about one half of its bore. On the basis of the good experimental results, the dedicated magnet can be used for MRI of peripheral regions of the body and for animal experimentation at very low cost.

Sciandrone, M.; Placidi, G.; Testa, L.; Sotgiu, A.

2000-03-01

273

Functional magnetic resonance imaging studies of opioid receptor-mediated modulation of noxious-evoked BOLD contrast in rats  

Microsoft Academic Search

Rationale  Functional magnetic resonance imaging (fMRI) in rats can non-invasively identify brain regions activated by physiological\\u000a stimuli and the effects of pharmacological intervention on these responses.\\u000a \\u000a \\u000a \\u000a Objectives  This study was conducted to investigate the effects of systemic administration of the ?-opioid receptor agonist morphine on\\u000a whole brain functional signal intensity in anaesthetised rats; to investigate whether pre-treatment with the opioid receptor\\u000a antagonist

Y. B. Shah; L. Haynes; M. J. W. Prior; C. A. Marsden; P. G. Morris; V. Chapman

2005-01-01

274

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

275

CARBON-13 Nuclear Magnetic Resonance in Solids.  

NASA Astrophysics Data System (ADS)

The rotational resonance phenomena induced by the modulation of the interactions in magnetic angle spinning (MAS) nuclear magnetic resonance (NMR) experiments have been demonstrated for the first time. In the study of chemical shielding, the rotational resonance occurs when a spin-lock field with an amplitude of nomega _{rm r} (n = 1,2) is applied where omega_{rm r} is the spinning speed. The magnetization, which nutates in the rotating frame at a frequency related to the chemical shift anisotropy (CSA), allows for the retrieval of the CSA from MAS NMR spectra at a high spinning speed. In addition, a similar rotational resonance phenomenon was studied in a homonuclear spin coupled system. The resonance occurs when the separation of the isotropic chemical shifts of the two spins equal omega_{ rm r}. The rotational resonance restores a splitting pattern in the MAS spectra and enhances the flip-flop motion of the two spins. Also, the sample spinning NMR of homonuclear coupled systems has been analyzed by a pseudo-spin model. In the case of the ^ {13}C dilabelled phthalic anhydride, the analyses at different spinning speeds lead to the determination of the orientation of the chemical shielding tensor. The quadrupolar effect in ^{13 }C-^{14}N coupled spins is manifested in the ^{13 }C MAS spectra by the appearance of an asymmetric doublet. A simple analytical solution to this quadrupolar effect was developed to study ^{13 }C-^{14}N systems for information on both the electric field gradient (EFG) tensor of the nitrogen and the ^{13 }C-^{14}N bond distance. Furthermore, the variable angle sample spinning technique has been applied to determine of the chemical shielding tensors with their orientation for these systems. The molecules studied include tetramethyl-pyrazine, dimethylglyoxime and triethylenediamine. The effect of relaxation in solid state NMR dipolar spectra was studied. The cross relaxation terms introduce a peak in the center of the expected Pake doublet. The dipolar spectra of methyl phosphonic acid at room temperature and methyl fluoride at low temperature (25 K) were used to study this effect.

Gan, Zhehong

276

Portal biliopathy, magnetic resonance imaging and magnetic resonance cholangiopancreatography findings: a case series.  

PubMed

Portal biliopathy (PB) is a rare disorder, characterized by biliary ductal and gallbladder wall abnormalities seen in patients with portal hypertension. It most commonly occurs due to idiopathic extrahepatic portal vein obstruction (EHPVO). The abnormalities consist mainly of bile duct compression, stenoses, fibrotic strictures and dilation of both extrahepatic and intrahepatic bile ducts, as well as gallbladder varices. PB may mimic cholangiocarcinoma, sclerosing cholangitis, or choledocholithiasis. Misdiagnosis can be avoided using appropriate imaging modalities to prevent complications. We present the magnetic resonance imaging (MRI) and magnetic resonance cholangiography (MRCP) features of three patients with PB. PMID:25216728

Baskan, Ozdil; Erol, Cengiz; Sahingoz, Yusuf

2014-09-12

277

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

Microsoft Academic Search

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

Linda Laatsch; Deborah Little; Keith Thulborn

2004-01-01

278

Neural Changes after Phonological Treatment for Anomia: An fMRI Study  

ERIC Educational Resources Information Center

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

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

2010-01-01

279

Measuring Attachment Representation in an fMRI Environment: A Pilot Study  

Microsoft Academic Search

This exploratory study is the first to examine the neural correlates of attachment status in adults. The study examined the feasibility of assessing attachment narratives in the functional magnetic resonance imaging (fMRI) environment by challenging subjects to tell attachment stories to specific attachment pictures from the Adult Attachment Projective (AAP) while being scanned. We investigated theoretically derived hypotheses regarding predicted

Anna Buchheim; Susanne Erk; Carol George; Horst Kächele; Martin Ruchsow; Manfred Spitzer; Tilo Kircher; Henrik Walter

2006-01-01

280

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

281

Using fMRI to Study Conceptual Change: Why and How?  

ERIC Educational Resources Information Center

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

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

2012-01-01

282

Brain Correlates of Aesthetic Expertise: A Parametric fMRI Study  

ERIC Educational Resources Information Center

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

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

2009-01-01

283

A Quantitative Comparison of Simultaneous BOLD fMRI and NIRS Recordings during Functional Brain Activation  

Microsoft Academic Search

Near-infrared spectroscopy (NIRS) has been used to noninvasively monitor adult human brain func- tion in a wide variety of tasks. While rough spatial correspondences with maps generated from func- tional magnetic resonance imaging (fMRI) have been found in such experiments, the amplitude cor- respondences between the two recording modalities have not been fully characterized. To do so, we si- multaneously

Gary Strangman; Joseph P. Culver; John H. Thompson; David A. Boas

2002-01-01

284

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

ERIC Educational Resources Information Center

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

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

2011-01-01

285

How Verbal and Spatial Manipulation Networks Contribute to Calculation: An fMRI Study  

ERIC Educational Resources Information Center

The manipulation of numbers required during calculation is known to rely on working memory (WM) resources. Here, we investigated the respective contributions of verbal and/or spatial WM manipulation brain networks during the addition of four numbers performed by adults, using functional magnetic resonance imaging (fMRI). Both manipulation and…

Zago, Laure; Petit, Laurent; Turbelin, Marie-Renee; Andersson, Frederic; Vigneau, Mathieu; Tzourio-Mazoyer, Nathalie

2008-01-01

286

Neural substrates of cross-modal olfactory recognition memory: An fMRI study  

Microsoft Academic Search

Ten young adults (aged 20 to 25 years) participated in a functional Magnetic Resonance Imaging (fMRI) study to investigate neural substrates of cross-modal olfactory recognition memory. Before entering the scanner, participants were presented with 16 familiar odors selected from the COLT (Murphy, C., Nordin, S., Acosta, L., 1997. Odor learning, recall, and recognition memory in young and elderly adults. Neuropsychology

Barbara Cerf-Ducastel; Claire Murphy

2006-01-01

287

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

288

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

289

I See What You Are Saying: Action as Cognition in fMRI Brain Mapping Practice  

Microsoft Academic Search

In cognitive neuroscience, functional magnetic resonance imaging (fMRI) is used to produce images of brain functions. These images play a central role in the practice of neuroscience. In this paper we are interested in how these brain images become understandable and meaningful for scientists. In order to explore this problem we observe how scientists use such semiotic resources as gesture,

Morana Ala?; Edwin Hutchins

2004-01-01

290

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

291

Reduction in BOLD fMRI response to primary visual stimulation following alcohol ingestion  

Microsoft Academic Search

The physiology of alcohol's effects on brain function is poorly understood. Emission tomographic imaging has revealed both acute and chronic alterations in resting cerebral hemodynamics and metabolism following alcohol ingestion. However, cerebral functional integrity under these conditions has received less attention. Functional magnetic resonance imaging (fMRI) offers a non-invasive method for assessing brain functional activation. In order to assess its

Jonathan M. Levin; Marjorie H. Ross; Jack H. Mendelson; Marc J. Kaufman; Nicholas Lange; Luis C. Maas; Nancy K. Mello; Bruce M. Cohen; Perry F. Renshaw

1998-01-01

292

Deficient prefrontal attentional control in late-life generalized anxiety disorder: an fMRI investigation  

Microsoft Academic Search

Younger adults with anxiety disorders are known to show an attentional bias toward negative information. Little is known regarding the role of biased attention in anxious older adults, and even less is known about the neural substrates of any such bias. Functional magnetic resonance imaging (fMRI) was used to assess the mechanisms of attentional bias in late life by contrasting

R B Price; D A Eldreth; J Mohlman

2011-01-01

293

Clustering of spatiotemporal signals: application to the analysis of FMRI data  

Microsoft Academic Search

In this paper, a new paradigm for the analysis of event-related functional magnetic resonance images (fMRI) is explored. These datasets are large collections of spatiotemporal time series that are indexed by their spatial locations. The analysis of such datasets requires to partition the spatial domain into regions within which the time series are similar. Basis functions is constructed on which

Francois G. Meyer; Jatuporn Chinrungrueng

2003-01-01

294

IVA for multi-subject FMRI analysis: A comparative study using a new simulation toolbox  

Microsoft Academic Search

Joint blind source separation (JBSS) techniques have proven to be a natural solution for achieving source separation of multiple data sets. JBSS algorithms, such as independent vector analysis (IVA), are a promising alternative to independent component analysis (ICA) based approaches for the analysis of multi-subject functional magnetic resonance imaging (fMRI) data. Unlike ICA, little is known about the effectiveness of

Josselin T. Dea; Matthew Anderson; Elena Allen; Vince D. Calhoun; Tulay Adali

2011-01-01

295

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

296

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

Microsoft Academic Search

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

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

2005-01-01

297

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

ERIC Educational Resources Information Center

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

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

2012-01-01

298

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

ERIC Educational Resources Information Center

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

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

2008-01-01

299

Cerebral Activation Patterns During Working Memory Performance in Multiple Sclerosis Using fMRI  

Microsoft Academic Search

Working memory deficits are common in Multiple Sclerosis (MS) and have been identified behaviorally in numerous studies. Despite recent advance in functional magnetic resonance imaging (fMRI), few published studies have examined cerebral activations associated with working memory dysfunction in MS. The present study examines brain activation patterns during performance of a working memory task in individuals with clinically definite MS,

Nancy D. Chiaravalloti; Frank G. Hillary; Joseph H. Ricker; Christopher Christodoulou; Andrew J. Kalnin; Wen-Ching Liu; Jason Steffener; John DeLuca

2005-01-01

300

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

ERIC Educational Resources Information Center

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

Seedhouse, Steven J.; Hoffmann, Markus M.

2008-01-01

301

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

302

ICA-based sparse features recovery from FMRI datasets  

Microsoft Academic Search

Spatial Independent Components Analysis (ICA) is increasingly used in the context of functional Magnetic Resonance Imaging (fMRI) to study cognition and brain pathologies. Salient features present in some of the extracted Independent Components (ICs) can be interpreted as brain networks, but the segmentation of the corresponding regions from ICs is still ill-controlled. Here we propose a new ICA-based procedure for

Gaël Varoquaux; Merlin Keller; Jean-Baptiste Poline; Philippe Ciuciu; Bertrand Thirion

2010-01-01

303

Nanodiamond graphitization: a magnetic resonance study  

NASA Astrophysics Data System (ADS)

We report on the first nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) study of the high-temperature nanodiamond-to-onion transformation. 1H, 13C NMR and EPR spectra of the initial nanodiamond samples and those annealed at 600, 700, 800 and 1800?° C were measured. For the samples annealed at 600 to 800?° C, our NMR data reveal the early stages of the surface modification, as well as a progressive increase in sp2 carbon content with increased annealing temperature. Such quantitative experimental data were recorded for the first time. These findings correlate with EPR data on the sensitivity of the dangling bond EPR line width to air content, progressing with rising annealing temperature, that evidences consequent graphitization of the external layers of the diamond core. The sample annealed at 1800?° C shows complete conversion of nanodiamond particles into carbon onions.

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

2013-06-01

304

Nanodiamond graphitization: a magnetic resonance study.  

PubMed

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

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

2013-06-19

305

Cardiac magnetic resonance imaging: artefacts for clinicians.  

PubMed

In recent years, the clinical importance of cardiac magnetic resonance (CMR) imaging has increased dramatically. As a consequence, more clinicians need to become familiar with this imaging modality, including its technical challenges. MR images are obtained through a physical process of proton excitation and the reception of resonating signals. Besides these physical principles, the motion of the heart and diaphragm, together with the presence of fast flowing blood in the vicinity, pose challenges to the acquisition of high-quality diagnostic images and are an important cause of image artefacts. Artefacts may render images non-diagnostic and measurements unreliable, and most artefacts can only be corrected during the acquisition itself. Hence, timely and accurate recognition of the type of artefact is crucial. This paper provides a concise description of the CMR acquisition process and the underlying MR physics for clinical cardiologists and trainees. Frequently observed CMR artefacts are illustrated and possible adjustments to minimise or eliminate these artefacts are explained. PMID:25339204

van der Graaf, A W M; Bhagirath, P; Ghoerbien, S; Götte, M J W

2014-12-01

306

Sensitivity and spatial resolution for electron-spin-resonance detection by magnetic resonance force microscopy  

E-print Network

The signal intensity of electron spin resonance in magnetic resonance force microscopy MRFM experiments that magnetic resonance force microscopy MRFM is a new 3D imaging technique8,9 with the potential of achieving force microscopy Z. Zhanga) Condensed Matter and Thermal Physics Group, Materials Science and Technology

Hammel, P. Chris

307

Collective electric and magnetic plasmonic resonances in spherical nanoclusters  

E-print Network

with the electric dipole efficiency Q sca indicating thatthe electric resonance the p e scattering efficiency Q scaelectric and magnetic resonances, previously identified from the analysis of the extinction and scattering efficiencies,

Vallecchi, Andrea; Albani, Matteo; Capolino, Filippo

2011-01-01

308

Separating slow BOLD from non-BOLD baseline drifts using multi-echo fMRI.  

PubMed

The functional magnetic resonance (fMRI) baseline is known to drift over the course of an experiment and is often attributed to hardware instability. These ultraslow fMRI fluctuations are inseparable from blood oxygenation level dependent (BOLD) changes in standard single echo fMRI and they are therefore typically removed before further analysis in both resting-state and task paradigms. However, some part of these fluctuations may be of neuronal origin, as neural activity can indeed fluctuate at the scale of several minutes or even longer, such as after the administration of drugs or during the ultradian rhythms. Here, we show that it is possible to separate the slow BOLD and non-BOLD drifts automatically using multi-echo fMRI and multi-echo independent components analysis (ME-ICA) denoising by demonstrating the detection of a visual signal evoked from a flickering checkerboard with slowly changing contrast. PMID:25449746

Evans, Jennifer W; Kundu, Prantik; Horovitz, Silvina G; Bandettini, Peter A

2015-01-15

309

Cardiovascular magnetic resonance imaging in small animals.  

PubMed

Noninvasive imaging studies involving small animals are becoming increasingly important in preclinical pharmacological, genetic, and biomedical cardiovascular research. Especially small animal magnetic resonance imaging (MRI) using high field and clinical MRI systems has gained significant importance in recent years. Compared to other imaging modalities, like computer tomography, MRI can provide an excellent soft tissue contrast, which enables the characterization of different kinds of tissues without the use of contrast agents. In addition, imaging can be performed with high spatial and temporal resolution. Small animal MRI cannot only provide anatomical information about the beating murine heart; it can also provide functional and molecular information, which makes it a unique imaging modality. Compared to clinical MRI examinations in humans, small animal MRI is associated with additional challenges. These included a smaller size of all cardiovascular structures and a up to ten times higher heart rate. Dedicated small animal monitoring devices make a reliable cardiac triggering and respiratory gating feasible. MRI in combination with molecular probes enables the noninvasive imaging of biological processes at a molecular level. Different kinds of iron oxide or gadolinium-based contrast agents can be used for this purpose. Compared to other molecular imaging modalities, like single photon emission computed tomography (SPECT) and positron emission tomography (PET), MRI can also provide imaging with high spatial resolution, which is of high importance for the assessment of the cardiovascular system. The sensitivity for detection of MRI contrast agents is however lower compared to sensitivity of radiation associated techniques like PET and SPECT. This chapter is divided into the following sections: (1) "Introduction," (2) "Principals of Magnetic Resonance Imaging," (3) "MRI Systems for Preclinical Imaging and Experimental Setup," and (4) "Cardiovascular Magnetic Resonance Imaging." PMID:22137434

Botnar, René M; Makowski, Marcus R

2012-01-01

310

Magnetic Resonance Imaging of the Pediatric Knee.  

