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1

Diffusion Microscopist Simulator: A General Monte Carlo Simulation System for Diffusion Magnetic Resonance Imaging  

PubMed Central

This article describes the development and application of an integrated, generalized, and efficient Monte Carlo simulation system for diffusion magnetic resonance imaging (dMRI), named Diffusion Microscopist Simulator (DMS). DMS comprises a random walk Monte Carlo simulator and an MR image synthesizer. The former has the capacity to perform large-scale simulations of Brownian dynamics in the virtual environments of neural tissues at various levels of complexity, and the latter is flexible enough to synthesize dMRI datasets from a variety of simulated MRI pulse sequences. The aims of DMS are to give insights into the link between the fundamental diffusion process in biological tissues and the features observed in dMRI, as well as to provide appropriate ground-truth information for the development, optimization, and validation of dMRI acquisition schemes for different applications. The validity, efficiency, and potential applications of DMS are evaluated through four benchmark experiments, including the simulated dMRI of white matter fibers, the multiple scattering diffusion imaging, the biophysical modeling of polar cell membranes, and the high angular resolution diffusion imaging and fiber tractography of complex fiber configurations. We expect that this novel software tool would be substantially advantageous to clarify the interrelationship between dMRI and the microscopic characteristics of brain tissues, and to advance the biophysical modeling and the dMRI methodologies. PMID:24130783

Yeh, Chun-Hung; Schmitt, Benoit; Le Bihan, Denis; Li-Schlittgen, Jing-Rebecca; Lin, Ching-Po; Poupon, Cyril

2013-01-01

2

A new method for joint susceptibility artefact correction and super-resolution for dMRI  

NASA Astrophysics Data System (ADS)

Diffusion magnetic resonance imaging (dMRI) has become increasingly relevant in clinical research and neuroscience. It is commonly carried out using the ultra-fast MRI acquisition technique Echo-Planar Imaging (EPI). While offering crucial reduction of acquisition times, two limitations of EPI are distortions due to varying magnetic susceptibilities of the object being imaged and its limited spatial resolution. In the recent years progress has been made both for susceptibility artefact correction and increasing of spatial resolution using image processing and reconstruction methods. However, so far, the interplay between both problems has not been studied and super-resolution techniques could only be applied along one axis, the slice-select direction, limiting the potential gain in spatial resolution. In this work we describe a new method for joint susceptibility artefact correction and super-resolution in EPI-MRI that can be used to increase resolution in all three spatial dimensions and in particular increase in-plane resolutions. The key idea is to reconstruct a distortion-free, high-resolution image from a number of low-resolution EPI data that are deformed in different directions. Numerical results on dMRI data of a human brain indicate that this technique has the potential to provide for the first time in-vivo dMRI at mesoscopic spatial resolution (i.e. 500?m) a spatial resolution that could bridge the gap between white-matter information from ex-vivo histology (?1?m) and in-vivo dMRI (?2000?m).

Ruthotto, Lars; Mohammadi, Siawoosh; Weiskopf, Nikolaus

2014-03-01

3

Quantitative magnetic resonance imaging of brain development in premature and mature newborns  

Microsoft Academic Search

Definition in the living premature infant of the anatomical and temporal characteristics of development of critical brain structures is crucial for insight into the time of greatest vulnerability of such brain structures. We utilized 3D Magnetic Resonance Imaging (3D-MRI) and image processing algorithms to quantitate total brain volume and total volumes of cerebral gray matter (GM), unmyelinated white matter (WM),

Simon Warfield; Ron Kikinis; Patrick D. Barnes; Gary P. Zientara; Ferenc A. Jolesz; Miles K. Tsuji; Joseph J. Volpe

1998-01-01

4

Respiratory Amplitude Guided 4D Magnetic Resonance Imaging  

PubMed Central

Purpose To evaluate the feasibility of prospectively guiding 4-dimensional (4D) magnetic resonance imaging (MRI) image acquisition using triggers at pre-selected respiratory amplitudes to achieve T2 weighting for abdominal motion tracking. Methods and Materials A respiratory amplitude based triggering system was developed and integrated into a commercial turbo spin echo (TSE) MRI sequence. Initial feasibility tests were performed on healthy human subjects. Four respiratory states, the middle and the end of inhalation and exhalation, were used to trigger 4DMRI image acquisition of the liver. To achieve T2 weighting, the echo time (TE) and repetition time (TR) were set to 75ms and 4108ms, respectively. Single-shot acquisition, together with parallel imaging and partial k-space imaging techniques, was used to improve image acquisition efficiency. 4D MRI image-sets composed of axial or sagittal slices were acquired. Results Respiratory data measured and logged by the MRI scanner showed that the triggers occurred at the appropriate respiratory levels. Liver motion could be easily observed on both 4DMRI image data-sets by sensing either the change of liver in size and shape (axial) or diaphragm motion (sagittal). Both 4DMRI image data-sets were T2 weighted as expected. Conclusions This work demonstrated the feasibility of achieving T2 weighted 4DMRI images using amplitude based respiratory triggers. With the aid of the respiratory amplitude based triggering system, the proposed method is compatible with most MRI sequences and therefore has the potential to improve tumor-tissue contrast in abdominal tumor motion imaging. PMID:23414769

Hu, Yanle; Caruthers, Shelton D.; Low, Daniel A.; Parikh, Parag J.; Mutic, Sasa

2013-01-01

5

Modeling the diffusion magnetic resonance imaging signal inside neurons  

NASA Astrophysics Data System (ADS)

The Bloch-Torrey partial differential equation (PDE) describes the complex transverse water proton magnetization due to diffusion-encoding magnetic field gradient pulses. The integral of the solution of this PDE yields the diffusion magnetic resonance imaging (dMRI) signal. In a complex medium such as cerebral tissue, it is difficult to explicitly link the dMRI signal to biological parameters such as the cellular geometry or the cellular volume fraction. Studying the dMRI signal arising from a single neuron can provide insight into how the geometrical structure of neurons influences the measured signal. We formulate the Bloch-Torrey PDE inside a single neuron, under no water exchange condition with the extracellular space, and show how to reduce the 3D simulation in the full neuron to a 3D simulation around the soma and 1D simulations in the neurites. We show that this latter approach is computationally much faster than full 3D simulation and still gives accurate results over a wide range of diffusion times.

Nguyen, D. V.; Li, J. R.; Grebenkov, D. S.; Le Bihan, D.

2014-03-01

6

Comparative mouse brain tractography of diffusion magnetic resonance imaging  

PubMed Central

Diffusion magnetic resonance imaging (dMRI) tractography can be employed to simultaneously analyse three-dimensional white matter tracts in the brain. Numerous methods have been proposed to model diffusion-weighted magnetic resonance data for tractography, and we have explored the functionality of some of these for studying white and grey matter pathways in ex vivo mouse brain. Using various deterministic and probabilistic algorithms across a range of regions of interest we found that probabilistic tractography provides a more robust means of visualizing both white and grey matter pathways than deterministic tractography. Importantly, we demonstrate the sensitivity of probabilistic tractography profiles to streamline number, step size, curvature, fiber orientation distribution, and whole-brain versus region of interest seeding. Using anatomically well-defined cortico-thalamic pathways, we show how density maps can permit the topographical assessment of probabilistic tractography. Finally, we show how different tractography approaches can impact on dMRI assessment of tract changes in a mouse deficient for the frontal cortex morphogen, fibroblast growth factor 17. In conclusion, probabilistic tractography can elucidate the phenotypes of mice with neurodegenerative or neurodevelopmental disorders in a quantitative manner. PMID:20303410

Moldrich, Randal X.; Pannek, Kerstin; Hoch, Renee; Rubenstein, John L.; Kurniawan, Nyoman D.; Richards, Linda J.

2010-01-01

7

Magnetic resonance imaging and spectroscopy  

SciTech Connect

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

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

1986-01-01

8

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

9

Nuclear magnetic resonance imaging.  

PubMed

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

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

1981-01-01

10

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

11

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,

12

Craniospinal magnetic resonance imaging  

SciTech Connect

This clinical sourcebook details the latest applications of MRI to craniospinal imaging and diagnosis. As each entity is described, the MRI findings are discussed and listed in order of importance-followed by a discussion of important imaging considerations. While focusing primarily on MRI, the text also correlates CT and other imaging modalities, where appropriate.

Pomeranz, S.J.

1988-01-01

13

Spiral parallel magnetic resonance imaging.  

PubMed

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

Meyer, Craig H; Hu, Peng

2006-01-01

14

Magnetic Resonance Imaging (MRI)  

MedlinePLUS

... the body. These images can be converted into three-dimensional (3-D) pictures of the scanned area that ... Taking Charge of Your Medical Care Contact Us Print Additional resources Send to a friend Reprint guidelines ...

15

Magnetic Resonance Imaging (MRI)  

Cancer.gov

Different tissues (including tumors) emit a more or less intense signal based on their chemical makeup, so a picture of the body organs can be displayed on a computer screen. Much like CT scans, MRI can produce three-dimensional images of sections of the body, but MRI is sometimes more sensitive than CT scans for distinguishing soft tissues.

16

Magnetic Resonance Imaging of concrete  

E-print Network

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

Burgoyne, Chris

17

Low field magnetic resonance imaging  

DOEpatents

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

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

2010-07-13

18

Gadolinium magnetic resonance imaging dacryocystography.  

PubMed

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

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

1993-06-15

19

Magnetic resonance imaging in lissencephaly  

Microsoft Academic Search

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

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

1987-01-01

20

Magnetic resonance imaging of acquired cardiac disease.  

PubMed Central

Over the last 15 years, advances in magnetic resonance imaging techniques have increased the accuracy and applicability of cardiovascular magnetic resonance imaging. These advances have improved the utility of magnetic resonance imaging in evaluating cardiac morphology, blood flow, and myocardial contractility, all significant diagnostic features in the evaluation of the patient with acquired heart disease. Utilization of cardiovascular magnetic resonance imaging has been limited, primarily due to clinical reliance upon nuclear scintigraphy and echocardiography. Recent developments in fast and ultrafast imaging should continue to enhance the significance of magnetic resonance imaging in this field. Widespread use of magnetic resonance imaging in the evaluation of the cardiovascular system will ultimately depend upon its maturation into a comprehensive, noninvasive imaging technique for the varying manifestations of acquired heart disease, including cardiomyopathy, ischemic heart disease, and acquired valvular disease. Images PMID:8792545

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

1996-01-01

21

Print |Close Tract-based statistical analyzes in dMRI in  

E-print Network

a set of population-obtained bundles. Data analysis. We applied the statistical analysis of WassermannPrint |Close Tract-based statistical analyzes in dMRI in autism spectrum disorder Submission No in autism spectrum disorder (ASD). Previous neuroimaging studies showed that the fusiform gyrus is involved

Paris-Sud XI, Université de

22

Nuclear magnetic resonance imaging (MRI).  

PubMed

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

Khurshid, S J; Hussain, A M

1991-10-01

23

Nitinol in magnetic resonance imaging.  

PubMed

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

Melzer; Michitsch; Konak; Schaefers; Bertsch, Th

2004-08-01

24

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

25

Magnetic Resonance Imaging - Parts I and II.  

National Technical Information Service (NTIS)

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

1994-01-01

26

Investigating the Capability to Resolve Complex White Matter Structures with High b-Value Diffusion Magnetic Resonance Imaging on the MGH-USC Connectom Scanner.  

PubMed

Abstract One of the major goals of the NIH Blueprint Human Connectome Project was to map and quantify the white matter connections in the brain using diffusion tractography. Given the prevalence of complex white matter structures, the capability of resolving local white matter geometries with multiple crossings in the diffusion magnetic resonance imaging (dMRI) data is critical. Increasing b-value has been suggested for delineation of the finer details of the orientation distribution function (ODF). Although increased gradient strength and duration increase sensitivity to highly restricted intra-axonal water, gradient strength limitations require longer echo times (TE) to accommodate the increased diffusion encoding times needed to achieve a higher b-value, exponentially lowering the signal-to-noise ratio of the acquisition. To mitigate this effect, the MGH-USC Connectom scanner was built with 300 mT/m gradients, which can significantly reduce the TE of high b-value diffusion imaging. Here we report comparisons performed across b-values based on q-ball ODF metrics to investigate whether high b-value diffusion imaging on the Connectom scanner can improve resolving complex white matter structures. The q-ball ODF features became sharper as the b-value increased, with increased power fraction in higher order spherical harmonic series of the ODF and increased peak heights relative to the overall size of the ODF. Crossing structures were detected in an increasingly larger fraction of white matter voxels and the spatial distribution of two-way and three-way crossing structures was largely consistent with known anatomy. Results indicate that dMRI with high diffusion encoding on the Connectom system is a promising tool to better characterize, and ultimately understand, the underlying structural organization and motifs in the human brain. PMID:25287963

Fan, Qiuyun; Nummenmaa, Aapo; Witzel, Thomas; Zanzonico, Roberta; Keil, Boris; Cauley, Stephen; Polimeni, Jonathan R; Tisdall, Dylan; Van Dijk, Koene R A; Buckner, Randy L; Wedeen, Van J; Rosen, Bruce R; Wald, Lawrence L

2014-11-01

27

Magnetic resonance imaging of radiation optic neuropathy  

SciTech Connect

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

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

1990-10-15

28

Functional Magnetic Resonance Imaging and Pediatric Anxiety  

ERIC Educational Resources Information Center

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

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

2008-01-01

29

Protocols in sports magnetic resonance imaging.  

PubMed

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

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

2003-02-01

30

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

31

Coronary Computed Tomography and Magnetic Resonance Imaging  

PubMed Central

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

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

2009-01-01

32

A Primer on Functional Magnetic Resonance Imaging  

Microsoft Academic Search

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

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

2007-01-01

33

Magnetic resonance angiogram and imaging.  

PubMed

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

Goodwin, L

2000-01-01

34

Array combination for parallel imaging in Magnetic Resonance Imaging  

E-print Network

In Magnetic Resonance Imaging, the time required to generate an image is proportional to the number of steps used to encode the spatial information. In rapid imaging, an array of coil elements and receivers are used to reduce the number of encoding...

Spence, Dan Kenrick

2007-09-17

35

Magnetic Resonance Imaging of coarse sediment  

Microsoft Academic Search

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

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

2008-01-01

36

Off-Resonance Correction of MR Images  

Microsoft Academic Search

In magnetic resonance imaging (MRI), the spatial inhomogeneity of the static magnetic field can cause degraded images if the reconstruction is based on inverse Fourier trans- formation. This paper presents and discusses a range of fast reconstruction algorithms that attempt to avoid such degra- dation by taking the field inhomogeneity into account. Some of these algorithms are new, others are

Hermann Schomberg

1999-01-01

37

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

38

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

39

PANDA: a pipeline toolbox for analyzing brain diffusion images.  

PubMed

Diffusion magnetic resonance imaging (dMRI) is widely used in both scientific research and clinical practice in in-vivo studies of the human brain. While a number of post-processing packages have been developed, fully automated processing of dMRI datasets remains challenging. Here, we developed a MATLAB toolbox named "Pipeline for Analyzing braiN Diffusion imAges" (PANDA) for fully automated processing of brain diffusion images. The processing modules of a few established packages, including FMRIB Software Library (FSL), Pipeline System for Octave and Matlab (PSOM), Diffusion Toolkit and MRIcron, were employed in PANDA. Using any number of raw dMRI datasets from different subjects, in either DICOM or NIfTI format, PANDA can automatically perform a series of steps to process DICOM/NIfTI to diffusion metrics [e.g., fractional anisotropy (FA) and mean diffusivity (MD)] that are ready for statistical analysis at the voxel-level, the atlas-level and the Tract-Based Spatial Statistics (TBSS)-level and can finish the construction of anatomical brain networks for all subjects. In particular, PANDA can process different subjects in parallel, using multiple cores either in a single computer or in a distributed computing environment, thus greatly reducing the time cost when dealing with a large number of datasets. In addition, PANDA has a friendly graphical user interface (GUI), allowing the user to be interactive and to adjust the input/output settings, as well as the processing parameters. As an open-source package, PANDA is freely available at http://www.nitrc.org/projects/panda/. This novel toolbox is expected to substantially simplify the image processing of dMRI datasets and facilitate human structural connectome studies. PMID:23439846

Cui, Zaixu; Zhong, Suyu; Xu, Pengfei; He, Yong; Gong, Gaolang

2013-01-01

40

Functional magnetic resonance imaging studies of language  

Microsoft Academic Search

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

Steven L. Small; Martha W. Burton

2002-01-01

41

Magnetic Resonance Imaging of Acute Stroke  

Microsoft Academic Search

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

Alison E. Baird; Steven Warach

1998-01-01

42

Magnetic resonance imaging of atherosclerosis  

Microsoft Academic Search

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

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

2005-01-01

43

Multispectral analysis of magnetic resonance images.  

PubMed

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

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

1985-01-01

44

Principles of imaging by nuclear magnetic resonance  

SciTech Connect

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

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

1984-03-01

45

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

46

Hosted by Yalin Wang Methods in Magnetic Resonance Imaging  

E-print Network

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

Reisslein, Martin

47

Introduction to magnetic resonance imaging  

SciTech Connect

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

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

1984-01-01

48

Granular convection observed by magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

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

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

1995-03-01

49

Granular convection observed by magnetic resonance imaging  

SciTech Connect

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

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

1995-03-17

50

Imaging Informational Conflict: A Functional Magnetic Resonance Imaging Study of  

E-print Network

. This is now known as the ``Stroop effect.'' Nevertheless, the majority of responses in Stroop task performance in different sizes (e.g., 3 3) for the physical comparison task. The Stroop effect manifests as interfImaging Informational Conflict: A Functional Magnetic Resonance Imaging Study of Numerical Stroop J

Butterworth, Brian

51

Magnetic resonance imaging in Mexico  

NASA Astrophysics Data System (ADS)

MR imaging has experienced an important growth worldwide and in particular in the USA and Japan. This imaging technique has also shown an important rise in the number of MR imagers in Mexico. However, the development of MRI has followed a typical way of Latin American countries, which is very different from the path shown in the industrialised countries. Despite the fact that Mexico was one the very first countries to install and operate MR imagers in the world, it still lacks of qualified clinical and technical personnel. Since the first MR scanner started to operate, the number of units has grown at a moderate space that now sums up approximately 60 system installed nationwide. Nevertheless, there are no official records of the number of MR units operating, physicians and technicians involved in this imaging modality. The MRI market is dominated by two important companies: General Electric (approximately 51%) and Siemens (approximately 17.5%), the rest is shared by other five companies. According to the field intensity, medium-field systems (0.5 Tesla) represent 60% while a further 35% are 1.0 T or higher. Almost all of these units are in private hospitals and clinics: there is no high-field MR imagers in any public hospital. Because the political changes in the country, a new public plan for health care is still in the process and will be published soon this year. This plan will be determined by the new Congress. North American Free Trade Agreement (NAFTA) and president Fox. Experience acquired in the past shows that the demand for qualified professionals will grow in the new future. Therefore, systematic training of clinical and technical professionals will be in high demand to meet the needs of this technique. The National University (UNAM) and the Metropolitan University (UAM-Iztapalapa) are collaborating with diverse clinical groups in private facilities to create a systematic training program and carry out research and development in MRI

Rodriguez, A. O.; Rojas, R.; Barrios, F. A.

2001-10-01

52

Magnetic resonance imaging of septic sacroiliitis  

Microsoft Academic Search

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

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

1994-01-01

53

Adaptive Fuzzy Segmentation of Magnetic Resonance Images  

Microsoft Academic Search

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

Dzung L. Pham; Jerry L. Prince

1999-01-01

54

Magnetic resonance imaging of the child's brain  

Microsoft Academic Search

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

Beverly L. Hershey; Robert A. Zimmerman

1986-01-01

55

Coolant quality for magnetic resonance imaging systems  

Microsoft Academic Search

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

Julie Wong; Garron K Morris

2008-01-01

56

ORIGINAL ARTICLE Magnetic Resonance Imaging and Head  

E-print Network

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

Gerig, Guido

57

Techniques for Automatic Magnetic Resonance Image Classification  

Microsoft Academic Search

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

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

2010-01-01

58

Reducing Field Distortion in Magnetic Resonance Imaging  

NASA Technical Reports Server (NTRS)

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

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

2010-01-01

59

Magnetic resonance imaging of pelvic bone tumors.  

PubMed

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

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

1996-02-01

60

Magnetic resonance imaging features of breast leukemia.  

PubMed

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

Kim, Suk Jung

2013-12-25

61

Imaging in breast cancer: Magnetic resonance spectroscopy  

PubMed Central

A technique called in vivo magnetic resonance spectroscopy (MRS) can be performed along with magnetic resonance imaging (MRI) to obtain information about the chemical content of breast lesions. This information can be used for several clinical applications, such as monitoring the response to cancer therapies and improving the accuracy of lesion diagnosis. Initial MRS studies of breast cancer show promising results, and a growing number of research groups are incorporating the technique into their breast MRI protocols. This article introduces 1H-MRS of the breast, reviews the literature, discusses current methods and technical issues, and describes applications for treatment monitoring and lesion diagnosis. PMID:15987466

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

2005-01-01

62

Chemical exchange magnetic resonance imaging (CHEMI)  

SciTech Connect

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

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

1988-09-01

63

Magnetic Resonance Imaging of Brain Function and Neurochemistry  

E-print Network

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

Duong, Timothy Q.

64

Statistical normalization techniques for magnetic resonance imaging???  

PubMed Central

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

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

2014-01-01

65

Magnetic Resonance Imaging Studies of Cigarette Smoking  

Microsoft Academic Search

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

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

66

Magnetic Resonance Imaging of the Kidney  

Microsoft Academic Search

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

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

67

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

68

New magnetic resonance imaging methods in nephrology  

PubMed Central

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

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

2013-01-01

69

Magnetic resonance imaging of pancreatitis: An update  

PubMed Central

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

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

2014-01-01

70

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

71

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

72

Gastrointestinal imaging-practical magnetic resonance imaging approach.  

PubMed

Over the past two decades, advances in cross-sectional imaging such as computed tomography and magnetic resonance imaging (MRI) have dramatically changed the concept of gastrointestinal imaging. MR is playing an increasing role in the evaluation of gastrointestinal disorders. MRI combines the advantages of excellent soft-tissue contrast, noninvasiveness, functional information and lack of ionizing radiation. Furthermore, recent developments of MRI have led to improved spatial and temporal resolution as well as decreased motion artifacts. In this article we describe the technical aspects of gastrointestinal MRI and present a practical approach for a well-known spectrum of gastrointestinal disease processes. PMID:25170393

Liu, Baodong; Ramalho, Miguel; AlObaidy, Mamdoh; Busireddy, Kiran K; Altun, Ersan; Kalubowila, Janaka; Semelka, Richard C

2014-08-28

73

Gastrointestinal imaging-practical magnetic resonance imaging approach  

PubMed Central

Over the past two decades, advances in cross-sectional imaging such as computed tomography and magnetic resonance imaging (MRI) have dramatically changed the concept of gastrointestinal imaging. MR is playing an increasing role in the evaluation of gastrointestinal disorders. MRI combines the advantages of excellent soft-tissue contrast, noninvasiveness, functional information and lack of ionizing radiation. Furthermore, recent developments of MRI have led to improved spatial and temporal resolution as well as decreased motion artifacts. In this article we describe the technical aspects of gastrointestinal MRI and present a practical approach for a well-known spectrum of gastrointestinal disease processes. PMID:25170393

Liu, Baodong; Ramalho, Miguel; AlObaidy, Mamdoh; Busireddy, Kiran K; Altun, Ersan; Kalubowila, Janaka; Semelka, Richard C

2014-01-01

74

Multiple-mouse Neuroanatomical Magnetic Resonance Imaging  

PubMed Central

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

Cahill, Lindsay S.; Henkelman, R. Mark

2011-01-01

75

Magnetic resonance imaging in acute mastoiditis  

PubMed Central

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

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

2014-01-01

76

Volumetric segmentation of magnetic resonance images  

NASA Astrophysics Data System (ADS)

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

Lee, James D.; Rodriguez, Jeffrey J.

1994-09-01

77

Quantitative Pulmonary Imaging Using Computed Tomography and Magnetic Resonance Imaging  

PubMed Central

Measurements of lung function, including spirometry and body plethesmography, are easy to perform and are the current clinical standard for assessing disease severity. However, these lung functional techniques do not adequately explain the observed variability in clinical manifestations of disease and offer little insight into the relationship of lung structure and function. Lung imaging and the image based assessment of lung disease has matured to the extent that it is common for clinical, epidemiologic, and genetic investigation to have a component dedicated to image analysis. There are several exciting imaging modalities currently being used for the non-invasive study of lung anatomy and function. In this review we will focus on two of them, x-ray computed tomography and magnetic resonance imaging. Following a brief introduction of each method we detail some of the most recent work being done to characterize smoking-related lung disease and the clinical applications of such knowledge. PMID:22142490

Washko, George R.; Parraga, Grace; Coxson, Harvey O.

2011-01-01

78

Metabolite specific proton magnetic resonance imaging  

SciTech Connect

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

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

1989-06-01

79

Cardiovascular Magnetic Resonance Imaging in Experimental Models  

PubMed Central

Cardiovascular magnetic resonance (CMR) imaging is the modality of choice for clinical studies of the heart and vasculature, offering detailed images of both structure and function with high temporal resolution. Small animals are increasingly used for genetic and translational research, in conjunction with models of common pathologies such as myocardial infarction. In all cases, effective methods for characterising a wide range of functional and anatomical parameters are crucial for robust studies. CMR is the gold-standard for the non-invasive examination of these models, although physiological differences, such as rapid heart rate, make this a greater challenge than conventional clinical imaging. However, with the help of specialised magnetic resonance (MR) systems, novel gating strategies and optimised pulse sequences, high-quality images can be obtained in these animals despite their small size. In this review, we provide an overview of the principal CMR techniques for small animals for example cine, angiography and perfusion imaging, which can provide measures such as ejection fraction, vessel anatomy and local blood flow, respectively. In combination with MR contrast agents, regional dysfunction in the heart can also be identified and assessed. We also discuss optimal methods for analysing CMR data, particularly the use of semi-automated tools for parameter measurement to reduce analysis time. Finally, we describe current and emerging methods for imaging the developing heart, aiding characterisation of congenital cardiovascular defects. Advanced small animal CMR now offers an unparalleled range of cardiovascular assessments. Employing these methods should allow new insights into the structural, functional and molecular basis of the cardiovascular system. PMID:21331311

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

2010-01-01

80

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

81

Nuclear magnetic resonance imaging of the kidney  

SciTech Connect

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

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

1983-02-01

82

Magnetic Resonance Imaging at Ultrahigh Fields  

PubMed Central

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

Ugurbil, Kamil

2014-01-01

83

Tools for cardiovascular magnetic resonance imaging.  

PubMed

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

Krishnamurthy, Ramkumar; Cheong, Benjamin; Muthupillai, Raja

2014-04-01

84

Cell tracking using magnetic resonance imaging  

PubMed Central

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

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

2007-01-01

85

Magnetic resonance imaging of the hip.  

PubMed

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

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

2008-03-01

86

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

87

Designing Magnetic Resonance Imaging Curriculum for Undergraduates  

NSDL National Science Digital Library

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

2009-10-29

88

Magnetic resonance imaging of placenta accreta  

PubMed Central

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

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

2013-01-01

89

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

90

Prospects for neutron probed magnetic resonance imaging  

SciTech Connect

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

Granroth, Garrett E [ORNL

2009-01-01

91

Small animal imaging with magnetic resonance microscopy.  

PubMed

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

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

2008-01-01

92

Rare Infraglottic Lesions in Magnetic Resonance Imaging  

PubMed Central

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

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

2014-01-01

93

Magnetic Resonance Imaging-guided Vascular Interventions  

PubMed Central

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

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

2007-01-01

94

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

95

Functional magnetic resonance imaging: imaging techniques and contrast mechanisms.  

PubMed Central

Functional magnetic resonance imaging (fMRI) is a widely used technique for generating images or maps of human brain activity. The applications of the technique are widespread in cognitive neuroscience and it is hoped they will eventually extend into clinical practice. The activation signal measured with fMRI is predicated on indirectly measuring changes in the concentration of deoxyhaemoglobin which arise from an increase in blood oxygenation in the vicinity of neuronal firing. The exact mechanisms of this blood oxygenation level dependent (BOLD) contrast are highly complex. The signal measured is dependent on both the underlying physiological events and the imaging physics. BOLD contrast, although sensitive, is not a quantifiable measure of neuronal activity. A number of different imaging techniques and parameters can be used for fMRI, the choice of which depends on the particular requirements of each functional imaging experiment. The high-speed MRI technique, echo-planar imaging provides the basis for most fMRI experiments. The problems inherent to this method and the ways in which these may be overcome are particularly important in the move towards performing functional studies on higher field MRI systems. Future developments in techniques and hardware are also likely to enhance the measurement of brain activity using MRI. PMID:10466145

Howseman, A M; Bowtell, R W

1999-01-01

96

Mapping motion from 4D-MRI to 3D-CT for use in 4D dose calculations: A technical feasibility study  

SciTech Connect

Purpose: Target sites affected by organ motion require a time resolved (4D) dose calculation. Typical 4D dose calculations use 4D-CT as a basis. Unfortunately, 4D-CT images have the disadvantage of being a 'snap-shot' of the motion during acquisition and of assuming regularity of breathing. In addition, 4D-CT acquisitions involve a substantial additional dose burden to the patient making many, repeated 4D-CT acquisitions undesirable. Here the authors test the feasibility of an alternative approach to generate patient specific 4D-CT data sets. Methods: In this approach motion information is extracted from 4D-MRI. Simulated 4D-CT data sets [which the authors call 4D-CT(MRI)] are created by warping extracted deformation fields to a static 3D-CT data set. The employment of 4D-MRI sequences for this has the advantage that no assumptions on breathing regularity are made, irregularities in breathing can be studied and, if necessary, many repeat imaging studies (and consequently simulated 4D-CT data sets) can be performed on patients and/or volunteers. The accuracy of 4D-CT(MRI)s has been validated by 4D proton dose calculations. Our 4D dose algorithm takes into account displacements as well as deformations on the originating 4D-CT/4D-CT(MRI) by calculating the dose of each pencil beam based on an individual time stamp of when that pencil beam is applied. According to corresponding displacement and density-variation-maps the position and the water equivalent range of the dose grid points is adjusted at each time instance. Results: 4D dose distributions, using 4D-CT(MRI) data sets as input were compared to results based on a reference conventional 4D-CT data set capturing similar motion characteristics. Almost identical 4D dose distributions could be achieved, even though scanned proton beams are very sensitive to small differences in the patient geometry. In addition, 4D dose calculations have been performed on the same patient, but using 4D-CT(MRI) data sets based on variable breathing patterns to show the effect of possible irregular breathing on active scanned proton therapy. Using a 4D-CT(MRI), including motion irregularities, resulted in significantly different proton dose distributions. Conclusions: The authors have demonstrated that motion information from 4D-MRI can be used to generate realistic 4D-CT data sets on the basis of a single static 3D-CT data set. 4D-CT(MRI) presents a novel approach to test the robustness of treatment plans in the circumstance of patient motion.

Boye, Dirk [Center for Proton Therapy, Paul Scherrer Institut, 5232 Villigen-PSI (Switzerland); Computer Vision Laboratory, ETH Zuerich, 8092 Zuerich (Switzerland); Lomax, Tony [Center for Proton Therapy, Paul Scherrer Institut, 5232 Villigen-PSI (Switzerland); ETH Zuerich, 8092 Zuerich (Switzerland); Knopf, Antje [Center for Proton Therapy, Paul Scherrer Institut, 5232 Villigen-PSI (Switzerland)

2013-06-15

97

Thoracic magnetic resonance imaging: pulmonary thromboembolism.  

PubMed

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

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

2013-05-01

98

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

99

Magnetic resonance spectroscopic imaging using parallel transmission at 7T  

E-print Network

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

Gagoski, Borjan Aleksandar

2011-01-01

100

Magnetic resonance imaging with an optical atomicmagnetometer  

SciTech Connect

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

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

2006-05-09

101

Magnetic resonance imaging of adolescent disc herniation.  

PubMed

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

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

1987-11-01

102

Nanoplatforms for magnetic resonance imaging of cancer  

PubMed Central

Summary The application of biomedical nanotechnology in magnetic resonance imaging (MRI) is expect to have a major impact leading to the development of new contrast drug candidates on the nanoscale (1–100 nm) that are able to react with specific biological targets at a molecular level. One of the major challenges in this regard is the construction of nanomaterials, especially used in molecular MRI diagnostics of cancer in vivo, specialized antitumor drug delivery or real-time evaluation of the efficacy of the implemented cancer treatment. In this paper, we tried to gain further insights into current trends of nanomedicine, with special focus on preclinical MRI studies in translation cancer research. PMID:22802828

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

2011-01-01

103

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

104

Myocardial tissue characterization with magnetic resonance imaging.  

PubMed

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

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

2014-11-01

105

Small Animal Imaging with Magnetic Resonance Microscopy  

PubMed Central

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

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

2009-01-01

106

Surface Plasmon Resonance Imaging Studies of Protein-Carbohydrate Interactions  

E-print Network

Surface Plasmon Resonance Imaging Studies of Protein-Carbohydrate Interactions Emily A. Smith; E-mail: corn@chem.wisc.edu; kiessling@chem.wisc.edu Abstract: Carbohydrate arrays fabricated on gold films were used to study carbohydrate-protein interactions with surface plasmon resonance (SPR) imaging

107

Magnetic Resonance Imaging System Based on Earth's Magnetic Field  

Microsoft Academic Search

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

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

2004-01-01

108

Bioengineering/Radiology 278: Magnetic Resonance Imaging Laboratory Winter 2012  

E-print Network

Bioengineering/Radiology 278: Magnetic Resonance Imaging Laboratory Winter 2012 Syllabus Week image data, reconstruct image Collect and transform an FID Make a B1 map 2 Frequency Encoding Sampling Chemical shift 1D imaging Sampling, bandwidth, resolution, FOV Chemical shift 3 Phase encoding K-space 2D

California at San Diego, University of

109

Magnetoliposomes as magnetic resonance imaging contrast agents.  

PubMed

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

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

2011-03-01

110

Roadmap: Radiologic Imaging Sciences Magnetic Resonance Imaging (with certification and ATS Radiologic Technology) -  

E-print Network

Roadmap: Radiologic Imaging Sciences ­ Magnetic Resonance Imaging (with certification and ATS Radiologic Technology) - Bachelor of Radiologic Imaging Sciences Technology [RE-BRIT-RIS-MRHA] Regional in radiologic technology; successfully completed the certification exam for the American Registry of Radiologic

Sheridan, Scott

111

Magnetic Resonance Imaging in Postprostatectomy Radiotherapy Planning  

SciTech Connect

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

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

2012-02-01

112

Magnetic resonance imaging evaluation of myocardial perfusion.  

PubMed

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

Passariello, R; De Santis, M

1998-06-18

113

Magnetic resonance imaging of oscillating electrical currents  

PubMed Central

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

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

2010-01-01

114

Magnetic resonance imaging of the clavicular ossification.  

PubMed

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

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

2007-07-01

115

Magnetic resonance imaging of cranial radiation lesions  

SciTech Connect

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

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

1987-07-01

116

Single echo acquisition magnetic resonance imaging  

E-print Network

imaging (phase encode in the slice select direction), resolution-enhanced imaging, large-scale (field-of-view) microscopy, and conformal surface imaging. Finally, using the primary enablement of the method Â? the ability to obtain complete MR images...

McDougall, Mary Preston

2006-04-12

117

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

118

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

119

Magnetic resonance imaging and ultrasound in hepatosplenic schistosomiasis mansoni.  

PubMed

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

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

2004-01-01

120

Magnetic Resonance Image Segmentation Based on Affinity Propagation  

Microsoft Academic Search

Accurate segmentation of magnetic resonance images (MRI) corrupted by intensity in homogeneity is a challenging problem and has received an enormous amount of attention lately. On the basis of the local image model, we propose a different segmentation method for MR brain images without estimation and correction for intensity heterogeneity. Firstly, we obtain clustering context which size is optimized by

Chunlian Li; Lili Dou; Sun Yu; Di Liu; Ying Lin

2009-01-01

121

In vivo visualization of gene expression using magnetic resonance imaging  

Microsoft Academic Search

High-resolution in vivo imaging of gene expression is not possible in opaque animals by existing techniques. Here we present a new approach for obtaining such images by magnetic resonance imaging (MRI) using an MRI contrast agent that can indicate reporter gene expression in living animals. We have prepared MRI contrast agents in which the access of water to the first

Angelique Y. Louie; Martina M. Hüber; Eric T. Ahrens; Ute Rothbächer; Rex Moats; Russell E. Jacobs; Scott E. Fraser; Thomas J. Meade

2000-01-01

122

Multimodal Magnetic Resonance Imaging for Brain Disorders: Advances and Perspectives  

E-print Network

of such structural and functional information obtained from brain imaging may be able to enhance our understandingMultimodal Magnetic Resonance Imaging for Brain Disorders: Advances and Perspectives Tianzi Jiang Modern brain imaging technologies play essen- tial roles in our understanding of brain information

Jiang,Tianzi

123

Magnetic resonance imaging: Review of imaging techniques and overview of liver imaging  

PubMed Central

Magnetic resonance imaging (MRI) of the liver is slowly transitioning from a problem solving imaging modality to a first line imaging modality for many diseases of the liver. The well established advantages of MRI over other cross sectional imaging modalities may be the basis for this transition. Technological advancements in MRI that focus on producing high quality images and fast imaging, increasing diagnostic accuracy and developing newer function-specific contrast agents are essential in ensuring that MRI succeeds as a first line imaging modality. Newer imaging techniques, such as parallel imaging, are widely utilized to shorten scanning time. Diffusion weighted echo planar imaging, an adaptation from neuroimaging, is fast becoming a routine part of the MRI liver protocol to improve lesion detection and characterization of focal liver lesions. Contrast enhanced dynamic T1 weighted imaging is crucial in complete evaluation of diseases and the merit of this dynamic imaging relies heavily on the appropriate timing of the contrast injection. Newer techniques that include fluoro-triggered contrast enhanced MRI, an adaptation from 3D MRA imaging, are utilized to achieve good bolus timing that will allow for optimum scanning. For accurate interpretation of liver diseases, good understanding of the newer imaging techniques and familiarity with typical imaging features of liver diseases are essential. In this review, MR sequences for a time efficient liver MRI protocol utilizing newer imaging techniques are discussed and an overview of imaging features of selected common focal and diffuse liver diseases are presented. PMID:21160685

Maniam, Santhi; Szklaruk, Janio

2010-01-01

124

Magnetic resonance imaging for the assessment of liver function.  

E-print Network

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

Nilsson, Henrik

2011-01-01

125

Fast neutron resonance radiography for element imaging : theory and applications  

E-print Network

Fast Neutron Resonance Radiography (NRR) has been devised as an elemental imaging method, with immediate applications to detecting explosives and drugs in passenger suitcases. In the NRR method, the 2-D elemental mapping ...

Chen, Gongyin, 1968-

2001-01-01

126

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

127

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

128

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

129

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

130

Magnetic resonance imaging: Implication in acute ischemic stroke management  

Microsoft Academic Search

Multimodality magnetic resonance imaging (MRI) techniques, including diffusion-weighted imaging (DWI), perfusion-weighted\\u000a imaging (PWI), fluid-attenuated inversion recovery (FLAIR), T2 susceptibility imaging, and magnetic resonance angiography\\u000a (MRA), quickly provide accurate information about ischemic penumbra (DWI\\/PWI mismatch), tissue perfusion, and vascular localization\\u000a in acute stroke setting. These techniques help physicians to select the proper candidates for thrombolysis and\\/or neuroprotective\\u000a treatment to salvage tissue

Oraporn Sitburana; Walter J. Koroshetz

2005-01-01

131

Multimodal Magnetic Resonance Imaging for Brain Disorders: Advances and Perspectives  

Microsoft Academic Search

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

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

2008-01-01

132

Addressing and imaging microring resonators with optical evanescent light  

NASA Astrophysics Data System (ADS)

We show that optical evanescent light can be used to simultaneously address and image microring resonators. The optical addressing function is based on control of the overlap between a three-dimensional evanescent light spot and a linear dielectric ridge connected to the resonator. When detected with a Photon Scanning Tunnelling Microscope (PSTM), the evanescent light tailing off the device provides precise optical images of the light distribution inside and around the resonator. The complete phenomenon has been calculated numerically using the three-dimensional Green Dyadic Method.

Quidant, R.; Weeber, J.-C.; Dereux, A.; Lévêque, G.; Weiner, J.; Girard, C.

2004-02-01

133

Pancoast tumor: the role of magnetic resonance imaging.  

PubMed

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

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

2013-01-01

134

Pancoast Tumor: The Role of Magnetic Resonance Imaging  

PubMed Central

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

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

2013-01-01

135

Imaging of the hip joint. Computed tomography versus magnetic resonance imaging  

NASA Technical Reports Server (NTRS)

The authors reviewed the applications and limitations of computed tomography (CT) and magnetic resonance (MR) imaging in the assessment of the most common hip disorders. Magnetic resonance imaging is the most sensitive technique in detecting osteonecrosis of the femoral head. Magnetic resonance reflects the histologic changes associated with osteonecrosis very well, which may ultimately help to improve staging. Computed tomography can more accurately identify subchondral fractures than MR imaging and thus remains important for staging. In congenital dysplasia of the hip, the position of the nonossified femoral head in children less than six months of age can only be inferred by indirect signs on CT. Magnetic resonance imaging demonstrates the cartilaginous femoral head directly without ionizing radiation. Computed tomography remains the imaging modality of choice for evaluating fractures of the hip joint. In some patients, MR imaging demonstrates the fracture even when it is not apparent on radiography. In neoplasm, CT provides better assessment of calcification, ossification, and periosteal reaction than MR imaging. Magnetic resonance imaging, however, represents the most accurate imaging modality for evaluating intramedullary and soft-tissue extent of the tumor and identifying involvement of neurovascular bundles. Magnetic resonance imaging can also be used to monitor response to chemotherapy. In osteoarthrosis and rheumatoid arthritis of the hip, both CT and MR provide more detailed assessment of the severity of disease than conventional radiography because of their tomographic nature. Magnetic resonance imaging is unique in evaluating cartilage degeneration and loss, and in demonstrating soft-tissue alterations such as inflammatory synovial proliferation.

Lang, P.; Genant, H. K.; Jergesen, H. E.; Murray, W. R.

1992-01-01

136

Advanced image reconstruction in parallel magnetic resonance imaging : constraints and solutions.  

E-print Network

Imaging speed is a crucial consideration for magnetic resonance imaging (MRI). The speed of conventional MRI is limited by hardware performance and physiological safety measures. "Parallel" MRI is a new technique that ...

Yeh, Ernest Nanjung, 1975-

2005-01-01

137

Fundamental and practical limits to image acceleration in parallel magnetic resonance imaging  

E-print Network

Imaging speed in conventional magnetic resonance imaging (MRI) is limited by the performance of magnetic field gradients and the rate of power deposition in tissue. Parallel MRI techniques overcome these constraints by ...

Ohliger, Michael A

2005-01-01

138

Slotted cage resonator for high-field magnetic resonance imaging of rodents  

NASA Astrophysics Data System (ADS)

A variation of the high-frequency cavity resonator coil was experimentally developed according to the theoretical frame proposed by Mansfield in 1990. Circular slots were used instead of cavities to form the coil endplates and it was called the slotted cage resonator coil. The theoretical principles were validated via a coil equivalent circuit and also experimentally with a coil prototype. The radio frequency magnetic field, B1, produced by several coil configurations was numerically simulated using the finite-element approach to investigate their performances. A transceiver coil, 8 cm long and 7.6 cm in diameter, and composed of 4 circular slots with a 15 mm diameter on both endplates, was built to operate at 300 MHz and quadrature driven. Experimental results obtained with the slotted cage resonator coil were presented and showed very good agreement with the theoretical expectations for the resonant frequency as a function of the coil dimensions and slots. A standard birdcage coil was also built for performance comparison purposes. Phantom images were then acquired to compute the signal-to-noise ratio of both coils showing an important improvement of the slotted cage coil over the birdcage coil. The whole-body images of the mouse were also obtained showing high-quality images. Volume resonator coils can be reliably built following the physical principles of the cavity resonator design for high-field magnetic resonance imaging applications of rodents.

Marrufo, O.; Vasquez, F.; Solis, S. E.; Rodriguez, A. O.

2011-04-01

139

Travelling wave magnetic resonance imaging at 3 T  

NASA Astrophysics Data System (ADS)

Waveguides have been successfully used to generate magnetic resonance images at 7 T with whole-body systems. The bore diameter limits the magnetic resonance signal transmitted because its specific cut-off frequency is greater than the majority of resonant frequencies in magnetic resonance imaging and spectroscopy. This restriction can be overcome by using a parallel-plate waveguide whose cut-off frequency is zero for the transverse electromagnetic modes and it can propagate any frequency. To study the potential benefits of travelling-wave excitation for whole-body imaging at 3 T, we compare numerical simulations of the principal mode propagation for a parallel-plate waveguide filled with a cylindrical phantom and two surface coils for all simulations at 1.5 T, 3 T, 4.7, 7 T, and 9.4 T. The principal mode shows very little variation of the field magnitude along the propagation direction at 3 T when compared to other higher resonant frequencies. Unlike the standard method for travelling-wave magnetic resonance imaging, a parallel-plate waveguide prototype was built and used together with a whole-body birdcage coil for signal transmission and a pair of circular coils for reception. Experimental B1 mapping was computed to investigate the feasibility of this approach and, the point spread function method was used to measure the imager performance. Human leg images were acquired to experimentally validate this approach. The numerical magnetic field and specific absorption rate of a simulated leg were computed and results are within the safety limits. The B1 mapping and point spread function results showed that it is possible to conduct travelling-wave imaging experiments with good imager performance. Human leg images were also obtained with the whole-body birdcage coil for comparison purposes. The simulated and in vivo travelling-wave results of the human leg correspond very well for the signal received. A similar image signal-to-noise ratio was observed for the travelling-wave approach and the conventional one. We have demonstrated the feasibility of travelling-wave magnetic resonance imaging at 3 T and whole-body magnetic resonance systems, using a parallel-plate waveguide with standard pulse sequences and only one coil array. This extends the use of the waveguide approach to a wider range of resonant frequencies.

Vazquez, F.; Martin, R.; Marrufo, O.; Rodriguez, A. O.

2013-08-01

140

Gadolinium-enhanced magnetic resonance imaging in acute myocardial infarction  

Microsoft Academic Search

To investigate the clinical application of gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA)-enhanced magnetic resonance imaging (MRI) in the management of acute myocardial infarction (AMI), we examined 44 patients with AMI within 1 month after onset. Enhanced images were classified into 4 types: nontransmural (type 1), transmural and homogeneous (type 2), transmural and marginal (type 3), and no enhancement (type 4). Each enhancement

Chiaki Yokota; Hiroshi Nonogi; Shunichi Miyazaki; Yoichi Goto; Masakazu Maeno; Satoshi Daikoku; Akira Itoh; Kazuo Haze; Naoaki Yamada

1995-01-01

141

Utility of magnetic resonance imaging in anorectal disease  

Microsoft Academic Search

Imaging of both benign and malignant anorectal diseases has traditionally posed a challenge to clinicians, and as a result history and physical exam have been relied on heavily. CT scanning and endorectal ultrasound have become popular in assessment of anatomy and staging of tumors, but have limitations. Magnetic resonance imaging (MRI) has the capability to fi ll in the gaps

Loren Berman; Gary M Israel; Shirley M McCarthy; Jeffrey C Weinreb; Walter E Longo

142

Measurement of flow through porous media by magnetic resonance imaging  

Microsoft Academic Search

Quantitative imaging of flow through porous media is possible utilizing pulsed gradient phase encoding techniques in MRI (magnetic resonance imaging). The random directional motion of the fluid in a porous medium causes signal attenuation due to the dispersion of the phase information when velocity phase encoding gradient pulses are applied. Isolation of the effect of molecular diffusion process which is

Oezdemirel

1992-01-01

143

Magnetic resonance imaging of the shoulder: rationale and current applications  

Microsoft Academic Search

Because it can demonstrate a wide range of tissue contrast with excellent resolution, magnetic resonance (MR) imaging has revolutionized imaging in many areas of the musculoskeletal system and has generated excitement among those interested in the painful shoulder. Shoulder impingement syndrome and glenohumeral instability constitute the two major categories of shoulder derangements. Correct diagnosis requires the use of appropriate pulse

R. Gary Holt; Clyde A. Helms; Lynne Steinbach; Christian Neumann; Peter L. Munk; Harry K. Genant

1990-01-01

144

Magnetic Resonance Imaging (MRI) (For Parents)  

MedlinePLUS

... cross-sectional black-and-white images of the body. These images can be converted into three-dimensional (3-D) ... feet. In some cases, it can provide clear images of body parts that can't be seen as well ...

145

Probing Tissue Microstructure with Restriction Spectrum Imaging: Histological and Theoretical Validation  

PubMed Central

Diffusion magnetic resonance imaging (dMRI) is a powerful tool for studying biological tissue microarchitectures in vivo. Recently, there has been increased effort to develop quantitative dMRI methods to probe both length scale and orientation information in diffusion media. Diffusion spectrum imaging (DSI) is one such approach that aims to resolve such information on the basis of the three-dimensional diffusion propagator at each voxel. However, in practice only the orientation component of the propagator function is preserved when deriving the orientation distribution function. Here, we demonstrate how a straightforward extension of the linear spherical deconvolution (SD) model can be used to probe tissue orientation structures over a range (or “spectrum”) of length scales with minimal assumptions on the underlying microarchitecture. Using high b-value Cartesian q-space data on a fixed rat brain sample, we demonstrate how this “restriction spectrum imaging” (RSI) model allows for separating the volume fraction and orientation distribution of hindered and restricted diffusion, which we argue stems primarily from diffusion in the extra- and intra-neurite water compartment, respectively. Moreover, we demonstrate how empirical RSI estimates of the neurite orientation distribution and volume fraction capture important additional structure not afforded by traditional DSI or fixed-scale SD-like reconstructions, particularly in grey matter. We conclude that incorporating length scale information in geometric models of diffusion offers promise for advancing state-of-the-art dMRI methods beyond white matter into grey matter structures while allowing more detailed quantitative characterization of water compartmentalization and histoarchitecture of healthy and diseased tissue. PMID:23169482

White, Nathan S.; Leergaard, Trygve B.; D’Arceuil, Helen; Bjaalie, Jan G.; Dale, Anders M.

2012-01-01

146

Probing tissue microstructure with restriction spectrum imaging: Histological and theoretical validation.  

PubMed

Water diffusion magnetic resonance imaging (dMRI) is a powerful tool for studying biological tissue microarchitectures in vivo. Recently, there has been increased effort to develop quantitative dMRI methods to probe both length scale and orientation information in diffusion media. Diffusion spectrum imaging (DSI) is one such approach that aims to resolve such information based on the three-dimensional diffusion propagator at each voxel. However, in practice, only the orientation component of the propagator function is preserved when deriving the orientation distribution function. Here, we demonstrate how a straightforward extension of the linear spherical deconvolution (SD) model can be used to probe tissue orientation structures over a range (or "spectrum") of length scales with minimal assumptions on the underlying microarchitecture. Using high b-value Cartesian q-space data on a rat brain tissue sample, we demonstrate how this "restriction spectrum imaging" (RSI) model allows for separating the volume fraction and orientation distribution of hindered and restricted diffusion, which we argue stems primarily from diffusion in the extraneurite and intraneurite water compartment, respectively. Moreover, we demonstrate how empirical RSI estimates of the neurite orientation distribution and volume fraction capture important additional structure not afforded by traditional DSI or fixed-scale SD-like reconstructions, particularly in gray matter. We conclude that incorporating length scale information in geometric models of diffusion offers promise for advancing state-of-the-art dMRI methods beyond white matter into gray matter structures while allowing more detailed quantitative characterization of water compartmentalization and histoarchitecture of healthy and diseased tissue. PMID:23169482

White, Nathan S; Leergaard, Trygve B; D'Arceuil, Helen; Bjaalie, Jan G; Dale, Anders M

2013-02-01

147

Planar microcoil-based magnetic resonance imaging of cells  

Microsoft Academic Search

We report magnetic resonance images of biological cells and cellular aggregates obtained in vitro using high-Q factor microfabricated planar coils at 500 MHz. An image of a ?1 mm diameter frog oocyte is acquired using a 500-?m microcoil, high-resolution images of intact mouse pancreatic islets(?100 ?m size) are successfully acquired for the first time. Due to their planer nature, compatibility

C. Massin; S. Eroglu; F. Vincent; B. S. Gimi; P.-A. Besse; R. L. Magin; R. S. Popovic

2003-01-01

148

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

149

Surface Plasmon Resonance Assisted Optical Imaging  

E-print Network

band) Focusing lens Prism mounted by a rotational mounting Iris Polarizer Monochromator Single colour Metal layer (Eg. Gold) P-polarized wave illumination Sensing region Reflected wave Dielectric (eg. Air)? Surface Plasmon Resonance is a condition of energy and momentum being transformed from P-polarized

Poon, Andrew Wing On

150

Parallel magnetic resonance imaging: characterization and comparison  

E-print Network

. ........ 28 20 Resolution phantoms ........................... 30 21 The GUI ................................. 32 22 Block diagram of the toolbox ...................... 34 23 Reference image for the 3 coil data. ................... 35 24 Image reconstruction... 36 Phantom image from the 64 channel linear array data ........ 45 37 SNR and artifact power for 64 channel linear array, R = 2, 16 cen- ter lines (X axis - 1: SENSE, 2: PILS, 3: SMASH, 4: GRAPPA, 5: SPACE RIP). ............................. 46 38 SNR...

Rane, Swati Dnyandeo

2005-11-01

151

Magnetic resonance imaging simulator: a teaching tool for radiology.  

PubMed

The increasing use of magnetic resonance imaging (MRI) as a clinical modality has put an enormous burden on medical institutions to cost effectively teach MRI scanning techniques to technologists and physicians. Since MRI scanner time is a scarce resource, it would be ideal if the teaching could be effectively performed off-line. In order to meet this goal, the radiology Department at the University of Pennsylvania has designed and developed a Magnetic Resonance Imaging Simulator. The simulator in its current implementation mimics the General Electric Signa (General Electric Magnetic Resonance Imaging System, Milwaukee, WI) scanner's user interface for image acquisition. The design is general enough to be applied to other MRI scanners. One unique feature of the simulator is its incorporation of an image-synthesis module that permits the user to derive images for any arbitrary combination of pulsing parameters for spin-echo, gradient-echo, and inversion recovery pulse sequences. These images are computed in 5 seconds. The development platform chosen is a standard Apple Macintosh II (Apple Computer, Inc, Cupertino, CA) computer with no specialized hardware peripherals. The user interface is implemented in HyperCard (Apple Computer Inc, Cupertino, CA). All other software development including synthesis and display functions are implemented under the Macintosh Programmer's Workshop 'C' environment. The scan parameters, demographics, and images are tracked using an Oracle (Oracle Corp, Redwood Shores, CA) data base. Images are currently stored on magnetic disk but could be stored on optical media with minimal effort. PMID:2085559

Rundle, D; Kishore, S; Seshadri, S; Wehrli, F

1990-11-01

152

Method for nuclear magnetic resonance imaging  

DOEpatents

A method for in vivo NMR imaging of the blood vessels and organs of a patient characterized by using a dark dye-like imaging substance consisting essentially of a stable, high-purity concentration of D/sub 2/O in a solution with water.

Kehayias, J.J.; Joel, D.D.; Adams, W.H.; Stein, H.L.

1988-05-26

153

PACS-based functional Magnetic Resonance Imaging  

Microsoft Academic Search

The picture archiving and communication system (PACS) technology reaches its 10th anniversary. Retrospectively no one could foresee the impact the PACS would have to the health care enterprise, but it is common consent today, that PACS is the key technology crucial to daily clinical image operations and especially to image related basic and clinical research. During the past 10 years

Stephan G. Erberich

2003-01-01

154

Correlating Hemodynamic Magnetic Resonance Imaging with high-field Intracranial Vessel Wall Imaging in Stroke  

PubMed Central

Vessel wall magnetic resonance imaging at ultra-high field (7 Tesla) can be used to visualize vascular lesions noninvasively and holds potential for improving stroke-risk assessment in patients with ischemic cerebrovascular disease. We present the first multi-modal comparison of such high-field vessel wall imaging with more conventional (i) 3 Tesla hemodynamic magnetic resonance imaging and (ii) digital subtraction angiography in a 69-year-old male with a left temporal ischemic infarct.

Langdon, Weston; Donahue, Manus J.; van der Kolk, Anja G.; Rane, Swati; Strother, Megan K.

2014-01-01

155

Magnetic resonance imaging of interstitial laser photocoagulation  

NASA Astrophysics Data System (ADS)

We have previously demonstrated the detection of reversible and irreversible changes on MR images oflaser energy deposition and tissue heating and cooling1. It is possible to monitor and control energy deposition during interstitial laser therapy. This presentation describes some first steps toward optimizing the power and total energy deposited in various tissues in vivo, by analyzing the irreversible tissue changes and their spatial distribution as revealed by spin echo imaging. We used various power settings of an Nd.YAG laser delivered by a fiber optic inserted into several tissues (brain, muscle, liver) of anesthetized rats and rabbits. MR imaging was performed at 1.9 T. Photothermally-produced lesions were seen on both T1- and Ta-weighted images. The overall size of the lesions correlated with the magnitude of the energy applied. The MR image appearance depended not only on the laser energy but also on the way it was delivered, on the type of tissue, and the MR pulse sequence applied. While Ti-weighted images adequately demonstrated an area of tissue destruction, T2- weighted images showed a more heterogeneous and more extensive lesion which could be better correlated with the complex histological representation of these lesions. Typically, when rabbit brain, liver, and muscle had been exposed to laser power of 2.5 Watts for a range of 55 to 120 seconds, depending on the tissue, a central area of signal void was surrounded by an inner hypointensity and an outer hyperintensity on T2-weighted images. The 3D extent of the lesions was well demonstrated on multislice images, providing correlation of the affected volumes seen on MRI with volumes seen in histological or histochemical preparations. We are developing an analytical model of laser heating and its effect on MR images to assess whether heating during imaging will produce unacceptable artifacts during surgery. The effect of heating is modeled as a change in magnetization during image acquisition. The region in which the change occurs is blurred by the Fourier transform of the change in magnetization as a function of time. Thus, blurring is minimized when changes occur slowly, compared to image acquisition times. We conclude that MRI can demonstrate the 3D extent of the lesions induced by lasers and can be used to investigate and optimize the control of induced tissue change within the affected volume.

Bleier, Alan R.; Higuchi, Nobuya; Panych, Lawrence P.; Jakab, Peter D.; Hrovat, Mirko I.; Jolesz, Ferenc A.

1990-06-01

156

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

157

Magnetic resonance imaging of transplanted stem cell fate in stroke  

PubMed Central

Nowadays, scientific findings in the field of regeneration of nervous system have revealed the possibility of stem cell based therapies for damaged brain tissue related disorders like stroke. Furthermore, to achieve desirable outcomes from cellular therapies, one needs to monitor the migration, engraftment, viability, and also functional fate of transplanted stem cells. Magnetic resonance imaging is an extremely versatile technique for this purpose, which has been broadly used to study stroke and assessment of therapeutic role of stem cells. In this review we searched in PubMed search engine by using following keywords; “Stem Cells”, “Cell Tracking”, “Stroke”, “Stem Cell Transplantation”, “Nanoparticles”, and “Magnetic Resonance Imaging” as entry terms and based on the mentioned key words, the search period was set from 1976 to 2012. The main purpose of this article is describing various advantages of molecular and magnetic resonance imaging of stem cells, with focus on translation of stem cell research to clinical research. PMID:25097631

Aghayan, Hamid Reza; Soleimani, Masoud; Goodarzi, Parisa; Norouzi-Javidan, Abbas; Emami-Razavi, Seyed Hasan; Larijani, Bagher; Arjmand, Babak

2014-01-01

158

Nuclear magnetic resonance imaging at microscopic resolution  

NASA Astrophysics Data System (ADS)

Resolution limits in NMR imaging are imposed by bandwidth considerations, available magnetic gradients for spatial encoding, and signal to noise. This work reports modification of a clinical NMR imaging device with picture elements of 500 × 500 × 5000 ?m to yield picture elements of 50 × 50 × 1000 ?m. Resolution has been increased by using smaller gradient coils permitting gradient fields >0.4 mT/cm. Significant improvements in signal to noise are achieved with smaller rf coils, close attention to choice of bandwidth, and signal averaging. These improvements permit visualization of anatomical structures in the rat brain with an effective diameter of 1 cm with the same definition as is seen in human imaging. The techniques and instrumentation should open a number of basic sciences such as embryology, plant sciences, and teratology to the potentials of NMR imaging.

Johnson, G. Allan; Thompson, Morrow B.; Gewalt, Sally L.; Hayes, Cecil E.

159

Bayesian Methods in Functional Magnetic Resonance Imaging  

E-print Network

is to develop useful models of single-subject task- related activation in order to develop effective imaging biomarkers. Each subject completed a Stroop exam in an MRI scanner. That is, the subject is shown a word

Jones, Galin

160

Instrumentation for parallel magnetic resonance imaging  

E-print Network

of arrays of sensors. In parallelization, multiple MR scanners (or multiple sensors) are used to collect images from different samples simultaneously. This allows for an increase in the throughput, not the inherent speed, of the MR experiment. Parallel...

Brown, David Gerald

2007-04-25

161

Magnetic resonance imaging findings in Axenfeld-Rieger syndrome  

PubMed Central

Axenfeld–Rieger syndrome (ARS) is a genetic disorder representing a disease spectrum resulting from neural crest cell maldevelopment. Glaucoma is a common complication from the incomplete formation of the iridocorneal angle structures. Neural crest cells also form structures of the forebrain and pituitary gland, dental papillae, aortic arch walls, genitalia, and long bones; therefore, patients with ARS manifest a wide range of systemic findings. To our knowledge, detailed magnetic resonance imaging findings have not been previously reported. We report a case of a 19-month-old Indian male diagnosed with ARS with emphasis on magnetic resonance imaging findings of the globes, brain, teeth, and skull base. PMID:23723681

Whitehead, Matthew T; Choudhri, Asim F; Salim, Sarwat

2013-01-01

162

Magnetic resonance imaging for lung cancer screen.  

PubMed

Lung cancer is the leading cause of cancer related death throughout the world. Lung cancer is an example of a disease for which a large percentage of the high-risk population can be easily identified via a smoking history. This has led to the investigation of lung cancer screening with low-dose helical/multi-detector CT. Evidences suggest that early detection of lung cancer allow more timely therapeutic intervention and thus a more favorable prognosis for the patient. The positive relationship of lesion size to likelihood of malignancy has been demonstrated previously, at least 99% of all nodules 4 mm or smaller are benign, while noncalcified nodules larger than 8 mm diameter bear a substantial risk of malignancy. In the recent years, the availability of high-performance gradient systems, in conjunction with phased-array receiver coils and optimized imaging sequences, has made MR imaging of the lung feasible. It can now be assumed a threshold size of 3-4 mm for detection of lung nodules with MRI under the optimal conditions of successful breath-holds with reliable gating or triggering. In these conditions, 90% of all 3-mm nodules can be correctly diagnosed and that nodules 5 mm and larger are detected with 100% sensitivity. Parallel imaging can significantly shorten the imaging acquisition time by utilizing the diversity of sensitivity profile of individual coil elements in multi-channel radiofrequency receive coil arrays or transmit/receive coil arrays to reduce the number of phase encoding steps required in imaging procedure. Compressed sensing technique accelerates imaging acquisition from dramatically undersampled data set by exploiting the sparsity of the images in an appropriate transform domain. With the combined imaging algorithm of parallel imaging and compressed sensing and advanced 32-channel or 64-channel RF hardware, overall imaging acceleration of 20 folds or higher can then be expected, ultimately achieve free-breathing and no ECG gating acquisitions in lung cancer MRI screening. Further development of protocols, more clinical trials and the use of advanced analysis tools will further evaluate the real significance of lung MRI. PMID:25276380

Wang, Yi-Xiang J; Lo, Gladys G; Yuan, Jing; Larson, Peder E Z; Zhang, Xiaoliang

2014-09-01

163

Magnetic resonance imaging for lung cancer screen  

PubMed Central

Lung cancer is the leading cause of cancer related death throughout the world. Lung cancer is an example of a disease for which a large percentage of the high-risk population can be easily identified via a smoking history. This has led to the investigation of lung cancer screening with low-dose helical/multi-detector CT. Evidences suggest that early detection of lung cancer allow more timely therapeutic intervention and thus a more favorable prognosis for the patient. The positive relationship of lesion size to likelihood of malignancy has been demonstrated previously, at least 99% of all nodules 4 mm or smaller are benign, while noncalcified nodules larger than 8 mm diameter bear a substantial risk of malignancy. In the recent years, the availability of high-performance gradient systems, in conjunction with phased-array receiver coils and optimized imaging sequences, has made MR imaging of the lung feasible. It can now be assumed a threshold size of 3-4 mm for detection of lung nodules with MRI under the optimal conditions of successful breath-holds with reliable gating or triggering. In these conditions, 90% of all 3-mm nodules can be correctly diagnosed and that nodules 5 mm and larger are detected with 100% sensitivity. Parallel imaging can significantly shorten the imaging acquisition time by utilizing the diversity of sensitivity profile of individual coil elements in multi-channel radiofrequency receive coil arrays or transmit/receive coil arrays to reduce the number of phase encoding steps required in imaging procedure. Compressed sensing technique accelerates imaging acquisition from dramatically undersampled data set by exploiting the sparsity of the images in an appropriate transform domain. With the combined imaging algorithm of parallel imaging and compressed sensing and advanced 32-channel or 64-channel RF hardware, overall imaging acceleration of 20 folds or higher can then be expected, ultimately achieve free-breathing and no ECG gating acquisitions in lung cancer MRI screening. Further development of protocols, more clinical trials and the use of advanced analysis tools will further evaluate the real significance of lung MRI.