PubMed

In pediatric patients, the high resolution and excellent soft-tissue contrast of magnetic resonance (MR) imaging allows for complete evaluation of osseous and soft-tissue structures around the knee joint, and its lack of ionizing radiation makes it a preferred modality for advanced imaging. Older children and adolescents are most commonly imaged to evaluate athletic and traumatic injuries, whereas in infants and school age children MR imaging is used to evaluate developmental conditions such as Blount disease or assess for causes of atraumatic pain such as infection or inflammatory arthritis. A thorough understanding of normal skeletal development is necessary to avoid misdiagnoses. PMID:25442031

Gill, Kara G; Nemeth, Blaise A; Davis, Kirkland W

2014-11-01

311

Magnetic resonance imaging of perianal fistulas.  

PubMed

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

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

2014-02-01

312

Review: Magnetic resonance imaging techniques in ophthalmology  

PubMed Central

Imaging the eye with magnetic resonance imaging (MRI) has proved difficult due to the eye’s propensity to move involuntarily over typical imaging timescales, obscuring the fine structure in the eye due to the resulting motion artifacts. However, advances in MRI technology help to mitigate such drawbacks, enabling the acquisition of high spatiotemporal resolution images with a variety of contrast mechanisms. This review aims to classify the MRI techniques used to date in clinical and preclinical ophthalmologic studies, describing the qualitative and quantitative information that may be extracted and how this may inform on ocular pathophysiology. PMID:23112569

Fagan, Andrew J.

2012-01-01

313

Multiparametric magnetic resonance imaging of prostate cancer.  

PubMed

In India, prostate cancer has an incidence rate of 3.9 per 100,000 men and is responsible for 9% of cancer-related mortality. It is the only malignancy that is diagnosed with an apparently blind technique, i.e., transrectal sextant biopsy. With increasing numbers of high-Tesla magnetic resonance imaging (MRI) equipment being installed in India, the radiologist needs to be cognizant about endorectal MRI and multiparametric imaging for prostate cancer. In this review article, we aim to highlight the utility of multiparamteric MRI in prostate cancer. It plays a crucial role, mainly in initial staging, restaging, and post-treatment follow-up. PMID:23599562

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

2012-07-01

314

Magnetic resonance imaging of small bowel neoplasms  

PubMed Central

Abstract Magnetic resonance (MR) imaging is rapidly increasing clinical acceptance to evaluate the small bowel and can be the initial imaging method to investigate small bowel diseases. MR examinations may provide the first opportunity to detect and characterize tumours of the small bowel. Intra- and extraluminal MR findings, combined with contrast enhancement and functional information, help to make an accurate diagnosis and consequently characterize small bowel neoplasms. MR enteroclysis should be recommended for the initial investigation in patients suspected of having small bowel tumours. In this article, the MR findings of primary small bowel neoplasms are described and the MR findings for the differential diagnosis are discussed. PMID:23524074

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

2013-01-01

315

Magnetic resonance imaging of the postoperative spine.  

PubMed

Magnetic resonance (MR) imaging is an excellent technique for evaluating the postoperative spine when the patient has chronic or recurrent symptoms. Potential causes of pain following lumbar surgery include arachnoiditis, stenosis, epidural fibrosis and disc herniations, pseudomeningocele, and infection. The postoperative cervical spine may be complicated by hematoma, canal or foraminal stenosis, disc herniation, and cord abnormality. This article reviews standard imaging protocols, the normal postoperative appearance of the spine, and the characteristic imaging findings for each of the abnormal postoperative conditions. PMID:11371319

Ross, J S

2000-01-01

316

Cardiac magnetic resonance in clinical cardiology  

PubMed Central

Over the last decades, cardiac magnetic resonance (CMR) has transformed from a research tool to a widely used diagnostic method in clinical cardiology. This method can now make useful, unique contributions to the work-up of patients with ischemic and non-ischemic heart disease. Advantages of CMR, compared to other imaging methods, include very high resolution imaging with a spatial resolution up to 0.5 mm × 0.5 mm in plane, a large array of different imaging sequences to provide in vivo tissue characterization, and radiation-free imaging. The present manuscript highlights the relevance of CMR in the current clinical practice and new perspectives in cardiology. PMID:25632313

Kumar, Andreas; Bagur, Rodrigo

2015-01-01

317

Magnetic resonance imaging of the immature skeleton.  

PubMed

Magnetic resonance (MR) is unique in its ability to allow assessment of bone marrow, epiphyseal, physeal, and articular cartilage as well as tendons and ligaments. An understanding of skeletal maturation and the accompanying changes on MR is of utmost importance in pediatric radiology. In particular, it is important to recognize the normal spectrum related to ossification and marrow transformation. This review will include a brief description of main indications and common pitfalls in musculoskeletal MR in children. Also, we will focus on the MR appearance of the growing pediatric skeleton on the most commonly used sequences. PMID:24179233

Boavida, Peter; Muller, Lil-Sofie; Rosendahl, Karen

2013-11-01

318

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

319

Pleural endometriosis: findings on magnetic resonance imaging.  

PubMed

Endometriosis is a benign gynecological disorder associated with pelvic pain and infertility, primarily affecting women of reproductive age. Thoracic endometriosis affects the pulmonary parenchyma or pleura. We report the cases of two patients with pleural endometriosis who presented with recurrent pneumothorax. In both cases, magnetic resonance imaging (MRI) of the chest showed right hydropneumothorax and well-defined, rounded nodules on the pleural surface in the right hemithorax. We conclude that MRI is a good option for the characterization of pleural endometriotic nodules and hemorrhagic pleural effusion. PMID:23288127

Marchiori, Edson; Zanetti, Gláucia; Rodrigues, Rosana Souza; Souza, Luciana Soares; Souza Junior, Arthur Soares; Francisco, Flávia Angélica Ferreira; Hochhegger, Bruno

2012-01-01

320

Multiparametric magnetic resonance imaging of prostate cancer  

PubMed Central

In India, prostate cancer has an incidence rate of 3.9 per 100,000 men and is responsible for 9% of cancer-related mortality. It is the only malignancy that is diagnosed with an apparently blind technique, i.e., transrectal sextant biopsy. With increasing numbers of high-Tesla magnetic resonance imaging (MRI) equipment being installed in India, the radiologist needs to be cognizant about endorectal MRI and multiparametric imaging for prostate cancer. In this review article, we aim to highlight the utility of multiparamteric MRI in prostate cancer. It plays a crucial role, mainly in initial staging, restaging, and post-treatment follow-up. PMID:23599562

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

2012-01-01

321

Magnetic resonance imaging of fibrosing mediastinitis  

SciTech Connect

Magnetic resonance imaging (MRI) was performed in seven patients with fibrosing mediastinitis. Comparison was made in each case to standard chest radiography and computed tomography (CT). Angiography was performed in three cases. Although MRI and CT were found to be equivalent in defining the extent of adenopathy, CT was superior at demonstrating calcifications, often important in making the diagnosis of fibrosing mediastinitis. MRI, however, offered complementary information, particularly in assessing vascular patency without the need for intravenous contrast media. On T2-weighted images, the adenopathy associated with fibrosing mediastinitis was noted to be of relatively low signal intensity, possibly indicating its benign nature.

Rholl, K.S.; Levitt, R.G.; Glazer, H.S.

1985-08-01

322

Magnetic Resonance Imaging of Cartilage Repair Procedures.  

PubMed

Cartilage injuries in the knee are common and can be a persistent source of pain or dysfunction. Many new surgical strategies have been developed to treat these lesions. It is important for the radiologist to have an understanding of these procedures and their appearance on magnetic resonance (MR) imaging. This article provides the radiologist with an overview of the surgical strategies for repairing cartilage lesions in the knee followed by a discussion of their postoperative appearance on MR imaging in normal and abnormal cases. Guidelines for adequate reporting of the MR imaging findings after cartilage repair in the knee are also included. PMID:25442028

Forney, Michael C; Gupta, Amit; Minas, Tom; Winalski, Carl S

2014-11-01

323

Creating a magnetic resonance imaging ontology.  

PubMed

The goal of this work is to build an ontology of Magnetic Resonance Imaging. The MRI domain has been analysed regarding MRI simulators and the DICOM standard. Tow MRI simulators have been analysed: JEMRIS, which is developed in XML and C++, has a hierarchical organisation and SIMRI, which is developed in C, has a good representation of MRI physical processes. To build the ontology we have used Protégé 4, owl2 that allows quantitative representations. The ontology has been validated by a reasoner (Fact++) and by a good representation of DICOM headers and of MRI processes. The MRI ontology would improved MRI simulators and eased semantic interoperability. PMID:21893854

Lasbleiz, Jérémy; Saint-Jalmes, Hervé; Duvauferrier, Régis; Burgun, Anita

2011-01-01

324

Creating a magnetic resonance imaging ontology  

PubMed Central

The goal of this work is to build an ontology of Magnetic Resonance Imaging. The MRI domain has been analysed regarding MRI simulators and the DICOM standard. Tow MRI simulators have been analysed: JEMRIS, which is developed in XML and C++, has a hierarchical organisation and SIMRI, which is developed in C, has a good representation of MRI physical processes. To build the ontology we have used Protégé 4, owl2 that allows quantitative representations. The ontology has been validated by a reasoner (Fact++) and by a good representation of DICOM headers and of MRI processes. The MRI ontology would improved MRI simulators and eased semantic interoperability. PMID:21893854

Lasbleiz, Jérémy; Saint-Jalmes, Hervé; Duvauferrier, Régis; Burgun, Anita

2011-01-01

325

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

326

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

327

Metabolite specific proton magnetic resonance imaging.  

PubMed Central

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. Images PMID:2734292

Hurd, R E; Freeman, D M

1989-01-01

328

In vivo nuclear magnetic resonance imaging  

NASA Technical Reports Server (NTRS)

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

Leblanc, A.

1986-01-01

329

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

330

Functional magnetic resonance imaging phase synchronization as a measure of dynamic functional connectivity.  

PubMed

Functional brain activity and connectivity have been studied by calculating intersubject and seed-based correlations of hemodynamic data acquired with functional magnetic resonance imaging (fMRI). To inspect temporal dynamics, these correlation measures have been calculated over sliding time windows with necessary restrictions on the length of the temporal window that compromises the temporal resolution. Here, we show that it is possible to increase temporal resolution by using instantaneous phase synchronization (PS) as a measure of dynamic (time-varying) functional connectivity. We applied PS on an fMRI dataset obtained while 12 healthy volunteers watched a feature film. Narrow frequency band (0.04-0.07 Hz) was used in the PS analysis to avoid artifactual results. We defined three metrics for computing time-varying functional connectivity and time-varying intersubject reliability based on estimation of instantaneous PS across the subjects: (1) seed-based PS, (2) intersubject PS, and (3) intersubject seed-based PS. Our findings show that these PS-based metrics yield results consistent with both seed-based correlation and intersubject correlation methods when inspected over the whole time series, but provide an important advantage of maximal single-TR temporal resolution. These metrics can be applied both in studies with complex naturalistic stimuli (e.g., watching a movie or listening to music in the MRI scanner) and more controlled (e.g., event-related or blocked design) paradigms. A MATLAB toolbox FUNPSY ( http://becs.aalto.fi/bml/software.html ) is openly available for using these metrics in fMRI data analysis. PMID:22559794

Glerean, Enrico; Salmi, Juha; Lahnakoski, Juha M; Jääskeläinen, Iiro P; Sams, Mikko

2012-01-01

331

Etiopathophysiological assessment of cases with chronic daily headache: A functional magnetic resonance imaging included investigation  

PubMed Central

Background Chronic daily headache (CDH) has gained little attention in functional neuro-imaging. When no structural abnormality is found in CDH, defining functional correlates between activated brain regions during headache bouts may provide unique insights towards understanding the pathophysiology of this type of headache. Methods We recruited four CDH cases for comprehensive assessments, including history taking, physical examinations and neuropsychological evaluations (The Addenbrooke's Cognitive Evaluation, Beck's Anxiety and Depression Inventories, Pittsburg Sleep Quality Index and Epworth Sleepiness Scale). Visual analogue scale (VAS) was used to self-rate the intensity of headache. Patients then underwent electroencephalography (EEG), transcranial Doppler (TCD) and functional magnetic resonance imaging (fMRI) evaluations during maximal (VAS = 8-10/10) and off-headache (VAS = 0-3/10) conditions. Data were used to compare in both conditions. We also used BOLD (blood oxygen level dependent) -group level activation map fMRI to possibly locate headache-related activated brain regions. Results General and neurological examinations as well as conventional MRIs were unremarkable. Neuropsychological assessments showed moderate anxiety and depression in one patient and minimal in others. Unlike three patients, maximal and off-headache TCD evaluation in one revealed increased middle cerebral artery blood flow velocity, at the maximal pain area. Although with no seizure history, the same patient's EEG showed paroxysmal epileptic discharges during maximal headache intensity, respectively. Group level activation map fMRI showed activated classical pain matrix regions upon headache bouts (periaqueductal grey, substantia nigra and raphe nucleus), and markedly bilateral occipital lobes activation. Conclusion The EEG changes were of note. Furthermore, the increased BOLD signals in areas outside the classical pain matrix (i.e. occipital lobes) during maximal headaches may suggest that activation of these areas can be linked to the increased neural activity or visual cortex hyperexcitability in response to visual stimuli. These findings can introduce new perspective towards more in-depth functional imaging studies in headaches of poorly understood pathophysiology. PMID:24250881

Hashemi, Akram; Nami, Mohammad Torabi; Oghabian, Mohammad Ali; Ganjgahi, Habib; Vahabi, Zahra

2012-01-01

332

Functional Magnetic Resonance Imaging Phase Synchronization as a Measure of Dynamic Functional Connectivity  

PubMed Central

Abstract Functional brain activity and connectivity have been studied by calculating intersubject and seed-based correlations of hemodynamic data acquired with functional magnetic resonance imaging (fMRI). To inspect temporal dynamics, these correlation measures have been calculated over sliding time windows with necessary restrictions on the length of the temporal window that compromises the temporal resolution. Here, we show that it is possible to increase temporal resolution by using instantaneous phase synchronization (PS) as a measure of dynamic (time-varying) functional connectivity. We applied PS on an fMRI dataset obtained while 12 healthy volunteers watched a feature film. Narrow frequency band (0.04–0.07?Hz) was used in the PS analysis to avoid artifactual results. We defined three metrics for computing time-varying functional connectivity and time-varying intersubject reliability based on estimation of instantaneous PS across the subjects: (1) seed-based PS, (2) intersubject PS, and (3) intersubject seed-based PS. Our findings show that these PS-based metrics yield results consistent with both seed-based correlation and intersubject correlation methods when inspected over the whole time series, but provide an important advantage of maximal single-TR temporal resolution. These metrics can be applied both in studies with complex naturalistic stimuli (e.g., watching a movie or listening to music in the MRI scanner) and more controlled (e.g., event-related or blocked design) paradigms. A MATLAB toolbox FUNPSY (http://becs.aalto.fi/bml/software.html) is openly available for using these metrics in fMRI data analysis. PMID:22559794

Salmi, Juha; Lahnakoski, Juha M.; Jääskeläinen, Iiro P.; Sams, Mikko

2012-01-01

333

Multi-projection magnetic resonance inverse imaging of the human visuomotor system  

PubMed Central

Using highly parallel radiofrequency (RF) detection, magnetic resonance inverse imaging (InI) can achieve 100 ms temporal resolution with whole brain coverage. This is achieved by trading off partition encoding steps and thus spatial resolution for a higher acquisition rate. The reduced spatial information is estimated by solving under-determined inverse problems using RF coil sensitivity information. Here we propose multi projection inverse imaging (mInI) to combine different projection images to improve the spatial resolution of InI. Specifically, coronal, sagittal, and transverse projection images were acquired from different runs of the fMRI acquisitions using a 32-channel head coil array. Simulations show that mInI improves the quality of the instantaneous image reconstruction significantly. Going from one projection to three projections, the spatial resolution quantified by the full width at half maximum of the point-spread function (PSF) is improved from 2.6 pixels to 1.4 pixels (4 mm nominal resolution per pixel). Considering the shape of the PSF, the effective spatial resolution is improved from 16.9 pixels to 4.7 pixels. In vivo fMRI experiments using a two-choice reaction time tasks shows visual and sensorimotor cortical activity spatially consistent with typical EPI data, yet mInI offers 100 ms temporal resolution with the whole brain coverage. The mInI data with three projections revealed that the sensorimotor cortex was activated 700 ms after the visual cortex. mInI can be applied to BOLD-contrast fMRI experiments to characterize the dynamics of the activated brain areas with a high spatiotemporal resolution. PMID:22326985

Tsai, Kevin Wen-Kai; Nummenmaa, Aapo; Witzel, Thomas; Chang, Wei-Tang; Kuo, Wen-Jui; Lin, Fa-Hsuan

2012-01-01

334

Semiblind Spatial ICA of fMRI Using Spatial Constraints  

PubMed Central

Independent component analysis (ICA) utilizing prior information, also called semiblind ICA, has demonstrated considerable promise in the analysis of functional magnetic resonance imaging (fMRI). So far, temporal information about fMRI has been used in temporal ICA or spatial ICA as additional constraints to improve estimation of task-related components. Considering that prior information about spatial patterns is also available, a semiblind spatial ICA algorithm utilizing the spatial information was proposed within the framework of constrained ICA with fixed-point learning. The proposed approach was first tested with synthetic fMRI-like data, and then was applied to real fMRI data from 11 subjects performing a visuomotor task. Three components of interest including two task-related components and the “default mode” component were automatically extracted, and atlas-defined masks were used as the spatial constraints. The default mode network, a set of regions that appear correlated in particular in the absence of tasks or external stimuli and is of increasing interest in fMRI studies, was found to be greatly improved when incorporating spatial prior information. Results from simulation and real fMRI data demonstrate that the proposed algorithm can improve ICA performance compared to a different semiblind ICA algorithm and a standard blind ICA algorithm. PMID:20017117

Lin, Qiu-Hua; Liu, Jingyu; Zheng, Yong-Rui; Liang, Hualou; Calhoun, Vince D.

2009-01-01

335

Features selection for clustering of fMRI data  

NASA Astrophysics Data System (ADS)

We address the problem of the analysis of event-related functional Magnetic Resonance Images (fMRI). We propose to separate the fMRI time series into "activated" and "non-activated" clusters. The fMRI time series are projected onto a basis, and the clustering is performed using the coefficients in that basis. We developed a new algorithm to select that basis which provides the optimal clustering of the time series. Our approach does not require any training datasets or any model of the hemodynamic response. The basis is constructed using a dictionary of wavelet packets. We search for the optimal basis in this dictionary using a new cost function that measures the clustering power of a set of wavelet packets. Our approach can be easily extended to classification problems. We have conducted several experiments with synthetic and in-vivo event-related fMRI data. Our method is capable of discovering the structures of the synthetic data. The method also successfully detected activated voxels in the in-vivo fMRI.

Meyer, Francois G.; Chinrungrueng, Jatuporn

2003-11-01

336

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

PubMed

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

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

2011-09-01

337

Increased fMRI signal with age in familial Alzheimer’s disease mutation carriers  

PubMed Central

Although many Alzheimer’s disease (AD) patients have a family history of the disease, it is rarely inherited in a predictable way. Functional magnetic resonance imaging (fMRI) studies of non-demented adults carrying familial AD mutations provide an opportunity to prospectively identify brain differences associated with early AD-related changes. We compared fMRI activity of 18 non-demented autosomal dominant AD mutation carriers with fMRI activity in 8 of their non-carrier relatives as they performed a novelty encoding task in which they viewed novel and repeated images. Because age of disease onset is relatively consistent within families, we also correlated fMRI activity with subjects’ distance from the median age of diagnosis for their family. Mutation carriers did not show significantly different voxelwise fMRI activity from non-carriers as a group. However, as they approached their family age of disease diagnosis, only mutation carriers showed increased fMRI activity in the fusiform and middle temporal gyri. This suggests that during novelty encoding, increased fMRI activity in the temporal lobe may relate to incipient AD processes. PMID:21129823

Braskie, Meredith N.; Medina, Luis D.; Rodriguez-Agudelo, Yaneth; Geschwind, Daniel H.; Macias-Islas, Miguel Angel; Cummings, Jeffrey L.; Bookheimer, Susan Y.; Ringman, John M.

2010-01-01

338

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

339

Magnetic resonance imaging predictors of treatment response in late-life depression.  

PubMed

In older adults, depression not only results in more years lived with disability than any other disease but it also carries additional risks of suicide, medical comorbidities, and family caregiving burden. Because it can take many months to identify an effective treatment regimen, it is of utmost importance to shorten the window of time and identify early on what medications and dosages will work effectively for individuals having depression. Late-life depression (LLD) has been associated with greater burden of age-related changes (eg, atrophy, white matter ischemic changes, and functional connectivity). Depression in midlife has been shown to alter affective reactivity and regulation, and functional magnetic resonance imaging (fMRI) studies in LLD have replicated the same abnormalities. Effective treatment can normalize these alterations. This article provides a review of the current literature using structural and functional neuroimaging to identify MRI predictors of treatment response in LLD. The majority of the literature on structural MRI has focused on the vascular depression hypothesis, and studies support the view that loss of brain volume and white matter integrity was associated with poorer treatment outcomes. Studies using fMRI have reported that lower task-based activity in the prefrontal cortex and limbic regions was associated with poorer outcome. These imaging markers may be integrated into clinical decision making to attain better treatment outcomes in the future. PMID:24381231

Aizenstein, Howard J; Khalaf, Alexander; Walker, Sarah E; Andreescu, Carmen

2014-03-01

340

Growth hormone deficiency and memory functioning in adults visualized by functional magnetic resonance imaging.  

PubMed

Cognitive functioning, especially memory performance, is known to be impaired in patients with childhood-onset growth hormone deficiency (CO-GHD), and growth hormone substitution has been found to counteract this memory impairment. Neuropsychological and functional magnetic resonance imagining (fMRI) data acquired during a working memory task in 13 childhood-onset GH-deficient patients were compared with 13 age, sex and education level matched healthy controls. Results demonstrated that there is no difference in the quality of the performance in the working memory task between GH-deficient patients and control subjects. However, memory speed was found to be subnormal in patients. Concerning mood, patients reported more complaints of fatigue, and less vigor. Imaging data showed that patients had increased activity in dorsolateral/ventrolateral prefrontal cortex, anterior cingulate cortex, parietal cortex, supplementary motor and motor cortex, as well as in the thalamus and precuneus area. Increasing task load was also associated with an increase in brain activity in similar areas in patients compared to control subjects. In conclusion, this fMRI study shows that GH-deficient patients have a subnormal memory speed, but no impaired quality of memory performance, which may be due to compensatory recruitment of dorsal prefrontal brain regions. These findings indicate that the GH-IGF-1 axis contributes to prefrontal functioning in patients with CO-GHD. PMID:16330884

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

2005-01-01

341

The impact of denoising on independent component analysis of functional magnetic resonance imaging data.  

PubMed

Independent component analysis (ICA) is a suitable method for decomposing functional magnetic resonance imaging (fMRI) activity into spatially independent patterns. Practice has revealed that low-pass filtering prior to ICA may improve ICA results by reducing noise and possibly by increasing source smoothness, which may enhance source independence; however, it eliminates useful information in high frequency features and it amplifies low signal fluctuations leading to independence loss. On the other hand, high-pass filtering may increase the independence by preserving spatial information, but its denoising properties are weak. Thus, such filtering strategies did not lead to simultaneous enhancements in independence and noise reduction; therefore, band-pass filtering or more sophisticated filtering methods are expected to be more appropriate. We used advanced wavelet filtering procedures, such as wavelet-based methods relying upon hard and soft coefficient thresholding and non-stationary Gaussian modelling based on geometrical prior information, to denoise artificial and real fMRI data. We compared the performance of these methods with the performance of traditional Gaussian smoothing techniques. First, we demonstrated both analytically and empirically the consistent performance increase of spatial filtering prior to ICA using spatial correlation and statistical sensitivity as quality measures. Second, all filtering methods were computationally efficient. Finally, denoising using low-pass filters was needed to improve ICA, suggesting that noise reduction may have a more significant effect on the component independence than the preservation of information contained within high frequencies. PMID:23261654

Pignat, Jean Michel; Koval, Oleksiy; Van De Ville, Dimitri; Voloshynovskiy, Sviatoslav; Michel, Christoph; Pun, Thierry

2013-02-15

342

Functional magnetic resonance imaging of internal source monitoring in schizophrenia: Recognition with and without recollection  

PubMed Central

Patients with schizophrenia tend to have impaired source monitoring and intact item recognition, suggesting an over-reliance of familiarity effects. We previously demonstrated that providing patients with a levels-of-processing (LOP) semantic encoding strategy normalized source monitoring. The current blood-oxygen-level-dependent (BOLD) functional magnetic resonance imaging (fMRI) study tests the hypothesis that patients will have abnormally increased frontotemporal activation despite intact performance. fMRI was measured in 13 patients and 13 demographically matched healthy controls during a LOP source monitoring paradigm. SPM2 was used for standard pre-processing and statistical analyses, with a corrected significance threshold of p<.05. Examination of accuracy and speed measures did not reveal any group differences in task performance. Regardless of source retrieval success both groups activated expected prefrontal and parietal regions, with no areas of relatively greater control versus patient activation. In support of the hypothesis, patients showed abnormally increased activation in temporolimbic areas including middle and superior temporal gyrus, thalamus, and parahippocampal gyrus. Activation in these areas was associated with worse positive and negative symptoms, but did not correlate with performance, suggesting inefficient rather than compensatory activation. PMID:16814525

Ragland, J. Daniel; Valdez, Jeffrey N.; Loughead, James; Gur, Ruben C.; Gur, Raquel E.

2015-01-01

343

Reward pathway dysfunction in gambling disorder: A meta-analysis of functional magnetic resonance imaging studies.  

PubMed

Recent emerging functional magnetic resonance imaging (fMRI) studies have identified many brain regions in which gambling cues or rewards elicit activation and may shed light upon the ongoing disputes regarding the diagnostic and neuroscientific issues of gambling disorder (GD). However, no studies to date have systemically reviewed fMRI studies of GD to analyze the brain areas activated by gambling-related cues and examine whether these areas were differentially activated between cases and healthy controls (HC). This study reviewed 62 candidate articles and ultimately selected 13 qualified voxel-wise whole brain analysis studies to perform a comprehensive series of meta-analyses using the effect size-signed differential mapping approach. Compared with HC, GD patients showed significant activation in right lentiform nucleus and left middle occipital gyrus. The increased activities in the lentiform nucleus compared to HC were also found in both GD subgroups, regardless of excluding or not excluding any kind of substance use disorder. In addition, the South Oaks Gambling Screen scores were associated with hyperactivity in right lentiform nucleus and bilateral parahippocampus, but negatively related to right middle frontal gyrus. These results suggest dysfunction within the frontostriatal cortical pathway in GD, which could contribute to our understanding of the categories and definition of GD and provide evidence for the reclassification of GD as a behavioral addiction in the DSM-5. PMID:25205368

Meng, Ya-jing; Deng, Wei; Wang, Hui-yao; Guo, Wan-jun; Li, Tao; Lam, Chaw; Lin, Xia

2014-12-15

344

Nuclear magnetic resonance in magnets with a helicoidal magnetic structure in an external magnetic field  

NASA Astrophysics Data System (ADS)

In this review, the static and dynamic properties of a magnet with a helicoidal magnetic structure placed in an external magnetic field are discussed. The results of the investigation of its ground state and spectra, as well as the amplitudes of the spin excitations are presented. The temperature and field dependences of the basic thermodynamic characteristics (heat capacity, magnetization, and magnetic susceptibility) have been calculated in the spin-wave approximation. The results of calculating the local and integral dynamic magnetic susceptibility are given. This set of data represents a methodical basis for constructing a consistent (in the framework of unified approximations) picture of the NMR absorption in the magnet under consideration. Both local NMR characteristics (resonance frequency, line broadening, enhancement coefficient) and integral characteristics (resultant shape of the absorption line with its specific features) have been calculated. The effective Hamiltonian of the Suhl-Nakamura interaction of nuclear spins through spin waves has been constructed. The second moment and the local broadening of the line of the NMR absorption caused by this interaction have been calculated. The role of the basic local inhomogeneities in the formation of the integral line of the NMR absorption has been analyzed. The opportunities for the experimental NMR investigations in magnets with a chiral spin structure are discussed.

Tankeyev, A. P.; Borich, M. A.; Smagin, V. V.

2014-11-01

345

A Functional Magnetic Resonance Imaging Predictor of Treatment Response to Venlafaxine in Generalized Anxiety Disorder  

PubMed Central

Background Functional magnetic resonance imaging (fMRI) holds promise as a noninvasive means of identifying neural responses that can be used to predict treatment response before beginning a drug trial. Imaging paradigms employing facial expressions as presented stimuli have been shown to activate the amygdala and anterior cingulate cortex (ACC). Here, we sought to determine whether pretreatment amygdala and rostral ACC (rACC) reactivity to facial expressions could predict treatment outcomes in patients with generalized anxiety disorder (GAD). Methods Fifteen subjects (12 female subjects) with GAD participated in an open-label venlafaxine treatment trial. Functional magnetic resonance imaging responses to facial expressions of emotion collected before subjects began treatment were compared with changes in anxiety following 8 weeks of venlafaxine administration. In addition, the magnitude of fMRI responses of subjects with GAD were compared with that of 15 control subjects (12 female subjects) who did not have GAD and did not receive venlafaxine treatment. Results The magnitude of treatment response was predicted by greater pretreatment reactivity to fearful faces in rACC and lesser reactivity in the amygdala. These individual differences in pretreatment rACC and amygdala reactivity within the GAD group were observed despite the fact that 1) the overall magnitude of pretreatment rACC and amygdala reactivity did not differ between subjects with GAD and control subjects and 2) there was no main effect of treatment on rACC-amygdala reactivity in the GAD group. Conclusions These findings show that this pattern of rACC-amygdala responsivity could prove useful as a predictor of venlafaxine treatment response in patients with GAD. PMID:17964548

Johnstone, Tom; Somerville, Leah H.; Nitschke, Jack B.; Polis, Sara; Alexander, Andrew L.; Davidson, Richard J.; Kalin, Ned H.

2008-01-01

346

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

347

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

NASA Astrophysics Data System (ADS)

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

Chen, Zikuan; Calhoun, Vince

2011-03-01

348

Stress reconfigurable tunable magnetoelectric resonators as magnetic sensors  

NASA Astrophysics Data System (ADS)

Magnetoelectric multiferroic materials are extremely attractive due to their potential in sensing, filtering and energy transduction applications. We report a magnetoelastic effect in doubly-clamped ferromagnetic magnetostrictive Metglas resonators, as well as the magnetic field dependence of the resonance frequency as a function of uniaxial stress. Magnetostrictive strain results in a resonance frequency shift when the resonator is exposed to a magnetic field. The resonance frequency can be tracked in real time as a function of magnetic field bias using a feedback loop based on the quadrature of the excited motion. This magnetically reconfigurable resonance response can be used as a simple, tunable, magnetoelectric (ME) magnetic field sensor. The effect of sample pre-tension on the field dependent magnetostrictive constant and the sensor sensitivity is examined, and the resolution of such a sensor is estimated.

Kiser, Jillian; Finkel, Peter; Dolabdjian, Christophe

2013-03-01

349

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

350

Reciprocity and gyrotropism in magnetic resonance transduction  

NASA Astrophysics Data System (ADS)

We give formulas for transduction in magnetic resonance—i.e., the appearance of an emf due to Larmor precession of spins—based upon the modified Lorentz reciprocity principle for gyrotropic (also called “nonreciprocal”) media, i.e., in which a susceptibility tensor is carried to its transpose by reversal of an external static field [cf., R. F. Harrington and A. T. Villeneuve IRE Trans. Microwave Theory and Technique MTT6, 308 (1958)]. Prior applications of reciprocity to magnetic resonance, despite much success, have ignored the gyrotropism which necessarily arises due to nuclear and/or unpaired electronic spins. For detection with linearly polarized fields, oscillating at the Larmor frequency, the emf is written in terms of a volume integral containing a product of two factors which we define as the antenna patterns, i.e., (H1x±iH1y) , where, e.g., for a single transceive antenna, the H ’s are just the spatially dependent oscillatory magnetic field strengths, per the application of some reference current at the antenna terminals, with the negative sign obtaining for transmission, and the positive for reception. Similar expressions hold for separate transmit and receive antennas; expressions are also given for circular polarization of the fields. We then exhibit a receive-only array antenna of two elements for magnetic resonance imaging of protons, which, due an intensity artifact arising from stray reactive coupling of the elements, produces, despite its own bilateral symmetry, asymmetric proton NMR images of a symmetric cylindrical phantom containing aqueous saline solution [J. Tropp and T. Schirmer, J. Magn. Reson. 151, 146 (2001)]. Modification of this two-port antenna, to function in transmit-receive mode, allows us to demonstrate highly nonreciprocal behavior: that is, to record images (of cylindrical test phantoms containing aqueous saline solution) whose appearance dramatically changes, when the roles of transmission and reception are swapped between the two antenna ports—giving in one instance a signal intensity pattern whose form resembles an umbrella (i.e., with a central column of moderate intensity surmounted by a bright canopy), and in the other, a distorted oval with slight concavities at its horizontal extremes, whose outline suggests that of a cat’s eye. The relation between image patterns and drive scheme can be shown to reverse if the static polarizing field is reversed. Electromagnetic and circuit calculations, together with the modified reciprocity principle, allow us to reproduce these pattern changes in numerical simulations, closely and convincingly. Although the imaging experiments are performed at a static field of 3.0T , and consequently a Larmor frequency of 128MHz , the nonreciprocal effects are not related to the shortness of the wavelength in aqueous medium, but appear equally in simulations based in either the quasistatic or full electromagnetic regimes. Finally, we show that although antenna patterns for transmission and reception are swapped with reversal of the polarizing field, meaning that the receive pattern equals the transmit pattern with the field reversed, this in no way invalidates the familiar rotating wave model of spin dynamics in magnetic resonance.