Lo, Gladys G.; Yuan, Jing; Larson, Peder E. Z.

2014-01-01

164

Combined magnetic resonance and bioluminescence imaging of live mice.  

PubMed

We perform combined magnetic resonance and bioluminescence imaging of live mice for the purpose of improving the accuracy of bioluminescence tomography. The imaging is performed on three live nude mice in which tritium-powered light sources are surgically implanted. High-resolution magnetic resonance images and multispectral, multiview bioluminescence images are acquired in the same session. An anatomical model is constructed by segmenting the magnetic resonance images for all major tissues. The model is subsequently registered with nonlinear transformations to the 3-D light exittance (exiting intensity) surface map generated from the luminescence images. A Monte Carlo algorithm, along with a set of tissue optical properties obtained from in vivo measurements, is used to solve the forward problem. The measured and simulated light exittance images are found to differ by a factor of up to 2. The greatest cause of this moderate discrepancy is traced to the small errors in source positioning, and to a lesser extent to the optical properties used for the tissues. Discarding the anatomy and using a homogeneous model leads to a marginally worse agreement between the simulated and measured data. PMID:17614726

Allard, Mathieu; Côté, Daniel; Davidson, Lorinda; Dazai, Jun; Henkelman, R Mark

2007-01-01

165

Travelling Wave Magnetic Resonance Imaging at 3 Tesla  

E-print Network

Waveguides have been successfully used to generate magnetic resonance images at 7 T with whole-body systems. The bore limits the magnetic resonance signal transmitted because its specific cut-off frequency is greater than the majority of resonant frequencies. This restriction can be overcome by using a parallel-plate waveguide whose cut-off frequency is zero for the transversal electric modes and it can propagate any frequency. To investigate the potential benefits for whole-body imaging at 3 T, we compare numerical simulations at 1.5 T, 3 T, 7 T, and 9 T via the propagation of the parallel-plate waveguide principal mode filled with a cylindrical phantom and two surface coils. B1 mapping was computed to investigate the feasibility of this approach at 3T. The point spread function method was used to measure the imager performance for the traveling-wave magnetic resonance imaging experiment. Human leg images were acquired to experimentally validate this approach. The principal mode shows very little field magni...

Vazquez, F; Marrufo, O; Rodriguez, A O

2013-01-01

166

Neural network diagnosis of avascular necrosis from magnetic resonance images  

NASA Astrophysics Data System (ADS)

We have explored the use of artificial neural networks to diagnose avascular necrosis (AVN) of the femoral head from magnetic resonance images. We have developed multi-layer perceptron networks, trained with conjugate gradient optimization, which diagnose AVN from single sagittal images of the femoral head with 100% accuracy on the training data and 97% accuracy on test data. These networks use only the raw image as input (with minimal preprocessing to average the images down to 32 X 32 size and to scale the input data values) and learn to extract their own features for the diagnosis decision. Various experiments with these networks are described.

Manduca, Armando; Christy, Paul S.; Ehman, Richard L.

1993-09-01

167

Transformation in mandibular imaging with sweep imaging with fourier transform magnetic resonance imaging  

PubMed Central

Objective Current imaging techniques are often sub-optimal for the detection of mandibular invasion by squamous cell carcinoma. The aim of this study was to determine the feasibility of a magnetic resonance imaging (MRI) based technique known as Sweep Imaging with Fourier Transform (SWIFT) to visualize the structural changes of intra-mandibular anatomy during invasion. Design Descriptive case study Setting Tertiary academic institution Method Two specimens from patients with oral carcinoma who underwent segmental mandibulectomy were imaged using a 9.4 Tesla Varian MRI system. The SWIFT images were correlated with histological sections. Results The SWIFT technique with in vitro specimens produced images with sufficient resolution (156–273) and contrast to allow accurate depiction of tumor invasion of cortical and medullary bone. Both specimens had histopathological evidence of mandibular invasion with tumor. A high degree of correlation was found between MR images and histopathologic findings. Conclusion SWIFT MRI offers three-dimensional assessment of cortical and medullary bone in fine detail with excellent qualitative agreement with histopathology. MR imaging with the SWIFT technique demonstrates great potential to identify mandibular invasion by oral carcinoma. PMID:21930980

Kendi, Ayse Tuba Karagulle; Khariwala, Samir S.; Zhang, Jinjin; Idiyatullin, Djaudat S.; Corum, Curtis A.; Michaeli, Shalom; Pambuccian, Stefan E.; Garwood, Michael; Yueh, Bevan

2012-01-01

168

Pattern recognition on brain magnetic resonance imaging in alpha dystroglycanopathies.  

PubMed

Alpha dystroglycanopathies are heterogeneous group of disorders both phenotypically and genetically. A subgroup of these patients has characteristic brain imaging findings. Four patients with typical imaging findings of alpha dystroglycanopathy are reported. Phenotypic features included: global developmental delay, contractures, hypotonia and oculomotor abnormalities in all. Other manifestations were consanguinity (3), seizures (3), macrocephaly (1), microcephaly (3), retinal changes (2) and hypogenitalism (2). Magnetic resonance imaging (MRI) of the brain revealed polymicrogyria, white matter changes, pontine hypoplasia, and subcortical cerebellar cysts in all the patients, ventriculomegaly, callosal abnormalities, and absent septum pellucidum in two and Dandy -Walker variant malformation in three. Magnetic resonace imaging of the first cousin of one the patient had the same characteristic imaging features. Brain imaging findings were almost identical despite heterogeneity in clinical presentation and histopathological features. Pattern recognition of MR imaging features may serve as a clue to the diagnosis of alpha dystroglycanopathy. PMID:20644281

Bindu, Parayil S; Gayathri, Narayanappa; Bharath, Rose D; Mahadevan, Anita; Sinha, Sanjib; Taly, A B

2010-01-01

169

Surface Plasmon Resonance Imaging SPR imaging is a label-free  

E-print Network

Surface Plasmon Resonance Imaging SPR imaging is a label-free method for monitoring bioaffinityA (2003). #12;Screening of Biomolecular Arrays with SPR Imaging DNA/DNA Protein/DNA RNA/DNA Protein measures reflectivity changes at a fixed angle and wavelength. #12;Flow Cell Gold Film Narrow Band

170

Roadmap: Radiologic Imaging Sciences -Magnetic Resonance Imaging (with AAS Radiologic Technology) -  

E-print Network

Roadmap: Radiologic Imaging Sciences - Magnetic Resonance Imaging (with AAS Radiologic Technology) - Bachelor of Radiologic and Imaging Sciences Technology [RE-BRIT-RIS-MRRT] Regional College Catalog Year and Physiology I for Allied Health (3) and BSCI 11020 Anatomy and Physiology II for Allied Health (3) or BSCI

Sheridan, Scott

171

Magnetic resonance imaging of the pediatric brain  

SciTech Connect

The atlas presents sequences of MRI sections parallel to the orbito-meatal plane in children from birth through the age of sixteen years. Each child was studied horizontally and sagitally and three-dimensional brain images were reconstructed to facilitate accurate identification of sulci and gyri. The images show crucial aspects of brain development such as the constancy of the brain stem and primitive brain from birth onward; the development of the telencephalon, characterized by deepening of sulci and growth of the cerebral cortex surface; and the different stages of white matter myelinization.

Salamon, G.; Raynaud, C.; Regis, J.; Rumeau, C.

1990-01-01

172

Magnetic resonance imaging with an optical atomic magnetometer.  

PubMed

We report an approach for the detection of magnetic resonance imaging without superconducting magnets and cryogenics: optical atomic magnetometry. This technique possesses a high sensitivity independent of the strength of the static magnetic field, extending the applicability of magnetic resonance imaging to low magnetic fields and eliminating imaging artifacts associated with high fields. By coupling with a remote-detection scheme, thereby improving the filling factor of the sample, we obtained time-resolved flow images of water with a temporal resolution of 0.1 s and spatial resolutions of 1.6 mm perpendicular to the flow and 4.5 mm along the flow. Potentially inexpensive, compact, and mobile, our technique provides a viable alternative for MRI detection with substantially enhanced sensitivity and time resolution for various situations where traditional MRI is not optimal. PMID:16885210

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

2006-08-22

173

Use of nuclear magnetic resonance imaging to study asphalt  

SciTech Connect

Magnetic resonance imaging (MRI) combines the basic principles of magnetic resonance with spatial encoding to obtain images of the distribution of fluids in samples. Because of the sensitivity of the hydrogen nucleus in NMR and because of its favorable relaxation times, water is the fluid most often imaged. This favorable aspect suggests that MRI might be used to obtain valuable information about water susceptibility and moisture damage mechanisms in asphalt. However, it has only been fairly recently that nonmedical applications of MRI have been increasing partly because of improvements in instrumentation and speed of data acquisition. MRI has been used to measure the distribution of fluids in porous rocks, ceramics, wood, other plant materials, synthetic polymers, solvent diffusion in polymers, coals, and bonding of adhesives. MRI measurements were made using spin echo or three dimensional imaging techniques.

Miknis, F.P.; Netzel, D.A. [Western Research Institute, Laramie, WY (United States)

1996-12-31

174

Magnetic resonance imaging for prostate cancer clinical application  

PubMed Central

As prostate cancer is a biologically heterogeneous disease for which a variety of treatment options are available, the major objective of prostate cancer imaging is to achieve more precise disease characterization. In clinical practice, magnetic resonance imaging (MRI) is one of the imaging tools for the evaluation of prostate cancer, the fusion of MRI or dynamic contrast-enhanced MRI (DCE-MRI) with magnetic resonance spectroscopic imaging (MRSI) is improving the evaluation of cancer location, size, and extent, while providing an indication of tumor aggressiveness. This review summarizes the role of MRI in the application of prostate cancer and describes molecular MRI techniques (including MRSI and DCE-MRI) for aiding prostate cancer management. PMID:23592906

Li, Bing; Du, Yong; Huang, Yayong; Meng, Jun; Xiao, Dongmei

2013-01-01

175

A variable torque motor compatible with magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

High magnetic fields used in magnetic resonance imaging (MRI) do not allow the employment of conventional motors due to various incompatibility issues. This paper reports on a new motor that can operate in or near high field magnets used for MRI. The motor was designed to be operational with the MRI equipment and could be used in a rotating imaging gantry inside the magnet designed for dual modality imaging. Furthermore, it could also be used for image guided robotic interventional procedures inside a MRI system if so desired. The prototype motor was developed using magnetic resonance (MR) compatible materials, and its functionality with MR imaging was evaluated experimentally by measuring the performance of the motor and its effect on the MR image quality. Since in our application, namely, single photon emission tomography, the motor has to perform precise stepping of the gantry in small angular steps the most important parameter is the start-up torque. The experimental results showed that the motor has a start-up torque up to 1.37 Nm and rotates at 196 rpm when a constant voltage difference of 12 V is applied at a magnetic field strength of 1 T. The MR image quality was quantified by measuring the signal-to-noise of images acquired under different conditions. The results presented here indicate that the motor is MR compatible and could be used for rotating an imaging gantry or a surgical device inside the magnet.

Roeck, W. W.; Ha, S.-H.; Farmaka, S.; Nalcioglu, O.

2009-04-01

176

Magnetic resonance imaging in pantothenate kinase-2-associated neurodegeneration  

PubMed Central

Pantothenate kinase-2-associated neurodegeneration (PKAN) is a rare autosomal recessive pediatric neurodegenerative disorder characterized by rigidity, dystonia, impaired postural reflexes, and progressive dementia. On T2-weighted magnetic resonance imaging images, marked low signal intensity is seen in the globus pallidus. This low signal intensity surrounds a central region of high signal intensity in the anteromedial globus pallidus, giving an eye-of-the-tiger appearance. PMID:22837773

Singh, Paramdeep; Saggar, Kavita; Kaur, Maneet; Pannu, Davinder Singh

2012-01-01

177

Safety and Monitoring for Cardiac Magnetic Resonance Imaging  

Microsoft Academic Search

Because of unsurpassed soft tissue resolution, lack of ionizing radiation, and multi-planar imaging capability, magnetic resonance\\u000a imaging (MRI) has become an important tool in the evaluation and treatment of cardiovascular disorders. However, an increasing\\u000a proportion of patients with cardiovascular disease have higher acuity of disease and ferromagnetic implants with potential\\u000a for interaction with the MRI environment. Familiarity with each device

Saman Nazarian; Henry R. Halperin; David A. Bluemke

178

Nuclear magnetic resonance imaging with hyperpolarised helium-3  

Microsoft Academic Search

SummaryBackground Magnetic resonance imaging (MRI) relies on magnetisation of hydrogen nuclei (protons) of water molecules in tissue as source of the signal. This technique has been valuable for studying tissues that contain significant amounts of water, but biological settings with low proton content, notably the lungs, are difficult to image. We report use of spin-polarised helium-3 for lung MRI.Methods A

M Ebert; T Grossmann; W Heil; E. W Otten; R Surkau; M Thelen; M Leduc; P Bachert; M. V Knopp; L. R Schad

1996-01-01

179

Neurophysiological Architecture of Functional Magnetic Resonance Images of Human Brain  

Microsoft Academic Search

We investigated large-scale systems organization of the whole human brain using functional magnetic resonance imaging (fMRI) data acquired from healthy volunteers in a no-task or 'resting' state. Images were parcellated using a prior anatomical template, yielding regional mean time series for each of 90 regions (major cortical gyri and subcortical nuclei) in each subject. Significant pairwise func- tional connections, defined

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

2005-01-01

180

Gated magnetic resonance imaging of congenital cardiac malformations  

SciTech Connect

Magnetic resonance (MR) images of a variety of cardiac malformations in 19 patients aged 1 week to 33 years were obtained using pulse plethysmographic- or ECG-gated spin echo pulse sequences. Coronal, axial, and sagittal images displaying intracardiac structures with excellent spatial and contrast resolution were acquired during systole or diastole. It is concluded that MR will be a valuable noninvasive method of diagnosing congenital heart disease.

Fletcher, B.D.; Jocobstein, M.D.; Nelson, A.D.; Riemenschneider, T.A.; Alfidi, R.J.

1984-01-01

181

Pictorial review: magnetic resonance imaging of colonic diverticulitis  

Microsoft Academic Search

Magnetic resonance imaging (MRI) is rapidly emerging as a useful imaging modality for the evaluation of the gastrointestinal\\u000a tract. Increasingly rapid sequences and improving hardware have significantly improved the visualisation of diseases of the\\u000a colon. MRI has a major advantage over CT in that there is no ionising radiation. In our institution, MRI has increasingly\\u000a been used as a complimentary

Orla Buckley; Tony Geoghegan; Grainne McAuley; Thara Persaud; Faisal Khosa; William C. Torreggiani

2007-01-01

182

Automated Analysis of Craniofacial Morphology Using Magnetic Resonance Images  

Microsoft Academic Search

Quantitative analysis of craniofacial morphology is of interest to scholars working in a wide variety of disciplines, such as anthropology, developmental biology, and medicine. T1-weighted (anatomical) magnetic resonance images (MRI) provide excellent contrast between soft tissues. Given its three-dimensional nature, MRI represents an ideal imaging modality for the analysis of craniofacial structure in living individuals. Here we describe how T1-weighted

M. Mallar Chakravarty; Rosanne Aleong; Gabriel Leonard; Michel Perron; G. Bruce Pike; Louis Richer; Suzanne Veillette; Zdenka Pausova; Tomás Paus; Tianzi Jiang

2011-01-01

183

Multilayer phased microcoil array for magnetic resonance imaging  

Microsoft Academic Search

We present for the first time wirebonded microcoils arranged in a planar phased-array configuration for large field of view (FOV) microscale magnetic resonance imaging (MRI) of 2D samples. The phased array consists of seven microcoils providing a sensitive area of 18.3 mm 2 . We demonstrate successful high-resolution imaging of a water phantom with 16 x 16 ?? m 2

O. G. Gruschke; L. Clad; N. Baxan; K. Kratt; M. Mohmmadzadeh; D. von Elverfeldt; A. Peter; J. Hennig; V. Badilita; U. Wallrabe; J. G. Korvink

2011-01-01

184

Very low field magnetic resonance imaging with spintronic sensors  

NASA Astrophysics Data System (ADS)

A very low field magnetic resonance imaging (MRI) setup based on magnetoresistive-superconducting mixed sensors is presented. A flux transformer is used to achieve coupling between the sample to image and the mixed sensor. The novel detector was implemented in a spin echo MRI experiment, exposing the mixed sensor to RF pulses without use of any RF switch. The performance of the novel detector is given in terms of signal-to-noise ratio and is compared with classical tuned coils.

Herreros, Q.; Dyvorne, H.; Campiglio, P.; Jasmin-Lebras, G.; Demonti, A.; Pannetier-Lecoeur, M.; Fermon, C.

2013-09-01

185

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

186

Mathematical challenges in magnetic resonance imaging (MRI)  

E-print Network

deposition (patient safety) Challenge: no general solution to Bloch equation = forward model selective) · Image reconstruction Nonuniform fast Fourier transform (NUFFT) Regularization issues view of MRI Applied field BBB(rrr,t) Patient magnetization pattern MMM(rrr,t) RF coil(s) (Faraday

Fessler, Jeffrey A.

187

Bachelor of Science, Radiologic Sciences, Magnetic Resonance Imaging Emphasis, Name ID# Date  

E-print Network

Bachelor of Science, Radiologic Sciences, Magnetic Resonance Imaging Emphasis, 2012-2013 Name ID Pharmacology and Contrast Medias RADSCI 430 Comparative Sectional Imaging RADSCI 440 Principles of Magnetic Resonance Imaging I RADSCI 440L Principles of Magnetic Resonance Imaging I Lab RADSCI 441 Procedural Case

Barrash, Warren

188

Bachelor of Science, Radiologic Sciences, Magnetic Resonance Imaging Emphasis, Name ID# Date  

E-print Network

Bachelor of Science, Radiologic Sciences, Magnetic Resonance Imaging Emphasis, 2014-2015 Name ID Pharmacology and Contrast Medias RADSCI 430 Comparative Sectional Imaging RADSCI 440 Principles of Magnetic Resonance Imaging I RADSCI 440L Principles of Magnetic Resonance Imaging I Lab RADSCI 441 Procedural Case

Barrash, Warren

189

Bachelor of Science, Radiologic Sciences, Magnetic Resonance Imaging Emphasis, Name ID# Date  

E-print Network

Bachelor of Science, Radiologic Sciences, Magnetic Resonance Imaging Emphasis, 2013-2014 Name ID Pharmacology and Contrast Medias RADSCI 430 Comparative Sectional Imaging RADSCI 440 Principles of Magnetic Resonance Imaging I RADSCI 440L Principles of Magnetic Resonance Imaging I Lab RADSCI 441 Procedural Case

Barrash, Warren

190

The Evolving Role of Diffusion Magnetic Resonance Imaging in Movement Disorders  

PubMed Central

Significant advances have allowed diffusion MRI (dMRI) to evolve into a powerful tool in the field of movement disorders that can be used to study disease states and connectivity between brain regions. dMRI represents a promising potential biomarker for Parkinson’s disease and other forms of parkinsonism, and may allow for the distinction of different forms of parkinsonism. Techniques such as tractography have contributed to our current thinking regarding the pathophysiology of dystonia and possible mechanisms of penetrance. dMRI measures could potentially assist in monitoring disease progression in Huntington’s disease, and in uncovering the nature of the processes and structures involved the development of essential tremor. The ability to represent structural connectivity in vivo also makes dMRI an ideal adjunctive tool for the surgical treatment of movement disorders. We will review recent studies utilizing dMRI in movement disorders research and present the current state of the science as well as future directions. PMID:24046183

Hess, Christopher W.; Ofori, Edward; Akbar, Umer; Okun, Michael S.; Vaillancourt, David E.

2013-01-01

191

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

192

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

E-print Network

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

Fessler, Jeffrey A.

193

Detection of Prostate Cancer from Multiparametric Magnetic Resonance Imaging  

E-print Network

050 051 052 053 Detection of Prostate Cancer from Multiparametric Magnetic Resonance Imaging Anonymous (MRI) based technique of detecting prostate cancer is developed. A machine learning algorithm, based. The classifier is trained to detect prostate cancer in the peripheral zone and using the trained classifier

de Freitas, Nando

194

The use of magnetic resonance imaging in exertional compartment syndromes  

Microsoft Academic Search

This prospective, double-blind study was carried out to assess the usefulness of magnetic resonance imaging (MRI) as a noninvasive method in the diagnosis of chronic compartment syndrome (CCS). As well, a new radiopharmaceutical known as methoxy isobutyl isoni trile that has been shown to be taken up by muscle in direct proportion to its blood flow was used to illustrate

A. Amendola; C. H. Rorabeck; D. Vellett; W. Vezina; B. Rutt; Linda Nott

1990-01-01

195

Magnetic resonance imaging to diagnose breast implant rupture  

Microsoft Academic Search

The purpose of this study was to prospectively evaluate the diagnostic accuracy of magnetic resonance imaging (MRI) as a method to discover an implant rupture in patients with breast augmentation or reconstruction. From January 1997 to February 1998, 20 breast implants in 12 patients (mean age 52.5 years) were removed surgically. Indications included local pain after reconstructive breast surgery (n=5

V. Wedler; C. Meuli-Simmen; R. Kubik-Huch; W. Künzi; V. Meyer

2002-01-01

196

Mediterranean Diet and Magnetic Resonance ImagingAssessed Cerebrovascular Disease  

E-print Network

of the previously reported relationship between Mediterranean-type diet (MeDi) and Alzheimer's disease (AD). WeMediterranean Diet and Magnetic Resonance Imaging­Assessed Cerebrovascular Disease Nikolaos in Alzheimer's Disease and the Aging Brain, University of California at Davis, Sacramento, CA 2Gertrude H

197

Hypothalamic Hamartoma: Comparison of Clinical Presentation and Magnetic Resonance Images  

Microsoft Academic Search

Background\\/Aims: Hypothalamic hamartoma (HH) is one of the most frequent causes of organic central precocious puberty (CPP). We compared the clinical presentation and the magnetic resonance images (MRI) of 19 patients with HH aged 5.7 ± 4.1 (SD) years at the first endocrine evaluation. They had isolated CPP (group 1, n = 9), CPP plus gelastic seizures (group 2, n

C. Debeneix; M. Bourgeois; C. Trivin; C. Sainte-Rose; R. Brauner; E. Strehl; S. Venturoli; R. Paradisi; E. Porcu; R. Mühlenberg; C. Kim; S. Wüller; R. Pfäffle; G. Heimann; M. Mauri; R. Alfayate; M. L. Graells; C. Miralles; M. Tanaka; S. Nakaya; M. Watanabe; T. Tateishi; H. Shimizu; S. Kobayashi

2001-01-01

198

NMR (Nuclear Magnetic Resonance) Imaging of Human Coronary Arteries.  

National Technical Information Service (NTIS)

Nuclear magnetic resonance imaging (MRI) is being studied as a method to detect the presence of atherosclerotic lesions in the coronary arteries of humans in a totally non-invasive manner, and to characterize the anatomic features of these lesions. For th...

L. Kaufman, L. Crooks, C. Higgins, J. Hale

1984-01-01

199

Dynamic Magnetic Resonance Perfusion Imaging of Brain Tumors  

Microsoft Academic Search

In this paper, we review the technique of contrast- enhanced magnetic resonance (MR) perfusion imaging of brain neoplasms, with an emphasis on its clinical applica- tions and utility. We start with a discussion of MR perfu- sion techniques available today and their relative merits and shortcomings. Next, the ability of MR perfusion to provide a preoperative assessment of tumor histology

DIEGO J. COVARRUBIAS; BRUCE R. ROSEN; MICHAEL H. LEVa

200

Remote auscultatory patient monitoring during magnetic resonance imaging  

Microsoft Academic Search

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

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

1991-01-01

201

Modeling Left Ventricle Wall Motion Using Tagged Magnetic Resonance Imaging  

E-print Network

A two-parameter computational model is proposed for the study of the regional motion of the left ventricle (LV) wall using tagged magnetic resonance imaging (tMRI) data. In this model, the LV wall motion is mathematically decomposed into two...

Alenezy, Mohammed D.

2009-04-17

202

Magnetic Resonance Imaging Correlates of Depression After Ischemic Stroke  

Microsoft Academic Search

Background: Depression affects up to 40% of patients with ischemic stroke. The relationship between site and size of brain infarcts and poststroke depression is still not well characterized. Further possible contribution and in- teraction of white matter lesions and brain atrophy has not been studied previously. We conducted a magnetic resonance image-based study of the radiologic corre- lates of depression

Risto Vataja; Tarja Pohjasvaara; Antero Leppavuori; Riitta Mantyla; Hannu Juhani Aronen; Oili Salonen; Markku Kaste; Timo Erkinjuntti

2001-01-01

203

A Quantum Mechanical Review of Magnetic Resonance Imaging  

E-print Network

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

Odaibo, Stephen G

2012-01-01

204

Towards a New Framework for Simulating Magnetic Resonance Imaging  

Microsoft Academic Search

Optimization of magnetic resonance imaging (MRI) protocols in the presence of complex anatomical structures and motions is an ongoing challenge, often calling for the use of simulation environments. Still, MRI simulations are traditionally hampered by the practical diculties of describing anatomically realistic objects and their motions in a compact but sucien tly resolved manner. Inspired by the poweful nite element

Paul Simedrea; Luca Antiga; David A. Steinman

205

Functional Connectivity Magnetic Resonance Imaging Classification of Autism  

ERIC Educational Resources Information Center

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

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

2011-01-01

206

Magnetic Resonance Imaging and Moisture Content Profiles of Drying Concrete  

Microsoft Academic Search

The spatial distribution of moisture in concrete, along with the role this moisture plays in various modes of deterioration, is of fundamental importance to the understanding of concrete behaviour. In this paper a new magnetic resonance imaging technique is utilized for the first time to obtain drying profiles of concrete with sub-millimetre resolution. This technique permits observation of the drying

S. D Beyea; B. J Balcom; T. W Bremner; P. J Prado; D. P Green; R. L Armstrong; P. E Grattan-Bellew

1998-01-01

207

Tagged magnetic resonance imaging of the heart: a survey  

Microsoft Academic Search

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

Leon Axel; Albert Montillo; Daniel Kim

2005-01-01

208

GEOMETRIC COMPUTATION OF HUMAN GYRIFICATION INDEXES FROM MAGNETIC RESONANCE IMAGES  

E-print Network

GEOMETRIC COMPUTATION OF HUMAN GYRIFICATION INDEXES FROM MAGNETIC RESONANCE IMAGES By Shu Su Tonya;Geometric Computation of Gyrification Indexes Chiu-Yen Kao 1 Geometric Computation of Human Gyrification Computation of Gyrification Indexes Chiu-Yen Kao 2 Abstract Human Brains are highly convoluted surfaces

209

Manganese encephalopathy: utility of early magnetic resonance imaging  

Microsoft Academic Search

The use of magnetic resonance imaging (MRI) provides visual evidence of cerebral deposits of paramagnetic metals. The usefulness of MRI is described in connection with the manganese poisoning of a 44 year old arc welder who had been engaged in the repair and recycling of railroad track made of manganese steel alloy.

K Nelson; J Golnick; T Korn; C Angle

1993-01-01

210

Low Cost Magnetic Resonance Imaging-Compatible Stepper  

E-print Network

female, 29.2 6 3.9 yr old) showing significant exercise-induced changes in heart rate Manuscript received echocardiography and pharmacological stress magnetic resonance imaging (MRI). MRI is the most accu- rate be adjusted for different body sizes. Pilot tests were con- ducted with 5 healthy subjects (3 male and 2

Chesler, Naomi C.

211

SOUND ISOLATION DESIGN FOR A MAGNETIC RESONANCE IMAGING SYSTEM (MRI)  

Microsoft Academic Search

Background: This Noise control case study is about problems, constraints and design solutions for a proposed magnetic resonance imaging system (MRI) installation in an existing medical research facility. This is a companion paper to a structural vibration control case study on the same installation presented by this author at ICSV10 in 2003. Objective: Manufacturer's data indicated that airborne sound level

Jack B. Evans

212

Maternal phenylketonuria: Magnetic resonance imaging of the brain in offspring  

Microsoft Academic Search

Phenylketonuria (PKU) produces white matter changes identifiable by magnetic resonance imaging. These changes occur postnatally. Offspring of untreated mothers with PKU also have a brain effect, expressed as microcephaly and mental retardation. This effect occurs prenatally. To determine whether the white matter changes seen in PKU are also present in maternal PKU offspring, despite the different developmental stages of exposure

Harvey L. Levy; Deborah Lobbregt; Patrick D. Barnes; Tina Young Poussaint

1996-01-01

213

MINI REVIEW Magnetic Resonance Imaging of the Retina  

E-print Network

MINI REVIEW Magnetic Resonance Imaging of the Retina: From Mice to Men Timothy Q. Duong* This mini-human primate, and human retinas. These techniques include T1- and T2-weighted anatomical, diffusion, blood flow. Applications to study the retinas in diabetic retinopathy, glaucoma, and retinal degener- ation are also

Duong, Timothy Q.

214

Magnetic Resonance Imaging with Composite (Dual) Gradients  

PubMed Central

The tradeoff between gradient performance factors, size of the imaging region, and physiological factors such as nerve stimulation typically leads to compromises in gradient design and ultimately suboptimal imaging performance. Local gradient systems can add some performance flexibility, but are cumbersome to set up and remove. In nearly all conventional MRI systems, the use of local gradients precludes the use of the more homogeneous whole body gradients. This paper presents the concept of dynamically selectable composite gradient systems where local gradients and whole body gradients can be selected independently and simultaneously. The relative performance of whole body, insert, and composite gradients is predicted for echoplanar (EPI), turbo spin echo (TSE), and steady state free precession (SSFP). A realization of the concept is presented. PMID:20160925

Parker, Dennis L.; Goodrich, K. Craig; Hadley, J. Rock; Kim, Seong-Eun; Moon, Sung M.; Chronik, Blaine A.; Fontius, Ulrich; Schmitt, Franz

2009-01-01

215

Magnetic resonance imaging of the gastrointestinal tract.  