Tropp, James

2006-12-01

351

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

352

Sample-detector coupling in atomic resolution magnetic resonance diffraction  

NASA Astrophysics Data System (ADS)

A technique for potential realization of atomic resolution magnetic resonance diffraction was recently proposed for the case of a crystalline sample in proximity of a ferromagnetic sphere [M. Barbic, J. Appl. Phys. 91, 9987 (2002)]. This article predicted the detection of distinct peaks in the number of resonant spin sites at different magnetic field values for specific sphere and crystal configurations. Here, the focus is on the specific detection coupling mechanisms between the resonant spin population of the sample and the magnetic sphere probe. We investigate and compare the force, torque, and flux detection mechanisms in order to provide guidance to the experimental efforts towards the realization of the atomic resolution magnetic resonance diffraction. We also investigate the dependence of the magnetic resonance diffraction spectrum on the relative position of the magnetic sphere with respect to the crystal lattice.

Barbic, Mladen; Scherer, Axel

2002-12-01

353

BROADBAND EXCITATION IN NUCLEAR MAGNETIC RESONANCE  

SciTech Connect

Theoretical methods for designing sequences of radio frequency (rf) radiation pulses for broadband excitation of spin systems in nuclear magnetic resonance (NMR) are described. The sequences excite spins uniformly over large ranges of resonant frequencies arising from static magnetic field inhomogeneity, chemical shift differences, or spin couplings, or over large ranges of rf field amplitudes. Specific sequences for creating a population inversion or transverse magnetization are derived and demonstrated experimentally in liquid and solid state NMR. One approach to broadband excitation is based on principles of coherent averaging theory. A general formalism for deriving pulse sequences is given, along with computational methods for specific cases. This approach leads to sequences that produce strictly constant transformations of a spin system. The importance of this feature in NMR applications is discussed. A second approach to broadband excitation makes use of iterative schemes, i.e. sets of operations that are applied repetitively to a given initial pulse sequences, generating a series of increasingly complex sequences with increasingly desirable properties. A general mathematical framework for analyzing iterative schemes is developed. An iterative scheme is treated as a function that acts on a space of operators corresponding to the transformations produced by all possible pulse sequences. The fixed points of the function and the stability of the fixed points are shown to determine the essential behavior of the scheme. Iterative schemes for broadband population inversion are treated in detail. Algebraic and numerical methods for performing the mathematical analysis are presented. Two additional topics are treated. The first is the construction of sequences for uniform excitation of double-quantum coherence and for uniform polarization transfer over a range of spin couplings. Double-quantum excitation sequences are demonstrated in a liquid crystal system. The second additional topic is the construction of iterative schemes for narrowband population inversion. The use of sequences that invert spin populations only over a narrow range of rf field amplitudes to spatially localize NMR signals in an rf field gradient is discussed.

Tycko, R.

1984-10-01

354

Increasing the reliability of data analysis of functional magnetic resonance imaging by applying a new blockwise permutation method.  

PubMed

A recent paper by Eklund et al. (2012) showed that up to 70% false positive results may occur when analyzing functional magnetic resonance imaging (fMRI) data using the statistical parametric mapping (SPM) software, which may mainly be caused by insufficient compensation for the temporal correlation between successive scans. Here, we show that a blockwise permutation method can be an effective alternative to the standard correction method for the correlated residuals in the general linear model, assuming an AR(1)-model as used in SPM for analyzing fMRI data. The blockwise permutation approach including a random shift developed by our group (Adolf et al., 2011) accounts for the temporal correlation structure of the data without having to provide a specific definition of the underlying autocorrelation model. 1465 publicly accessible resting-state data sets were re-analyzed, and the results were compared with those of Eklund et al. (2012). It was found that with the new permutation method the nominal familywise error rate for the detection of activated voxels could be maintained approximately under even the most critical conditions in which Eklund et al. found the largest deviations from the nominal error level. Thus, the method presented here can serve as a tool to ameliorate the quality and reliability of fMRI data analyses. PMID:25165444

Adolf, Daniela; Weston, Snezhana; Baecke, Sebastian; Luchtmann, Michael; Bernarding, Johannes; Kropf, Siegfried

2014-01-01

355

Increasing the reliability of data analysis of functional magnetic resonance imaging by applying a new blockwise permutation method  

PubMed Central

A recent paper by Eklund et al. (2012) showed that up to 70% false positive results may occur when analyzing functional magnetic resonance imaging (fMRI) data using the statistical parametric mapping (SPM) software, which may mainly be caused by insufficient compensation for the temporal correlation between successive scans. Here, we show that a blockwise permutation method can be an effective alternative to the standard correction method for the correlated residuals in the general linear model, assuming an AR(1)-model as used in SPM for analyzing fMRI data. The blockwise permutation approach including a random shift developed by our group (Adolf et al., 2011) accounts for the temporal correlation structure of the data without having to provide a specific definition of the underlying autocorrelation model. 1465 publicly accessible resting-state data sets were re-analyzed, and the results were compared with those of Eklund et al. (2012). It was found that with the new permutation method the nominal familywise error rate for the detection of activated voxels could be maintained approximately under even the most critical conditions in which Eklund et al. found the largest deviations from the nominal error level. Thus, the method presented here can serve as a tool to ameliorate the quality and reliability of fMRI data analyses. PMID:25165444

Adolf, Daniela; Weston, Snezhana; Baecke, Sebastian; Luchtmann, Michael; Bernarding, Johannes; Kropf, Siegfried

2014-01-01

356

Magnetic Resonance Imaging as a Tool to Predict Meniscal Reparability  

Microsoft Academic Search

One hundred six patients who underwent high field strength magnetic resonance imaging and subsequent arthroscopy of the knee were evaluated to determine the accuracy of magnetic resonance imaging in predicting meniscal tear reparability. Each scan was independently read by three examiners with varying degrees of expertise: a musculoskeletal radiologist, a senior orthopaedic surgeon, and a general radiologist. Each suspected tear

Matthew J. Matava; Kevin Eck; William Totty; Rick W. Wright; Robert A. Shively

1999-01-01

357

Midinfrared Resonant Magnetic Nanostructures Exhibiting a Negative Permeability  

Microsoft Academic Search

We experimentally demonstrate the first midinfrared (mid-IR) resonant magnetic nanostructures exhibiting a strong magnetic response corresponding to a negative permeability. This result is an important step toward the achievement of a negative refractive index in the IR. The possibility of extending negative permeability to higher frequencies is discussed; a structure with a negative effective permeability at a near-IR resonance frequency

Shuang Zhang; Wenjun Fan; B. K. Minhas; Andrew Frauenglass; K. J. Malloy; S. R. Brueck

2005-01-01

358

Magnetic resonance imaging in entomology: a critical review  

Microsoft Academic Search

Magnetic resonance imaging (MRI) enables in vivo imaging of organisms. The recent development of the magnetic resonance microscope (MRM) has enabled organisms within the size range of many insects to be imaged. Here, we introduce the principles of MRI and MRM and review their use in entomology. We show that MRM has been successfully applied in studies of parasitology, development,

Ratnieks F. L. W

359

The Nobel Prize in Medicine for Magnetic Resonance Imaging  

ERIC Educational Resources Information Center

Nobel Prize in Medicine awarded in December 2003 to chemist Paul C. Lauterbur and physicist Peter Mansfield for the development of magnetic resonance imaging (MRI), a long overdue recognition of the huge impact MRI has had in medical diagnostics and research is mentioned. MRI was derived, and remains an extension of nuclear magnetic resonance

Fry, Charles G.

2004-01-01

360

Graph theory based algorithm for magnetic resonance brain images segmentation  

Microsoft Academic Search

Image segmentation is often required as a preliminary and indispensable stage in the computer aided medical image process, particularly during the clinical analysis of magnetic resonance (MR) brain images. The segmentation of magnetic resonance image (MRI) is a challenging problem that has received an enormous amount of attention lately. In this paper, we propose a simple and effective segmentation method

Jianzhong Wang; Di Liu; Lili Dou; Baoxue Zhang; Jun Kong; Yinghua Lu

2008-01-01

361

Magnetic Resonance Imaging of Electroconvection in a Polar Organic Solvent  

E-print Network

Magnetic Resonance Imaging of Electroconvection in a Polar Organic Solvent Scott A. Riley, California 95616 Received October 20, 1999; revised February 2, 2000 Molecular motion in the polar organic solvent nitrobenzene induced by an electric field is studied by magnetic resonance imaging. Rf pulse

Augustine, Mathew P.

362

Nuclear magnetic resonance in environmental engineering: Principles and applications  

Microsoft Academic Search

This paper gives an introduction to nuclear magnetic resonance spectroscopy (NMR) and magnetic resonance imaging (MRI) in relation to applications in the field of environmental science and engineering. The underlying principles of high resolution solution and solid state NMR, relaxation time measurements and imaging are presented. Then, the use of NMR is illustrated and reviewed in studies of biodegradation and

P. N. L. Lens; M. A. Hemminga

1998-01-01

363

Design of LLC resonant converter using planar magnetic component  

Microsoft Academic Search

This paper presents the design and implementation of LLC resonant converter using planar magnetic component. In the LLC resonant converter, ZVS turn-on and ZCS turn-off of MOSFETs and diode rectifiers can be achieved over the entire operating range, respectively. Therefore, the switching loss is reduced and we can operate the converter at higher switching frequency. At that frequency, planar magnetic

Sihun Yang; Seiya Abe; Masahito Shoyama

2009-01-01

364

MBP 9662a: Nuclear Magnetic Resonance Prof. Blaine A. Chronik  

E-print Network

of Physics and Astronomy Office: Room 241, Physics & Astronomy Building Phone: 661-2111 x24067 (phone mailMBP 9662a: Nuclear Magnetic Resonance Prof. Blaine A. Chronik Fall Semester, 2010 1 of 3 Medical Biophysics 9662a "Introductory Nuclear Magnetic Resonance" or "MRI 1: no gradients" Fall Semester, 2010

Lennard, William N.

365

Global resonances in the evolution of solar magnetic fields  

Microsoft Academic Search

Decomposition of the pattern of solar magnetic fields in spherical harmonics for a data set of 25 years and power spectrum analysis of the harmonic coefficients reveals a strikingly resonant modal structure. The resonances for the modes of odd and even parity are decoupled from each other, indicating an underlying selection rule. This new 'emission line' spectrum of solar magnetic

J. O. Stenflo; M. Vogel

1986-01-01

366

Nuclear magnetic resonance technology in acupoint catgut embedding therapy for the treatment of menopausal panic disorder: its applications  

NASA Astrophysics Data System (ADS)

Nuclear Magnetic Resonance (NMR) is a diagnostic method which is non-invasive and non-ionizing irradiative to the human body. It not only suits structural, but also functional imaging. The NMR technique develops rapidly in its application in life science, which has become the hotspot in recent years. Menopausal panic disorder (MPD) is a typical psychosomatic disease during climacteric period, which may affect physical and mental health. Looking for a convenient, effective, and safe method, which is free of toxic-side effects to control the disease, is a modern medical issue. Based on reviewing the etiology and pathogenesis of MPD according to dual traditional Chinese medicine (TCM) and western medicine, further analyzed the advantages and principles for selecting acupoint prescription by tonifying kidney and benefiting marrow therapy for acupoint catgut-embedding to this disease. The application of Nuclear Magnetic Resonance Spectroscopy (NMRS) and Magnetic Resonance Imaging (MRI) technologies in mechanism research on acupoint catgut embedding for the treatment of MPD was discussed. It's pointed out that this intervention method is safe and effective to treat MPD. Breakthrough will be achieved from the research of the selection of acupoint prescription and therapeutic mechanism of acupoint catgut embedding for the treatment of menopausal panic disorder by utilizing the Functional Nuclear Magnetic Resonance Imaging (fMRI) and Metabonomics technologies.

Chen, Gui-zhen; Zhang, Sha-sha; Xu, Yun-xiang; Wang, Xiao-yun

2012-03-01

367

Nuclear magnetic resonance technology in acupoint catgut embedding therapy for the treatment of menopausal panic disorder: its applications  

NASA Astrophysics Data System (ADS)

Nuclear Magnetic Resonance (NMR) is a diagnostic method which is non-invasive and non-ionizing irradiative to the human body. It not only suits structural, but also functional imaging. The NMR technique develops rapidly in its application in life science, which has become the hotspot in recent years. Menopausal panic disorder (MPD) is a typical psychosomatic disease during climacteric period, which may affect physical and mental health. Looking for a convenient, effective, and safe method, which is free of toxic-side effects to control the disease, is a modern medical issue. Based on reviewing the etiology and pathogenesis of MPD according to dual traditional Chinese medicine (TCM) and western medicine, further analyzed the advantages and principles for selecting acupoint prescription by tonifying kidney and benefiting marrow therapy for acupoint catgut-embedding to this disease. The application of Nuclear Magnetic Resonance Spectroscopy (NMRS) and Magnetic Resonance Imaging (MRI) technologies in mechanism research on acupoint catgut embedding for the treatment of MPD was discussed. It's pointed out that this intervention method is safe and effective to treat MPD. Breakthrough will be achieved from the research of the selection of acupoint prescription and therapeutic mechanism of acupoint catgut embedding for the treatment of menopausal panic disorder by utilizing the Functional Nuclear Magnetic Resonance Imaging (fMRI) and Metabonomics technologies.

Chen, Gui-zhen; Zhang, Sha-sha; Xu, Yun-xiang; Wang, Xiao-yun

2011-11-01

368

Magnet driver for producing ultra-high gradient magnetic fields for magnetic resonance imaging  

Microsoft Academic Search

Pulsed gradient magnetic fields are required for magnetic resonance imaging (MRI). Many imaging sequences (e.g., echo planar imaging, diffusion tensor imaging) could be improved with shorter gradient pulses. MRI systems currently available typically require ramp times of hundreds of microseconds. The goal of the work described here is to achieve very high gradient fields, with very short rise times to

Howard D. Sanders; Steven C. Glidden; Daniel M. Warnow; Irving N. Weinberg; Pavel Stepanov; Roland Probst; Alan McMillan; Rao Gullapalli; Piotr M. Starewicz; William F. B. Punchard; Kai-Ming Lo; Stanley Thomas Fricke

2011-01-01

369

[Magnetic resonance imaging in multiple sclerosis].  

PubMed

The contribution of magnetic resonance imaging techniques to the clinical prognosis of multiple sclerosis. Magnetic resonance imaging (MRI) is a diagnostic technique with a high sensitivity for the detection of lesions, but with a poor pathological specificity. In the case of multiple sclerosis (MS), the improvement of diagnostic efficacy depends on a careful analysis of the clinical presentation and the use of increasingly stringent MRI criteria aimed at improving the specificity of the conventional MRI T2 sequences. New sequences such as fast spin-echo (also called turbo spin-echo) and FLAIR (fluid attenuated inversion recovery, a method derived from inversion recovery) have improved the visualization of lesions. MRI can under certain conditions be used to monitor the evolution of MS. Acute-phase monitoring is focused on observed changes in disease activity such as the appearance, recurrence or extension of lesions after i.v. injection of contrast medium, i.e., gadolinium (Gd)-enhanced MRI. In the chronic phase, the lesions is the aspect used as the monitoring criterion. However, MRI is still only a secondary criterion in phase III therapeutic trials due to its insufficient correlation with the disability. In neurological daily practice, conventional MRI is only of limited interest at the individual level in patient follow-up, as its prognostic value is poor. Moreover, the difficulty in determining the lesion load can only be excluded in the context of clinical trials, in which certain methodological precautions are taken. This is why techniques other than MRI are being investigated to obtain a better correlation with the clinical course of the disease, for instance the quantification of 'black holes' on T1 weighted images, and the measurement of cerebral and spinal atrophy. Adapted MRI techniques allow a weighted signal to be obtained via the movement (diffusion imaging), by the complexity of the molecular structure (magnetization transfer imaging), by chemical shift (spectroscopic imaging), or by local oxygenation (functional MRI). These new MRI techniques allow a more precise assessment of the pathological mechanisms involved in MS, such as edema, blood brain barrier break-down, demyelinisation, gliosis, cellular infiltration and axonal loss; they provide a better means of establishing the correlation between clinical impact and the destructive nature of the MS lesion. The importance of axonal loss has recently been confirmed in MS by analyzing MRI spectroscopic and neuropathological findings. In addition to magnetization transfer imaging, MR diffusion imaging and functional MRI are being intensively studied in order to assess their contribution to the study of reversibility of the degenerative process. PMID:10815291

Tourbah, A; Berry, I

2000-03-01

370

Plasma-induced magnetic responses during nonlinear dynamics of magnetic islands due to resonant magnetic perturbations  

NASA Astrophysics Data System (ADS)

Resonant magnetic perturbations (RMPs) produce magnetic islands in toroidal plasmas. Self-healing (annihilation) of RMP-induced magnetic islands has been observed in helical systems, where a possible mechanism of the self-healing is shielding of RMP penetration by plasma flows, which is well known in tokamaks. Thus, fundamental physics of RMP shielding is commonly investigated in both tokamaks and helical systems. In order to check this mechanism, detailed informations of magnetic island phases are necessary. In experiments, measurement of radial magnetic responses is relatively easy. In this study, based on a theoretical model of rotating magnetic islands, behavior of radial magnetic fields during the self-healing is investigated. It is confirmed that flips of radial magnetic fields are typically observed during the self-healing. Such behavior of radial magnetic responses is also observed in LHD experiments.

Nishimura, Seiya

2014-12-01

371

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

372

The magnetic resonance imaging-linac system.  

PubMed

The current image-guided radiotherapy systems are suboptimal in the esophagus, pancreas, kidney, rectum, lymph node, etc. These locations in the body are not easily accessible for fiducials and cannot be visualized sufficiently on cone-beam computed tomographies, making daily patient set-up prone to geometrical uncertainties and hinder dose optimization. Additional interfraction and intrafraction uncertainties for those locations arise from motion with breathing and organ filling. To allow real-time imaging of all patient tumor locations at the actual treatment position a fully integrated 1.5-T, diagnostic quality, magnetic resonance imaging with a 6-MV linear accelerator is presented. This system must enable detailed dose painting at all body locations. PMID:24931095

Lagendijk, Jan J W; Raaymakers, Bas W; van Vulpen, Marco

2014-07-01

373

Magnetic resonance imaging of renal transplants  

SciTech Connect

Nineteen patients were examined to determine the clinical potential of magnetic resonance imaging (MRI) for evaluation of renal transplants. Of the six living-related transplants with good renal function that were imaged, five demonstrated good corticomedullary differentiation (CMD) and one faint CMD. Three transplants with acute rejection were imaged, and all demonstrated a decrease in CMD and decrease in overall signal intensity compared with baseline. No CMD was seen in the three chronically rejecting transplants imaged. The appearance of cadaveric transplants and acute tubular necrosis was quite variable. All perinephric fluid collections were well depicted by MRI. Lymphoceles could be distinguished from hematomas. MRI may prove to be a useful adjunct in the evaluation of renal transplant and perinephric fluid collections.

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

1984-12-01

374

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

375

Oxygenation-sensitive cardiovascular magnetic resonance  

PubMed Central

Oxygenation-sensitive cardiovascular magnetic resonance (CMR) is a non-contrast technique that allows the non-invasive assessment of myocardial oxygenation. It capitalizes on the fact that deoxygenated hemoglobin in blood can act as an intrinsic contrast agent, changing proton signals in a fashion that can be imaged to reflect the level of blood oxygenation. Increases in O2 saturation increase the BOLD imaging signal (T2 or T2*), whereas decreases diminish it. This review presents the basic concepts and limitations of the BOLD technique, and summarizes the preclinical and clinical studies in the assessment of myocardial oxygenation with a focus on recent advances. Finally, it provides future directions and a brief look at emerging techniques of this evolving CMR field. PMID:23706167

2013-01-01

376

Magnetic Resonance Imaging of the Knee  

PubMed Central

Context: Magnetic resonance imaging (MRI) affords high-resolution visualization of the soft tissue structures (menisci, ligaments, cartilage, etc) and bone marrow of the knee. Evidence Acquisition: Pertinent clinical and research articles in the orthopaedic and radiology literature over the past 30 years using PubMed. Results: Ligament tears can be accurately assessed with MRI, but distinguishing partial tears from ruptures of the anterior cruciate ligament (ACL) can be challenging. Determining the extent of a partial tear is often extremely difficult to accurately assess. The status of the posterolateral corner structures, menisci, and cartilage can be accurately evaluated, although limitations in the evaluation of certain structures exist. Patellofemoral joint, marrow, tibiofibular joint, and synovial pathology can supplement physical examination findings and provide definitive diagnosis. Conclusions: MRI provides an accurate noninvasive assessment of knee pathology. PMID:24381701

Hash, Thomas W.

2013-01-01

377

Magnetic Earth Ionosphere Resonant Frequencies (MEIRF) project  

NASA Technical Reports Server (NTRS)

The West Virginia State College Community College Division NASA Magnetic Earth Ionosphere Resonant Frequencies (MEIRF) study is described. During this contract period, the two most significant and professionally rewarding events were the presentation of the research activity at the Sir Isaac Newton Conference in St. Petersburg, Russia, and the second Day of Discovery Conference, focusing on economic recovery in West Virginia. An active antenna concept utilizing a signal feedback principle similar to regenerative receivers used in early radio was studied. The device has potential for ELF research and other commercial applications for improved signal reception. Finally, work continues to progress on the development of a prototype monitoring station. Signal monitoring, data display, and data storage are major areas of activity. In addition, we plan to continue our dissemination of research activity through presentations at seminars and other universities.

Spaniol, Craig

1993-01-01

378

Magnetic resonance enterography of Crohn's disease.  

PubMed

Magnetic resonance enterography (MRE) has been reported to be a useful modality for the evaluation of luminal inflammation and extraintestinal complications in Crohn's disease (CD). A recent study indicated that the diagnostic ability of MRE was comparable to the diagnostic ability of other devices, such as ileocolonoscopy. MRE can be performed repeatedly because there is no radiation exposure. Therefore, MRE is useful as a method of follow-up for younger patients with established CD. It is useful for evaluating the efficacy of medical treatments, such as biologics. MRE can detect small intestinal lesions even if the endoscope does not pass through the stenosis. The concerns of availability of expertise and the costs associated with MRE should be addressed so MRE can be widely used for CD patients in the near future. PMID:25186521

Naganuma, Makoto; Hisamatsu, Tadakazu; Kanai, Takanori; Ogata, Haruhiko

2015-01-01

379

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

380

Magnetic resonance imaging of pancreatitis: an update.  

PubMed

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. PMID:25356038

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

2014-10-28

381

Magnetic resonance imaging of atherosclerotic vascular disease.  

PubMed

Atherosclerosis is a chronic, progressive, and often widespread arterial disorder in which the morphology and composition of the arterial segments containing atheroma are of considerable importance. Magnetic resonance imaging (MRI) allows non-invasive assessment of early arterial disease without the use of ionizing radiation. Arterial compliance, flow-wave velocity, and the pattern of flow within the aorta may all be disturbed by the disease, but these parameters are all accessible to MRI. In addition, atheroma can be directly imaged. Thus, MRI is valuable not only in the detection of disease, but also in the study of its natural history and the effects of interventions such as the control of risk factors and the use of lipid-lowering agents. PMID:8297541

Underwood, R S; Mohiaddin, R H

1993-11-01

382

Bilateral filtering of magnetic resonance phase images.  

PubMed

High-pass filtering is required for the removal of background field inhomogeneities in magnetic resonance phase images. This high-pass filtering smooths across boundaries between areas with large differences in phase. The most prominent boundary is the surface of the brain where areas with large phase values inside the brain are located close to areas outside the brain where the phase is, on average, zero. Cortical areas, which are of great interest in brain MRI, are therefore often degraded by high-pass filtering. Here, we propose the use of the bilateral filter for the high-pass filtering step. The bilateral filter is essentially a Gaussian filter that stops smoothing at boundaries. We show that the bilateral filter improves image quality at the brain's surface, without sacrificing contrast within the brain. PMID:21664782

McPhee, Kelly C; Denk, Christian; Al-Rekabi, Zeinab; Rauscher, Alexander

2011-09-01

383

Magnetic resonance imaging after exposure to microgravity  

NASA Technical Reports Server (NTRS)

A number of physiological changes were demonstrated in bone, muscle, and blood from exposure of humans and animals to microgravity. Determining mechanisms and the development of effective countermeasures for long-duration space missions is an important NASA goal. Historically, NASA has had to rely on tape measures, x-ray, and metabolic balance studies with collection of excreta and blood specimens to obtain this information. The development of magnetic resonance imaging (MRI) offers the possibility of greatly extending these early studies in ways not previously possible; MRI is also non-invasive and safe; i.e., no radiation exposure. MRI provides both superb anatomical images for volume measurements of individual structures and quantification of chemical/physical changes induced in the examined tissues. This investigation will apply MRI technology to measure muscle, intervertebral disc, and bone marrow changes resulting from exposure to microgravity.

Leblanc, Adrian

1993-01-01

384

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

385

In vivo nuclear magnetic resonance imaging  

NASA Technical Reports Server (NTRS)

A number of physiological changes have been demonstrated in bone, muscle and blood after exposure of humans and animals to microgravity. Determining mechanisms and the development of effective countermeasures for long duration space missions is an important NASA goal. The advent of tomographic nuclear magnetic resonance imaging (NMR or MRI) gives NASA a way to greatly extend early studies of this phenomena in ways not previously possible; NMR is also noninvasive and safe. NMR provides both superb anatomical images for volume assessments of individual organs and quantification of chemical/physical changes induced in the examined tissues. The feasibility of NMR as a tool for human physiological research as it is affected by microgravity is demonstrated. The animal studies employed the rear limb suspended rat as a model of mucle atrophy that results from microgravity. And bedrest of normal male subjects was used to simulate the effects of microgravity on bone and muscle.

Leblanc, A.; Evans, H.; Bryan, R. N.; Johnson, P.; Schonfeld, E.; Jhingran, S. G.

1984-01-01

386

Endometriosis: the role of magnetic resonance imaging.  

PubMed

Several imaging options are available today to diagnose endometriosis. Currently, the two techniques most used are sonography and magnetic resonance imaging (MRI). Three-dimensional (3D) sonography has proved to be particularly sensitive in the diagnosis of endometriosis. In recent years, MRI has emerged as a high reproducible method to explore endometriosis; moreover, its capability to evaluate tissue signal is an extremely powerful system in the differential diagnosis with other pathologies and for the identification of malignant degeneration. The purpose of this paper is to present the state-of-the-art of MRI of endometriosis by performing a review of the literature and showing the epidemiology, pathogenesis, and classification of endometriosis. In this work, the technique that should be used, MR findings of endometriosis and the principles of differential diagnosis are explained. PMID:24676084

Saba, Luca; Sulcis, Rosa; Melis, Gian Benedetto; Cecco, Carlo Nicola de; Laghi, Andrea; Piga, Mario; Guerriero, Stefano

2014-03-27

387

Rotating-frame gradient fields for magnetic resonance imaging and nuclear magnetic resonance in low fields  

DOEpatents

A system and method for Fourier encoding a nuclear magnetic resonance (NMR) signal is disclosed. A static magnetic field B.sub.0 is provided along a first direction. An NMR signal from the sample is Fourier encoded by applying a rotating-frame gradient field B.sub.G superimposed on the B.sub.0, where the B.sub.G comprises a vector component rotating in a plane perpendicular to the first direction at an angular frequency .omega.in a laboratory frame. The Fourier-encoded NMR signal is detected.

Bouchard, Louis-Serge; Pines, Alexander; Demas, Vasiliki

2014-01-21

388

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

389

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

390

Joint sparse representation of brain activity patterns in multi-task FMRI data.  

PubMed

A single-task functional magnetic resonance imaging (fMRI) experiment may only partially highlight alterations to functional brain networks affected by a particular disorder. Multivariate analysis across multiple fMRI tasks may increase the sensitivity of fMRI-based diagnosis. Prior research using multi-task analysis in fMRI, such as those that use joint independent component analysis (jICA), has mainly assumed that brain activity patterns evoked by different tasks are independent. This may not be valid in practice. Here, we use sparsity, which is a natural characteristic of fMRI data in the spatial domain, and propose a joint sparse representation analysis (jSRA) method to identify common information across different functional subtraction (contrast) images in data from a multi-task fMRI experiment. Sparse representation methods do not require independence, or that the brain activity patterns be nonoverlapping. We use functional subtraction images within the joint sparse representation analysis to generate joint activation sources and their corresponding sparse modulation profiles. We evaluate the use of sparse representation analysis to capture individual differences with simulated fMRI data and with experimental fMRI data. The experimental fMRI data was acquired from 16 young (age: 19-26) and 16 older (age: 57-73) adults obtained from multiple speech comprehension tasks within subjects, where an independent measure (namely, age in years) can be used to differentiate between groups. Simulation results show that this method yields greater sensitivity, precision, and higher Jaccard indexes (which measures similarity and diversity of the true and estimated brain activation sources) than does the jICA method. Moreover, superiority of the jSRA method in capturing individual differences was successfully demonstrated using experimental fMRI data. PMID:25073167

Ramezani, M; Marble, K; Trang, H; Johnsrude, I S; Abolmaesumi, P

2015-01-01

391

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.

Svetlana Kotochigova

2014-10-14

392

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

393

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

394

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

395

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.

396

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

397

MAGNETIC RESONANCE IMAGE SYNTHESIS THROUGH PATCH REGRESSION.  

PubMed

Magnetic resonance imaging (MRI) is widely used for analyzing human brain structure and function. MRI is extremely versatile and can produce different tissue contrasts as required by the study design. For reasons such as patient comfort, cost, and improving technology, certain tissue contrasts for a cohort analysis may not have been acquired during the imaging session. This missing pulse sequence hampers consistent neuroanatomy research. One possible solution is to synthesize the missing sequence. This paper proposes a data-driven approach to image synthesis, which provides equal, if not superior synthesis compared to the state-of-the-art, in addition to being an order of magnitude faster. The synthesis transformation is done on image patches by a trained bagged ensemble of regression trees. Validation was done by synthesizing T 2-weighted contrasts from T 1-weighted scans, for phantoms and real data. We also synthesized 3 Tesla T 1-weighted magnetization prepared rapid gradient echo (MPRAGE) images from 1.5 Tesla MPRAGEs to demonstrate the generality of this approach. PMID:24443686

Jog, Amod; Roy, Snehashis; Carass, Aaron; Prince, Jerry L

2013-12-31

398

Resonance magnetic x-ray-scattering study of erbium  

Microsoft Academic Search

The magnetic phases of erbium have been studied by resonance x-ray-scattering techniques. When the incident x-ray energy is tuned near the LIII absorption edge, large resonant enhancements of the magnetic scattering are observed above 18 K. We have measured the energy and polarization dependence of this magnetic scattering and analyzed it using a simple model based on electric dipole and

M. K. Sanyal; Doon Gibbs; J. Bohr; M. Wulff

1994-01-01

399

Neurochemistry of Drug Action: Insights from Proton Magnetic Resonance Spectroscopic Imaging And Their Relevance to Addiction  

PubMed Central

Proton magnetic resonance spectroscopy (1H MRS) is a non-invasive imaging technique that permits measurement of particular compounds or metabolites within the tissue of interest. In the brain, 1H MRS provides a snapshot of the neurochemical environment within a defined volume of interest. A search of the literature demonstrates the widespread utility of this technique for characterizing tumors, tracking the progress of neurodegenerative disease, and for understanding the neurobiological basis of psychiatric disorders. As of relatively recently, 1H MRS has found its way into substance abuse research, and it is beginning to become recognized as a valuable complement in the brain imaging toolbox that also contains positron emission tomography (PET), single photon emission computed tomography (SPECT), and functional magnetic resonance imaging (fMRI). Drug abuse studies employing 1H MRS have identified a number biochemical changes in the brain. The most consistent alterations across drug class were reductions in N-acetylaspartate and elevations in myo-inositol, while changes in choline, creatine, and amino acid transmitters also were abundant. Together, the studies discussed herein provide evidence that drugs of abuse may have a profound impact on neuronal health, energy metabolism and maintenance, inflammatory processes, cell membrane turnover, and neurotransmission, and these biochemical changes may underlie the neuropathology within brain tissue that subsequently gives rise to the cognitive and behavioral impairments associated with drug addiction. PMID:20201852

Licata, Stephanie C.; Renshaw, Perry F.

2011-01-01

400

Magnetic Transitions of Multiferroic Frustrated Magnets Revealed by Resonant Soft X-ray Magnetic Scattering  

NASA Astrophysics Data System (ADS)

The coexistence of magnetism and ferroelectricity with cross coupling, termed multiferroicity, rarely occurs. The discovery of gigantic magnetoelectric coupling in frustrated magnets has revived interest in their multiferroic behavior. Here, we review the measurements of resonant soft-X-ray magnetic scattering in the multiferroic frustrated magnets TbMn2O5, LiCu2O2, and CoCr2O4. In addition to the experimental technique used, the evolution of the wave vector of magnetic ordering about the temperature of multiferroic transitions is discussed. We proffer scattering evidence of multiferroicity and a pathway for understanding the intricate coupling between magnetism and ferroelectricity in magnets with spin spirals. Our results also reveal the low-dimension nature of a quantum spin-chain multiferroics and the evolution of the interrelation between the polarization P, the magnetization M, and the spiral wave vector Q.