PubMed

Comprehensive bowel examination results from the combined use of T2-weighted single-shot and breath hold T1-weighted gradient echo, minus/plus fat suppression, and gadolinium-enhanced 3D gradient echo (3D VIBE, T1 FAME, 3D THRIVE). Gadolinium-enhanced imaging should be performed dynamically, but the venous 60- to 90-second delayed phase images with fat suppression are generally the most valuable. Removal of fat signal for detection of enhancing normal and abnormal structures is critical. Newly available True-FISP (FIESTA, BFFE) sequences obtained in the 2D form can be very helpful in delineation of bowel wall pathology and overall bowel anatomy, particularly when combined with a water-based intraluminal distending agent. Advantages include rapid acquisition, high signal-to-noise, and motion insensitivity. Generalized protocol for comprehensive evaluation of the entire abdomen and pelvis can be used for the following bowel indications: type and severity of inflammatory bowel disease (IBD); identifying enteric abscesses and fistulae; preoperative staging of malignant neoplasms, including rectal carcinoma; differentiating postoperative and radiation therapy changes from recurrent carcinoma; follow-up evaluation of metastases response to localized ablative or systemic chemotherapy. For improved visualization of bowel wall in dedicated examinations, bowel distension should be achieved using either orally or rectally delivered contrast agents to produce either bright or dark lumen. We have found 2D True-FISP without fat suppression superior to 3D True-FISP and to single-shot echo-train sequences to provide a T2-weighted image of bowel morphology. Strengths include: performed without fat suppression results in the very dark bowel wall being sandwiched between intermediate high signal fat adjacent to bowel serosa, and very high lumen signal from water-distending agent; 2D True-FISP provides motion insensitivity that is lost if 3D is used; True-FISP produces better edge sharpness than single-shot echo-train, higher contrast, and resists flow void artifacts commonly seen with single-shot echo-train imaging combined with a water distending agent. Drawbacks of this technique include: artifacts related to extreme sensitivity to field inhomogeneity, including air-soft tissue interfaces at the patient skin surface, and from retained bowel gas; retained bowel gas is dark against dark bowel wall, impairing bowel wall assessment; and True-FISP does not provide sensitivity for edema, which is superior on single-shot echo-train imaging. Small/large bowel indications for MRI include: inflammatory bowel disease, infectious disease including abscess evaluation or for appendicitis, inflammatory conditions including ischemia, and partial obstruction, malnutrition, and neoplasm search. PMID:16314698

Martin, Diego R; Danrad, Raman; Herrmann, Karin; Semelka, Richard C; Hussain, Shahid M

2005-02-01

216

Magnetic Resonance Imaging Part I--Physical Principles  

PubMed Central

Magnetic resonance (MR) imaging is the most complex imaging technology available to clinicians. Whereas most imaging technologies depict differences in one, or occasionally two, tissue characteristics, MR imaging has five tissue variables—spin density, T1 and T2 relaxation times and flow and spectral shifts—from which to construct its images. These variables can be combined in various ways by selecting pulse sequences and pulse times to emphasize any desired combination of tissue characteristics in the image. This selection is determined by the user of the MR system before imaging data are collected. If the selection is not optimal, the imaging process must be repeated at a cost of time and resources. The optimal selection of MR imaging procedures and the proper interpretation of the resultant images require a thorough understanding of the basic principles of MR imaging. Included in this understanding should be at least the rudiments of how an MR imaging signal is produced and why it decays with time; the significance of relaxation constants; the principles of scanning methods such as saturation recovery, inversion recovery and spin echo; how data obtained by these methods are used to form an image, and how the imaging data are complied by multi-slice and volumetric processes. In selecting an MR imaging unit, information about different magnet designs (resistive, superconductive and permanent) is useful. Although no bioeffects are thought to be associated with an MR imaging examination, some knowledge of the attempts to identify bioeffects is helpful in alleviating concern in patients. Images PMID:6506686

Hendee, William R.; Morgan, Christopher J.

1984-01-01

217

Magnetic resonance imaging of hepatocellular carcinoma: a pictorial review of novel insights into pathophysiological features revealed by magnetic resonance imaging  

Microsoft Academic Search

Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide. Magnetic resonance (MR) imaging is one of\\u000a the most powerful modalities for the assessment of HCC with sufficient sensitivity and specificity. In addition to its capacity\\u000a for lesion detection, MR imaging delineates some unique in vivo pathophysiological features of tumors, which cannot be assessed\\u000a by other modalities. Chemical shift

Ryota Shimofusa; Takuya Ueda; Takashi Kishimoto; Masayuki Nakajima; Masaharu Yoshikawa; Fukuo Kondo; Hisao Ito

2010-01-01

218

Noninvasive Imaging of Head-Brain Conductivity Profiles Using Magnetic Resonance Electrical Impedance Imaging  

PubMed Central

Magnetic resonance electrical impedance tomography (MREIT) is a recently introduced non-invasive conductivity imaging modality, which combines the magnetic resonance current density imaging (CDI) and the traditional electrical impedance tomography (EIT) techniques. MREIT is aimed at providing high spatial resolution images of electrical conductivity, by avoiding solving the well-known ill-posed problem in the traditional EIT. In this paper, we review our research activities in MREIT imaging of head-brain tissue conductivity profiles. We have developed several imaging algorithms and conducted a series of computer simulations for MREIT imaging of the head and brain tissues. Our work suggests MREIT brain imaging may become a useful tool in imaging conductivity distributions of the brain and head. PMID:18799394

Zhang, Xiaotong; Yan, Dandan; Zhu, Shanan; He, Bin

2008-01-01

219

RAPID COMMUNICATION: Magnetic resonance imaging inside metallic vessels  

NASA Astrophysics Data System (ADS)

We introduce magnetic resonance imaging (MRI) measurements inside metallic vessels. Until now, MRI has been unusable inside metallic vessels because of eddy currents in the walls. We have solved the problem and generated high quality images by employing a magnetic field gradient monitoring method. The ability to image within metal enclosures and structures means many new samples and systems are now amenable to MRI. Most importantly this study will form the basis of new MRI-compatible metallic pressure vessels, which will permit MRI of macroscopic systems at high pressure.

Han, Hui; Balcom, Bruce J.

2010-10-01

220

Para-Hydrogen-Enhanced Gas-Phase Magnetic Resonance Imaging  

SciTech Connect

Herein, we demonstrate magnetic resonance imaging (MRI) inthe gas phase using para-hydrogen (p-H2)-induced polarization. A reactantmixture of H2 enriched in the paraspin state and propylene gas is flowedthrough a reactor cell containing a heterogenized catalyst, Wilkinson'scatalyst immobilized on modified silica gel. The hydrogenation product,propane gas, is transferred to the NMR magnet and is spin-polarized as aresult of the ALTADENA (adiabatic longitudinal transport and dissociationengenders net alignment) effect. A polarization enhancement factor of 300relative to thermally polarized gas was observed in 1D1H NMR spectra.Enhancement was also evident in the magnetic resonance images. This isthe first demonstration of imaging a hyperpolarized gaseous productformed in a hydrogenation reaction catalyzed by a supported catalyst.This result may lead to several important applications, includingflow-through porous materials, gas-phase reaction kinetics and adsorptionstudies, and MRI in low fields, all using catalyst-free polarizedfluids.

Bouchard, Louis-S.; Kovtunov, Kirill V.; Burt, Scott R.; Anwar,M. Sabieh; Koptyug, Igor V.; Sagdeev, Renad Z.; Pines, Alexander

2007-02-23

221

Magnetic resonance imaging of benign bone lesions: cysts and tumors.  

PubMed

A benign bone lesion may have a typical appearance on plain radiographs. This is the case with benign cortical defects and osteochondroma. With most other lesions, cross-sectional imaging is needed to complete the study of the tumor. The nidus of osteoid osteoma is well demonstrated on computed tomography, but magnetic resonance imaging also will show the nidus in most cases. Magnetic resonance imaging is considered the modality of choice for evaluation of other benign musculoskeletal lesions because it is highly sensitive to changes in the signal intensity of bone marrow and adjacent soft tissues. It provides useful information for diagnosis of the lesion as in primary or secondary aneurysmal bone cyst, chondroblastoma, osteoblastoma, fibrous dysplasia, and osteofibrous dysplasia, and it helps differentiate these lesions from osteomyelitis, Langerhans' cell histiocytosis, and stress fracture. Bone scanning is most useful for depicting multiple silent lesions as may be seen in multiple osteochondromatosis, nonossifying fibromas, and polyostotic fibrous dysplasia. PMID:12409690

Azouz, E Michel

2002-08-01

222

Nuclear magnetic resonance imaging with hyper-polarized noble gases  

SciTech Connect

This is the final report of a six-month, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The nuclei of noble gases can be hyper polarized through a laser-driven spin exchange to a degree many orders of magnitude larger than that attainable by thermal polarization without requiring a strong magnetic field. The increased polarization from the laser pumping enables a good nuclear magnetic resonance (NMR) signal from a gas. The main goal of this project was to demonstrate diffusion-weighted imaging of such hyper-polarized noble gas with magnetic resonance imaging (MRI). Possible applications include characterizing porosity of materials and dynamically imaging pressure distributions in biological or acoustical systems.

Schmidt, D.M.; George, J.S.; Penttila, S.I.; Caprihan, A.

1997-10-01

223

The origins and future of nuclear magnetic resonance imaging  

SciTech Connect

What began as a curiosity of physics has become the preeminent method of diagnostic medical imaging and may displace x-ray-based techniques in the 21st century. During the past two decades nuclear magnetic resonance has revolutionized chemistry, biochemistry, biology and, more recently, diagnostic medicine. Nuclear magnetic resonance imaging, (MRI) as it is commonly called, is fundamentally different from x-ray-based techniques in terms of the principles of spatial encoding and mechanisms of signal and contrast generation involved. MRI has a far richer ultimate potential than any other imaging technique known today, and its technology and applications are still far from maturation, which may not occur until early in the 21st century. 23 refs., 6 figs.

Wehrli, F.W. (Univ. of Pennsylvania Medical Center, Philadelphia, PA (United States))

1992-06-01

224

Magnetic resonance imaging of brain tumors.  

PubMed

Since MR is a new imaging modality, a major question to answer is, "What is the role of MRI in relation to older, more traditional diagnostic techniques?" Several studies comparing CT and MRI for brain evaluation have shown MRI to be more sensitive, although not more specific. The advantages of MRI center around its ability to reveal abnormalities that may not be detectable or only poorly seen on CT. In cases in which only a nonspecific mass effect may be depicted on CT, the MR may define the precise extent and location of a tumor. Furthermore, MRI with its increased contrast discrimination and its ability to obtain images in many planes can better define the precise location of a lesion relative to key neuroanatomic structures. This is extremely important for optimal surgical and radiotherapy planning. The disadvantages of MRI include the fact that small calcifications cannot be seen and one cannot yet evaluate the presence of an altered blood-brain barrier. Despite these disadvantages, we feel that MRI should be the primary study for diagnosis of brain abnormalities. When an abnormality is detected and further information is desired, a complementary CT study should be performed in order to evaluate areas of blood-brain barrier alteration and the presence of abnormal calcification. PMID:3332409

Maravilla, K R; Sory, W C

1986-03-01

225

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

226

Magnetic resonance images of neuronal migration anomalies.  

PubMed

Neuronal migration anomalies are a spectrum of brain malformations caused by insults to migrating neuroblasts during the sixth week to fifth month of gestation. To study the characteristics of MRI findings in migration anomalies, MR images of 36 patients (28 children and 8 adults) with migration anomalies were evaluated. Five patients had lissencephaly, eight had pachygyria, twelve had schizencephaly, six had heterotopias of gray matter, three had hemimegalencephaly, and two had polymicrogyria. The frequency of migration anomalies was 0.51% of all cranial MRI studies and 1.21% of pediatric cranial MRI studies at our hospital. The major clinical presentations of these patients were seizure (64%), development delay (42%), motor deficits (42%) and mental retardation (25%). Twenty-five patients (69%) associated with other brain anomalies, including: other migration anomalies in 12 cases (33%), absence of the septum pellucidum in 10 cases (28%), Dandy-Walker malformation/variant in 5 cases, arachnoid cyst in 4 cases, agenesis of the corpus callosum in 3 cases, holoprosencephaly in 2 cases, mega cisterna magna in 1 case and cephalocele in 1 case. Some of them presented with multiple complicated anomalies. As MR imaging provides superb gray-white matter distinction, details of cortical anatomy and multiplanar capability, it can clearly delineate the detail morphologic changes of the brain caused by neuronal migration disorders as well as the associated anomalies. PMID:9780601

Jaw, T S; Sheu, R S; Liu, G C; Chou, M S

1998-08-01

227

A new presentation method for magnetic resonance angiography images based on skeletonization  

E-print Network

A new presentation method for magnetic resonance angiography images based on skeletonization Ingela angiography (MRA) images are usually presented as maximum intensity projections (MIP), and the choice angiography, arteries, stenosis detection 1. INTRODUCTION Magnetic resonance angiography (MRA) 1

Nyström, Ingela

228

Correlative neuroanatomy of computed tomography and magnetic resonance imaging  

SciTech Connect

Since the development of computed tomography (CT) more than a decade ago, still another form of imaging has become available that provides displays of normal and abnormal human structures. Magnetic resonance imaging is given complete coverage in this book. It describes both CT and MR anatomy that explains basic principles and the current status of imaging the brain and spine. The author uses three-dimensional concepts to provide the reader with a simple means to compare the main structures of the brain, skull and spine. Combining normal, gross neuroanatomic illustrations with CT and MR images of normal and abnormal conditions, the book provides diagnostic guidance. Drawings, photographs and radiologic images are used to help.

Groot, J. (ed.)

1984-01-01

229

Magnetic Resonance Imaging in patients with ICDs and Pacemakers  

PubMed Central

Magnetic resonance (MR) imaging has unparalleled soft-tissue imaging capabilities. The presence of devices such as pacemakers and implantable cardioverter/defibrillators (ICDs), however, is historically considered a contraindication to MR imaging. These devices are now smaller, with less magnetic material and improved electromagnetic interference protection. This review summarizes the potential hazards of the device-MR environment interaction, and presents updated information regarding in-vivo and in-vitro experiments. Recent reports on patients with implantable pacemakers and ICDs who underwent MR scan shows that under certain conditions patients with these implanted systems may benefit from this imaging modality. The data presented suggests that certain modern pacemaker and ICD systems may indeed be MR safe. This may have major clinical implications on current imaging practice. PMID:16943868

Nair, Prashant; Roguin, Ariel

2005-01-01

230

Reproducibility of Magnetic Resonance Perfusion Imaging  

PubMed Central

Dynamic MR biomarkers (T2*-weighted or susceptibility-based and T1-weighted or relaxivity-enhanced) have been applied to assess tumor perfusion and its response to therapies. A significant challenge in the development of reliable biomarkers is a rigorous assessment and optimization of reproducibility. The purpose of this study was to determine the measurement reproducibility of T1-weighted dynamic contrast-enhanced (DCE)-MRI and T2*-weighted dynamic susceptibility contrast (DSC)-MRI with two contrast agents (CA) of different molecular weight (MW): gadopentetate (Gd-DTPA, 0.5 kDa) and Gadomelitol (P792, 6.5 kDa). Each contrast agent was tested with eight mice that had subcutaneous MDA-MB-231 breast xenograft tumors. Each mouse was imaged with a combined DSC-DCE protocol three times within one week to achieve measures of reproducibility. DSC-MRI results were evaluated with a contrast to noise ratio (CNR) efficiency threshold. There was a clear signal drop (>95% probability threshold) in the DSC of normal tissue, while signal changes were minimal or non-existent (<95% probability threshold) in tumors. Mean within-subject coefficient of variation (wCV) of relative blood volume (rBV) in normal tissue was 11.78% for Gd-DTPA and 6.64% for P792. The intra-class correlation coefficient (ICC) of rBV in normal tissue was 0.940 for Gd-DTPA and 0.978 for P792. The inter-subject correlation coefficient was 0.092. Calculated Ktrans from DCE-MRI showed comparable reproducibility (mean wCV, 5.13% for Gd-DTPA, 8.06% for P792). ICC of Ktrans showed high intra-subject reproducibility (ICC?=?0.999/0.995) and inter-subject heterogeneity (ICC?=?0.774). Histograms of Ktrans distributions for three measurements had high degrees of overlap (sum of difference of the normalized histograms <0.01). These results represent homogeneous intra-subject measurement and heterogeneous inter-subject character of biological population, suggesting that perfusion MRI could be an imaging biomarker to monitor or predict response of disease. PMID:24587040

Zhang, Xiaomeng; Pagel, Mark D.; Baker, Amanda F.; Gillies, Robert J.

2014-01-01

231

Three-dimensional reconstruction system for imaging of the temporomandibular joint using magnetic resonance imaging.  

PubMed

This study was undertaken to develop a three-dimensional reconstruction system using magnetic resonance (MR) images in order to visualize three-dimensional images of the temporomandibular joint (TMJ) including the disk. The computerized reconstruction program (written using Visual Basic for Windows, Microsoft Corp.) could reliably generate three-dimensional images of the TMJ. Image processing techniques made the tracing of images unnecessary, reduced complex human manipulation and associated measurement errors. This system, capable of treating fifty thousand pixels or more, generates smooth three-dimensional images of the TMJ. PMID:10230154

Motoyoshi, M; Sadowsky, P L; Bernreuter, W; Fukui, M; Namura, S

1999-03-01

232

Elastomeric actuator devices for magnetic resonance imaging  

NASA Technical Reports Server (NTRS)

The present invention is directed to devices and systems used in magnetic imaging environments that include an actuator device having an elastomeric dielectric film with at least two electrodes, and a frame attached to the actuator device. The frame can have a plurality of configurations including, such as, for example, at least two members that can be, but not limited to, curved beams, rods, plates, or parallel beams. These rigid members can be coupled to flexible members such as, for example, links wherein the frame provides an elastic restoring force. The frame preferably provides a linear actuation force characteristic over a displacement range. The linear actuation force characteristic is defined as .+-.20% and preferably 10% over a displacement range. The actuator further includes a passive element disposed between the flexible members to tune a stiffness characteristic of the actuator. The passive element can be a bi-stable element. The preferred embodiment actuator includes one or more layers of the elastomeric film integrated into the frame. The elastomeric film can be made of many elastomeric materials such as, for example, but not limited to, acrylic, silicone and latex.

Dubowsky, Steven (Inventor); Hafez, Moustapha (Inventor); Jolesz, Ferenc A. (Inventor); Kacher, Daniel F. (Inventor); Lichter, Matthew (Inventor); Weiss, Peter (Inventor); Wingert, Andreas (Inventor)

2008-01-01

233

Nuclear magnetic resonance imaging with 90-nm resolution.  

PubMed

Magnetic resonance imaging (MRI) is a powerful imaging technique that typically operates on the scale of millimetres to micrometres. Conventional MRI is based on the manipulation of nuclear spins with radio-frequency fields, and the subsequent detection of spins with induction-based techniques. An alternative approach, magnetic resonance force microscopy (MRFM), uses force detection to overcome the sensitivity limitations of conventional MRI. Here, we show that the two-dimensional imaging of nuclear spins can be extended to a spatial resolution better than 100 nm using MRFM. The imaging of 19F nuclei in a patterned CaF(2) test object was enabled by a detection sensitivity of roughly 1,200 nuclear spins at a temperature of 600 mK. To achieve this sensitivity, we developed high-moment magnetic tips that produced field gradients up to 1.4 x 10(6) T m(-1), and implemented a measurement protocol based on force-gradient detection of naturally occurring spin fluctuations. The resulting detection volume was less than 650 zeptolitres. This is 60,000 times smaller than the previous smallest volume for nuclear magnetic resonance microscopy, and demonstrates the feasibility of pushing MRI into the nanoscale regime. PMID:18654288

Mamin, H J; Poggio, M; Degen, C L; Rugar, D

2007-05-01

234

Cardiac motion tracking using CINE harmonic phase (HARP) magnetic resonance imaging  

Microsoft Academic Search

This article introduces a new image processing technique for rapid analysis of tagged cardiac magnetic resonance image sequences. The method uses isolated spectral peaks in SPAMM- tagged magnetic resonance images, which contain information about cardiac motion. The inverse Fourier transform of a spectral peak is a complex image whose calculated angle is called a harmonic phase (HARP) image. It is

Nael F. Osman; William S. Kerwin; Elliot R. McVeigh; Jerry L. Prince

1999-01-01

235

Preoperative magnetic resonance imaging protocol for endoscopic cranial base image-guided surgery  

Microsoft Academic Search

ObjectiveDespite the increasing utilization of image-guided surgery, no radiology protocols for obtaining magnetic resonance (MR) imaging of adequate quality are available in the current literature. At our institution, more than 300 endonasal cranial base procedures including pituitary, extended pituitary, and other anterior skullbase procedures have been performed in the past 3 years. To facilitate and optimize preoperative evaluation and assessment,

Christopher R. Grindle; Joseph M. Curry; Melissa D. Kang; James J. Evans; Marc R. Rosen

2011-01-01

236

SNR analysis of 3D magnetic resonance tomosynthesis (MRT) imaging  

NASA Astrophysics Data System (ADS)

In conventional 3D Fourier transform (3DFT) MR imaging, signal-to-noise ratio (SNR) is governed by the well-known relationship of being proportional to the voxel size and square root of the imaging time. Here, we introduce an alternative 3D imaging approach, termed MRT (Magnetic Resonance Tomosynthesis), which can generate a set of tomographic MR images similar to multiple 2D projection images in x-ray. A multiple-oblique-view (MOV) pulse sequence is designed to acquire the tomography-like images used in tomosynthesis process and an iterative back-projection (IBP) reconstruction method is used to reconstruct 3D images. SNR analysis is performed and shows that resolution and SNR tradeoff is not governed as with typical 3DFT MR imaging case. The proposed method provides a higher SNR than the conventional 3D imaging method with a partial loss of slice-direction resolution. It is expected that this method can be useful for extremely low SNR cases.

Kim, Min-Oh; Kim, Dong-Hyun

2012-03-01

237

Clinical examination or whole-body magnetic resonance imaging: the Holy Grail of spondyloarthritis imaging  

PubMed Central

Whole-body magnetic resonance imaging allows acquisition of diagnostic images in the shortest scan time, leading to better patient compliance and artifact-free images. Methods of clinical examination of the anterior chest wall joints vary between physician groups and consideration of the rules of rib motion is suggested. The type of joint and its synovial lining may also aid imaging/clinical correlation. This well-written study by experts in the field with a standardized design and methodology allows good scientific analysis and suggests the advantages of whole-body magnetic resonance imaging in anterior chest wall imaging. Selection of clinical examination criteria and specific joints may have had an influence on the study results and the lack of association reported. PMID:22380535

2012-01-01

238

Diffusion-weighted magnetic resonance imaging in shaken baby syndrome  

Microsoft Academic Search

PURPOSE: To evaluate the role of diffusion-weighted magnetic resonance imaging (DWIMRI) in the diagnosis and management of children with suspected or confirmed Shaken Baby Syndrome (SBS).METHODS: This was a retrospective interventional case series of all infants and children younger than 2 years of age admitted to a children’s hospital. We retrospectively reviewed medical records and neuroimaging findings of all children

Valérie Biousse; Daniel Y Suh; Nancy J Newman; Patricia C Davis; Timothy Mapstone; Scott R Lambert

2002-01-01

239

Magnetic resonance imaging findings in diffuse lymphangiomatosis: neuroradiological manifestations.  

PubMed

We report magnetic resonance (MR) findings in a patient with histologically proven lymphangiomatosis with a history of chylothorax, diffuse lung infiltrates, spinal involvement, cystic lesions of the mediastinum, and mesentery thickening. The patient also had diffuse infiltration of the right brachial plexus, with similar imaging findings as the spinal lesions. Although osseous and extraosseous involvement may be seen frequently with lymphangiomatosis, involvement of the brachial plexus has not been previously reported. PMID:17520434

Ozturk, A; Yousem, D M

2007-06-01

240

Magnetic resonance imaging of the peripheral nervous system  

Microsoft Academic Search

The diagnostic work up of patients with peripheral neuropathy largely depends on clinical and electrophysiological investigations.\\u000a In contrast to disorders of the CNS, magnetic resonance imaging (MRI) has not been widely used as a diagnostic tool in the\\u000a PNS except for detection of nerve compressing mass lesions. Normal nerves appear isointense to the surrounding tissue on T1-\\u000a and T2-weighted (w)

Guido Stoll; Martin Bendszus; Jose Perez; Mirko Pham

2009-01-01

241

Decoding brain states using functional magnetic resonance imaging  

Microsoft Academic Search

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

Dongha Lee; Changwon Jang; Hae-Jeong Park

2011-01-01

242

Magnetic resonance imaging of nonhealing pressure ulcers and myocutaneous flaps  

Microsoft Academic Search

Objective: To evaluate the use of magnetic resonance imaging (MRI) in making clinical decisions when assessing nonhealing pressure ulcers and nonhealing myocutaneous flaps for the presence of an abscess, osteomyelitis, sinus tracts, and fluid collections.Design: Retrospective review of patient charts and radiographic studies.Setting: Regional spinal cord injury center.Subjects: Twelve patients who had MRI as part of their evaluation for a

Carolyn M. Ruan; Eva Escobedo; Scott Harrison; Barry Goldstein

1998-01-01

243

Corpus callosum size in schizophrenia – a magnetic resonance imaging analysis  

Microsoft Academic Search

Previous MRI studies have shown differences in corpus callosum size between schizophrenic patients and controls. The corpus\\u000a callosum (CC), as the main interhemispheric fiber tract, plays an important role in interhemispheric integration and communication.\\u000a Though MRI studies suggest smaller CC in schizophrenia, there are still conflicting findings. Using in vivo magnetic resonance\\u000a imaging, it was investigated whether the midsagittal area

E. M. Meisenzahl; T. Frodl; J. Greiner; G. Leinsinger; K.-P. Maag; D. Heiss; K. Hahn; U. Hegerl; H.-J. Möller

1999-01-01

244

Magnetic resonance imaging in the evaluation of ligament injuries  

Microsoft Academic Search

Magnetic resonance imaging has had a dramatic effect on the means by which we diagnose ligament injuries. Tears resulting\\u000a from either acute trauma or overuse can be detected noninvasively, directing appropriate therapy be it conservative or surgical.\\u000a For the elite athlete, earlier diagnosis leads to earlier intervention, or alternatively, a normal MRI examination can result\\u000a in an earlier return to

Shella Farooki; Leanne L. Seeger

1999-01-01

245

Magnetic resonance imaging of the fetal lung: a pictorial essay  

Microsoft Academic Search

Ultrasound, which is now a widely available and generally accepted, low-cost technique with real-time properties, is the screening\\u000a investigation of choice in fetal medicine. However, enthusiasm for fetal prenatal magnetic resonance imaging (MRI) is rising,\\u000a because of the absence of known biological risks, the increasing ease of performing of fetal MRI and the superb contrast resolution\\u000a provided. Over the last

M. Cannie; J. Jani; F. De Keyzer; F. Van Kerkhove; J. Meersschaert; L. Lewi; J. Deprest; S. Dymarkowski

2008-01-01

246

Magnetic resonance properties of hydrogen: imaging the posterior fossa  

Microsoft Academic Search

Posterior fossa scans were performed on five healthy volunteers using a nuclear magnetic resonance (NMR) machine constructed by Thorn-EMI Ltd. Three different NMR scanning sequences were used. In the first, a type of saturation-recovery technique was used to produce images strongly dependent on the density of hydrogen nuclei, but with some dependence on the spin-lattice relaxation time (Tâ). In the

I. R. Young; M. Burl; G. J. Clarke

1981-01-01

247

Blood Flow Magnetic Resonance Imaging of Retinal Degeneration  

E-print Network

Blood Flow Magnetic Resonance Imaging of Retinal Degeneration Yingxia Li,1 Haiying Cheng,1 Qiang Shen,1,2,3,4,5,6 Moon Kim,7 Peter M. Thule,7,8 Darin E. Olson,7,8 Machelle T. Pardue,7,9 and Timothy Q. Duong1,2,3,4,5,6,7 PURPOSE. This study aims to investigate quantitative basal blood flow as well

Duong, Timothy Q.

248

Application of magnetic resonance imaging in cervical spondylotic myelopathy  

PubMed Central

Cervical spondylotic myelopathy (CSM) is the most common cause of spinal cord dysfunction and is caused by static or dynamic repeated compression of the spinal cord resulting from degenerative arthritis of the cervical spine and some biological injuries to the cervical spine. The T2 signal change on conventional magnetic resonance imaging (MRI) is most commonly associated with neurological deficits. Diffusion tensor imaging and MR spectroscopy show altered microstructure and biochemistry that reflect patient-specific pathogenesis and can be used to predict neurological outcome and response to intervention. Functional MRI can help to assess the neurological functional recovery after decompression surgery for CSM. PMID:25349665

Zhang, Chuan; Das, Sushant K; Yang, Dong-Jun; Yang, Han-Feng

2014-01-01

249

Application of magnetic resonance imaging in cervical spondylotic myelopathy.  

PubMed

Cervical spondylotic myelopathy (CSM) is the most common cause of spinal cord dysfunction and is caused by static or dynamic repeated compression of the spinal cord resulting from degenerative arthritis of the cervical spine and some biological injuries to the cervical spine. The T2 signal change on conventional magnetic resonance imaging (MRI) is most commonly associated with neurological deficits. Diffusion tensor imaging and MR spectroscopy show altered microstructure and biochemistry that reflect patient-specific pathogenesis and can be used to predict neurological outcome and response to intervention. Functional MRI can help to assess the neurological functional recovery after decompression surgery for CSM. PMID:25349665

Zhang, Chuan; Das, Sushant K; Yang, Dong-Jun; Yang, Han-Feng

2014-10-28

250

Magnetic resonance imaging of the abnormal female pelvis  

SciTech Connect

Twenty-three women with 27 instances of pelvic pathology were evaluated by magnetic resonance imaging (MRI). Different pulse sequences were used, which varied the dependence of the images on T1 and T2. Sonography was performed on 22 of the 23 patients. Five patients had CT examinations, including the patient who did not have sonography. MRI was also done in four normal volunteers. The spatial resolution of the MRI scans with short TR and TE intervals approached that of CT. There was overlap of MRI signal characteristics between various pathologic entities and also within the same entity (e.g., cystadenomas and endometriomas).

Butler, H.; Bryan, P.J.; LiPuma, J.P.; Cohen, A.M.; El Yousef, S.; Andriole, J.G.; Lieberman, J.

1984-12-01

251

MRI (Magnetic Resonance Imaging) : tour an MRI machine  

NSDL National Science Digital Library

In this resource, appropriate for students in high school and beyond, the user navigates through a five-page illustrated explanation of MRI (magnetic resonance imaging). Each page profiles a different step in the MRI process. The resource addresses the science behind how MRI works, revealing how a strong magnet and radio wave pulses affect the targeted area of the body and allow that area to be imaged. As part of a set of materials about brain scanning technologies, this resource focuses on brain MRI. Copyright 2005 Eisenhower National Clearinghouse

Productions, David G.; York, Thirteen/wnet N.

2001-01-01

252

Detection of tumors with 19F magnetic resonance imaging.  

PubMed

Previous 19F magnetic resonance imaging studies showed that the reticuloendothelial system can be imaged with an emulsion of perfluorooctyl bromide (PFOB). Similar techniques can be used to detect previously implanted RIF-1 tumors in mice after intravenous PFOB administration. Accumulation of PFOB within these neoplasms is due to egress of the emulsion through tumor capillary fenestrations. This is the first report in which 19F MRI and PFOB are used to detect tumors. This technique may allow clinical detection of cancer with 19F MRI. PMID:3384616

Ratner, A V; Muller, H H; Bradley-Simpson, B; Johnson, D E; Hurd, R E; Sotak, C; Young, S W

1988-05-01

253

Magnetic resonance imaging in the evaluation of cognitive function.  

PubMed

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

Bigler, Erin D

2014-10-01

254

Vaginal masses: magnetic resonance imaging features with pathologic correlation.  