Huang, Di-Jing; Okamoto, Jun; Huang, Shih-Wen; Mou, Chung-Yu

2010-01-01

401

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

402

Changes in Brain Activation Induced by the Training of Hypothesis Generation Skills: An fMRI Study  

ERIC Educational Resources Information Center

The aim of the present study is to investigate the learning-related changes in brain activation induced by the training of hypothesis generation skills regarding biological phenomena. Eighteen undergraduate participants were scanned twice with functional magnetic resonance imaging (fMRI) before and after training over a period of 2 months. The…

Kwon, Yong-Ju; Lee, Jun-Ki; Shin, Dong-Hoon; Jeong, Jin-Su

2009-01-01

403

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

404

Source Monitoring 15 Years Later: What Have We Learned from fMRI about the Neural Mechanisms of Source Memory?  

ERIC Educational Resources Information Center

Focusing primarily on functional magnetic resonance imaging (fMRI), this article reviews evidence regarding the roles of subregions of the medial temporal lobes, prefrontal cortex, posterior representational areas, and parietal cortex in source memory. In addition to evidence from standard episodic memory tasks assessing accuracy for neutral…

Mitchell, Karen J.; Johnson, Marcia K.

2009-01-01

405

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

406

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

407

Functional Neuroanatomy of Emotion: A Meta-Analysis of Emotion Activation Studies in PET and fMRI  

Microsoft Academic Search

Neuroimagingstudies with positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) have begun to describe the functional neuroanatomy of emotion. Taken separately, specific studies vary in task dimensions and in type(s) of emotion studied and are limited by statistical power and sensitivity. By examining findings across studies, we sought to determine if common or segregated patterns of activations exist

K. Luan Phan; Tor Wager; Stephan F. Taylor; Israel Liberzon

2002-01-01

408

MBSR vs aerobic exercise in social anxiety: fMRI of emotion regulation of negative self-beliefs  

E-print Network

), self-referential processes (Goldin et al., 2009c) and attention allocation and regulation (Slagter etMBSR vs aerobic exercise in social anxiety: fMRI of emotion regulation of negative self to negative self-beliefs using functional magnetic resonance imaging. Participants were 56 patients

Gross, James J.

409

Relations between the Neural Bases of Dynamic Auditory Processing and Phonological Processing: Evidence from fMRI  

Microsoft Academic Search

Functional magnetic resonance imaging (fMRI) was used to examine how the brain responds to temporal compression of speech and to determine whether the same regions are also involved in phonological processes associated with reading. Recorded speech was temporally compressed to varying degrees and presented in a sentence verification task. Regions involved in phonological processing were identified in a separate scan

Russell A. Poldrack; Elise Temple; Athanassios Protopapas; Srikantan Nagarajan; Paula Tallal; Michael Merzenich; John D. E. Gabrieli

2001-01-01

410

Neural correlates of episodic and semantic memory retrieval in borderline personality disorder: An fMRI study  

Microsoft Academic Search

Verbal memory impairment in borderline personality disorder (BPD) is still a matter of debate. In this study we combine investigations of both, memory retrieval as well as underlying neural circuits in BPD. Functional magnetic resonance imaging (fMRI) was used to study regional brain activation in 18 right-handed female patients with BPD and 18 matched controls during the retrieval of an

Christoph Mensebach; Thomas Beblo; Martin Driessen; Katja Wingenfeld; Markus Mertens; Nina Rullkoetter; Wolfgang Lange; Hans J. Markowitsch; Isabella Ollech; Anamaria Silva Saveedra; Harald Rau; Friedrich G. Woermann

2009-01-01

411

Cluster validation indices for fMRI data: Fuzzy C-Means with feature partitions versus cluster merging strategies  

Microsoft Academic Search

Fuzzy C-Means (FCM) is a standard technique for exploratory analysis and is readily adaptable to integrate unique data characteristics and auxiliary feature relations. Distinguishing between the spatial and temporal features of functional magnetic resonance imaging (fMRI) time courses (TC) has proved effective in reducing the presence of false positives for stimulation studies. The fuzzy partitions generated by this FCM variant

M. D. Alexiuk; N. J. Pizzi

2004-01-01

412

Multiresolution fMRI activation detection using translation invariant wavelet transform and statistical analysis based on resampling  

Microsoft Academic Search

A new method is proposed for activation detection in event-related functional magnetic resonance imaging (fMRI). The method is based on the analysis of selected resolution levels (a subspace) in the translation invariant wavelet transform (TIWT) domain. Using a priori knowledge about the activation signal and trends, we analyze their power in different resolution levels in the TIWT domain and select

Gholam-Ali Hossein-Zadeh; Hamid Soltanian-Zadeh; Babak A. Ardekani

2003-01-01

413

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

Microsoft Academic Search

Functional magnetic resonance imaging (fMRI) relies on detecting small changes in signal during brain activities, in presence of various noise, including those caused by respiration and cardiac pulsation. In the resting state, there is no explicit task event except the baseline neuroactivities of awakeness and other unknowns. However, the resting state is accompanied with the cardiac and respiration pulsations, which

Zikuan Chen; Vince Calhoun

2011-01-01

414

Neural correlates of sexual arousal in the spinal cords of able-bodied men: A spinal fMRI investigation  

Microsoft Academic Search

The purpose of this study was to determine whether functional magnetic resonance imaging of the spinal cord (spinal fMRI) could be used to map neural activity throughout the lower thoracic, lumbar and sacral spinal cord regions during sexual arousal in healthy men. To this end, it was found that viewing erotic films and genital self-stimulation both elicited predominantly increased signal,

Natalie Kozyrev; Chase R. Figley; Marcalee S. Alexander; J. Scott Richards; Rachael L. Bosma; Patrick W. Stroman

2012-01-01

415

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

416

Modulation of Auditory and Visual Processing by Delta9Tetrahydrocannabinol and Cannabidiol: an fMRI Study  

Microsoft Academic Search

Although the effects of cannabis on perception are well documented, little is known about their neural basis or how these may contribute to the formation of psychotic symptoms. We used functional magnetic resonance imaging (fMRI) to assess the effects of Delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD) during visual and auditory processing in healthy volunteers. In total, 14 healthy volunteers were scanned

Toby T Winton-Brown; Paul Allen; Sagnik Bhattacharrya; Stefan J Borgwardt; Paolo Fusar-Poli; Jose A Crippa; Marc L Seal; Rocio Martin-Santos; Dominic Ffytche; Antonio W Zuardi; Zerrin Atakan; Philip K McGuire

2011-01-01

417

Design of matrix shim coils system for nuclear magnetic resonance  

Microsoft Academic Search

A high purity magnetic field matrix shim system for Nuclear Magnetic Resonance has been designed and constructed. The stochastic methods, suitably determined by the parameters obtained from the theoretical analysis, are used for optimization of its coils. The approach to the design ensures the high purity of correcting magnetic fields and minimizes the total shim system power consumption. The measuring

Pavel Konzbul; K. Sveda; A. Srnka

2000-01-01

418

GMAC: a Matlab toolbox for spectral Granger causality analysis of fMRI data.  

PubMed

Investigation of causal interactions within brain networks using Granger causality analysis (GCA) is a key challenge in studying neural activity on the basis of functional magnetic resonance imaging (fMRI). The article describes an open-source software toolbox GMAC (Granger multivariate autoregressive connectivity) implementing multivariate spectral GCA. Available features are: fMRI data importing/exporting, network nodes definition, time series preprocessing, multivariate autoregressive modeling, spectral Granger causality indexes estimation, statistical significance assessment using surrogate data, network analysis and visualization of connectivity results. All functions have been integrated into a user-friendly graphical interface developed in the Matlab environment, easily accessible to both technical and clinical users. PMID:22925560

Tana, Maria Gabriella; Sclocco, Roberta; Bianchi, Anna Maria

2012-10-01

419

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

420

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

421

Nonparametric variogram modeling with hole effect structure in analyzing the spatial characteristics of fMRI data.  

PubMed

When analyzing functional neuroimaging data, it is particularly important to consider the spatial structure of the brain. Some researchers have applied geostatistical methods in the analysis of functional magnetic resonance imaging (fMRI) data to enhance the detection of activated brain regions. In this paper, we propose a nonparametric variogram model for the complicated spatial characteristics of fMRI data. The new periodic variogram model can well describe the fluctuating spatial structure of fMRI data, considering both the nonlinear physical relationship between the proximate voxels and the functional relationship between distant voxels. We demonstrate the effectiveness of the new variogram model using fMRI data from a saccade study. PMID:25448385

Ye, Jun; Lazar, Nicole A; Li, Yehua

2015-01-30

422

Nuclear magnetic double resonance based on strong rf magnetic-field-induced coupling between spin systems  

Microsoft Academic Search

The origin of the rf magnetic-field-induced coupling between spin systems is discussed. A new nuclear-double-resonance technique employing this coupling is proposed, which has particular value in measuring pure nuclear-quadrupole-resonance spectra of integer-spin nuclei by nuclear double resonance. The sensitivity of the new technique is discussed for the case of 1H-14N double resonance in zero static magnetic field, as well as

J. Seliger; R. Blinc; M. Mali; R. Osredkar; A. Prelesnik

1975-01-01

423

Real-time magnetic resonance imaging investigation of resonance tuning in soprano singing  

PubMed Central

This article investigates using real-time magnetic resonance imaging the vocal tract shaping of 5 soprano singers during the production of two-octave scales of sung vowels. A systematic shift of the first vocal tract resonance frequency with respect to the fundamental is shown to exist for high vowels across all subjects. No consistent systematic effect on the vocal tract resonance could be shown across all of the subjects for other vowels or for the second vocal tract resonance. PMID:21110548

Bresch, Erik; Narayanan, Shrikanth

2010-01-01

424

Resonant x-ray magnetic scattering in holmium  

SciTech Connect

We review the results of resonant x-ray magnetic scattering experiments on the rare earth metal holmium. When the incident incident x-ray energy is tuned near the L{sub III} absorption edge, large resonant enhancements of the magnetic scattering and resonant integer harmonics are observed. These results are analyzed within the theory of x-ray resonance exchange scattering assuming electric dipole (2p {yields} 5d) and quadrupole (2p {yields} 4f) transitions among atomic orbitals. 30 refs., 5 figs.

Gibbs, D.

1991-01-01

425

Advances in cardiac magnetic resonance imaging of congenital heart disease.  

PubMed

Due to advances in cardiac surgery, survival of patients with congenital heart disease has increased considerably during the past decades. Many of these patients require repeated cardiovascular magnetic resonance imaging to assess cardiac anatomy and function. In the past decade, technological advances have enabled faster and more robust cardiovascular magnetic resonance with improved image quality and spatial as well as temporal resolution. This review aims to provide an overview of advances in cardiovascular magnetic resonance hardware and acquisition techniques relevant to both pediatric and adult patients with congenital heart disease and discusses the techniques used to assess function, anatomy, flow and tissue characterization. PMID:25552386

Driessen, Mieke M P; Breur, Johannes M P J; Budde, Ricardo P J; van Oorschot, Joep W M; van Kimmenade, Roland R J; Sieswerda, Gertjan Tj; Meijboom, Folkert J; Leiner, Tim

2015-01-01

426

Bipolar programmable current supply for superconducting nuclear magnetic resonance magnets  

NASA Astrophysics Data System (ADS)

In high resolution continuous-wave nuclear magnetic resonance (NMR) work well-reproducible, linear sweeps of current are needed. We have developed a microcontroller based programmable current supply, tested with superconducting magnets with inductance of 10 mH and 10 H. We achieved a resolution and noise of 4 ppm. The supply has an internal sweep with programmable ramping rate and a possibility for remote operation from a computer with either GPIB or RS232 interface. It is based on an 18-bit D/A converter. The maximum output current is ±10 A, the sweep rate can be set between 1 ?A/s-140 mA/s, and the maximum output voltage is ±2.5 V. In work at ultralow temperatures, especially in superconducting quantum interference device NMR, all rf interference to the experiment should be avoided. One of the sources of this kind of unwanted input is the digital switching noise of fast logic devices. We discuss this problem in the context of our design.

Koivuniemi, Jaakko; Luusalo, Reeta; Hakonen, Pertti

1998-09-01

427

Functional topography of the corpus callosum investigated by DTI and fMRI.  

PubMed

This short review examines the most recent functional studies of the topographic organization of the human corpus callosum, the main interhemispheric commissure. After a brief description of its anatomy, development, microstructure, and function, it examines and discusses the latest findings obtained using diffusion tensor imaging (DTI) and tractography (DTT) and functional magnetic resonance imaging (fMRI), three recently developed imaging techniques that have significantly expanded and refined our knowledge of the commissure. While DTI and DTT have been providing insights into its microstructure, integrity and level of myelination, fMRI has been the key technique in documenting the activation of white matter fibers, particularly in the corpus callosum. By combining DTT and fMRI it has been possible to describe the trajectory of the callosal fibers interconnecting the primary olfactory, gustatory, motor, somatic sensory, auditory and visual cortices at sites where the activation elicited by peripheral stimulation was detected by fMRI. These studies have demonstrated the presence of callosal fiber tracts that cross the commissure at the level of the genu, body, and splenium, at sites showing fMRI activation. Altogether such findings lend further support to the notion that the corpus callosum displays a functional topographic organization that can be explored with fMRI. PMID:25550994

Fabri, Mara; Pierpaoli, Chiara; Barbaresi, Paolo; Polonara, Gabriele

2014-12-28

428

Functional topography of the corpus callosum investigated by DTI and fMRI  

PubMed Central

This short review examines the most recent functional studies of the topographic organization of the human corpus callosum, the main interhemispheric commissure. After a brief description of its anatomy, development, microstructure, and function, it examines and discusses the latest findings obtained using diffusion tensor imaging (DTI) and tractography (DTT) and functional magnetic resonance imaging (fMRI), three recently developed imaging techniques that have significantly expanded and refined our knowledge of the commissure. While DTI and DTT have been providing insights into its microstructure, integrity and level of myelination, fMRI has been the key technique in documenting the activation of white matter fibers, particularly in the corpus callosum. By combining DTT and fMRI it has been possible to describe the trajectory of the callosal fibers interconnecting the primary olfactory, gustatory, motor, somatic sensory, auditory and visual cortices at sites where the activation elicited by peripheral stimulation was detected by fMRI. These studies have demonstrated the presence of callosal fiber tracts that cross the commissure at the level of the genu, body, and splenium, at sites showing fMRI activation. Altogether such findings lend further support to the notion that the corpus callosum displays a functional topographic organization that can be explored with fMRI.

Fabri, Mara; Pierpaoli, Chiara; Barbaresi, Paolo; Polonara, Gabriele

2014-01-01

429

Boosting BOLD fMRI by K-Space Density Weighted Echo Planar Imaging  

PubMed Central

Functional magnetic resonance imaging (fMRI) has become a powerful and influential method to non-invasively study neuronal brain activity. For this purpose, the blood oxygenation level-dependent (BOLD) effect is most widely used. T2* weighted echo planar imaging (EPI) is BOLD sensitive and the prevailing fMRI acquisition technique. Here, we present an alternative to its standard Cartesian recordings, i.e. k-space density weighted EPI, which is expected to increase the signal-to-noise ratio in fMRI data. Based on in vitro and in vivo pilot measurements, we show that fMRI by k-space density weighted EPI is feasible and that this new acquisition technique in fact boosted spatial and temporal SNR as well as the detection of local fMRI activations. Spatial resolution, spatial response function and echo time were identical for density weighted and conventional Cartesian EPI. The signal-to-noise ratio gain of density weighting can improve activation detection and has the potential to further increase the sensitivity of fMRI investigations. PMID:24040262

Zeller, Mario; Müller, Alexander; Gutberlet, Marcel; Nichols, Thomas; Hahn, Dietbert; Köstler, Herbert; Bartsch, Andreas J.

2013-01-01

430

Functional magnetic resonance imaging study of Piaget's conservation-of-number task in preschool and school-age children: a neo-Piagetian approach.  