PubMed

The detection of vaginal lesions has increased with the expanding use of cross-sectional imaging. Magnetic resonance imaging (MRI) - with its high-contrast resolution and multiplanar capabilities - is often useful for characterizing vaginal masses. Vaginal masses can be classified as congenital, inflammatory, cystic (benign), and neoplastic (benign or malignant) in etiology. Recognition of the typical MR imaging features of such lesions is important because it often determines the treatment approach and may obviate surgery. Finally, vaginal MR imaging can be used to evaluate post-treatment changes related to previous surgery and radiation therapy. In this article, we will review pertinent vaginal anatomy, vaginal and pelvic MRI technique, and the MRI features of a variety of vaginal lesions with pathological correlation. PMID:17924224

Elsayes, K M; Narra, V R; Dillman, J R; Velcheti, V; Hameed, O; Tongdee, R; Menias, C O

2007-10-01

255

Biosensing and Imaging Based on Bioluminescence Resonance Energy Transfer  

PubMed Central

Bioluminescence resonance energy transfer (BRET) operates with biochemical energy generated by bioluminescent proteins to excite fluorophores and offers additional advantages over fluorescence energy transfer (FRET) for in vivo imaging and biosensing. While fluorescent proteins are frequently used as BRET acceptors, both small molecule dyes and nanoparticles can also serve as acceptor fluorophores. Semiconductor fluorescent nanocrystals or quantum dots (QDs) are particularly well-suited for use as BRET acceptors due to their high quantum yields, large Stokes shifts and long wavelength emission. This review examines the potential of QDs for BRET-based bioassays and imaging, and highlights examples of QD BRET for biosensing and imaging applications. Future development of new BRET acceptors should further expand the multiplexing capability of BRET and improve its applicability and sensitivity for in vivo imaging applications. PMID:19216068

Xia, Zuyong; Rao, Jianghong

2009-01-01

256

Improved Guided Image Fusion for Magnetic Resonance and Computed Tomography Imaging  

PubMed Central

Improved guided image fusion for magnetic resonance and computed tomography imaging is proposed. Existing guided filtering scheme uses Gaussian filter and two-level weight maps due to which the scheme has limited performance for images having noise. Different modifications in filter (based on linear minimum mean square error estimator) and weight maps (with different levels) are proposed to overcome these limitations. Simulation results based on visual and quantitative analysis show the significance of proposed scheme. PMID:24695586

Jameel, Amina

2014-01-01

257

Tumor Vascularity Assessed By Magnetic Resonance Imaging and Intravital Microscopy Imaging1  

Microsoft Academic Search

Gadopentetate dimeglumine (Gd-DTPA)-based dynamic contrast-enhanced magnetic resonance imaging (DCE- MRI) is considered to be a useful method for characterizing the vascularity of tumors. However, detailed studies of experimental tumors comparing DCE-MRI-derived parametric images with images of the morphology and function of the microvascular network have not been reported. In this communication, we describe a novel MR- compatible mouse dorsal window

Jon-Vidar Gaustad; Kjetil G. Brurberg; Trude G. Simonsen; Camilla S. Mollatt; Einar K. Rofstad

2008-01-01

258

Sparse magnetic resonance imaging reconstruction using the bregman iteration  

NASA Astrophysics Data System (ADS)

Magnetic resonance imaging (MRI) reconstruction needs many samples that are sequentially sampled by using phase encoding gradients in a MRI system. It is directly connected to the scan time for the MRI system and takes a long time. Therefore, many researchers have studied ways to reduce the scan time, especially, compressed sensing (CS), which is used for sparse images and reconstruction for fewer sampling datasets when the k-space is not fully sampled. Recently, an iterative technique based on the bregman method was developed for denoising. The bregman iteration method improves on total variation (TV) regularization by gradually recovering the fine-scale structures that are usually lost in TV regularization. In this study, we studied sparse sampling image reconstruction using the bregman iteration for a low-field MRI system to improve its temporal resolution and to validate its usefulness. The image was obtained with a 0.32 T MRI scanner (Magfinder II, SCIMEDIX, Korea) with a phantom and an in-vivo human brain in a head coil. We applied random k-space sampling, and we determined the sampling ratios by using half the fully sampled k-space. The bregman iteration was used to generate the final images based on the reduced data. We also calculated the root-mean-square-error (RMSE) values from error images that were obtained using various numbers of bregman iterations. Our reconstructed images using the bregman iteration for sparse sampling images showed good results compared with the original images. Moreover, the RMSE values showed that the sparse reconstructed phantom and the human images converged to the original images. We confirmed the feasibility of sparse sampling image reconstruction methods using the bregman iteration with a low-field MRI system and obtained good results. Although our results used half the sampling ratio, this method will be helpful in increasing the temporal resolution at low-field MRI systems.

Lee, Dong-Hoon; Hong, Cheol-Pyo; Lee, Man-Woo

2013-01-01

259

Microtesla magnetic resonance imaging with a superconducting quantum interference device  

SciTech Connect

We have constructed a magnetic resonance imaging (MRI) scanner based on a dc Superconducting QUantum Interference Device (SQUID) configured as a second-derivative gradiometer. The magnetic field sensitivity of the detector is independent of frequency; it is therefore possible to obtain high-resolution images by prepolarizing the nuclear spins in a field of 300 mT and detecting the signal at 132 fYT, corresponding to a proton Larmor frequency of 5.6 kHz. The reduction in the measurement field by a factor of 10,000 compared with conventional scanners eliminates inhomogeneous broadening of the nuclear magnetic resonance lines, even in fields with relatively poor homogeneity. The narrow linewidths result in enhanced signal-to-noise ratio and spatial resolution for a fixed strength of the magnetic field gradients used to encode the image. We present two-dimensional images of phantoms and pepper slices, obtained in typical magnetic field gradients of 100 fYT/m, with a spatial resolution of about 1mm. We further demonstrate a slice-selected image of an intact pepper. By varying the time delay between removal of the polarizing field and initiation of the spin echo sequence we acquire T1-weighted contrast images of water phantoms, some of which are doped with a paramagnetic salt; here, T1 is the nuclear spin-lattice relaxation time. The techniques presented here could readily be adapted to existing multichannel SQUID systems used for magnetic source imaging of brain signals. Further potential applications include low-cost systems for tumor screening and imaging peripheral regions of the body.

McDermott, Robert; Lee, SeungKyun; ten Haken, Bennie; Trabesinger, Andreas H.; Pines, Alexander; Clarke, John

2004-03-15

260

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

Microsoft Academic Search

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

Peter G. Morris

1999-01-01

261

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

PubMed

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

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

2013-07-01

262

Respiratory Amplitude Guided 4-Dimensional Magnetic Resonance Imaging  

SciTech Connect

Purpose: To evaluate the feasibility of prospectively guiding 4-dimensional (4D) magnetic resonance imaging (MRI) image acquisition using triggers at preselected respiratory amplitudes to achieve T{sub 2} weighting for abdominal motion tracking. Methods and Materials: A respiratory amplitude-based triggering system was developed and integrated into a commercial turbo spin echo MRI sequence. Initial feasibility tests were performed on healthy human study participants. Four respiratory states, the middle and the end of inhalation and exhalation, were used to trigger 4D MRI image acquisition of the liver. To achieve T{sub 2} weighting, the echo time and repetition time were set to 75 milliseconds and 4108 milliseconds, respectively. Single-shot acquisition, together with parallel imaging and partial k-space imaging techniques, was used to improve image acquisition efficiency. 4D MRI image sets composed of axial or sagittal slices were acquired. Results: Respiratory data measured and logged by the MRI scanner showed that the triggers occurred at the appropriate respiratory levels. Liver motion could be easily observed on both 4D MRI image datasets by sensing either the change of liver in size and shape (axial) or diaphragm motion (sagittal). Both 4D MRI image datasets were T{sub 2}-weighted as expected. Conclusions: This study demonstrated the feasibility of achieving T{sub 2}-weighted 4D MRI images using amplitude-based respiratory triggers. With the aid of the respiratory amplitude-based triggering system, the proposed method is compatible with most MRI sequences and therefore has the potential to improve tumor-tissue contrast in abdominal tumor motion imaging.

Hu, Yanle, E-mail: yhu@radonc.wustl.edu [Department of Radiation Oncology, Washington University School of Medicine, St. Louis, Missouri (United States)] [Department of Radiation Oncology, Washington University School of Medicine, St. Louis, Missouri (United States); Caruthers, Shelton D. [Department of Medicine, Washington University School of Medicine, St. Louis, Missouri (United States)] [Department of Medicine, Washington University School of Medicine, St. Louis, Missouri (United States); Low, Daniel A. [Department of Radiation Oncology, University of California Los Angeles, Los Angeles, California (United States)] [Department of Radiation Oncology, University of California Los Angeles, Los Angeles, California (United States); Parikh, Parag J.; Mutic, Sasa [Department of Radiation Oncology, Washington University School of Medicine, St. Louis, Missouri (United States)] [Department of Radiation Oncology, Washington University School of Medicine, St. Louis, Missouri (United States)

2013-05-01

263

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

PubMed Central

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

Sharma, Rakesh; Sharma, Avdhesh

2004-01-01

264

Magnetic resonance imaging (MRI): considerations and applications in radiotherapy treatment planning  

Microsoft Academic Search

The emerging utilisation of conformal radiotherapy (RT) planning requires sophisticated imaging modalities. Magnetic resonance imaging (MRI) has introduced several added imaging benefits that may confer an advantage over the use of computed tomography (CT) in RT planning such as improved soft tissue definition, unrestricted multiplannar and volumetric imaging as well as physiological and biochemical information with magnetic resonance (MR) angiography

Vincent S. Khoo; David P. Dearnaley; David J. Finnigan; Anwar Padhani; Steven F. Tanner; Martin O. Leach

1997-01-01

265

Fast spin echo magnetic resonance imaging: Clinical application in screening for acoustic neuroma  

Microsoft Academic Search

The advent of magnetic resonance imaging has greatly improved our ability to diagnose acoustic tumors, but it is a relatively expensive imaging modality. In the present climate of medical cost restraints, methods that reduce costs but maintain quality are extremely desirable. We report a new magnetic resonance imaging technique that uses fast spin echo without gadolinium. It provides ultrahigh-resolution images

CLOUGH SHELTON; H. RIC HARNSBERGER; ROBERT ALLEN; BRIAN KING

1996-01-01

266

Development of a hybrid magnetic resonance and ultrasound imaging system.  

PubMed

A system which allows magnetic resonance (MR) and ultrasound (US) image data to be acquired simultaneously has been developed. B-mode and Doppler US were performed inside the bore of a clinical 1.5 T MRI scanner using a clinical 1-4?MHz US transducer with an 8-metre cable. Susceptibility artefacts and RF noise were introduced into MR images by the US imaging system. RF noise was minimised by using aluminium foil to shield the transducer. A study of MR and B-mode US image signal-to-noise ratio (SNR) as a function of transducer-phantom separation was performed using a gel phantom. This revealed that a 4?cm separation between the phantom surface and the transducer was sufficient to minimise the effect of the susceptibility artefact in MR images. MR-US imaging was demonstrated in vivo with the aid of a 2?mm VeroWhite 3D-printed spherical target placed over the thigh muscle of a rat. The target allowed single-point registration of MR and US images in the axial plane to be performed. The system was subsequently demonstrated as a tool for the targeting and visualisation of high intensity focused ultrasound exposure in the rat thigh muscle. PMID:25177702

Sherwood, Victoria; Civale, John; Rivens, Ian; Collins, David J; Leach, Martin O; ter Haar, Gail R

2014-01-01

267

Development of a Hybrid Magnetic Resonance and Ultrasound Imaging System  

PubMed Central

A system which allows magnetic resonance (MR) and ultrasound (US) image data to be acquired simultaneously has been developed. B-mode and Doppler US were performed inside the bore of a clinical 1.5 T MRI scanner using a clinical 1–4?MHz US transducer with an 8-metre cable. Susceptibility artefacts and RF noise were introduced into MR images by the US imaging system. RF noise was minimised by using aluminium foil to shield the transducer. A study of MR and B-mode US image signal-to-noise ratio (SNR) as a function of transducer-phantom separation was performed using a gel phantom. This revealed that a 4?cm separation between the phantom surface and the transducer was sufficient to minimise the effect of the susceptibility artefact in MR images. MR-US imaging was demonstrated in vivo with the aid of a 2?mm VeroWhite 3D-printed spherical target placed over the thigh muscle of a rat. The target allowed single-point registration of MR and US images in the axial plane to be performed. The system was subsequently demonstrated as a tool for the targeting and visualisation of high intensity focused ultrasound exposure in the rat thigh muscle. PMID:25177702

Sherwood, Victoria; Rivens, Ian; Collins, David J.; Leach, Martin O.; ter Haar, Gail R.

2014-01-01

268

Combined Magnetic Resonance Imaging and Spectroscopic Imaging Approach to Molecular Imaging of Prostate Cancer  

PubMed Central

Magnetic resonance spectroscopic imaging (MRSI) provides a noninvasive method of detecting small molecular markers (historically the metabolites choline and citrate) within the cytosol and extracellular spaces of the prostate, and is performed in conjunction with high-resolution anatomic imaging. Recent studies in pre-prostatectomy patients have indicated that the metabolic information provided by MRSI combined with the anatomical information provided by MRI can significantly improve the assessment of cancer location and extent within the prostate, extracapsular spread, and cancer aggressiveness. Additionally, pre- and post-therapy studies have demonstrated the potential of MRI/MRSI to provide a direct measure of the presence and spatial extent of prostate cancer after therapy, a measure of the time course of response, and information concerning the mechanism of therapeutic response. In addition to detecting metabolic biomarkers of disease behavior and therapeutic response, MRI/MRSI guidance can improve tissue selection for ex vivo analysis. High-resolution magic angle spinning (1H HR-MAS) spectroscopy provides a full chemical analysis of MRI/MRSI-targeted tissues prior to pathologic and immunohistochemical analyses of the same tissue. Preliminary 1H HR-MAS spectroscopy studies have already identified unique spectral patterns for healthy glandular and stromal tissues and prostate cancer, determined the composition of the composite in vivo choline peak, and identified the polyamine spermine as a new metabolic marker of prostate cancer. The addition of imaging sequences that provide other functional information within the same exam (dynamic contrast uptake imaging and diffusion-weighted imaging) have also demonstrated the potential to further increase the accuracy of prostate cancer detection and characterization. PMID:12353259

Kurhanewicz, John; Swanson, Mark G.; Nelson, Sarah J.; Vigneron, Daniel B.

2005-01-01

269

Linear constraint minimum variance beamformer functional magnetic resonance inverse imaging  

PubMed Central

Accurate estimation of the timing of neural activity is required to fully model the information flow among functionally specialized regions whose joint activity underlies perception, cognition and action. Attempts to detect the fine temporal structure of task-related activity would benefit from functional imaging methods allowing higher sampling rates. Spatial filtering techniques have been used in magnetoencephalography source imaging applications. In this work, we use the linear constraint minimal variance (LCMV) beamformer localization method to reconstruct single-shot volumetric functional magnetic resonance imaging (fMRI) data using signals acquired simultaneously from all channels of a high density radio-frequency (RF) coil array. The LCMV beamformer method generalizes the existing volumetric magnetic resonance inverse imaging (InI) technique, achieving higher detection sensitivity while maintaining whole-brain spatial coverage and 100 ms temporal resolution. In this paper, we begin by introducing the LCMV reconstruction formulation and then quantitatively assess its performance using both simulated and empirical data. To demonstrate the sensitivity and inter-subject reliability of volumetric LCMV InI, we employ an event-related design to probe the spatial and temporal properties of task-related hemodynamic signal modulations in primary visual cortex. Compared to minimum-norm estimate (MNE) reconstructions, LCMV offers better localization accuracy and superior detection sensitivity. Robust results from both single subject and group analyses demonstrate the excellent sensitivity and specificity of volumetric InI in detecting the spatial and temporal structure of task-related brain activity. PMID:18672071

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

2011-01-01

270

The rotating biplanar linac-magnetic resonance imaging system.  

PubMed

We have successfully built linac-magnetic resonance imaging (MR) systems based on a linac waveguide placed between open MR planes (perpendicular) or through the central opening of one of the planes (parallel) to improve dosimetric properties. It rotates on a gantry to irradiate at any angle. Irradiation during MR imaging and automatic 2-dimensional MR image-based target tracking and automatic beam steering to the moving target have been demonstrated with our systems. The functioning whole-body system (0.6-T MR and 6-MV linac) has been installed in an existing clinical vault without removing the walls or the ceiling and without the need of a helium exhaust vent. PMID:24931093

Fallone, Biagio Gino

2014-07-01

271

The Spleen Revisited: An Overview on Magnetic Resonance Imaging  

PubMed Central

Despite being well visualized by different cross-sectional imaging techniques, the spleen is many times overlooked during the abdominal examination. The major reason is the low frequency of splenic abnormalities, the majority consisting of incidental findings. There has been a steady increase in the number of performed abdominal magnetic resonance imaging (MRI) studies; therefore, it is important to be familiar to the major MRI characteristics of disease processes involving the spleen, in order to interpret the findings correctly, reaching whenever possible the appropriate diagnosis. The spleen may be involved in several pathologic conditions like congenital diseases, trauma, inflammation, vascular disorders and hematologic disorders, benign and malignant tumors, and other disease processes that focally or diffusely affect the spleen. This paper presents a description and representative MRI images for many of these disorders. PMID:24377046

Palas, Joao; Matos, Antonio P.; Ramalho, Miguel

2013-01-01

272

Magnetic resonance imaging using chemical exchange saturation transfer  

NASA Astrophysics Data System (ADS)

Magnetic resonance imaging (MRI) has been widely used as a valuable diagnostic imaging modality that exploits water content and water relaxation properties to provide both structural and functional information with high resolution. Chemical exchange saturation transfer (CEST) in MRI has been recently introduced as a new mechanism of image contrast, wherein exchangeable protons from mobile proteins and peptides are indirectly detected through saturation transfer and are not observable using conventional MRI. It has been demonstrated that CEST MRI can detect important tissue metabolites and byproducts such as glucose, glycogen, and lactate. Additionally, CEST MRI is sensitive to pH or temperature and can calibrate microenvironment dependent on pH or temperature. In this work, we provide an overview on recent trends in CEST MRI, introducing general principles of CEST mechanism, quantitative description of proton transfer process between water pool and exchangeable solute pool in the presence or absence of conventional magnetization transfer effect, and its applications

Park, Jaeseok

2012-10-01

273

Magnetic resonance imaging features of equine nigropallidal encephalomalacia.  

PubMed

Magnetic resonance imaging (MR) was used to make a diagnosis of equine nigropallidal encephalomalacia in a horse. Equine nigropallidal encephalomalacia is a neurodegenerative disease that has many characteristics with Parkinson-like diseases in humans. Historically, horses were euthanized based on clinical signs and exposure to the toxic weed, yellow star thistle (Centaurea solstitialis). Previously, the disease has only been confirmed on necropsy. MR imaging can provide accurate and sensitive visualization of typical lesions seen in the brain of horses affected with equine nigropallidal encephalomalacia. Lesions were seen on T1-weighted, T2-weighted and proton density images. There was no contrast enhancement following Gd-DTPA administration. Lesions seen on MR were confirmed at necropsy. Using MR to confirm a diagnosis of equine nigropallidal encephalomalacia will prevent unnecessary suffering of horses and expense to owners that would otherwise incur, while further diagnostics are performed. PMID:11499702

Sanders, S G; Tucker, R L; Bagley, R S; Gavin, P R

2001-01-01

274

Clinical applications for diffusion magnetic resonance imaging in radiotherapy.  

PubMed

In this article, we review the clinical applications of diffusion magnetic resonance imaging (MRI) in the radiotherapy treatment of several key clinical sites, including those of the central nervous system, the head and neck, the prostate, and the cervix. Diffusion-weighted MRI (DWI) is an imaging technique that is rapidly gaining widespread acceptance owing to its ease and wide availability. DWI measures the mobility of water within tissue at the cellular level without the need of any exogenous contrast agent. For radiotherapy treatment planning, DWI improves upon conventional imaging techniques, by better characterization of tumor tissue properties required for tumor grading, diagnosis, and target volume delineation. Because DWI is also a sensitive marker for alterations in tumor cellularity, it has potential clinical applications in the early assessment of treatment response following radiation therapy. PMID:24931097

Tsien, Christina; Cao, Yue; Chenevert, Thomas

2014-07-01

275

Magnetic Resonance Imaging (MRI) for the Assessment of Myocardial Viability  

PubMed Central

Executive Summary In July 2009, the Medical Advisory Secretariat (MAS) began work on Non-Invasive Cardiac Imaging Technologies for the Assessment of Myocardial Viability, an evidence-based review of the literature surrounding different cardiac imaging modalities to ensure that appropriate technologies are accessed by patients undergoing viability assessment. This project came about when the Health Services Branch at the Ministry of Health and Long-Term Care asked MAS to provide an evidentiary platform on effectiveness and cost-effectiveness of noninvasive cardiac imaging modalities. After an initial review of the strategy and consultation with experts, MAS identified five key non-invasive cardiac imaging technologies that can be used for the assessment of myocardial viability: positron emission tomography, cardiac magnetic resonance imaging, dobutamine echocardiography, and dobutamine echocardiography with contrast, and single photon emission computed tomography. A 2005 review conducted by MAS determined that positron emission tomography was more sensitivity than dobutamine echocardiography and single photon emission tomography and dominated the other imaging modalities from a cost-effective standpoint. However, there was inadequate evidence to compare positron emission tomography and cardiac magnetic resonance imaging. Thus, this report focuses on this comparison only. For both technologies, an economic analysis was also completed. A summary decision analytic model was then developed to encapsulate the data from each of these reports (available on the OHTAC and MAS website). The Non-Invasive Cardiac Imaging Technologies for the Assessment of Myocardial Viability is made up of the following reports, which can be publicly accessed at the MAS website at: www.health.gov.on.ca/mas or at www.health.gov.on.ca/english/providers/program/mas/mas_about.html Positron Emission Tomography for the Assessment of Myocardial Viability: An Evidence-Based Analysis Magnetic Resonance Imaging for the Assessment of Myocardial Viability: An Evidence-Based Analysis Objective The objective of this analysis is to assess the effectiveness and cost-effectiveness of cardiovascular magnetic resonance imaging (cardiac MRI) for the assessment of myocardial viability. To evaluate the effectiveness of cardiac MRI viability imaging, the following outcomes were examined: the diagnostic accuracy in predicting functional recovery and the impact of cardiac MRI viability imaging on prognosis (mortality and other patient outcomes). Clinical Need: Condition and Target Population Left Ventricular Systolic Dysfunction and Heart Failure Heart failure is a complex syndrome characterized by the heart’s inability to maintain adequate blood circulation through the body leading to multiorgan abnormalities and, eventually, death. Patients with heart failure experience poor functional capacity, decreased quality of life, and increased risk of morbidity and mortality. In 2005, more than 71,000 Canadians died from cardiovascular disease, of which, 54% were due to ischemic heart disease. Left ventricular (LV) systolic dysfunction due to coronary artery disease (CAD) 1 is the primary cause of heart failure accounting for more than 70% of cases. The prevalence of heart failure was estimated at one percent of the Canadian population in 1989. Since then, the increase in the older population has undoubtedly resulted in a substantial increase in cases. Heart failure is associated with a poor prognosis: one-year mortality rates were 32.9% and 31.1% for men and women, respectively in Ontario between 1996 and 1997. Treatment Options In general, there are three options for the treatment of heart failure: medical treatment, heart transplantation, and revascularization for those with CAD as the underlying cause. Concerning medical treatment, despite recent advances, mortality remains high among treated patients, while, heart transplantation is affected by the limited availability of donor hearts and consequently has long waiting lists. The third option, revascularization, is used

2010-01-01

276

Magnetic Resonance Imaging Conditional Pacemakers: Rationale, Development and Future Directions  

PubMed Central

Pacemakers and other cardiac implantable electronic devices (CIEDs) have long been considered an absolute contraindication to magnetic resonance imaging (MRI), a crucial and growing imaging modality. In the last 20 years, protocols have been developed to allow MR scanning of CIED patients with a low complication rate. However, this practice has remained limited to a relatively small number of centers, and many pacemaker patients continue to be denied access to clinically indicated imaging. The introduction of MRI conditional pacemakers has provided a widely applicable and satisfactory solution to this problem. Here, the interactions of pacemakers with the MR environment, the results of MR scanning in patients with conventional CIEDs, the development and clinical experience with MRI conditional devices, and future directions are reviewed. PMID:23071382

Cronin, Edmond M; Wilkoff, Bruce L

2012-01-01

277

Magnetic resonance microscopy of prostate tissue: How basic science can inform clinical imaging development  

PubMed Central

This commentary outlines how magnetic resonance imaging (MRI) microscopy studies of prostate tissue samples and whole organs have shed light on a number of clinical imaging mysteries and may enable more effective development of new clinical imaging methods.

Bourne, Roger

2013-01-01

278

New applications of magnetic resonance imaging for thoracic oncology.  

PubMed

Since the clinical introduction of magnetic resonance imaging (MRI), the chest has been one of its most challenging applications, and since the 1980s many physicists and radiologists have been trying to evaluate images for various lung diseases as well as mediastinal and pleural diseases. However, thoracic MRI could not yield image quality sufficient for a convincing diagnosis within an acceptable examination time, so MRI did not find acceptance as a substitute for computed tomography (CT) and other modalities. Until the 2000, thoracic MRI was generally used only for select, minor clinical indications. Within the past decade, however, technical advances in sequencing, scanners and coils, adaptation of parallel imaging techniques, utilization of contrast media, and development of postprocessing tools have been developed. In addition, pulmonary functional MRI has been extensively researched, and MR is being assessed as a new research and diagnostic tool for pulmonary diseases. State-of-the art thoracic MRI now has the potential as a substitute for traditional imaging techniques and/or to play a complimentary role in patient management. In this review, we focus on these advances in MRI for thoracic oncologic imaging, especially for pulmonary nodule assessment, lung cancer staging, mediastinal tumor diagnosis and malignant mesothelioma evaluation, prediction of postoperative lung function, and prediction or evaluation of therapeutic effectiveness. We also discuss the potential and limitations of these advances for routine clinical practice in comparison with other modalities such as CT, positron emission tomography (PET), PET/CT, or nuclear medicine studies. PMID:24481757

Ohno, Yoshiharu

2014-02-01

279

Nuclear magnetic resonance proton imaging of bone pathology  

SciTech Connect

Thirty-two patients with diversified pathology were examined with a supraconductive NMR imager using spin echo with different TR and TE to obtain T1 and T2 weighted images. They included 20 tumors (12 primary, eight metastasis), six osteomyelitis, three fractures, two osteonecrosis, and one diffuse metabolic (Gaucher) disease. In all cases except for the stress fractures, the bone pathology was clearly visualized in spite of the normal lack of signal from the compact cortical bone. Nuclear magnetic resonance (NMR) imaging proved to be at least as sensitive as radionuclide scintigraphy but much more accurate than all other imaging procedures including computed tomography (CT) and angiography to assess the extension of the lesions, especially in tumors extended to soft tissue. This is due both to easy acquisition of sagittal and coronal sections and to different patterns of pathologic modifications of T1 and T2 which are beginning to be defined. It is hoped that more experience in clinical use of these patterns will help to discriminate between tumor extension and soft-tissue edema. We conclude that while radionuclide scintigraphy will probably remain the most sensitive and easy to perform screening test for bone pathology, NMR imaging, among noninvasive diagnostic procedures, appears to be at least as specific as CT. In addition, where the extension of the lesions is concerned, NMR imaging is much more informative than CT. In pathology of the spine, the easy visualization of the spinal cord should decrease the need for myelography.

Atlan, H.; Sigal, R.; Hadar, H.; Chisin, R.; Cohen, I.; Lanir, A.; Soudry, M.; Machtey, Y.; Schreiber, R.; Benmair, J.

1986-02-01

280

Second-opinion magnetic resonance imaging for suspected fetal central nervous system abnormalities  

Microsoft Academic Search

Objective: The purpose of this study was to evaluate the relationship of magnetic resonance imaging and gestational age in the setting of fetuses with suspected abnormalities of the central nervous system that were detected by ultrasound scanning. Study design: Multiplanar magnetic resonance studies were performed in fetuses with suspected central nervous system abnormalities on ultrasound scanning. Magnetic resonance imaging was

Diane M. Twickler; Kevin P. Magee; Jacqueline Caire; Michael Zaretsky; James L. Fleckenstein; Ronald M. Ramus

2003-01-01

281

Magnetic Resonance Imaging (MRI) of Oak Trees Infected With Phytophthora ramorum to  

E-print Network

91 Magnetic Resonance Imaging (MRI) of Oak Trees Infected With Phytophthora ramorum to Determine Potential Avenues of Infection in Bark1 Edwin R. Florance2 Abstract Non-destructive magnetic resonance as an avenue of infection for P. ramorum. Key words: magnetic resonance imaging, microscopy, periderm

Standiford, Richard B.

282

Magnetic resonance imaging and electromyography as indexes of muscle function  

NASA Technical Reports Server (NTRS)

A hypothesis is tested that exercise-induced magnetic resonance (MR) contrast shifts would relate to electromyography (EMG) amplitude if both measures reflect muscle use during exercise. Both magnetic resonance images (MRI) and EMG data were obtained for separate eccentric (ECC) and cocentric (CON) exercise of increasing intensity for seven subjects 30-32 yr old. CON and ECC actions caused increased integrated EMG (IEMG) and T2 values which were strongly related with relative resistance. The rate of increase and absolute value of both T2 and IEMG were found to be greater for CON than for ECC actions. For both actions IEMG and T2 were correlated. Data obtained suggest that surface IEMG accurately reflects the contractile behavior of muscle and exercise-induced increases in MRI T2 values reflect certain processes that scale with muscle use.

Adams, Gregory R.; Duvoisin, Marc R.; Dudley, Gary A.

1992-01-01

283

Magnetic resonance imaging and spectroscopy of the murine cardiovascular system  

PubMed Central

Magnetic resonance imaging (MRI) has emerged as a powerful and reliable tool to noninvasively study the cardiovascular system in clinical practice. Because transgenic mouse models have assumed a critical role in cardiovascular research, technological advances in MRI have been extended to mice over the last decade. These have provided critical insights into cardiac and vascular morphology, function, and physiology/pathophysiology in many murine models of heart disease. Furthermore, magnetic resonance spectroscopy (MRS) has allowed the nondestructive study of myocardial metabolism in both isolated hearts and in intact mice. This article reviews the current techniques and important pathophysiological insights from the application of MRI/MRS technology to murine models of cardiovascular disease. PMID:23292717

Akki, Ashwin; Gupta, Ashish

2013-01-01

284

[Fetal magnetic resonance imaging evaluation of congenital diaphragmatic hernia].  

PubMed

A diaphragmatic hernia is defined as the protrusion of abdominal viscera into the thoracic cavity through a normal or pathological orifice. The herniated viscera compress the lungs, resulting in pulmonary hypoplasia and secondary pulmonary hypertension, which are the leading causes of neonatal death in patients with congenital diaphragmatic hernia. Congenital diaphragmatic hernia is diagnosed by sonography in routine prenatal screening. Although magnetic resonance imaging is fundamentally used to determine whether the liver is located within the abdomen or has herniated into the thorax, it also can provide useful information about other herniated structures and the degree of pulmonary hypoplasia. The aim of this article is to review the fetal magnetic resonance findings for congenital diaphragmatic hernia and the signs that enable us to establish the neonatal prognosis when evaluating pulmonary hypoplasia. PMID:23523414

Sebastià, C; Garcia, R; Gomez, O; Paño, B; Nicolau, C

2014-01-01

285

Innovative computing for diagnoses from medical, magnetic-resonance imaging  

SciTech Connect

The author presents a final report on a Laboratory-Directed Research and Development (LDRD) project, Innovative Computing for Diagnoses from Medical, Magnetic-Resonance Imaging, performed during fiscal years 1992 and 1993. The project defined a role for high-performance computing in surgery: the supercomputer can automatically summarize the three-dimensional extents of lesions and other clinically-relevant structures, and can deliver these summaries to workstation-based, augmented-reality environments at the clinical site. The author developed methods and software to make these summaries from the digital data already acquired using clinical, magnetic-resonance machines. In joint work with Albuquerque`s Department of Veterans Affairs Hospital, the author applied this work, and obtained a basis for planning, for rehearsal, and for guidance during surgery.

Diegert, C.

1997-01-01

286

Magnetic resonance imaging safety of deep brain stimulator devices.  

PubMed

Magnetic resonance imaging (MRI) has become the standard of care for the evaluation of different neurological disorders of the brain and spinal cord due to its multiplanar capabilities and excellent soft tissue resolution. With the large and increasing population of patients with implanted deep brain stimulation (DBS) devices, a significant proportion of these patients with chronic neurological diseases require evaluation of their primary neurological disease processes by MRI. The presence of an implanted DBS device in a magnetic resonance environment presents potential hazards. These include the potential for induction of electrical currents or heating in DBS devices, which can result in neurological tissue injury, magnetic field-induced device migration, or disruption of the operational aspects of the devices. In this chapter, we review the basic physics of potential interactions of the MRI environment with implanted DBS devices, summarize results from phantom studies and clinical series, and discuss present recommendations for safe MRI in patients with implanted DBS devices. PMID:24112886

Oluigbo, Chima O; Rezai, Ali R

2013-01-01

287

Updating magnetic resonance imaging of small bowel: Imaging protocols and clinical indications  

PubMed Central

High soft tissue contrast resolution, acquisition of multi-planar images and the possibility to obtain functional information make magnetic resonance an interesting imaging technique to evaluate the small bowel disease. The absence of ionizing radiation is an important feature of magnetic resonance imaging (MRI) examinations because inflammatory diseases such as Crohn’s disease (CD) are studied most frequently, which are prevalent among children and young adults. MRI, using modern equipment and a rigorous technical approach, can offer detailed morphologic information and functional data on the small bowel. This article discusses the MRI protocols for small bowel and the MR imaging findings of small bowel diseases, such as CD and small bowel neoplasms. PMID:18528938

Zhu, Jiong; Xu, Jian-Rong; Gong, Hong-Xia; Zhou, Yan

2008-01-01

288

Hyperpolarized Xenon-129 Magnetic Resonance Imaging of Functional Lung Microstructure  

NASA Astrophysics Data System (ADS)

Hyperpolarized 129Xe (HXe) is a non-invasive contrast agent for lung magnetic resonance imaging (MRI), which upon inhalation follows the functional pathway of oxygen in the lung by dissolving into lung tissue structures and entering the blood stream. HXe MRI therefore provides unique opportunities for functional lung imaging of gas exchange which occurs from alveolar air spaces across the air-blood boundary into parenchymal tissue. However challenges in acquisition speed and signal-to-noise ratio have limited the development of a HXe imaging biomarker to diagnose lung disease. This thesis addresses these challenges by introducing parallel imaging to HXe MRI. Parallel imaging requires dedicated hardware. This work describes design, implementation, and characterization of a 32-channel phased-array chest receive coil with an integrated asymmetric birdcage transmit coil tuned to the HXe resonance on a 3 Tesla MRI system. Using the newly developed human chest coil, a functional HXe imaging method, multiple exchange time xenon magnetization transfer contrast (MXTC) is implemented. MXTC dynamically encodes HXe gas exchange into the image contrast. This permits two parameters to be derived regionally which are related to gas-exchange functionality by characterizing tissue-to-alveolar-volume ratio and alveolar wall thickness in the lung parenchyma. Initial results in healthy subjects demonstrate the sensitivity of MXTC by quantifying the subtle changes in lung microstructure in response to orientation and lung inflation. Our results in subjects with lung disease show that the MXTC-derived functional tissue density parameter exhibits excellent agreement with established imaging techniques. The newly developed dynamic parameter, which characterizes the alveolar wall, was elevated in subjects with lung disease, most likely indicating parenchymal inflammation. In light of these observations we believe that MXTC has potential as a biomarker for the regional quantification of 1) emphysematous tissue destruction in chronic obstructive pulmonary disease (using the tissue density parameter) and 2) parenchymal inflammation or thickening (using the wall thickness parameter). By simultaneously quantifying two lung function parameters, MXTC provides a more comprehensive picture of lung microstructure than existing lung imaging techniques and could become an important non-invasive and quantitative tool to characterize pulmonary disease.

Dregely, Isabel

289

Fast magnetic resonance temperature imaging for focused ultrasound thermal therapy  

NASA Astrophysics Data System (ADS)

The current standard for temperature sensitive imaging using magnetic resonance (MR) is 2-D, spoiled, fast gradient-echo (fGRE) phase-difference imaging exploiting temperature dependent changes in the proton resonance frequency (PRF). The echo-time (TE) for optimal sensitivity is larger than the typical repetition time (TR) of an fGRE sequence. Since TE must be less than TR in the fGRE sequence, this limits the technique's achievable sensitivity, spatial, and temporal resolution. This adversely affects both accuracy and volume coverage of the measurements. Accurate measurement of the rapid temperature changes associated with pulsed thermal therapies, such as high-intensity focused ultrasound (FUS), at optimal temperature sensitivity requires faster acquisition times than those currently available. Use of fast MR acquisition strategies, such as interleaved echo-planar and spiral imaging, can provide the necessary increase in temporal performance and sensitivity while maintaining adequate signal-to-noise and in-plane spatial resolution. This research explored the adaptation and optimization of several fast MR acquisition methods for thermal monitoring of pulsed FUS thermal therapy. Temperature sensitivity, phase- difference noise and phase-difference to phase- difference-to noise ratio for the different pulse sequences were evaluated under varying imaging parameters in an agar gel phantom to establish optimal sequence parameters for temperature monitoring. The temperature sensitivity coefficient of the gel phantom was measured, allowing quantitative temperature extrapolations. Optimized fast sequences were compared based on the ability to accurately monitor temperature changes at the focus of a high-intensity focused ultrasound unit, volume coverage, and contrast-to-noise ratio in the temperature maps. Operating parameters, which minimize complex phase- difference measurement errors introduced by use of the fast-imaging methods, were established.

Stafford, Roger Jason

290

Dynamic magnetic resonance imaging of head and neck lesions.  

PubMed

Dynamic magnetic resonance imaging (MRI) has been used to improve the detection of tumors, to determine the tumor extension, and to make differential diagnosis. Most malignant lesions of the head and neck show early enhancement and early washout of contrast media on dynamic MRI, but the tumor characterization remains unclear. Pharmacokinetic analysis of dynamic MRI can provide information about the permeability of Gd-DTPA in the tumor that may reflect the oxygen concentration of the tumor and the amount of drug delivered to the tumor. This information may be useful in the prediction of radiation and/or chemotherapy response of the tumor. PMID:10551627

Baba, Y; Yamashita, Y; Onomichi, M; Murakami, R; Takahashi, M

1999-04-01

291

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

292

The fundamentals of fetal magnetic resonance imaging: Part 2.  

PubMed

Careful assessment of fetal anatomy by a combination of ultrasound and fetal magnetic resonance imaging offers the clinical teams and counselors caring for the patient information that can be critical for the management of both the mother and the fetus. In the second half of this 2-part review, we focus on space-occupying lesions in the fetal body. Because developing fetal tissues are programmed to grow rapidly, mass lesions can have a substantial effect on the formation of normal adjacent organs. Congenital diaphragmatic hernia and lung masses, fetal teratoma, and intra-abdominal masses are discussed, with an emphasis on differential etiologies and on fundamental management considerations. PMID:24974309

Plunk, Matthew R; Chapman, Teresa

2014-01-01

293

Serial fetal magnetic resonance imaging of cloacal exstrophy.  

PubMed

Cloacal exstrophy (CE) is a rare congenital malformation involving the urinary, intestinal, and genital systems. We present a case of CE in which characteristic findings were detected at two serial fetal magnetic resonance imaging (MRI) sessions. At 18 weeks' gestation, the initial fetal MRI revealed a cystic mass protruding from the infra-umbilical abdominal wall. During fetal development, the cystic mass disappeared, and an omphalocele and heterogeneous soft tissue mass were recognized at 28 weeks' gestation. The bladder was not visualized on either examination. CE can be diagnosed by prenatal MRI, thereby permitting prenatal counseling and appropriate postnatal management. PMID:21956372

Yamano, Toshiko; Ando, Kumiko; Ishikura, Reiichi; Hirota, Shozo

2011-11-01

294

Biological Effects and Safety in Magnetic Resonance Imaging: A Review  

PubMed Central

Since the introduction of Magnetic Resonance Imaging (MRI) as a diagnostic technique, the number of people exposed to electromagnetic fields (EMF) has increased dramatically. In this review, based on the results of a pioneer study showing in vitro and in vivo genotoxic effects of MRI scans, we report an updated survey about the effects of non-ionizing EMF employed in MRI, relevant for patients’ and workers’ safety. While the whole data does not confirm a risk hypothesis, it suggests a need for further studies and prudent use in order to avoid unnecessary examinations, according to the precautionary principle. PMID:19578460

Hartwig, Valentina; Giovannetti, Giulio; Vanello, Nicola; Lombardi, Massimo; Landini, Luigi; Simi, Silvana

2009-01-01

295

[Tethered spinal cord and lipoma. Contribution of magnetic resonance imaging].  

PubMed

A 12 year-old boy was investigated for progressive deformity of the left foot developing over 2 years. The foot was hollow with equinus varus and claw toes. Signs of a lesion of left L5 and S1 roots were present and spina bifida at L5 was noted on X-rays. Magnetic resonance imaging (MRI) showed a tethered spinal cord associated with a lipoma at the level of the S1 vertebra. Modes of presentation and physiopathology of disorders related to tethered cords are reviewed and the diagnostic value of MRI is emphasized. PMID:3538290

Awada, A; Chatta, G; Majdalani, A; Gautier, J C

1986-01-01

296

Magnetic resonance imaging of electrochemical cells containing bulk metal.  

PubMed

The development of improved energy-storage devices, as well as corrosion prevention and metal-electrofinishing technologies, requires knowledge of local composition and transport behaviour in electrolytes near bulk metals, in situ and in real time. It remains a challenge to acquire such data and new analytical methods are required. Recent work shows that magnetic resonance imaging (MRI) is able to map concentration gradients and visualise electrochemical processes in electrochemical cells containing bulk metals. This recent work, along with the challenges, and solutions, associated with MRI of these electrochemical cells are reviewed. PMID:24789698

Britton, Melanie M

2014-06-23

297

O'Donoghue's triad: magnetic resonance imaging evidence  

Microsoft Academic Search

Objective  The objective was to search for magnetic resonance imaging evidence of medial collateral ligament (MCL) injury in knees with\\u000a proven tears of the anterior cruciate ligament (ACL) and medial meniscus; the three abnormalities that make up O'Donoghue's\\u000a triad. Although the MCL injury can be unapparent clinically, knee joint stability may be compromised.\\u000a \\u000a \\u000a \\u000a Design  The superficial portion of the MCL was evaluated

Ronald B. Staron; Nogah Haramati; Frieda Feldman; Howard A. Kiernan; H. Charles Pfaff; Stuart J. Rubin; Alicia Zwass

1994-01-01

298

Interpretation of the magnetic resonance imaging signal from a foam  

SciTech Connect

Foams are important in a variety of industries including food, petroleum and chemical processing. Recently several research groups have demonstrated the effectiveness of measuring vertical phase density in foams as a function of time by magnetic resonance imaging (MRI). The advantage of using MRI for studying the stability of such multiphase systems lies in the ability to uniquely determine the density as a function of position noninvasively. Data obtained from these experiments should prove to be a sensitive test of theoretical models of these systems. The objective of this communication is to describe difficulties associated with interpretation of the MRI signal from foams.

McCarthy, M.J. (California Univ., Davis, CA (USA). Dept. of Food Science and Technology)

1990-02-01

299

Ventilation and perfusion magnetic resonance imaging of the lung  

PubMed Central

Summary A close interaction between the respiratory pump, pulmonary parenchyma and blood circulation is essential for a normal lung function. Many pulmonary diseases present, especially in their initial phase, a variable regional impairment of ventilation and perfusion. In the last decades various techniques have been established to measure the lung function. Besides the global pulmonary function tests (PFTs) imaging techniques gained increasing importance to detect local variations in lung function, especially for ventilation and perfusion assessment. Imaging modalities allow for a deeper regional insight into pathophysiological processes and enable improved planning of invasive procedures. In contrast to computed tomography (CT) and the nuclear medicine techniques, magnetic resonance imaging (MRI), as a radiation free imaging modality gained increasing importance since the early 1990 for the assessment of pulmonary function. The major inherent problems of lung tissue, namely the low proton density and the pulmonary and cardiac motion, were overcome in the last years by a constant progress in MR technology. Some MR techniques are still under development, a process which is driven by scientific questions regarding the physiology and pathophysiology of pulmonary diseases, as well as by the need for fast and robust clinically applicable imaging techniques as safe therapy monitoring tools. MRI can be considered a promising ionizing-free alternative to techniques like CT or nuclear medicine techniques for the evaluation of lung function. The goal of this article is to provide an overview on selected MRI techniques for the assessment of pulmonary ventilation and perfusion. PMID:22802864

Bauman, Grzegorz; Eichinger, Monika

2012-01-01

300

Prostate cancer magnetic resonance imaging (MRI): multidisciplinary standpoint  

PubMed Central

Prostate cancer is the most common cancer diagnosed in men and a leading cause of death. Accurate assessment is a prerequisite for optimal clinical management and therapy selection of prostate cancer. There are several parameters and nomograms to differentiate between patients with clinically insignificant disease and patients in need of treatment. Magnetic resonance imaging (MRI) is a technique which provides more detailed anatomical images due to high spatial resolution, superior contrast resolution, and multiplanar capability. State-of-the-art MRI techniques, such as diffusion weighted imaging (DWI), MR spectroscopic imaging (MRSI), dynamic contrast enhanced MRI (DCE-MRI), improve interpretation of prostate cancer imaging. In this article, we review the major role of MRI in the advanced management of prostate cancer to noninvasively improve tumor staging, biologic potential, treatment planning, therapy response, local recurrence, and to guide target biopsy for clinical suspected cancer with previous negative biopsy. Finally, future challenges and opportunities in prostate cancer management in the area of functional MRI are discussed as well. PMID:23630657

Li, Liang; Feng, Zhaoyan; Hu, Zhiquan; Wang, Guoping; Yuan, Xianglin; Wang, He; Hu, Daoyu

2013-01-01

301

Image guided interstitial laser thermotherapy: a canine model evaluated by magnetic resonance imaging and quantitative autoradiography  

Microsoft Academic Search

Summary Objective. To determine the applicability and safety of a new canine model suitable for correlative magnetic resonance imaging (MRI) studies and morphological\\/pathophysiological examination over time after interstitial laser thermotherapy (ILTT) in brain tissue. Material and methods. A laser fibre (Diode Laser 830?nm) with an integrated temperature feedback system was inserted into the right frontal white matter in 18 dogs

A. Muacevic; M. Peller; L. Ruprecht; D. Berg; L. Fend; R. Sroka; H. J. Reulen; M. Reiser; J. Ch. Tonn; F. W. Kreth

2005-01-01

302

Stroke Assessment with Diffusional Kurtosis Imaging  

PubMed Central

Background and Purpose Despite being the gold standard technique for stroke assessment, conventional diffusion magnetic resonance imaging (dMRI) provides only partial information about tissue microstructure. Diffusional kurtosis imaging (DKI) is an advanced dMRI method that yields, in addition to conventional diffusion information, the diffusional kurtosis (K), which may help improve characterization of tissue microstructure. In particular, this additional information permits the description of white matter (WM) in terms of WM-specific diffusion metrics (WMM). The goal of this study is to elucidate possible biophysical mechanisms underlying ischemia using these new WMM. Methods We performed a retrospective review of clinical and DKI data of forty-four acute/subacute ischemic stroke patients. Patients with a history of brain neoplasm or intracranial hemorrhages were excluded from this study. ROI analysis was performed to measure percent change of diffusion metrics in ischemic WM lesions compared to the contralateral hemisphere. Results K maps exhibit distinct ischemic lesion heterogeneity that is not apparent on apparent diffusion coefficient (ADC) maps. K metrics also have significantly higher absolute percent change than complementary conventional diffusion metrics. Our WMM reveal an increase in axonal density and a larger decrease in the intra-axonal (Da) compared to extra-axonal (De) diffusion microenvironment of the ischemic WM lesion. Conclusions The well-known decrease in the ADC of WM following ischemia is found to be mainly driven by a significant drop in Da. Our results suggest that ischemia preferentially alters intra-axonal environment, consistent with a proposed mechanism of focal enlargement of axons known as axonal swelling or beading. PMID:22933581

Hui, Edward S.; Fieremans, Els; Jensen, Jens H.; Tabesh, Ali; Feng, Wuwei; Bonilha, Leonardo; Spampinato, Maria V.; Adams, Robert; Helpern, Joseph A.

2012-01-01

303

Applications of Manganese-Enhanced Magnetic Resonance Imaging in Neuroscience  

NASA Astrophysics Data System (ADS)

Manganese-Enhanced Magnetic Resonance Imaging (MEMRI) has proven itself to be a beneficial technique in the field of Neuroscience. This thesis applies MEMRI to studies in neuroscience by first establishing the limitations concerning the use of MEMRI in live rats. Experiment 1 used an osmotic pump for manganese (Mn) delivery to the lateral ventricles for acquisition of anatomical images using MEMRI. From my knowledge, this was the first method demonstrating slow infusion of Mn to the lateral ventricles. In Experiment 2, MEMRI was used for volumetric analysis the whole brain and hippocampus of prenatally stressed rats. To my knowledge, this study was the first to investigate the effect of generational prenatal stress on the structure of a rat's brain using MEMRI and histology. Additionally, Experiment 2 investigated the use of a subcutaneous osmotic pump to deliver Mn for MEMRI. A summary on the use of MEMRI in Neuroscience concludes this thesis, with a discussion on the methods used and related technical considerations.

McCreary, J. Keiko

304

3-D Display Of Magnetic Resonance Imaging Of The Spine  

NASA Astrophysics Data System (ADS)

The original data is produced through standard magnetic resonance imaging (MRI) procedures with a surface coil applied to the lower back of a normal human subject. The 3-D spine image data consists of twenty-six contiguous slices with 256 x 256 pixels per slice. Two methods for visualization of the 3-D spine are explored. One method utilizes a verifocal mirror system which creates a true 3-D virtual picture of the object. Another method uses a standard high resolution monitor to simultaneously show the three orthogonal sections which intersect at any user-selected point within the object volume. We discuss the application of these systems in assessment of low back pain.

Nelson, Alan C.; Kim, Yongmin; Haralick, Robert M.; Anderson, Paul A.; Johnson, Roger H.; DeSoto, Larry A.

1988-06-01

305

Magnetic resonance imaging of chemical waves in porous media  

NASA Astrophysics Data System (ADS)

Magnetic resonance imaging (MRI) provides a powerful tool for the investigation of chemical structures in optically opaque porous media, in which chemical concentration gradients can be visualized, and diffusion and flow properties are simultaneously determined. In this paper we give an overview of the MRI technique and review theory and experiments on the formation of chemical waves in a tubular packed bed reactor upon the addition of a nonlinear chemical reaction. MR images are presented of reaction-diffusion waves propagating in the three-dimensional (3D) network of channels in the reactor, and the 3D structure of stationary concentration patterns formed via the flow-distributed oscillation mechanism is demonstrated to reflect the local hydrodynamics in the packed bed. Possible future directions regarding the influence of heterogeneities on transport and reaction are discussed.

Taylor, Annette F.; Britton, Melanie M.

2006-09-01

306

Magnetic resonance imaging of the preterm infant brain.  

PubMed

Despite improvements in neonatal care, survivors of preterm birth are still at a significantly increased risk of developing life-long neurological difficulties including cerebral palsy and cognitive difficulties. Cranial ultrasound is routinely used in neonatal practice, but has a low sensitivity for identifying later neurodevelopmental difficulties. Magnetic Resonance Imaging (MRI) can be used to identify intracranial abnormalities with greater diagnostic accuracy in preterm infants, and theoretically might improve the planning and targeting of long-term neurodevelopmental care; reducing parental stress and unplanned healthcare utilisation; and ultimately may improve healthcare cost effectiveness. Furthermore, MR imaging offers the advantage of allowing the quantitative assessment of the integrity, growth and function of intracranial structures, thereby providing the means to develop sensitive biomarkers which may be predictive of later neurological impairment. However further work is needed to define the accuracy and value of diagnosis by MR and the techniques's precise role in care pathways for preterm infants. PMID:25055863

Doria, Valentina; Arichi, Tomoki; Edwards, David A

2014-01-01

307

Magnetic resonance imaging of the pericardium: normal and pathologic findings  

SciTech Connect

Twenty normal subjects and ten patients with pericardial abnormalities underwent ECG-gated magnetic resonance (MR) imaging of the thorax using a 0.35-tesla superconducting system. The patients with pericardial abnormalities were also evaluated with serial chest radiography, ultrasound, computed tomography, and/or angiography. ECG gating was necessary to identify the normal pericardium, which was visualized as a 1- to 2-mm-wide curvilinear structure of low signal intensity. Pericardial thickening in constrictive pericarditis was clearly delineated on gated MR images. Pericardial inflammation caused a marked increase in signal intensity as well as thickening of the pericardium. Pericardial effusions and pericardial adhesions were also demonstrated. A simple pericardial cyst and a complex pericardial mass were identified and differentiated from pericardial fat and diaphragmatic eventration. MR appears to be an important modality for the evaluation of pericardial disease.

Stark, D.D.; Higgins, C.B.; Lanzer, P.; Lipton, M.J.; Schiller, N.; Crooks, L.E.; Botvinick, E.B.; Kaufman, L.

1984-02-01

308

Simultaneous magnetic resonance imaging and consolidation measurement of articular cartilage.  

PubMed

Magnetic resonance imaging (MRI) offers the opportunity to study biological tissues and processes in a non-disruptive manner. The technique shows promise for the study of the load-bearing performance (consolidation) of articular cartilage and changes in articular cartilage accompanying osteoarthritis. Consolidation of articular cartilage involves the recording of two transient characteristics: the change over time of strain and the hydrostatic excess pore pressure (HEPP). MRI study of cartilage consolidation under mechanical load is limited by difficulties in measuring the HEPP in the presence of the strong magnetic fields associated with the MRI technique. Here we describe the use of MRI to image and characterize bovine articular cartilage deforming under load in an MRI compatible consolidometer while monitoring pressure with a Fabry-Perot interferometer-based fiber-optic pressure transducer. PMID:24803188

Wellard, Robert Mark; Ravasio, Jean-Philippe; Guesne, Samuel; Bell, Christopher; Oloyede, Adekunle; Tevelen, Greg; Pope, James M; Momot, Konstantin I

2014-01-01

309

The role of magnetic resonance imaging in hypertrophic cardiomyopathy  

PubMed Central

Hypertrophic cardiomyopathy (HCM) is the most common inheritable cardiac disorder, with an estimated prevalence of 1:500 in the general population. Most cases of HCM are phenotypically expressed in adolescence or early adulthood but age-related penetrance with certain phenotypes is increasingly recognized. Clinical manifestations of HCM are usually the result of systolic and/or diastolic dysfunction, left ventricular outflow tract (LVOT) obstruction, arrhythmias and sudden cardiac death (SCD). In recent years magnetic resonance imaging (MRI) has become established as an important tool for the evaluation of suspected HCM as it can reliably establish the diagnosis, help distinguish HCM from other causes of left ventricular hypertrophy (LVH) and identify those patients at greatest risk of SCD. This article reviews the current status of MRI in the evaluation of the HCM patient including imaging protocols, disease characterization and the emerging role of MRI for risk stratification and proband screening. PMID:25392824

Elassaly, Mohamed; Ganeshan, Arul; Watkin, Richard W.; Simpson, Helen

2014-01-01

310

The role of magnetic resonance imaging in hypertrophic cardiomyopathy.  

PubMed

Hypertrophic cardiomyopathy (HCM) is the most common inheritable cardiac disorder, with an estimated prevalence of 1:500 in the general population. Most cases of HCM are phenotypically expressed in adolescence or early adulthood but age-related penetrance with certain phenotypes is increasingly recognized. Clinical manifestations of HCM are usually the result of systolic and/or diastolic dysfunction, left ventricular outflow tract (LVOT) obstruction, arrhythmias and sudden cardiac death (SCD). In recent years magnetic resonance imaging (MRI) has become established as an important tool for the evaluation of suspected HCM as it can reliably establish the diagnosis, help distinguish HCM from other causes of left ventricular hypertrophy (LVH) and identify those patients at greatest risk of SCD. This article reviews the current status of MRI in the evaluation of the HCM patient including imaging protocols, disease characterization and the emerging role of MRI for risk stratification and proband screening. PMID:25392824

Hoey, Edward T D; Elassaly, Mohamed; Ganeshan, Arul; Watkin, Richard W; Simpson, Helen

2014-10-01

311

Accelerated magnetic resonance imaging using the sparsity of multi-channel coil images.  

PubMed

Joint estimation of coil sensitivities and output image (JSENSE) is a promising approach that improves the reconstruction of parallel magnetic resonance imaging (pMRI). However, when acceleration factor increases, the signal to noise ratio (SNR) of JSENSE reconstruction decreases as quickly as that of the conventional pMRI. Although sparse constraints have been used to improve the JSENSE reconstruction in recent years, these constraints only use the sparsity of the output image, which cannot fully exploit the prior information of pMRI. In this paper, we use the sparsity of coil images, instead of the output image, to exploit more prior information for JSENSE. Numerical simulation, phantom and in vivo experiments demonstrate that the proposed method has better performance than the SparseSENSE method and the constrained JSENSE method using the sparsity of the output image only. PMID:24268132

Xie, Guoxi; Song, Yibiao; Shi, Caiyun; Feng, Xiang; Zheng, Hairong; Weng, Dehe; Qiu, Bensheng; Liu, Xin

2014-02-01

312

Measurement of flow through porous media by magnetic resonance imaging  

SciTech Connect

Quantitative imaging of flow through porous media is possible utilizing pulsed gradient phase encoding techniques in MRI (magnetic resonance imaging). The random directional motion of the fluid in a porous medium causes signal attenuation due to the dispersion of the phase information when velocity phase encoding gradient pulses are applied. Isolation of the effect of molecular diffusion process which is random not only in space but also in time in achieved by acquiring images with velocity compensated gradient pulses for measurement of the diffusion constant. PFOB (perfluorooctyl bromide) was used as an intravascular contrast agent in the experiments on the rabbit kidney models for extraction of all available information about the parameters governing the microvascular flow process in one MRI setup. A pulse sequence program was developed on a 1.5 T whole body MRI system to incorporate the multislice data collection, chemical-shift artifact correction, and cardiac gating algorithms. The complete imaging setup also included several radio frequency coils for F-19 imaging and an image reconstruction program with a motion artifact suppression algorithm required for collection of flow sensitive images in in-vivo studies. The results obtained from the experiments on the rabbit kidneys verified the proposed formulation for the quantitative analysis of microvascular flow. These studies on the animal models indicated that the measurement of microvascular flow on an absolute scale can be realized using the phase sensitive pulsed gradient velocity encoding methods. Utilization of the measurement and analysis techniques can be possible in the controlled experiments such as monitoring tumor responses to a certain kind of therapy through the evaluation of the microvascular flow.

Oezdemirel, B.

1992-01-01

313

Surface Plasmon Resonance Imaging Using a High Numerical Aperture Microscope Objective  

E-print Network

) phenomenon1 occurs when the external light energy resonantly induces the free electrons of the metal to achieve two-dimensional (2D) imaging, which is called surface plasmon resonance imaging (SPRI). Since its) microscopy,9 which solves the image distortion and movement problem. The use of a high NA and high

Zare, Richard N.

314

Imaging diagnosis--magnetic resonance imaging findings in a dog with sequential brain infarction.  

PubMed

An adult greyhound was evaluated on three occasions for acute, intracranial neurologic signs. Based on magnetic resonance (MR) imaging, there were T2-hyperintense and T1-hypointense, noncontrast enhancing lesions in the cerebellum, and brain stem. Using diffusion-weighted imaging (DWI), the lesions were characterized initially by restricted water diffusion. The presumptive diagnosis on each occasion was acute ischemic cerebrovascular accident leading to infarction. This allowed us to characterize the changes in appearance of infarcted neural tissue on the standard MR sequences over time, and to confirm that the DWI could be successfully used in low-field imaging. © 2012 Veterinary Radiology & Ultrasound. PMID:22731883

Major, Alison C; Caine, Abby; Rodriguez, Sue B; Cherubini, Giunio B

2012-01-01

315

The physics of functional magnetic resonance imaging (fMRI).  

PubMed

Functional magnetic resonance imaging (fMRI) is a methodology for detecting dynamic patterns of activity in the working human brain. Although the initial discoveries that led to fMRI are only about 20 years old, this new field has revolutionized the study of brain function. The ability to detect changes in brain activity has a biophysical basis in the magnetic properties of deoxyhemoglobin, and a physiological basis in the way blood flow increases more than oxygen metabolism when local neural activity increases. These effects translate to a subtle increase in the local magnetic resonance signal, the blood oxygenation level dependent (BOLD) effect, when neural activity increases. With current techniques, this pattern of activation can be measured with resolution approaching 1 mm(3) spatially and 1 s temporally. This review focuses on the physical basis of the BOLD effect, the imaging methods used to measure it, the possible origins of the physiological effects that produce a mismatch of blood flow and oxygen metabolism during neural activation, and the mathematical models that have been developed to understand the measured signals. An overarching theme is the growing field of quantitative fMRI, in which other MRI methods are combined with BOLD methods and analyzed within a theoretical modeling framework to derive quantitative estimates of oxygen metabolism and other physiological variables. That goal is the current challenge for fMRI: to move fMRI from a mapping tool to a quantitative probe of brain physiology. PMID:24006360

Buxton, Richard B

2013-09-01

316

Use of Functional Magnetic Resonance Imaging (Blood Oxygenation Level-Dependent Imaging, Diffusion Tensor Imaging and Magnetic Resonance Spectroscopy) in Brain Development Research  

Microsoft Academic Search

The development of several new magnetic resonance imaging (MRI) techniques has facilitated serial observations of the developing human brain in utero. For example, the noninvasive technique of functional MRI, which is used to study brain anatomy, function and metabolism in both humans and animals, has already enhanced our understanding of brain development and behavior relations. Currently, three main kinds of

Fei Fei Yang; Shu Guang Yuan; David T. Yew

2008-01-01

317

Work in progress: nuclear magnetic resonance imaging of the gallbladder  

SciTech Connect

A preliminary study of the relation between food intake and intensity of gallbladder bile on nuclear magnetic resonance (NMR) images was made. Twelve subjects (seven volunteers, five patients) were imaged following a minimum of 14 hours of fasting. Six of seven volunteers were reimaged one hour after stimulation by either a fatty meal or an alcoholic beverage. An additional seven patients were imaged two hours after a hospital breakfast. It was found that concentrated bile emits a high-intensity spin echo signal (SE), while hepatic bile in the gallbladder produces a low-intensity SE signal. Following ingestion of cholecystogogue, dilute hepatic bile settles on top of the concentrated bile, each emitting SE signals of different intensity. The average T1 value of concentrated bile was 594 msec, while the T1 vaue of dilute hepatic bile was 2,646 msec. The average T2 values were 104 msec for concentrated bile and 126 msec for dilute bile. The most likely cause for the different SE intensities of bile is the higher water content, and therefore longer T1 or T2 relaxation times, of hepatic bile. It is suggested that NMR imaging has the ability to provide physiological information about the gallbladder and that it may prove to be a simple and safe clinical test of gallbladder function.

Hricak, H.; Filly, R.A.; Margulis, A.R.; Moon, K.L.; Crooks, L.E.; Kaufman, L.

1983-05-01

318

Magnetic resonance imaging of microstructure transition in stainless steel.  

PubMed

Magnetic resonance images are prone to artifacts caused by metallic objects. Such artifacts may not only hamper image interpretation, but also have been shown to provide information about the magnetic properties of the substances involved. In this work, we aim to explore the potential of MRI to detect, localize and characterize changes in magnetic properties that may occur when certain alloys have been exposed to a thermomechanical stress. For this purpose, stainless steel 304 L wires were drawn to induce a change from paramagnetic austenitic into ferromagnetic martensitic microstructure. The changes in magnetic behavior were quantified by analyzing the geometric distortion in spin echo and the geometric distortion and intravoxel dephasing in gradient echo images at 0.5, 1.5 and 3 T. The results of both imaging strategies were in agreement and in accordance with independent measurements with a vibrating sample magnetometer. Drawing wire to 2% of its cross-sectional area was found to increase the volume fraction of the ferromagnetic martensite from 0.3% to 80% and to enhance the magnetization up to two or three orders of magnitude. The results demonstrate the potential of MRI to locate and quantify stress-induced changes in the magnetic properties of alloys in a completely noninvasive and nondestructive way. PMID:16735191

Peeters, Johannes M; van Faassen, Ernst E H; Bakker, Chris J G

2006-06-01

319

Magnetic resonance imaging of brain angiogenesis after stroke  

PubMed Central

Stroke is a major cause of mortality and long-term disability worldwide. The initial changes in local perfusion and tissue status underlying loss of brain function are increasingly investigated with noninvasive imaging methods. In addition, there is a growing interest in imaging of processes that contribute to post-stroke recovery. In this review, we discuss the application of magnetic resonance imaging (MRI) to assess the formation of new vessels by angiogenesis, which is hypothesized to participate in brain plasticity and functional recovery after stroke. The excellent soft tissue contrast, high spatial and temporal resolution, and versatility render MRI particularly suitable to monitor the dynamic processes involved in vascular remodeling after stroke. Here we review recent advances in the field of MR imaging that are aimed at assessment of tissue perfusion and microvascular characteristics, including cerebral blood flow and volume, vascular density, size and integrity. The potential of MRI to noninvasively monitor the evolution of post-ischemic angiogenic processes is demonstrated from a variety of in vivo studies in experimental stroke models. Finally, we discuss some pitfalls and limitations that may critically affect the accuracy and interpretation of MRI-based measures of (neo)vascularization after stroke. PMID:20552268

Deddens, Lisette H.