PubMed

Jean Piaget's theory is a central reference point in the study of logico-mathematical development in children. One of the most famous Piagetian tasks is number conservation. Failures and successes in this task reveal two fundamental stages in children's thinking and judgment, shifting at approximately 7 years of age from visuospatial intuition to number conservation. In the current study, preschool children (nonconservers, 5-6 years of age) and school-age children (conservers, 9-10 years of age) were presented with Piaget's conservation-of-number task and monitored by functional magnetic resonance imaging (fMRI). The cognitive change allowing children to access conservation was shown to be related to the neural contribution of a bilateral parietofrontal network involved in numerical and executive functions. These fMRI results highlight how the behavioral and cognitive stages Piaget formulated during the 20th century manifest in the brain with age. PMID:21636095

Houdé, Olivier; Pineau, Arlette; Leroux, Gaëlle; Poirel, Nicolas; Perchey, Guy; Lanoë, Céline; Lubin, Amélie; Turbelin, Marie-Renée; Rossi, Sandrine; Simon, Grégory; Delcroix, Nicolas; Lamberton, Franck; Vigneau, Mathieu; Wisniewski, Gabriel; Vicet, Jean-René; Mazoyer, Bernard

2011-11-01

431

Sensitive magnetic force detection with a carbon nanotube resonator  

SciTech Connect

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 [Institute for Quantum Computing, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Haapamaki, Chris [Institute for Quantum Computing, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Baugh, Jonathan, E-mail: baugh@iqc.ca [Institute for Quantum Computing, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada)

2014-03-21

432

Magnetic resonance imaging at ultrahigh fields.  

PubMed

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, ultrahigh 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

2014-05-01

433

Advancing magnetic resonance imaging in Crohn's disease.  

PubMed

Crohn's disease (CD) is a lifelong chronic inflammatory bowel disease associated with diarrhea, abdominal pain, bloody stool and often perianal fistulae. Inflammation in CD involves the entire gastrointestinal tract, especially including the small and large bowels, causing irreversible bowel damage. Frequent imaging examinations are necessary to monitor disease activity and to evaluate response to therapeutic interventions, and, furthermore, to predict recurrence in order to provide appropriate treatment. The suitable imaging modality should be reproducible, well tolerated, safe and free of ionizing radiation. In recent years, imaging used in CD has dramatically changed. Cross-sectional imaging techniques such as computed tomography and magnetic resonance imaging (MRI) are used to investigate not only extraluminal abnormalities, but also intraluminal changes. Recently, new techniques such as MR enteroclysis, enterography, colonography and enterocolonography have been developed. These recent advances enable the use of MRI to assess bowel disorders with high sensitivity, specificity and accuracy. MRI can evaluate simultaneously the bowel surface, bowel wall, abdominal abscesses and perianal lesions, such as perianal fistulae and perianal abscesses, without the problem of overlapping bowel loops. Therefore, MRI has the potential for evaluation of the overall disease activity of CD without radiation exposure. We believe that MRI is a suitable first choice imaging modality in the assessment of CD. PMID:24458109

Fujii, Toshimitsu; Naganuma, Makoto; Kitazume, Yoshio; Saito, Eiko; Nagahori, Masakazu; Ohtsuka, Kazuo; Watanabe, Mamoru

2014-01-01

434

Fast noniterative registration of magnetic resonance images  

NASA Astrophysics Data System (ADS)

EvIdent (EVent IDENTification) is an exploratory data analysis system for the detection and investigation of novelty, identified for a region of interest and its characteristics, within a set of images. For functional magnetic resonance imaging, for instance, a characteristic of the region of interest is a time course, which represents the intensity value of voxels over several discrete instances in time. An essential preprocessing step is the rapid registration of these images prior to analysis. Two dimensional image registration coefficients are obtained within EvIdent by solving a regression problem based on integration of a linearized matching equation over a set of patches in the image space. The registration method is robust to noise, offers a flexible hierarchical procedure, is easily generalizable to 3D registration, and is well suited to parallel processing. EvIdent, written in Java and C++, offers a sophisticated data model, an extensible algorithm framework, and a suite of graphical user interface constructs. We describe the registration algorithm and its implementation within the EvIdent software.

Pizzi, Nicolino J.; Alexander, Murray; Vivanco, Rodrigo A.; Somorjai, Raymond L.

2001-07-01

435

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

436

Prenatal Imaging: Ultrasonography and Magnetic Resonance Imaging  

PubMed Central

The Eunice Kennedy Shriver National Institute of Child Health and Human Development held a workshop on September 18–19, 2006, to summarize the available evidence on the role and performance of current fetal imaging technology and to establish a research agenda. Ultrasonography is the imaging modality of choice for pregnancy evaluation due to its relatively low cost, real-time capability, safety, and operator comfort and experience. First-trimester ultrasonography extends the available window for fetal observation and raises the possibility of performing an early anatomic survey. Three-dimensional ultrasonography has the potential to expand the clinical application of ultrasonography by permitting local acquisition of volumes and remote review and interpretation at specialized centers. New advances allow performance of fetal magnetic resonance imaging (MRI) without maternal or fetal sedation, with improved characterization and prediction of prognosis of certain fetal central nervous system anomalies such as ventriculomegaly when compared with ultrasonography. Fewer data exist on the usefulness of fetal MRI for non–central nervous system anomalies. PMID:18591320

Reddy, Uma M.; Filly, Roy A.; Copel, Joshua A.

2009-01-01

437

Magnetic Resonance Imaging of the Elbow  

PubMed Central

Context: The elbow is a complex joint and commonly injured in athletes. Evaluation of the elbow by magnetic resonance imaging (MRI) is an important adjunct to the physical examination. To facilitate accurate diagnosis, a concise structured approach to evaluation of the elbow by MRI is presented. Evidence Acquisition: A PubMed search was performed using the terms elbow and MR imaging. No limits were set on the range of years searched. Articles were reviewed for relevance with an emphasis of the MRI appearance of normal anatomy and common pathology of the elbow. Results: The spectrum of common elbow disorders varies from obvious acute fractures to chronic overuse injuries whose imaging manifestations can be subtle. MRI evaluation should include bones; lateral, medial, anterior, and posterior muscle groups; the ulnar and radial collateral ligaments; as well as nerves, synovium, and bursae. Special attention should be paid to the valgus extension overload syndrome and the MRI appearance of associated injuries when evaluating throwing athletes. Conclusion: MRI evaluation of the elbow should follow a structured approach to facilitate thoroughness, accuracy, and speed. Such an approach should cover bone, cartilage, muscle, tendons, ligaments, synovium, bursae, and nerves. PMID:24381699

Sampath, Srinath C.; Sampath, Srihari C.; Bredella, Miriam A.

2013-01-01

438

Magnetic resonance enterography: state of the art.  

PubMed

: Crohn's disease is a chronic inflammatory bowel disease of the gastrointestinal tract manifested by frequent periods of relapses and remissions of symptoms. The small bowel is most frequently affected. Progression of transmural inflammation can lead to stricturing or penetrating complications. At the time of diagnosis, approximately 10% of patients have disease beyond the reach of the colonoscope. Imaging can aid in clinical evaluation by depicting small bowel involvement and extraenteric disease. Magnetic resonance enterography (MRE) has emerged as a valuable tool and is being used with increasing frequency for the diagnosis and management of Crohn's disease. This article will discuss the current state of the art in MRE. In addition to reviewing the literature reporting its utility, we will present case examples illustrating how MRE best depicts the various findings of Crohn's disease within 4 imaging categories of disease: active inflammatory, fibrostenotic, fistulizing/perforating, and reparative or regenerative. We will present additional important clinical considerations in routine use of MRE, including implications for monitoring disease activity and response to treatment, cost-effectiveness, and appropriate use in the context of the American College of Radiology Appropriateness Criteria. PMID:25222657

Stoddard, Paul B; Ghazi, Leyla J; Wong-You-Cheong, Jade; Cross, Raymond K; Vandermeer, Fauzia Q

2015-01-01

439

[Magnetic resonance imaging of cardiovascular thrombi].  

PubMed

Magnetic resonance imaging (MRI) was performed for 10 patients with cardiovascular thrombi using a 0.1-Tesla resistive type apparatus (ASAHI MARK-J). In all cases thrombi were clearly imaged by NMR and their shapes closely resembled those imaged by X-ray CT. Mural thrombi located within left ventricular aneurysms of two patients with old anteroseptal myocardial infarction were semilunar in form. A mural thrombus in the right ventricle of a patient with cardiovascular Behcet's disease was also clearly imaged. Mural thrombi within the enlarged left atrium of two patients with mitral valve stenosis and insufficiency were clearly demonstrated in both cross- and longitudinal sections. In three patients with thoracic aortic aneurysm, mural thrombi were recognized within the local dilatations of the aorta. In two patients with dissecting aortic aneurysm, mural thrombi were visualized within false lumen using MRI. Mean T1 values and standard deviations for the left ventricular cavity, the left ventricular wall, and the thrombi were 639 +/- 49, 349 +/- 17 and 316 +/- 84 msec, respectively. Mean T1 values of the thrombi were usually shorter than those of the left ventricular wall. Some supposedly fresh thrombi had longer T1 values, however. PMID:3837061

Imai, H; Sakakibara, M; Yoshida, K; Watanabe, S; Masuda, Y; Inagaki, Y; Ikehira, H; Fukuda, N; Tateno, Y

1985-09-01

440

Vibration safety limits for magnetic resonance elastography  

PubMed Central

Magnetic resonance elastography (MRE) has been demonstrated to have potential as a clinical tool for assessing the stiffness of tissue in vivo. An essential step in MRE is the generation of acoustic mechanical waves within tissue via a coupled mechanical driver. Motivated by an increasing volume of human imaging trials using MRE, the objectives of this study were to audit the vibration amplitude of exposure for our IRB-approved human MRE studies, to compare these values to a conservative regulatory standard for vibrational exposure, and to evaluate the applicability and implications of this standard for MRE. MRE displacement data were examined from 29 MRE exams, including the liver, brain, kidney, breast, and skeletal muscle. Vibrational acceleration limits from a European Union directive limiting occupational exposure to whole-body and extremity vibrations (EU 2002/44/EC) were adjusted for time and frequency of exposure, converted to maximum displacement values, and compared to the measured in vivo displacements. The results indicate that the vibrational amplitudes used in MRE studies are below the EU whole-body vibration limit and the EU guidelines represent a useful standard that could be readily accepted by Institutional Review Boards to define standards for vibrational exposures for MRE studies in humans. PMID:18263949

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

2010-01-01

441

Magnetic resonance imaging of the skin.  

PubMed

A thorough examination of the skin is essential to screen various diseases accurately, evaluate the effectiveness of topically applied drugs and assess the results of dermatological surgeries such as skin grafts. The assessment of skin properties is also crucial in the cosmetics industry, where it is important to evaluate the effects skin care products have on these properties. The simplest and most widely used method of skin evaluation, the 'naked eye' assessment, enables researchers to assess only the skin surface and involves a large amount of inter-observer variability. Thanks to a great progress that has been made in physics, electronics and computer engineering in recent years, sophisticated imaging methods are increasingly available in day-to-day studies. The aim of this review was to present one of these techniques, namely the magnetic resonance imaging (MRI), and to discuss its possible use in skin examination and analysis. We present basic principles of MRI, as well as several interesting applications in the field of dermatology, and discuss the advantages and limitations of this method. PMID:20180890

Stefanowska, J; Zakowiecki, D; Cal, K

2010-08-01

442

Multifrequency inversion in magnetic resonance elastography  

NASA Astrophysics Data System (ADS)

Time-harmonic shear wave elastography is capable of measuring viscoelastic parameters in living tissue. However, finite tissue boundaries and waveguide effects give rise to wave interferences which are not accounted for by standard elasticity reconstruction methods. Furthermore, the viscoelasticity of tissue causes dispersion of the complex shear modulus, rendering the recovered moduli frequency dependent. Therefore, we here propose the use of multifrequency wave data from magnetic resonance elastography (MRE) for solving the inverse problem of viscoelasticity reconstruction by an algebraic least-squares solution based on the springpot model. Advantages of the method are twofold: (i) amplitude nulls appearing in single-frequency standing wave patterns are mitigated and (ii) the dispersion of storage and loss modulus with drive frequency is taken into account by the inversion procedure, thereby avoiding subsequent model fitting. As a result, multifrequency inversion produces fewer artifacts in the viscoelastic parameter map than standard single-frequency parameter recovery and may thus support image-based viscoelasticity measurement. The feasibility of the method is demonstrated by simulated wave data and MRE experiments on a phantom and in vivo human brain. Implemented as a clinical method, multifrequency inversion may improve the diagnostic value of time-harmonic MRE in a large variety of applications.

Papazoglou, Sebastian; Hirsch, Sebastian; Braun, Jürgen; Sack, Ingolf

2012-04-01

443

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

444

Monitoring tissue engineering using magnetic resonance imaging.  

PubMed

Assessment of tissue regeneration is essential to optimize the stages of tissue engineering (cell proliferation, tissue development and implantation). Optical and X-ray imaging have been used in tissue engineering to provide useful information, but each has limitations: for example, poor depth penetration and radiation damage. Magnetic resonance imaging (MRI) largely overcomes these restrictions, exhibits high resolution (approximately 100 microm) and can be applied both in vitro and in vivo. Recently, MRI has been used in tissue engineering to generate spatial maps of tissue relaxation times (T(1), T(2)), water diffusion coefficients, and the stiffness (shear moduli) of developing engineered tissues. In addition, through the use of paramagnetic and superparamagnetic contrast agents, MRI can quantify cell death, assess inflammation, and visualize cell trafficking and gene expression. After tissue implantation MRI can be used to observe the integration of a tissue implant with the surrounding tissues, and to check for early signs of immune rejection. In this review, we describe and evaluate the growing role of MRI in the assessment of tissue engineered constructs. First, we briefly describe the underlying principles of MRI and the expected changes in relaxation times (T(1), T(2)) and the water diffusion coefficient that are the basis for MR contrast in developing tissues. Next, we describe how MRI can be applied to evaluate the tissue engineering of mesenchymal tissues (bone, cartilage, and fat). Finally, we outline how MRI can be used to monitor tissue structure, composition, and function to improve the entire tissue engineering process. PMID:19134545

Xu, Huihui; Othman, Shadi F; Magin, Richard L

2008-12-01

445

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

446

Stress reconfigurable tunable magnetoelectric resonators as magnetic sensors  

NASA Astrophysics Data System (ADS)

We report a magnetoelastic effect in doubly clamped ferromagnetic magnetostrictive Metglas resonators with electrically and magnetically reconfigurable frequency response. The field-induced resonance frequency shift is due to magnetostrictive strain, which is shown to have a strong dependence on uniaxial stress. Here, we demonstrate that this magnetic field induced behavior can be used as the basis for a simple, tunable, magnetoelectric magnetic field sensor. The effect of tension on the field dependent magnetostrictive constant and the sensor sensitivity is examined, and the equivalent magnetic noise floor of such a sensor is estimated.

Kiser, Jillian; Finkel, Peter; Gao, Junqi; Dolabdjian, Christophe; Li, Jiefang; Viehland, D.

2013-01-01

447

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

448

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

449

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

450

Monitoring Locally Induced Hyperthermia with Magnetic Resonance Imaging.  

E-print Network

??abstract__Abstract__ Magnetic resonance thermometry is a relatively new and unique technology for non-invasive monitoring of (local) therapeutic temperature changes that is not yet in common… (more)

M.W. Vogel (M.)

2005-01-01

451

Acoustic ringing effects in pulsed nuclear magnetic resonance probes  

Microsoft Academic Search

The troublesome spurious ringing phenomenon found in pulsed nuclear magnetic resonance probes is explained in terms of the electromagnetic generation and detection of ultrasonic waves. A few techniques for eliminating this problem are discussed.

M. L. Buess; G. L. Petersen

1978-01-01

452

Acoustic ringing effects in pulsed nuclear magnetic resonance probes.  

PubMed

The troublesome spurious ringing phenomenon found in pulsed nuclear magnetic resonance probes is explained in terms of the electromagnetic generation and detection of ultrasonic waves. A few techniques for eliminating this problem are discussed. PMID:18699271

Buess, M L; Petersen, G L

1978-08-01

453

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

454

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

455

LASER-POLARIZED 129Xe MAGNETIC RESONANCE SPECTROSCOPY AND IMAGING;  

E-print Network

LASER-POLARIZED 129Xe MAGNETIC RESONANCE SPECTROSCOPY AND IMAGING; THE DEVELOPMENT OF A METHOD.....................................................................13 2.2 Spin Exchange Polarization of 129 Xe......................................................................................19 3 129 Xe polarization and delivery system

Rosen, Matthew S

456

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

457

Magnetic Resonance Imaging Method For Estimating Cone Of Uncertainty  

Cancer.gov

The National Institute of Child Health and Human Development (NICHD), Section on Tissue Biophysics and Biomimetics, is seeking statements of capability or interest from parties interested in collaborative research to further develop, evaluate, or commercialize magnetic resonance imaging techniques.

458

Profile of compressive myelopathy as evaluated by magnetic resonance imaging.  

PubMed

To evaluate spectrum of diseases causing compressive myelopathy and accuracy of magnetic resonance imaging in diagnosing these conditions, a total of 69 clinically diagnosed cases of compressive myelopathy were evaluated by magnetic resonance imaging and results were tabulated. Caries spine was the commonest condition (24.6%) followed by metastasis spine (17.4%), ossified posterior longitudinal ligament (7.8%), primary bone tumours, nerve sheath tumours, intramedullary tumours and rare conditions like epidural abscess, spontaneous epidural haematoma, subdural haematoma, epidural lipomatosis, etc. Sensitivity, specificity and accuracy for diagnosing caries by magnetic resonance imaging was found to be 94%, 98% and 97% while that of metastasis spine was 91%, 98% and 97% respectively. Magnetic resonance imaging is the modality of choice for diagnosing compressive myelopathy. PMID:18705249

Yadav, Rohtas K; Agarwal, Shalini; Saini, Jitender

2008-02-01

459

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

460

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

461

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

462

21 CFR 892.1000 - Magnetic resonance diagnostic device.  

Code of Federal Regulations, 2012 CFR

... Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES RADIOLOGY DEVICES Diagnostic Devices § 892.1000 Magnetic resonance diagnostic device. (a) Identification....

2012-04-01

463

21 CFR 892.1000 - Magnetic resonance diagnostic device.  

... Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES RADIOLOGY DEVICES Diagnostic Devices § 892.1000 Magnetic resonance diagnostic device. (a) Identification....

2014-04-01

464

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. No Drawings

Engelstad, B.L.; Raymond, K.N.; Huberty, J.P.; White, D.L.

1991-04-23

465

21 CFR 892.1000 - Magnetic resonance diagnostic device.  

Code of Federal Regulations, 2011 CFR

... Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES RADIOLOGY DEVICES Diagnostic Devices § 892.1000 Magnetic resonance diagnostic device. (a) Identification....

2011-04-01

466

21 CFR 892.1000 - Magnetic resonance diagnostic device.  

Code of Federal Regulations, 2013 CFR

... Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES RADIOLOGY DEVICES Diagnostic Devices § 892.1000 Magnetic resonance diagnostic device. (a) Identification....

2013-04-01

467

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

468

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

PubMed Central

Background While traditionally quite distinct, functional neuroimaging (e.g. functional magnetic resonance imaging: fMRI) and functional interference techniques (e.g. transcranial magnetic stimulation: TMS) increasingly address similar questions of functional brain organization, including connectivity, interactions, and causality in the brain. Time-resolved TMS over multiple brain network nodes can elucidate the relative timings of functional relevance for behavior (“TMS chronometry”), while fMRI functional or effective connectivity (fMRI EC) can map task-specific interactions between brain regions based on the interrelation of measured signals. The current study empirically assessed the relation between these different methods. Methodology/Principal Findings One group of 15 participants took part in two experiments: one fMRI EC study, and one TMS chronometry study, both of which used an established cognitive paradigm involving one visuospatial judgment task and one color judgment control task. Granger causality mapping (GCM), a data-driven variant of fMRI EC analysis, revealed a frontal-to-parietal flow of information, from inferior/middle frontal gyrus (MFG) to posterior parietal cortex (PPC). FMRI EC-guided Neuronavigated TMS had behavioral effects when applied to both PPC and to MFG, but the temporal pattern of these effects was similar for both stimulation sites. At first glance, this would seem in contradiction to the fMRI EC results. However, we discuss how TMS chronometry and fMRI EC are conceptually different and show how they can be complementary and mutually constraining, rather than contradictory, on the basis of our data. Conclusions/Significance The findings that fMRI EC could successfully localize functionally relevant TMS target regions on the single subject level, and conversely, that TMS confirmed an fMRI EC identified functional network to be behaviorally relevant, have important methodological and theoretical implications. Our results, in combination with data from earlier studies by our group (Sack et al., 2007, Cerebral Cortex), lead to informed speculations on complex brain mechanisms, and TMS disruption thereof, underlying visuospatial judgment. This first in-depth empirical and conceptual comparison of fMRI EC and TMS chronometry thereby shows the complementary insights offered by the two methods. PMID:20011541

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

2009-01-01

469

Assessment of coronary artery stenosis by magnetic resonance imaging.  

PubMed Central

OBJECTIVE: The findings of magnetic resonance and x-ray angiography were compared for assessment of coronary artery stenosis in this validation study. BACKGROUND: Magnetic resonance angiography of the coronary arteries has recently been described, but there has been no comparison with x-ray angiography of localisation or assessment of important characteristics of coronary stenosis. METHODS: A breath hold, segmented k-space, 2D gradient echo imaging technique incorporating fat suppression was used in 39 patients (55 coronary stenoses) with known coronary artery disease. RESULTS: Overall, 47 stenoses (85%) were assessed by magnetic resonance (29 of 33 stenoses in the left anterior descending artery, one of one in the left main stem, 14 of 17 in the right coronary artery, and three of four in the left circumflex artery were detected). There was close agreement between magnetic resonance and x-ray angiography for the distance of the stenosis from the arterial origin (magnetic resonance mean (SD) 27 (16) mm versus x-ray angiography 27 (16) mm, P = NS, mean difference -0.2 mm). The distance to 39 stenoses (83%) agreed to within 5 mm, with increased scatter for more distal stenoses. The severity of magnetic resonance signal loss, assessed visually at the site of stenosis, varied significantly according to the percentage diameter stenosis (F = 30, P < 0.0001); stenosis severity with severe signal loss was 89 (7)%, with partial signal was 70 (16)%, and with irregular wall only 37 (11)%, with significant differences among the three groups (P < 0.001). A significant correlation was found between the proportional magnetic resonance signal loss at the stenosis and the percentage diameter stenosis severity (r = -0.67, P < 0.0001). The length of stenosis measured by magnetic resonance (6 (3) mm) was greater than by x-ray angiography (5 (2) mm, P < 0.006, mean difference +1.1 mm). Spearman's rank test showed that there was significant overestimation of stenosis length by magnetic resonance as stenosis severity increased (rs = 0.34, P < 0.02). CONCLUSIONS: Accurate localisation of coronary stenosis and a qualitative assessment of stenosis severity are possible by magnetic resonance, but stenosis length is overestimated as severity increases, probably because of disturbed patterns of flow with turbulence distal to severe stenoses. Reasonable results for the detection of coronary artery stenosis by magnetic resonance were achieved in this highly selected population, but further progress in imaging techniques is necessary before moving towards appreciable clinical application. Images PMID:8673749

Pennell, D. J.; Bogren, H. G.; Keegan, J.; Firmin, D. N.; Underwood, S. R.

1996-01-01

470

Specificity of stimulus-evoked fMRI responses in the mouse: the influence of systemic physiological changes associated with innocuous stimulation under four different anesthetics.  

PubMed

Functional magnetic resonance (fMRI) in mice has become an attractive tool for mechanistic studies, for characterizing models of human disease, and for evaluation of novel therapies. Yet, controlling the physiological state of mice is challenging, but nevertheless important as changes in cardiovascular parameters might affect the hemodynamic readout which constitutes the basics of the fMRI signal. In contrast to rats, fMRI studies in mice report less robust brain activation of rather widespread character to innocuous sensory stimulation. Anesthesia is known to influence the characteristics of the fMRI signal. To evaluate modulatory effects imposed by the anesthesia on stimulus-evoked fMRI responses, we compared blood oxygenation level dependent (BOLD) and cerebral blood volume (CBV) signal changes to electrical hindpaw stimulation using the four commonly used anesthetics isoflurane, medetomidine, propofol and urethane. fMRI measurements were complemented by assessing systemic physiological parameters throughout the experiment. Unilateral stimulation of the hindpaw elicited widespread fMRI responses in the mouse brain displaying a bilateral pattern irrespective of the anesthetic used. Analysis of magnitude and temporal profile of BOLD and CBV signals indicated anesthesia-specific modulation of cerebral hemodynamic responses and differences observed for the four anesthetics could be largely explained by their known effects on animal physiology. Strikingly, independent of the anesthetic used our results reveal that fMRI responses are influenced by stimulus-induced cardiovascular changes, which indicate an arousal response, even to innocuous stimulation. This may mask specific fMRI signal associated to the stimulus. Hence, studying the processing of peripheral input in mice using fMRI techniques constitutes a major challenge and adapted paradigms and/or alternative fMRI readouts should also be considered when studying sensory processing in mice. PMID:24495809

Schroeter, Aileen; Schlegel, Felix; Seuwen, Aline; Grandjean, Joanes; Rudin, Markus

2014-07-01

471

Ferromagnetic resonance of a magnetic dimer with dipolar coupling  

NASA Astrophysics Data System (ADS)

We develop a general formalism for analyzing the ferromagnetic resonance characteristics of a magnetic dimer consisting of two magnetic elements (in a horizontal or vertical configuration) coupled by dipolar interaction, taking account of their finite-size and aspect ratio. We study the effect on the resonance frequency and resonance field of the applied magnetic field (in amplitude and direction), the inter-element coupling, and the (uniaxial) anisotropy in various configurations. We obtain analytical expressions for the resonance frequency in various regimes of the interlayer coupling. We (numerically) investigate the behavior of the resonance field in the corresponding regimes. The critical value of the applied magnetic field at which the resonance frequency vanishes may be an increasing or a decreasing function of the dimer's coupling, depending on the anisotropy configuration. It is also a function of the nanomagnets aspect ratio in the case of in-plane anisotropy. This and several other results of this work, when compared with experiments using the standard ferromagnetic resonance with fixed frequency, or the network analyzer with varying frequency and applied magnetic field, provide a useful means for characterizing the effective anisotropy and coupling within systems of stacked or assembled nanomagnets. Comparing with the experimental data for the frequency splitting of coupled FeV nano disks, we find that our theory provides the same order of magnitude for the dipolar coupling.

Franco, A. F.; Déjardin, J. L.; Kachkachi, H.

2014-12-01

472

Magnetic Resonance Force Microscopy Measurement of Entangled Spin States  

E-print Network

We simulate magnetic resonance force microscopy measurements of an entangled spin state. One of the entangled spins drives the resonant cantilever vibrations, while the other remote spin does not interact directly with the quasiclassical cantilever. The Schr\\"odinger cat state of the cantilever reveals two possible outcomes of the measurement for both entangled spins.

G. P. Berman; F. Borgonovi; G. Chapline; P. C. Hammel; V. I. Tsifrinovich

2001-10-10

473

Design guideline for magnetic integration in LLC resonant converters  

Microsoft Academic Search

The aim of this paper is to present a comprehensive design methodology for the magnetic integration of the series and shunt inductances of the resonant tank in an LLC resonant converter within the transformer. The design procedure applies to symmetrical core-bobbin structures with two separate slots for the primary and secondary windings. A specific leakage inductance Asigma. (per square turn)

S. De Simone; C. Adragna; C. Spini

2008-01-01

474

Spin wave resonance detection using magnetic tunnel junction structure  

Microsoft Academic Search

We have demonstrated that spin wave resonance in a permalloy microstrip can be detected by an electrical method based on magnetic tunnel junction structures. The detection method promises high spatial resolution and sensitivity. Both even and odd spin wave resonance modes can be clearly observed in a permalloy microstrip. The spin wave induced voltage is proportional to the input microwave

Chong Bi; Xin Fan; Liqing Pan; Xiaoming Kou; Jun Wu; Qinghui Yang; Huaiwu Zhang; John Q. Xiao

2011-01-01

475

Characterization of microwave magnetic narrow band filters by ferromagnetic resonance  

NASA Astrophysics Data System (ADS)

Ferromagnetic resonance cavity and microstrip excitation experiments have been performed on a straight edge yttrium iron garnet resonator. Both excitation systems have been modeled as band-stop configurations and a mapping from the swept bias magnetic field domain to the frequency domain has been elaborated to compare them in terms of the dispersion and the amplitude of the magnetostatic wave modes.

Bousbahi, Khaled; Marcelli, Romolo

2000-05-01

476

Magnetic resonance imaging of the elbow. Part I: Normal anatomy, imaging technique, and osseous abnormalities  

Microsoft Academic Search

Part I of this comprehensive review on magnetic resonance imaging of the elbow discusses normal elbow anatomy and the technical factors involved in obtaining high-quality magnetic resonance images of the elbow. Part I also discusses the role of magnetic resonance imaging in evaluating patients with osseous abnormalities of the elbow. With proper patient positioning and imaging technique, magnetic resonance imaging

Richard Kijowski; Michael Tuite; Matthew Sanford

2004-01-01

477

Simultaneous Measurement of Magnetic Resonance and Neuronal Signals  

NASA Astrophysics Data System (ADS)

Nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) at ultra low magnetic fields (ULF, ˜ microT) have advantages over their counterparts at higher magnetic fields, despite the reduction in signal strength. Among these advantages are that the instrumentation uses superconducting quantum interference devices (SQUIDs), and is now compatible with simultaneous measurements of biomagnetic signals, such as magnetoencephalography (MEG). This presents a new opportunity for noninvasive simultaneous functional and anatomical brain imaging. We present here the physical basis and experimental evidence for a variety of ULF-MRI techniques being developed at Los Alamos to enable simultaneous anatomical and functional imaging of the human brain. We conclude by presenting a novel technique, based on the resonant interaction between the magnetic fields such as those that arise from neural activity and the spin population in ULF-MRI experiments, that may enable direct tomographic imaging of the consequences of neural activity.

Espy, Michelle

2007-03-01

478

How Doctors Generate Diagnostic Hypotheses: A Study of Radiological Diagnosis with Functional Magnetic Resonance Imaging  

PubMed Central

Background In medical practice, diagnostic hypotheses are often made by physicians in the first moments of contact with patients; sometimes even before they report their symptoms. We propose that generation of diagnostic hypotheses in this context is the result of cognitive processes subserved by brain mechanisms that are similar to those involved in naming objects or concepts in everyday life. Methodology and Principal Findings To test this proposal we developed an experimental paradigm with functional magnetic resonance imaging (fMRI) using radiological diagnosis as a model. Twenty-five radiologists diagnosed lesions in chest X-ray images and named non-medical targets (animals) embedded in chest X-ray images while being scanned in a fMRI session. Images were presented for 1.5 seconds; response times (RTs) and the ensuing cortical activations were assessed. The mean response time for diagnosing lesions was 1.33 (SD ±0.14) seconds and 1.23 (SD ±0.13) seconds for naming animals. 72% of the radiologists reported cogitating differential diagnoses during trials (3.5 seconds). The overall pattern of cortical activations was remarkably similar for both types of targets. However, within the neural systems shared by both stimuli, activation was significantly greater in left inferior frontal sulcus and posterior cingulate cortex for lesions relative to animals. Conclusions Generation of diagnostic hypotheses and differential diagnoses made through the immediate visual recognition of clinical signs can be a fast and automatic process. The co-localization of significant brain activation for lesions and animals suggests that generating diagnostic hypotheses for lesions and naming animals are served by the same neuronal systems. Nevertheless, diagnosing lesions was cognitively more demanding and associated with more activation in higher order cortical areas. These results support the hypothesis that medical diagnoses based on prompt visual recognition of clinical signs and naming in everyday life are supported by similar brain systems. PMID:22194902

Melo, Marcio; Scarpin, Daniel J.; Amaro, Edson; Passos, Rodrigo B. D.; Sato, João R.; Friston, Karl J.; Price, Cathy J.

2011-01-01

479

High-throughput optogenetic functional magnetic resonance imaging with parallel computations  

PubMed Central

Optogenetic functional magnetic resonance imaging (ofMRI) technology enables cell-type specific, temporally precise neuronal control and accurate, in vivo readout of resulting activity across the whole brain. With the ability to precisely control excitation and inhibition parameters, and to accurately record the resulting activity, there is an increased need for a high-throughput method to bring the ofMRI studies to their full potential. In this paper, an advanced system that can allow real-time fMRI with interactive control and analysis in a fraction of the MRI acquisition repetition time (TR) is proposed. With such high processing speed, sufficient time will be available for integration of future developments that can further enhance ofMRI data quality or better streamline the study. We designed and implemented a highly optimized, massively parallel system using graphics processing unit (GPU)s which achieves reconstruction, motion correction, and analysis of 3D volume data in approximately 12.80 ms. As a result, with a 750 ms TR and 4 interleaf fMRI acquisition, we can now conduct sliding window reconstruction, motion correction, analysis and display in approximately 1.7% of the TR. Therefore, a significant amount of time can now be allocated to integrating advanced but computationally intensive methods that can enable higher image quality and better analysis results all within a TR. Utilizing the proposed high-throughput imaging platform with sliding window reconstruction, we were also able to observe the much-debated initial dips in our ofMRI data. Combined with methods to further improve SNR, the proposed system will enable efficient real-time, interactive, high-throughput ofMRI studies. PMID:23747482

Fang, Zhongnan; Lee, Jin Hyung

2013-01-01

480

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

481

Fetal magnetic resonance imaging in obstetric practice  

PubMed Central

Ultrasonography (USG) is the primary imaging method for prenatal diagnosis of fetal abnormalities since its discovery. Although it is the primary method of fetal imaging, it cannot provide sufficient information about the fetus in some conditions such as maternal obesity, oligohydramnios and engagement of the fetal head. At this stage, magnetic resonance imaging (MRI) facilitates examination by providing more specific information. The need and importance of fetal MRI applications further increased by the intrauterine surgery which is currently gaining popularity. Som