2010-01-01

320

Active resonant subwavelength grating for scannerless range imaging sensors.  

SciTech Connect

In this late-start LDRD, we will present a design for a wavelength-agile, high-speed modulator that enables a long-term vision for the THz Scannerless Range Imaging (SRI) sensor. It takes the place of the currently-utilized SRI micro-channel plate which is limited to photocathode sensitive wavelengths (primarily in the visible and near-IR regimes). Two of Sandia's successful technologies--subwavelength diffractive optics and THz sources and detectors--are poised to extend the capabilities of the SRI sensor. The goal is to drastically broaden the SRI's sensing waveband--all the way to the THz regime--so the sensor can see through image-obscuring, scattering environments like smoke and dust. Surface properties, such as reflectivity, emissivity, and scattering roughness, vary greatly with the illuminating wavelength. Thus, objects that are difficult to image at the SRI sensor's present near-IR wavelengths may be imaged more easily at the considerably longer THz wavelengths (0.1 to 1mm). The proposed component is an active Resonant Subwavelength Grating (RSG). Sandia invested considerable effort on a passive RSG two years ago, which resulted in a highly-efficient (reflectivity greater than gold), wavelength-specific reflector. For this late-start LDRD proposal, we will transform the passive RSG design into an active laser-line reflector.

Kemme, Shanalyn A.; Nellums, Robert O.; Boye, Robert R.; Peters, David William

2006-11-01

321

Radiation-induced optic neuropathy: A magnetic resonance imaging study  

SciTech Connect

Optic neuropathy induced by radiation is an infrequent cause of delayed visual loss that may at times be difficult to differentiate from compression of the visual pathways by recurrent neoplasm. The authors describe six patients with this disorder who experienced loss of vision 6 to 36 months after neurological surgery and radiation therapy. Of the six patients in the series, two had a pituitary adenoma and one each had a metastatic melanoma, multiple myeloma, craniopharyngioma, and lymphoepithelioma. Visual acuity in the affected eyes ranged from 20/25 to no light perception. Magnetic resonance (MR) imaging showed sellar and parasellar recurrence of both pituitary adenomas, but the intrinsic lesions of the optic nerves and optic chiasm induced by radiation were enhanced after gadolinium-diethylenetriaminepenta-acetic acid (DTPA) administration and were clearly distinguishable from the suprasellar compression of tumor. Repeated MR imaging showed spontaneous resolution of gadolinium-DTPA enhancement of the optic nerve in a patient who was initially suspected of harboring recurrence of a metastatic malignant melanoma as the cause of visual loss. The authors found the presumptive diagnosis of radiation-induced optic neuropathy facilitated by MR imaging with gadolinium-DTPA. This neuro-imaging procedure may help avert exploratory surgery in some patients with recurrent neoplasm in whom the etiology of visual loss is uncertain.

Guy, J.; Mancuso, A.; Beck, R.; Moster, M.L.; Sedwick, L.A.; Quisling, R.G.; Rhoton, A.L. Jr.; Protzko, E.E.; Schiffman, J. (Univ. of Florida, Gainesville (USA))

1991-03-01

322

jSIPRO - analysis tool for magnetic resonance spectroscopic imaging.  

PubMed

Magnetic resonance spectroscopic imaging (MRSI) involves a huge number of spectra to be processed and analyzed. Several tools enabling MRSI data processing have been developed and widely used. However, the processing programs primarily focus on sophisticated spectra processing and offer limited support for the analysis of the calculated spectroscopic maps. In this paper the jSIPRO (java Spectroscopic Imaging PROcessing) program is presented, which is a java-based graphical interface enabling post-processing, viewing, analysis and result reporting of MRSI data. Interactive graphical processing as well as protocol controlled batch processing are available in jSIPRO. jSIPRO does not contain a built-in fitting program. Instead, it makes use of fitting programs from third parties and manages the data flows. Currently, automatic spectra processing using LCModel, TARQUIN and jMRUI programs are supported. Concentration and error values, fitted spectra, metabolite images and various parametric maps can be viewed for each calculated dataset. Metabolite images can be exported in the DICOM format either for archiving purposes or for the use in neurosurgery navigation systems. PMID:23870172

Jiru, Filip; Skoch, Antonin; Wagnerova, Dita; Dezortova, Monika; Hajek, Milan

2013-10-01

323

Grid Computing Application for Brain Magnetic Resonance Image Processing  

NASA Astrophysics Data System (ADS)

This work emphasizes the use of grid computing and web technology for automatic post-processing of brain magnetic resonance images (MRI) in the context of neuropsychiatric (Alzheimer's disease) research. Post-acquisition image processing is achieved through the interconnection of several individual processes into pipelines. Each process has input and output data ports, options and execution parameters, and performs single tasks such as: a) extracting individual image attributes (e.g. dimensions, orientation, center of mass), b) performing image transformations (e.g. scaling, rotation, skewing, intensity standardization, linear and non-linear registration), c) performing image statistical analyses, and d) producing the necessary quality control images and/or files for user review. The pipelines are built to perform specific sequences of tasks on the alphanumeric data and MRIs contained in our database. The web application is coded in PHP and allows the creation of scripts to create, store and execute pipelines and their instances either on our local cluster or on high-performance computing platforms. To run an instance on an external cluster, the web application opens a communication tunnel through which it copies the necessary files, submits the execution commands and collects the results. We present result on system tests for the processing of a set of 821 brain MRIs from the Alzheimer's Disease Neuroimaging Initiative study via a nonlinear registration pipeline composed of 10 processes. Our results show successful execution on both local and external clusters, and a 4-fold increase in performance if using the external cluster. However, the latter's performance does not scale linearly as queue waiting times and execution overhead increase with the number of tasks to be executed.

Valdivia, F.; Crépeault, B.; Duchesne, S.

2012-02-01

324

Dedicated Magnetic Resonance Imaging in the Radiotherapy Clinic  

SciTech Connect

Purpose: To introduce a novel technology arrangement in an integrated environment and outline the logistics model needed to incorporate dedicated magnetic resonance (MR) imaging in the radiotherapy workflow. An initial attempt was made to analyze the value and feasibility of MR-only imaging compared to computed tomography (CT) imaging, testing the assumption that MR is a better choice for target and healthy tissue delineation in radiotherapy. Methods and Materials: A 1.5-T MR unit with a 70-cm-bore size was installed close to a linear accelerator, and a special trolley was developed for transporting patients who were fixated in advance between the MR unit and the accelerator. New MR-based workflow procedures were developed and evaluated. Results: MR-only treatment planning has been facilitated, thus avoiding all registration errors between CT and MR scans, but several new aspects of MR imaging must be considered. Electron density information must be obtained by other methods. Generation of digitally reconstructed radiographs (DRR) for x-ray setup verification is not straight forward, and reliable corrections of geometrical distortions must be applied. The feasibility of MR imaging virtual simulation has been demonstrated, but a key challenge to overcome is correct determination of the skeleton, which is often needed for the traditional approach of beam modeling. The trolley solution allows for a highly precise setup for soft tissue tumors without the invasive handling of radiopaque markers. Conclusions: The new logistics model with an integrated MR unit is efficient and will allow for improved tumor definition and geometrical precision without a significant loss of dosimetric accuracy. The most significant development needed is improved bone imaging.

Karlsson, Mikael [Radiation Physics Section, Department of Radiation Sciences, Umea University, 90187 Umea (Sweden)], E-mail: Mikael.Karlsson@radfys.umu.se; Karlsson, Magnus G. [Department of Radiation Physics, Umea University Hospital, 90185 Umea (Sweden); Nyholm, Tufve [Radiation Physics Section, Department of Radiation Sciences, Umea University, 90187 Umea (Sweden); Department of Radiation Physics, Umea University Hospital, 90185 Umea (Sweden); Amies, Christopher [Siemens Medical Systems, Oncology Care Systems Group, Concord, California (United States); Zackrisson, Bjoern [Section of Oncology, Department of Radiation Sciences, Umea University, 90187 Umea (Sweden)

2009-06-01

325

Magnetic resonance cholangiopancreatography image enhancement for automatic disease detection  

PubMed Central

AIM: To sufficiently improve magnetic resonance cholangiopancreatography (MRCP) quality to enable reliable computer-aided diagnosis (CAD). METHODS: A set of image enhancement strategies that included filters (i.e. Gaussian, median, Wiener and Perona-Malik), wavelets (i.e. contourlet, ridgelet and a non-orthogonal noise compensation implementation), graph-cut approaches using lazy-snapping and Phase Unwrapping MAxflow, and binary thresholding using a fixed threshold and dynamic thresholding via histogram analysis were implemented to overcome the adverse characteristics of MRCP images such as acquisition noise, artifacts, partial volume effect and large inter- and intra-patient image intensity variations, all of which pose problems in application development. Subjective evaluation of several popular pre-processing techniques was undertaken to improve the quality of the 2D MRCP images and enhance the detection of the significant biliary structures within them, with the purpose of biliary disease detection. RESULTS: The results varied as expected since each algorithm capitalized on different characteristics of the images. For denoising, the Perona-Malik and contourlet approaches were found to be the most suitable. In terms of extraction of the significant biliary structures and removal of background, the thresholding approaches performed well. The interactive scheme performed the best, especially by using the strengths of the graph-cut algorithm enhanced by user-friendly lazy-snapping for foreground and background marker selection. CONCLUSION: Tests show promising results for some techniques, but not others, as viable image enhancement modules for automatic CAD systems for biliary and liver diseases. PMID:21160667

Logeswaran, Rajasvaran

2010-01-01

326

Sodium magnetic resonance imaging (MRI) provides an independent and physiologically relevant window for  

E-print Network

Sodium magnetic resonance imaging (MRI) provides an independent and physiologically relevant window will prevent ineffective treatments. These findings are a basis for immediate and important clinical

327

Advanced theory of driven birdcage resonator with losses for biomedical magnetic resonance imaging and spectroscopy.  

PubMed

A complete time-dependent physics theory of symmetric unperturbed driven hybrid birdcage resonator was developed for general application. In particular, the theory can be applied for radiofrequency (RF) coil engineering, computer simulations of coil-sample interaction, etc. Explicit time dependence is evaluated for different forms of driving voltage. The major steps of the solution development are shown and appropriate explanations are given. Green's functions and spectral density formula were developed for any form of periodic driving voltage. The concept of distributed power losses based on transmission line theory is developed for evaluation of local losses of a coil. Three major types of power losses are estimated as equivalent series resistances in the circuit of the birdcage resonator. Values of generated resistances in legs and end-rings are estimated. An application of the theory is shown for many practical cases. Experimental curve of B(1) field polarization dependence is measured for eight-sections birdcage coil. It was shown that the steady-state driven resonance frequencies do not depend on damping factor unlike the free oscillation (transient) frequencies. An equivalent active resistance is generated due to interaction of RF electromagnetic field with a sample. Resistance of the conductor (enhanced by skin effect), Eddy currents and dielectric losses are the major types of losses which contribute to the values of generated resistances. A biomedical sample for magnetic resonance imaging and spectroscopy is the source of the both Eddy current and dielectric losses of a coil. As demonstrated by the theory, Eddy current loss is the major effect of coil shielding. PMID:20869184

Novikov, Alexander

2011-02-01

328

Advanced Theory of Driven Birdcage Resonator with Losses for Biomedical Magnetic Resonance Imaging and Spectroscopy  

PubMed Central

A complete time-dependent physics theory of symmetric unperturbed driven Hybrid Birdcage resonator was developed for general application. In particular, the theory can be applied for RF coil engineering, computer simulations of coil-sample interaction, etc. Explicit time dependence is evaluated for different forms of driving voltage. The major steps of the solution development are shown and appropriate explanations are given. Green’s functions and spectral density formula were developed for any form of periodic driving voltage. The concept of distributed power losses based on transmission line theory is developed for evaluation of local losses of a coil. Three major types of power losses are estimated as equivalent series resistances in the circuit of the Birdcage resonator. Values of generated resistances in Legs and End-Rings are estimated. An application of the theory is shown for many practical cases. Experimental curve of B1 field polarization dependence is measured for eight-sections Birdcage coil. It was shown, that the steady-state driven resonance frequencies do not depend on damping factor unlike the free oscillation (transient) frequencies. An equivalent active resistance is generated due to interaction of RF electromagnetic field with a sample. Resistance of the conductor (enhanced by skin effect), Eddy currents and dielectric losses are the major types of losses which contribute to the values of generated resistances. A biomedical sample for magnetic resonance imaging and spectroscopy is the source of the both Eddy current and dielectric losses of a coil. As demonstrated by the theory, Eddy currents losses is the major effect of coil shielding. PMID:20869184

Novikov, Alexander

2010-01-01

329

Towards simultaneous single emission microscopy and magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

In recent years, the combined nuclear imaging and magnetic resonance imaging (MRI) has drawn extensive research effort. They can provide simultaneously acquired anatomical and functional information inside the human/small animal body in vivo. In this dissertation, the development of an ultrahigh resolution MR-compatible SPECT (Single Photon Emission Computed Tomography) system that can be operated inside a pre-existing clinical MR scanner for simultaneous dual-modality imaging of small animals will be discussed. This system is constructed with 40 small pixel CdTe detector modules assembled in a fully stationary ring SPECT geometry. Series of experiments have demonstrated that this system is capable of providing an imaging resolution of <500?m, when operated inside MR scanners. The ultrahigh resolution MR-compatible SPECT system is built around a small pixel CdTe detector module that we recently developed. Each module consists of CdTe detectors having an overall size of 2.2 cm x 1.1 cm, divided into 64 x 32 pixels of 350 mum in size. A novel hybrid pixel-waveform (HPWF) readout system is also designed to alleviate several challenges for using small-pixel CdTe detectors in ultrahigh-resolution SPECT imaging applications. The HPWF system utilizes a modified version of a 2048-channel 2-D CMOS ASIC to readout the anode pixel, and a digitizing circuitry to sample the signal waveform induced on the cathode. The cathode waveform acquired with the HPWF circuitry offers excellent spatial resolution, energy resolution and depth of interaction (DOI) information, even with the presence of excessive charge-sharing/charge-loss between the small anode pixels. The HPWF CdTe detector is designed and constructed with a minimum amount of ferromagnetic materials, to ensure the MR-compatibility. To achieve sub-500?m imaging resolution, two special designed SPECT apertures have been constructed with different pinhole sizes of 300?m and 500?m respectively. It has 40 pinhole inserts that are made of cast platinum (90%)-iridium (10%) alloy, which provides the maximum stopping power and are compatible with MR scanners. The SPECT system is installed on a non-metal gantry constructed with 3-D printing using nylon powder material. This compact system can work as a "low-cost" desktop ultrahigh resolution SPECT system. It can also be directly operated inside an MR scanner. Accurate system geometrical calibration and corresponding image reconstruction methods for the MRC-SPECT system is developed. In order to account for the magnetic field induced distortion in the SPECT image, a comprehensive charge collection model inside strong magnetic field is adopted to produce high resolution SPECT image inside MR scanner.

Cai, Liang

330

Magnetic Resonance Imaging in Acute Ischemic Stroke Treatment  

PubMed Central

Although intravenous administration of tissue plasminogen activator is the only proven treatment after acute ischemic stroke, there is always a concern of hemorrhagic risk after thrombolysis. Therefore, selection of patients with potential benefits in overcoming potential harms of thrombolysis is of great importance. Despite the practical issues in using magnetic resonance imaging (MRI) for acute stroke treatment, multimodal MRI can provide useful information for accurate diagnosis of stroke, evaluation of the risks and benefits of thrombolysis, and prediction of outcomes. For example, the high sensitivity and specificity of diffusion-weighted image (DWI) can help distinguish acute ischemic stroke from stroke-mimics. Additionally, the lesion mismatch between perfusion-weighted image (PWI) and DWI is thought to represent potential salvageable tissue by reperfusion therapy. However, the optimal threshold to discriminate between benign oligemic areas and the penumbra is still debatable. Signal changes of fluid-attenuated inversion recovery image within DWI lesions may be a surrogate marker for ischemic lesion age and might indicate risks of hemorrhage after thrombolysis. Clot sign on gradient echo image may reflect the nature of clot, and their location, length and morphology may provide predictive information on recanalization by reperfusion therapy. However, previous clinical trials which solely or mainly relied on perfusion-diffusion mismatch for patient selection, failed to show benefits of MRI-based thrombolysis. Therefore, understanding the clinical implication of various useful MRI findings and comprehensively incorporating those variables into therapeutic decision-making may be a more reasonable approach for expanding the indication of acute stroke thrombolysis. PMID:25328872

Kim, Bum Joon; Kang, Hyun Goo; Kim, Hye-Jin; Ahn, Sung-Ho; Kim, Na Young; Warach, Steven

2014-01-01

331

Magnetic resonance imaging in acute ischemic stroke treatment.  

PubMed

Although intravenous administration of tissue plasminogen activator is the only proven treatment after acute ischemic stroke, there is always a concern of hemorrhagic risk after thrombolysis. Therefore, selection of patients with potential benefits in overcoming potential harms of thrombolysis is of great importance. Despite the practical issues in using magnetic resonance imaging (MRI) for acute stroke treatment, multimodal MRI can provide useful information for accurate diagnosis of stroke, evaluation of the risks and benefits of thrombolysis, and prediction of outcomes. For example, the high sensitivity and specificity of diffusion-weighted image (DWI) can help distinguish acute ischemic stroke from stroke-mimics. Additionally, the lesion mismatch between perfusion-weighted image (PWI) and DWI is thought to represent potential salvageable tissue by reperfusion therapy. However, the optimal threshold to discriminate between benign oligemic areas and the penumbra is still debatable. Signal changes of fluid-attenuated inversion recovery image within DWI lesions may be a surrogate marker for ischemic lesion age and might indicate risks of hemorrhage after thrombolysis. Clot sign on gradient echo image may reflect the nature of clot, and their location, length and morphology may provide predictive information on recanalization by reperfusion therapy. However, previous clinical trials which solely or mainly relied on perfusion-diffusion mismatch for patient selection, failed to show benefits of MRI-based thrombolysis. Therefore, understanding the clinical implication of various useful MRI findings and comprehensively incorporating those variables into therapeutic decision-making may be a more reasonable approach for expanding the indication of acute stroke thrombolysis. PMID:25328872

Kim, Bum Joon; Kang, Hyun Goo; Kim, Hye-Jin; Ahn, Sung-Ho; Kim, Na Young; Warach, Steven; Kang, Dong-Wha

2014-09-01

332

Magnetic resonance imaging in laboratory petrophysical core analysis  

NASA Astrophysics Data System (ADS)

Magnetic resonance imaging (MRI) is a well-known technique in medical diagnosis and materials science. In the more specialized arena of laboratory-scale petrophysical rock core analysis, the role of MRI has undergone a substantial change in focus over the last three decades. Initially, alongside the continual drive to exploit higher magnetic field strengths in MRI applications for medicine and chemistry, the same trend was followed in core analysis. However, the spatial resolution achievable in heterogeneous porous media is inherently limited due to the magnetic susceptibility contrast between solid and fluid. As a result, imaging resolution at the length-scale of typical pore diameters is not practical and so MRI of core-plugs has often been viewed as an inappropriate use of expensive magnetic resonance facilities. Recently, there has been a paradigm shift in the use of MRI in laboratory-scale core analysis. The focus is now on acquiring data in the laboratory that are directly comparable to data obtained from magnetic resonance well-logging tools (i.e., a common physics of measurement). To maintain consistency with well-logging instrumentation, it is desirable to measure distributions of transverse (T2) relaxation time-the industry-standard metric in well-logging-at the laboratory-scale. These T2 distributions can be spatially resolved over the length of a core-plug. The use of low-field magnets in the laboratory environment is optimal for core analysis not only because the magnetic field strength is closer to that of well-logging tools, but also because the magnetic susceptibility contrast is minimized, allowing the acquisition of quantitative image voxel (or pixel) intensities that are directly scalable to liquid volume. Beyond simple determination of macroscopic rock heterogeneity, it is possible to utilize the spatial resolution for monitoring forced displacement of oil by water or chemical agents, determining capillary pressure curves, and estimating wettability. The history of MRI in petrophysics is reviewed and future directions considered, including advanced data processing techniques such as compressed sensing reconstruction and Bayesian inference analysis of under-sampled data. Although this review focuses on rock core analysis, the techniques described are applicable in a wider context to porous media in general, such as cements, soils, ceramics, and catalytic materials.

Mitchell, J.; Chandrasekera, T. C.; Holland, D. J.; Gladden, L. F.; Fordham, E. J.

2013-05-01

333

[Optimized magnetic resonance sequences and parameters with operative assisted images for radical prostatectomy at 3 tesla-magnetic resonance image].  

PubMed

The objective of our study was to optimize magnetic resonance image (MRI) sequences and parameters using operative assisted images (three-dimensional images) for radical prostatectomy at 3 tesla (T) MRI. Five healthy volunteers underwent MRI on the 3.0 T scanner. Various sequences and parameters [Cube (TE/TR = 18, 50, 90 ms/2000 ms), FIESTA (TE/TR/FA = 2.4 ms/5 ms/40 degrees, 90 degrees), fSPGR (TE/TR/FA = 2.3 ms/11.2 ms/20 degrees), slice thickness = 1.2 mm, matrix = 192 x 160] were respectively compared. Several structures of the pelvis (the central zones and transition zones of the prostate, the peripheral zones of the prostate, seminal vesicles, rectum wall, bladder, muscle and fat) were determined. The signal intensities of these structures were measured on reformatted axial images and compared against several structures of the pelvis. Correlation with various sequences and parameters was based on the signal-to-noise ratio (SNR), the contrast ratio (CR) and the presence of artifacts. Student's t-test was used for statistical analysis. With Cube (TE/TR = 50 ms/2000 ms), the average value of visual evaluation with artifacts was high, and SNR and CR were higher than for other sequence and parameters. Optimized MRI sequences and parameters were Cube (TE/TR = 50 ms/2000 ms) which provides improved SNR and CR and the presence of artifacts with operative assisted images for radical prostatectomy. These operative assisted images obtained from Cube (TE/TR = 50 ms/2000 ms) are likely to be useful for surgery. PMID:23964533

Shirase, Ryuji; Sakurai, Yuuki; Nagahama, Hiroshi; Harada, Kuniaki; Takashima, Hiroyuki; Nakanishi, Mitsuhiro; Harada, Kohei; Shishido, Hiroki; Imamura, Rui; Sakata, Motomichi; Hatakenaka, Masamitsu

2013-05-01

334

Imaging surface plasmon resonance system for screening affinity ligands.  

PubMed

A surface plasmon resonance (SPR) system for screening ligands for application in affinity chromatography is described. A combinatorial library of 13 ligands was synthesised, characterised and immobilised to agarose beads and gold SPR devices. Binding and elution behaviour and a range of K(AX) values (10(3) to 10(5) M(-1)) were measured against two target proteins, an insulin analogue (MI3) and a recombinant clotting factor (rFVIIa), in order to create a relational database between the traditional chromatographic format and the new SPR screening system. The SPR transducer surface was fabricated with affinity ligands in a two-dimensional, spatially addressable format, which was durable (>100 cycles) and stable over 6 months. The imaging SPR system comprised a direct optical, CCD-based, instrument capable of imaging the change in refractive index created by biochemical interactions and allowed affinity ligands to be evaluated 15-fold faster with 130-fold less target protein than conventional chromatographic methods. The binding and elution data from both the SPR and chromatographic systems for both target proteins were comparable, with the K(AX) value generating a nearly linear correlation (R(2)=0.875) and a slope bias of approximately 2.5+/-0.25-fold higher for the SPR system. The imaging SPR system has proven capable of screening and evaluating affinity ligands for potential use in the recovery of biopharmaceutical proteins. PMID:12906898

Morrill, Paul R; Millington, R B; Lowe, Christopher R

2003-08-15

335

Nanoparticle Pharmacokinetic Profiling in vivo using Magnetic Resonance Imaging  

PubMed Central

Contrast agents targeted to molecular markers of disease are currently being developed with the goal of identifying disease early and evaluating treatment effectiveness using non-invasive imaging modalities such as MRI. Pharmacokinetic profiling of the binding of targeted contrast agents, while theoretically possible with MRI, has thus far only been demonstrated with more sensitive imaging techniques. Paramagnetic liquid perfluorocarbon nanoparticles were formulated to target ?v?3-integrins associated with early atherosclerosis in cholesterol-fed rabbits in order to produce a measurable signal increase on magnetic resonance images after binding. In this work, we combine quantitative information of the in vivo binding of this agent over time obtained via MRI with blood sampling to derive pharmacokinetic parameters using simultaneous and individual fitting of the data to a three compartment model. A doubling of tissue exposure (or area under the curve) is obtained with targeted as compared to control nanoparticles, and key parameter differences are discovered that may aid in development of models for targeted drug delivery. PMID:19025903

Neubauer, Anne M.; Sim, Hoon; Winter, Patrick M.; Caruthers, Shelton D.; Williams, Todd A.; Robertson, J. David; Sept, David; Lanza, Gregory M.; Wickline, Samuel A.

2008-01-01

336

Development of vocal tract length during early childhood: A magnetic resonance imaging studya)  

E-print Network

thickness, hard- and soft-palate length, tongue length, naso-oro-pharyngeal length, mandibular length; Vorperian, 2000 . Using ad- vances in imaging technology, such as magnetic resonance imaging MRI , the goal

Yandell, Brian S.

337

Magnetic resonance imaging of suspected cervicocranial arterial dissections.  

PubMed

The authors propose that the optimal screening protocol for evaluation of suspected cervicocranial arterial dissections is magnetic resonance imaging (MRI) that includes three components: 1) contrast-enhanced three-dimensional time-of-flight magnetic resonance angiography (MRA) through the superior mediastinum, neck, and skull base; 2) three-dimensional multiple overlapping thin-section acquisition MRA of the skull base and Circle of Willis region; and 3) axial non-contrast, non-fat-suppressed T1-weighted, fat-suppressed T1-weighted, and T2-weighted spin-echo MRI from the level of the aortic arch through the level of the circle of Willis. MRA permits visualization of vascular luminal narrowing or obliteration, which can suggest vascular dissection but can also be caused by congenital variation, dysplasia, intraluminal thrombus, vasospasm, or extramural compression by tumor. By directly visualizing the blood vessel wall, axial T1-weighted and T2-weighted spin-echo MRI can identify the intramural hemorrhage of vascular dissection. This protocol is designed to maximize the sensitivity of a noninvasive technique and may eliminate the need for conventional endovascular angiography. PMID:15662248

Shah, Gaurang V; Quint, Douglas J; Trobe, Jonathan D

2004-12-01

338

Building structural descriptions from coronal magnetic resonance images  

NASA Astrophysics Data System (ADS)

This paper presents several components of a system designed for the automated segmentation of coronal magnetic resonance images. Structural descriptions of several anatomical features are built in a hierarchial fashion. We begin with low-level edge detection and a constant curvature decomposition. This is followed by a graph-theoretic approach to generate structure hypotheses. After defining an object-centered coordinate system, we develop unary attributes and binary relations to make hypothesis evaluations and classifications. We handle the problem of describing three-dimensional structures from two-dimensional information using a novel slice-to-slice matching approach. These 3-D descriptions can later be used to build a topologically-structured modelbased which has broad applications. We also define a general structure matching framework which greatly simplifies the problem of incorporation new information into the system.

Raman, Subha V.; Boyer, Kim L.

1993-07-01

339

Magnetic resonance imaging of abdominal aortic aneurysms. [Aneurysm  

SciTech Connect

Magnetic resonance imaging (MRI) was performed in 20 patients with radiologically or surgically proven abdominal aortic aneurysms using a Siemens Magnetom scanner with a 0.35-T superconductive magnet. Of nine patients who underwent surgical repair, MRI correctly demonstrated the origin of the aortic aneurysm in nine and accurately determined the status of the iliac arteries in eight. Of 11 patients who did not have surgical repair, MRI findings correlated well with other radiologic studies. MRI was found to be more reliable than sonography in determining the relation between the aneurysm and the renal arteries as well as the status of the iliac arteries. Despite these advantages, the authors still advocate sonography as the screening procedure of choice in patients with suspected abdominal aortic aneurysms because of its lower cost and ease of performance. MRI should be reserved for patients who have had unsuccessful or equivocal sonographic examinations.

Lee, J.K.T.; Ling, D.; Heiken, J.P.; Glazer, H.S.; Sicard, G.A.; Totty, W.G.; Levitt, R.G.; Murphy, W.A.

1984-12-01

340

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

341

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

PubMed

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

Leslie, R A; James, M F

2000-08-01

342

Recycling of 3He from lung magnetic resonance imaging.  

PubMed

We have developed the means to recycle (3) He exhaled by patients after imaging the lungs using magnetic resonance of hyperpolarized (3) He. The exhaled gas is collected in a helium leak proof bag and further compressed into a steel bottle. The collected gas contains about 1-2% of (3) He, depending on the amount administered and the number of breaths collected to wash out the (3) He gas from the lungs. (3) He is separated from the exhaled air using zeolite molecular sieve adsorbent at 77 K followed by a cold head at 8 K. Residual gaseous impurities are finally absorbed by a commercial nonevaporative getter. The recycled (3) He gas features high purity, which is required for repolarization by metastability exchange optical pumping. At present, we achieve a collection efficiency of 80-84% for exhaled gas from healthy volunteers and cryogenic separation efficiency of 95%. PMID:22135249

Salhi, Z; Grossmann, T; Gueldner, M; Heil, W; Karpuk, S; Otten, E W; Rudersdorf, D; Surkau, R; Wolf, U

2012-06-01

343

Magnetic resonance imaging of the gallbladder: spectrum of abnormalities.  

PubMed

Various pathologies involving the gallbladder can manifest clinically, producing nonspecific clinical symptoms and making diagnosis difficult and challenging. Real-time sonography is the most widely used diagnostic study for the gallbladder and the primary screening examination of choice. With increasing use of magnetic resonance imaging (MRI) and MR cholangiopancreatography (MRCP), gallbladder pathology is frequently seen. Understanding the basic patterns of various disease manifestations and appearance on MRI is the key to making an accurate diagnosis. Given its inherent tissue contrast and contrast sensitivity, MRI in conjunction with MRCP can be a very valuable test in evaluating gallbladder pathology. Gallbladder pathology can be classified into congenital (such as absence), inflammatory (acute, hemorrhagic, and chronic cholecystitis), traumatic, benign (polyps) and malignant tumors (gallbladder carcinoma and lymphoma), and other disease processes can be seen in cholelithiasis, cholesterosis, thickened gallbladder wall, and Mirrizzi syndrome. PMID:17520421

Elsayes, K M; Oliveira, E P; Narra, V R; El-Merhi, F M; Brown, J J

2007-06-01

344

Primate comparative neuroscience using magnetic resonance imaging: promises and challenges  

PubMed Central

Primate comparative anatomy is an established field that has made rich and substantial contributions to neuroscience. However, the labor-intensive techniques employed mean that most comparisons are often based on a small number of species, which limits the conclusions that can be drawn. In this review we explore how new developments in magnetic resonance imaging have the potential to apply comparative neuroscience to a much wider range of species, allowing it to realize an even greater potential. We discuss (1) new advances in the types of data that can be acquired, (2) novel methods for extracting meaningful measures from such data that can be compared between species, and (3) methods to analyse these measures within a phylogenetic framework. Together these developments will allow researchers to characterize the relationship between different brains, the ecological niche they occupy, and the behavior they produce in more detail than ever before. PMID:25339857

Mars, Rogier B.; Neubert, Franz-Xaver; Verhagen, Lennart; Sallet, Jerome; Miller, Karla L.; Dunbar, Robin I. M.; Barton, Robert A.

2014-01-01

345

Imaging diagnosis--Conventional and functional magnetic resonance imaging of a brain abscess in a goat.  

PubMed

A 2-month-old female goat was presented for depressed mental status and multifocal central neurologic signs 3 weeks after hot-iron disbudding. Conventional magnetic resonance imaging (MRI) findings included a large intra axial mass in the left frontal lobe that was T2 hyperintense and T1 hypointense centrally with a contrast-enhancing peripheral capsule and perilesional T2 hyperintensity. A restrictive pattern was present in diffusion-weighted imaging. Magnetic resonance spectroscopy demonstrated an increased amount of succinate, acetate, amino acids, lipids; minimal amounts of lactate; and decreased amounts of N-acetyl aspartate and choline. A cerebral abscess due to Trueperella pyogenes was confirmed from necropsy and tissue culture. PMID:23663051

Dennler, Matthias; Carrera, Inés; Beckmann, Katrin; Ritz, Julia; Rütten, Maja; Kircher, Patrick R

2014-01-01

346

Enhanced dynamic electron paramagnetic resonance imaging of in vivo physiology  

NASA Astrophysics Data System (ADS)

It is well established that low oxygen concentration (hypoxia) in tumors strongly affects their malignant state and resistance to therapy. The importance of tumor oxygenation status has led to increased interest in the development of robust oxygen imaging modalities. One such method is electron paramagnetic resonance imaging (EPRI). EPRI has provided a non-invasive, quantitative imaging modality with sensitivity deep in tissues, capable of investigating static oxygen concentration (pO2) in vivo and has helped to corroborate the correlation between chronic states of hypoxia and tumor malignancy. However, when studying the complicated physiology of a living animal, the situation tends to be inherently dynamic. It has been found that in certain tumor regions there may exist steady states of hypoxia, or chronic hypoxia, whereas in other regions there may exist transient states of hypoxia, or acute hypoxia. It has been postulated that the negative prognostic implications associated with hypoxic tumors may be amplified for acutely hypoxic tumors. However, controversial data and a current lack in methods with the capability to noninvasively image tumor pO2 in vivo with sufficient spatial, temporal, and pO 2 resolution preclude definitive conclusions on the relationships between the different forms of hypoxia and the differences in their clinical implications. A particularly promising oxygen imaging modality that can help to study both chronic and acute hypoxia and elucidate important physiological and clinical differences is rapid Dynamic EPRI. The focus of this work is the development of methods enabling Dynamic EPRI of in vivo physiology as well as its potential applications. This work describes methods which enhance various aspects of EPRI in order to establish a more robust Dynamic EPRI capable of noninvasively studying and quantifying acute hypoxia in vivo. These enhancements are achieved through improvements that span from methods for the acquisition of individual projections to techniques for the reconstruction of complete 3D images of pO2. A hybrid T1/T2 imaging methodology is developed for acquiring individual projections using a specific series of pulse sequences, which enhances the accuracy of measured spin probe concentration and pO2. A maximally spaced projection sequencing algorithm is devised for more optimized acquisition of a full set of projections. Principal component analysis filtration is applied for post processing of acquired projection data in order to enhance signal to noise ratio (SNR) and isolate temporal features in Dynamic EPRI data. Image reconstruction techniques are improved by accelerating 3D image reconstruction using a GPU implementation as well as a rapid lookup table fitting method for determination of the spectral dimension and generation of pO2 images. Additionally, novel nitroxide EPRI imaging agents are presented which can differentially target the intracellular tumor environment and thus potentially provide higher SNR tumor imaging. Dynamic EPRI, as enabled using the above methods, is shown to provide a methodology with great potential for furthering our understanding of acute hypoxia and its role in the progression of cancer to a malignant state as well as how it affects therapeutic efficacy. Dynamic EPRI will help to disentangle the relationship between chronic and acute hypoxia in tumors and will aid in the determination of how to integrate tumor oxygenation status into clinical practice and the treatment of cancer.

Redler, Gage

347

Penumbral imaging by using perfusion computed tomography and perfusion-weighted magnetic resonance imaging: current concepts.  

PubMed

Perfusion computed tomography and perfusion-weighted magnetic resonance imaging are used to evaluate the extent of the area with ischemic penumbra; however, different parameters, algorithms, and software packages show significant discrepancies in the size of perfusion abnormalities, which should be minimized. Recently, cross-validation studies were performed using digital phantoms and have elucidated the precision and reliability of various penumbral imaging techniques. These research initiatives can promote further multicenter trials on recanalization therapies by providing accurate inclusion/exclusion criteria for appropriate patient selection. PMID:23153549

Sasaki, Makoto; Kudo, Kohsuke; Christensen, Soren; Yamashita, Fumio; Goodwin, Jonathan; Higuchi, Satomi; Ogawa, Akira

2013-11-01

348

Imaging of transplanted islets by positron emission tomography, magnetic resonance imaging, and ultrasonography  

PubMed Central

While islet transplantation is considered a useful therapeutic option for severe diabetes mellitus (DM), the outcome of this treatment remains unsatisfactory. This is largely due to the damage and loss of islets in the early transplant stage. Thus, it is important to monitor the condition of the transplanted islets, so that a treatment can be selected to rescue the islets from damage if needed. Recently, numerous trials have been performed to investigate the efficacy of different imaging modalities for visualizing transplanted islets. Positron emission tomography (PET) and magnetic resonance imaging (MRI) are the most commonly used imaging modalities for this purpose. Some groups, including ours, have also tried to visualize transplanted islets by ultrasonography (US). In this review article, we discuss the recent progress in islet imaging. PMID:24231367

Sakata, Naoaki; Yoshimatsu, Gumpei; Tsuchiya, Haruyuki; Aoki, Takeshi; Mizuma, Masamichi; Motoi, Fuyuhiko; Katayose, Yu; Kodama, Tetsuya; Egawa, Shinichi; Unno, Michiaki

2013-01-01

349

Concurrent multiscale imaging with magnetic resonance imaging and optical coherence tomography  

NASA Astrophysics Data System (ADS)

We develop a novel platform based on a tele-operated robot to perform high-resolution optical coherence tomography (OCT) imaging under continuous large field-of-view magnetic resonance imaging (MRI) guidance. Intra-operative MRI (iMRI) is a promising guidance tool for high-precision surgery, but it may not have sufficient resolution or contrast to visualize certain small targets. To address these limitations, we develop an MRI-compatible OCT needle probe, which is capable of providing microscale tissue architecture in conjunction with macroscale MRI tissue morphology in real time. Coregistered MRI/OCT images on ex vivo chicken breast and human brain tissues demonstrate that the complementary imaging scales and contrast mechanisms have great potential to improve the efficiency and the accuracy of iMRI procedure.

Liang, Chia-Pin; Yang, Bo; Kim, Il Kyoon; Makris, George; Desai, Jaydev P.; Gullapalli, Rao P.; Chen, Yu

2013-04-01

350

Fast method for brain image segmentation: application to proton magnetic resonance spectroscopic imaging.  

PubMed

The interpretation of brain metabolite concentrations measured by quantitative proton magnetic resonance spectroscopic imaging (MRSI) is assisted by knowledge of the percentage of gray matter (GM), white matter (WM), and cerebrospinal fluid (CSF) within each MRSI voxel. Usually, this information is determined from T(1)-weighted magnetic resonance images (MRI) that have a much higher spatial resolution than the MRSI data. While this approach works well, it is time-consuming. In this article, a rapid data acquisition and analysis procedure for image segmentation is described, which is based on collection of several, thick slice, fast spin echo images (FSE) of different contrast. Tissue segmentation is performed with linear "Eigenimage" filtering and normalization. The method was compared to standard segmentation techniques using high-resolution 3D T(1)-weighted MRI in five subjects. Excellent correlation between the two techniques was obtained, with voxel-wise regression analysis giving GM: R2 = 0.893 +/- 0.098, WM: R2 = 0.892 +/- 0.089, ln(CSF): R2 = 0.831 +/- 0.082). Test-retest analysis in one individual yielded an excellent agreement of measurements with R2 higher than 0.926 in all three tissue classes. Application of FSE/EI segmentation to a sample proton MRSI dataset yielded results similar to prior publications. It is concluded that FSE imaging in conjunction with Eigenimage analysis is a rapid and reliable way of segmenting brain tissue for application to proton MRSI. PMID:16187272

Bonekamp, David; Horská, Alena; Jacobs, Michael A; Arslanoglu, Atilla; Barker, Peter B

2005-11-01

351

PTFOS: Flexible and Absorbable Intracranial Electrodes for Magnetic Resonance Imaging  

PubMed Central

Intracranial electrocortical recording and stimulation can provide unique knowledge about functional brain anatomy in patients undergoing brain surgery. This approach is commonly used in the treatment of medically refractory epilepsy. However, it can be very difficult to integrate the results of cortical recordings with other brain mapping modalities, particularly functional magnetic resonance imaging (fMRI). The ability to integrate imaging and electrophysiological information with simultaneous subdural electrocortical recording/stimulation and fMRI could offer significant insight for cognitive and systems neuroscience as well as for clinical neurology, particularly for patients with epilepsy or functional disorders. However, standard subdural electrodes cause significant artifact in MRI images, and concerns about risks such as cortical heating have generally precluded obtaining MRI in patients with implanted electrodes. We propose an electrode set based on polymer thick film organic substrate (PTFOS), an organic absorbable, flexible and stretchable electrode grid for intracranial use. These new types of MRI transparent intracranial electrodes are based on nano-particle ink technology that builds on our earlier development of an EEG/fMRI electrode set for scalp recording. The development of MRI-compatible recording/stimulation electrodes with a very thin profile could allow functional mapping at the individual subject level of the underlying feedback and feed forward networks. The thin flexible substrate would allow the electrodes to optimally contact the convoluted brain surface. Performance properties of the PTFOS were assessed by MRI measurements, finite difference time domain (FDTD) simulations, micro-volt recording, and injecting currents using standard electrocortical stimulation in phantoms. In contrast to the large artifacts exhibited with standard electrode sets, the PTFOS exhibited no artifact due to the reduced amount of metal and conductivity of the electrode/trace ink and had similar electrical properties to a standard subdural electrode set. The enhanced image quality could enable routine MRI exams of patients with intracranial electrode implantation and could also lead to chronic implantation solutions. PMID:22984396

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

2012-01-01

352

[Functional imaging of the lung using a gaseous contrast agent: (3)helium-magnetic resonance imaging].  

PubMed

Current imaging methods of the lung concentrate on morphology as well as on the depiction of the pulmonary parenchyma. The need of an advanced and more subtle imaging technology compared to conventional radiography is met by computed topography as the method of choice. Nevertheless, computed tomography yields very limited functional information. This is to be derived from arterial blood gas analysis, spirometry and body plethysmography. These methods, however, lack the scope for regional allocation of any pathology. Magnetic resonance imaging of the lung has been advanced by the use of hyperpolarised (3)Helium as an inhaled gaseous contrast agent. The inhalation of the gas provides functional data by distribution, diffusion and relaxation of its hyperpolarised state. Because anatomical landmarks of the lung can be visualised as well, functional information can be linked with regional information. Furthermore, the method provides high spatial and temporal resolution and lacks the potential side-effects of ionising radiation. Four different modalities have been established: 1. Spin density imaging studies the distribution of gas, normally after a single inhalation of contrast gas in inspiratory breath hold. 2. Dynamic cine imaging studies the distribution of gas with respect to regional time constants of pulmonary gas inflow. 3. Diffusion weighted imaging can exhibit the presence and severity of pulmonary airspace enlargement, as in pulmonary emphysema. 4. Oxygen sensitive imaging displays intrapulmonary oxygen partial pressure and its distribution. Currently, the method is limited by comparably high costs and limited availability. As there have been recent developments which might bring this modality closer to clinical use, this review article will comprise the methodology as well as the current state of the art and standard of knowledge of magnetic resonance imaging of the lung using hyperpolarised (3)Helium. PMID:15871081

Gast, K K; Heussel, C P; Schreiber, W G; Kauczor, H-U

2005-05-01

353

Tumor Vascularity Assessed By Magnetic Resonance Imaging and Intravital Microscopy Imaging1  

PubMed Central

Gadopentetate dimeglumine (Gd-DTPA)-based dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is considered to be a useful method for characterizing the vascularity of tumors. However, detailed studies of experimental tumors comparing DCE-MRI-derived parametric images with images of the morphology and function of the microvascular network have not been reported. In this communication, we describe a novel MR-compatible mouse dorsal window chamber and report comparative DCE-MRI and intravital microscopy studies of A-07-GFP tumors xenografted to BALB/c nu/nu mice. Blood supply time (BST) images (i.e., images of the time from when arterial blood enters a tumor through the supplying artery until it reaches a vessel segment within the tumor) and morphologic images of the microvascular network were produced by intravital microscopy. Images of E·F (E is the initial extraction fraction of Gd-DTPA and F is perfusion) were produced by subjecting DCE-MRI series to Kety analysis. The E·F images mirrored the morphology (microvascular density) and the function (BST) of the microvascular networks well. Tumor regions showing high E·F values colocalized with tumor regions showing high microvascular density and low BST values. Significant correlations were found between E·F and microvascular density and between E·F and BST, both within and among tumors. PMID:18392132

Gaustad, Jon-Vidar; Brurberg, Kjetil G; Simonsen, Trude G; Mollatt, Camilla S; Rofstad, Einar K

2008-01-01

354

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

NASA Astrophysics Data System (ADS)

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

Herrera, Sheryl Lyn

355

Gray matter alterations in early aging: a diffusion magnetic resonance imaging study.  

PubMed

Many studies have observed altered neurofunctional and structural organization in the aging brain. These observations from functional neuroimaging studies show a shift in brain activity from the posterior to the anterior regions with aging (PASA model), as well as a decrease in cortical thickness, which is more pronounced in the frontal lobe followed by the parietal, occipital, and temporal lobes (retrogenesis model). However, very little work has been done using diffusion MRI (dMRI) with respect to examining the structural tissue alterations underlying these neurofunctional changes in the gray matter. Thus, for the first time, we propose to examine gray matter changes using diffusion MRI in the context of aging. In this work, we propose a novel dMRI based measure of gray matter "heterogeneity" that elucidates these functional and structural models (PASA and retrogenesis) of aging from the viewpoint of diffusion MRI. In a cohort of 85 subjects (all males, ages 15-55 years), we show very high correlation between age and "heterogeneity" (a measure of structural layout of tissue in a region-of-interest) in specific brain regions. We examine gray matter alterations by grouping brain regions into anatomical lobes as well as functional zones. Our findings from dMRI data connects the functional and structural domains and confirms the "retrogenesis" hypothesis of gray matter alterations while lending support to the neurofunctional PASA model of aging in addition to showing the preservation of paralimbic areas during healthy aging. PMID:24382651

Rathi, Y; Pasternak, O; Savadjiev, P; Michailovich, O; Bouix, S; Kubicki, M; Westin, C-F; Makris, N; Shenton, M E

2014-08-01

356

The Superiority of Magnetic Resonance Imaging in Differentiating the Cause of Hip Pain in Endurance Athletes  

Microsoft Academic Search

The accuracy of magnetic resonance imaging of the hip was prospectively evaluated in 19 military subjects engaged in endurance training. These patients had hip pain, negative radiographs, and radionuclide bone scans consistent with femoral neck stress fracture. Twenty-two hips were identified as positive for femoral neck stress fracture by bone scan. Each patient under went magnetic resonance imaging and 6-week

Alexander Y. Shin; William D. Morin; John D. Germany; Steven B. Jones; Anthony S. Lapinsky

1996-01-01

357

Semi-automatic segmentation of knee osteoarthritic cartilage in magnetic resonance images  

Microsoft Academic Search

Knee osteoarthritis is one of the major socio- economic burdens of today. Magnetic resonance imaging facili- tates analysis of disease progression by visualization of structural and biochemical changes in cartilage tissue. Segmentation of cartilages from magnetic resonance images is therefore important in clinical investigations. Today, segmentations are obtained using time-consuming manual or semi-automatic algorithms that are subject to some degree

Kasper Marstal; Henrik Gudbergsen; Mikael Boesen; Olga Kubassova; Rasmus Bouert; Henning Bliddal

2011-01-01

358

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

359

Automatic Segmentation of Non-enhancing Brain Tumors in Magnetic Resonance Images  

E-print Network

Automatic Segmentation of Non-enhancing Brain Tumors in Magnetic Resonance Images Lynn M. Fletcher,hall,goldgof@csee.usf.edu, murtagh@rad.usf.edu. #12;2 Abstract Tumor segmentation from magnetic resonance MR images may aid in tumor. An initial segmentation is computed using an unsupervised fuzzy clustering algorithm. Then, integrated domain

Hall, Lawrence O.

360

H. M.'s Medial Temporal Lobe Lesion: Findings from Magnetic Resonance Imaging  

E-print Network

H. M.'s Medial Temporal Lobe Lesion: Findings from Magnetic Resonance Imaging Suzanne Corkin,1 not been elucidated. We conducted magnetic resonance imaging studies to specify precisely the extent of his). The caudal 2 cm, approximately, of the hippocam- pus body (normal length, 4 cm) was intact, although atrophic

Corkin, Suzanne

361

Spatially encoded NMR and the acquisition of 2D magnetic resonance images within a single scan  

E-print Network

Spatially encoded NMR and the acquisition of 2D magnetic resonance images within a single scan Yoav out analytical characterizations on chemical and biochemical samples [2,3] 2D NMR probably finds its resonance imaging (MRI). In spite of the dissimilar information being sought in 2D NMR and 2D MRI

Frydman, Lucio

362

Near-infrared frequency-domain optical spectroscopy and magnetic resonance imaging: a combined  

E-print Network

noninvasive near-IR frequency-domain optical spectroscopy (NIRS) and magnetic resonance imaging (MRI in the diffu- sion tensor MRI. Mean optical coefficients (reduced scattering) re- mained unchanged in allNear-infrared frequency-domain optical spectroscopy and magnetic resonance imaging: a combined

363

Fiber Tractography in Diffusion Tensor Magnetic Resonance Imaging: A Survey and Beyond  

E-print Network

@cs.uky.edu, URL: http://www.cs.uky.edu/~jzhang. #12;2 dimensional (3D) representations of tissue architecture1 Fiber Tractography in Diffusion Tensor Magnetic Resonance Imaging: A Survey and Beyond Jun Zhang, 2005 Abstract Diffusion tensor magnetic resonance imaging (DT-MRI) is the first noninvasive in vivo

Zhang, Jun

364

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

Microsoft Academic Search

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

Christopher R. Genovese

2000-01-01

365

Magnetic resonance imaging of sequelae of central pontine myelinolysis in chronic alcohol abusers  

Microsoft Academic Search

Central pontine myelinolysis (CPM) is one of the serious neurological complications of alcoholism. This study evaluated magnetic resonance images of sequelae of CPM. Approximately 600 alcoholic patients were examined by a 1.0-T magnetic resonance imaging device, and 11 patients were retrospectively found to have a central pontine lesion, a presumed sequela of CPM. The lesions had various shapes and most

Akira Uchino; Takefumi Yuzuriha; Masaru Murakami; Koichi Endoh; Shigeto Hiejima; Hiroshi Koga; Sho Kudo

2003-01-01

366

A method for correlating in vivo prostate magnetic resonance imaging and histopathology using individualized magnetic resonance -based molds  

PubMed Central

A method for the design and rapid manufacture of a patient specific tissue slicing device based on in vivo images in order to facilitate the process of correlating the images with histopathology is presented. The method is applied to radical prostatectomy specimens where the customized mold is designed using magnetic resonance (MR) images of each patient obtained prior to surgery. In this case, the mold holds the prostate in place while a knife with a single blade or multiple blades is inserted in slots which are positioned to obtain tissue blocks corresponding to the slices in the MR images. The resulting histological specimens demonstrate good anatomical correlation with the MR images. PMID:19895076

Shah, Vijay; Pohida, Thomas; Turkbey, Baris; Mani, Haresh; Merino, Maria; Pinto, Peter A.; Choyke, Peter; Bernardo, Marcelino

2009-01-01

367

Development of a Clinical Functional Magnetic Resonance Imaging Service  

PubMed Central

One of the limitations of anatomical based imaging approaches is its relative inability to identify whether specific brain functions may be compromised by the location of brain lesions or contemplated brain surgeries. For this reason, methods for identifying the regions of eloquent brain that should not be disturbed are absolutely critical to the surgeon. By accurately identifying these regions preoperatively, virtually every pre-surgical decision from the surgical approach, operative goals (biopsy, sub-total vs. gross-total resection), and the potential need for awake craniotomy with intraoperative cortical-mapping is affected. Of the many techniques available to the surgeon, functional magnetic resonance imaging (fMRI) has become the primary modality of choice due to the ability of MRI to serve as a “one-stop shop” for assessing both anatomy and functionality of the brain. Given their prevalence, brain tumors serve as the model pathology for the included discussion; however, a similar case can be made for the use of fMRI in other neurological conditions, most notably epilepsy. The value of fMRI was validated in 2007 when the Centers for Medicare and Medicaid Services (CMS) established three new current procedural terminology (CPT) codes for clinical fMRI based upon its use for pre-therapeutic planning. In this article we will discuss the specific requirements for establishing an fMRI program, including specific software and hardware requirements. In addition, the nature of the fMRI CPT codes will be discussed. PMID:21435578

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

2013-01-01

368

Stable cerasomes for simultaneous drug delivery and magnetic resonance imaging  

PubMed Central

Magnetic liposomes have been frequently used as nanocarriers for targeted drug delivery and magnetic resonance imaging in recent years. Despite great potentials, their morphological/structural instability in the physiological environment still remains an intractable challenge for clinical applications. In this study, stable hybrid liposomal cerasomes (ie, liposomes partially coated with silica) which can co-encapsulate Fe3O4 nanoparticles and the anticancer drug paclitaxel were developed using thin film hydration method. Compared with the drug loaded liposomes, the paclitaxel-loaded magnetic cerasomes (PLMCs) exhibited much higher storage stability and better sustained release behavior. Cellular uptake study showed that the utilization of an external magnetic field significantly facilitated the internalization of PLMCs into cancer cells, resulting in potentiated drug efficacy of killing tumor cells. The T2 relaxivity (r2) of our PLMCs was much higher than that of free Fe3O4 nanoparticles, suggesting increased sensitivity in T2-weighted imaging. Given its excellent biocompatibility also shown in the study, such dual functional PLMC is potentially a promising nanosystem for effective cancer diagnosis and therapy. PMID:25395848

Cao, Zhong; Zhu, Wenjian; Wang, Wei; Zhang, Chunyang; Xu, Ming; Liu, Jie; Feng, Shi-Ting; Jiang, Qing; Xie, Xiaoyan

2014-01-01

369

Measurement of AC magnetic field distribution using magnetic resonance imaging.  

PubMed

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

Ider, Y Z; Muftuler, L T

1997-10-01

370

Stress perfusion magnetic resonance imaging of the heart.  

PubMed

Extensive research has documented that rapid imaging during the first pass of a magnetic resonance imaging (MRI) contrast agent provides good sensitivity to detect myocardial blood flow deficits caused by coronary disease, cardiomyopathies, or microvascular dysfunction in patients without obstructive lesions in the coronary arteries. The autoregulatory mechanisms of the coronary circulation serve the purpose of maintaining sufficient blood flow at baseline in the presence of flow-obstructing coronary lesions. Stress testing is most commonly used in this setting to determine the hemodynamic effect of coronary lesions in the epicardial arteries when the small-vessel resistance has been minimized by vasodilation. The protocols for perfusion MRI combined with vasodilation have been successfully tested in large patient studies. Besides the absence of any ionizing radiation, MRI offers the advantages of relatively high spatial resolution to detect perfusion defects limited to the inner layer of the heart muscle. Furthermore, MRI can be used for noninvasive quantitative measurements of myocardial blood flow that compare well with invasive measurements with labeled microspheres. Additional useful markers, such as the dynamic distribution volume, the delay in the arrival of the contrast agent in a myocardial region relative to the enhancement in the arterial input, and the capillary permeability-surface area product, may, in the future, further enhance the capabilities to characterize with MRI coronary atherosclerosis, coronary vascular dysfunction, and adaptive mechanisms in the coronary circulation, such as arteriogenesis, that reduce ischemia. PMID:18690159

Jerosch-Herold, Michael; Muehling, Olaf

2008-02-01

371

Accurate Measurement of Magnetic Resonance Imaging Gradient Characteristics  

PubMed Central

Recently, gradient performance and fidelity has become of increasing interest, as the fidelity of the magnetic resonance (MR) image is somewhat dependent on the fidelity of the gradient system. In particular, for high fidelity non-Cartesian imaging, due to non-fidelity of the gradient system, it becomes necessary to know the actual k-space trajectory as opposed to the requested trajectory. In this work we show that, by considering the gradient system as a linear time-invariant system, the gradient impulse response function (GIRF) can be reliably measured to a relatively high degree of accuracy with a simple setup, using a small phantom and a series of simple experiments. It is shown experimentally that the resulting GIRF is able to predict actual gradient performance with a high degree of accuracy. The method captures not only the frequency response but also gradient timing errors and artifacts due to mechanical vibrations of the gradient system. Some discussion is provided comparing the method presented here with other analogous methods, along with limitations of these methods.

Liu, Hui; Matson, Gerald B.

2014-01-01

372

A Localized Surface Plasmon Resonance Imaging Instrument for Multiplexed Biosensing  

PubMed Central

Localized surface plasmon resonance (LSPR) spectroscopy has been widely used for label-free, highly-sensitive measurements of interactions at a surface. LSPR imaging (LSPRi) has the full advantages of LSPR, but enables high-throughput, multiplexed measurements by simultaneously probing multiple individually addressable sensors on a single sample surface. Each spatially distinct sensor can be tailored to provide data regarding different surface functionalities or reaction environments. Previously, LSPRi has focused on single particle sensing where the size scale is very small. Here, we create defined macroscale arrays of nanoparticles that are compatible with common patterning methods such as dip-pen nanolithography and multi-channel microfluidic delivery devices. With this new LSPR sensing format, we report the first demonstration of multiplexed LSPR imaging and show that the increased throughput of our instrument enables the collection of a complete Langmuir binding curve on a single sensor surface. In addition, the multiplexed LSPR sensor is highly selective, as demonstrated by the hybridization of single-stranded DNA to complementary sequences immobilized on the sensor surface. The LSPR arrays described in this work exhibit uniform sensitivity and tailorable optical properties, making them an ideal platform for high-throughput, label-free analysis of a variety of molecular binding interactions. PMID:23560643

Ruemmele, Julia A.; Hall, W. Paige; Ruvuna, Laura K.; Van Duyne, Richard P.

2013-01-01

373

Magnetic resonance imaging of live freshwater mussels (Unionidae)  

USGS Publications Warehouse

We examined the soft tissues of live freshwater mussels, Eastern elliptio Elliptio complanata, via magnetic resonance imaging (MRI), acquiring data with a widely available human whole-body MRI system. Anatomical features depicted in the profile images included the foot, stomach, intestine, anterior and posterior adductor muscles, and pericardial cavity. Noteworthy observations on soft tissue morphology included a concentration of lipids at the most posterior aspect of the foot, the presence of hemolymph-filled fissures in the posterior adductor muscle, the presence of a relatively large hemolymph-filled sinus adjacent to the posterior adductor muscle (at the ventral-anterior aspect), and segmentation of the intestine (a diagnostic description not reported previously in Unionidae). Relatively little is known about the basic biology and ecological physiology of freshwater mussels. Traditional approaches for studying anatomy and tissue processes, and for measuring sub-lethal physiological stress, are destructive or invasive. Our study, the first to evaluate freshwater mussel soft tissues by MRI, clarifies the body plan of unionid mussels and demonstrates the efficacy of this technology for in vivo evaluation of the structure, function, and integrity of mussel soft tissues. ?? 2008, The American Microscopical Society, Inc.

Michael, Holliman F.; Davis, D.; Bogan, A.E.; Kwak, T.J.; Gregory, Cope W.; Levine, J.F.

2008-01-01

374

Nuclear magnetic resonance whole-body imager operating at 3. 5 Kgauss  

Microsoft Academic Search

The theoretical advantages of nuclear magnetic resonance imaging at higher field strengths are discussed. Examples of images created at 3.5 KGauss (0.35 T) are demonstrated. The authors present a method of collecting several tomographic images sequentially during the time required for a single image.

Lawrence Crooks; Mitsuaki Arakawa; John Hoenninger; Jeffrey Watts; R. McRee; L. Kaufman; Peter L. Davis; Alexander R. Margulis; Jack DeGroot

1982-01-01

375

Characterization of regional pulmonary mechanics from serial magnetic resonance imaging data 1  

Microsoft Academic Search

Rationale and Objectives. The aim of this study was to investigate a method for quantifying lung motion from the registration of successive images in serial magnetic resonance imaging acquisitions during normal respiration.Materials and Methods. Estimates of pulmonary motion were obtained by summing the normalized cross-correlation over serially acquired lung images to identify corresponding locations between the images. The estimated motions

James Gee; Tessa Sundaram; Ichiro Hasegawa; Hidemasa Uematsu; Hiroto Hatabu

2003-01-01

376

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

PubMed

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

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

2008-01-01

377

Magnetic resonance imaging of hypoxic injury to the murine placenta  

PubMed Central

We assessed the use of magnetic resonance imaging (MRI) to define placental hypoxic injury associated with fetal growth restriction. On embryonic day 18.5 (E18.5) we utilized dynamic contrast-enhanced (DCE)-MRI on a 4.7-tesla small animal scanner to examine the uptake and distribution of gadolinium-based contrast agent. Quantitative DCE parameter analysis was performed for the placenta and fetal kidneys of three groups of pregnant C57BL/6 mice: 1) mice that were exposed to FiO2 = 12% between E15.5 and E18.5, 2) mice in normoxia with food restriction similar to the intake of hypoxic mice between E15.5 and E18.5, and 3) mice in normoxia that were fed ad libitum. After imaging, we assessed fetoplacental weight, placental histology, and gene expression. We found that dams exposed to hypoxia exhibited fetal growth restriction (weight reduction by 28% and 14%, respectively, P < 0.05) with an increased placental-to-fetal ratio. By using MRI-based assessment of placental contrast agent kinetics, referenced to maternal paraspinous muscle, we found decreased placental clearance of contrast media in hypoxic mice, compared with either control group (61%, P < 0.05). This was accompanied by diminished contrast accumulation in the hypoxic fetal kidneys (23%, P < 0.05), reflecting reduced transplacental gadolinium transport. These changes were associated with increased expression of placental Phlda2 and Gcm1 transcripts. Exposure to hypoxia near the end of mouse pregnancy reduces placental perfusion and clearance of contrast. MRI-based DCE imaging provides a novel tool for dynamic, in vivo assessment of placental function. PMID:19923363

Tomlinson, Tracy M.; Garbow, Joel R.; Anderson, Jeff R.; Engelbach, John A.; Nelson, D. Michael

2010-01-01

378

Application of Advanced Magnetic Resonance Imaging Techniques in Evaluation of the Lower Extremity  

PubMed Central

Synopsis This article reviews current magnetic resonance imaging techniques for imaging the lower extremity, focusing on imaging of the knee, ankle, and hip joints. Recent advancements in MRI include imaging at 7 Tesla, using multiple receiver channels, T2* imaging, and metal suppression techniques, allowing more detailed visualization of complex anatomy, evaluation of morphological changes within articular cartilage, and imaging around orthopedic hardware. PMID:23622097

Braun, Hillary J.; Dragoo, Jason L.; Hargreaves, Brian A.; Levenston, Marc E.; Gold, Garry E.

2012-01-01

379

Derivative encoding for parallel magnetic resonance imaging Molecular Imaging Branch, National Institute of Mental Health Intramural Research Program, NIH,  

E-print Network

Derivative encoding for parallel magnetic resonance imaging a) Jun Shenb) Molecular Imaging Branch September 2011) Purpose: To introduce a linear shift-invariant relationship between the partial derivatives- tives can be used for image unwrapping. Methods: Fourier transform of k space derivatives contains

Shen, Jun

380

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 Upstate Medical University, Syracuse, NY 13210, USA c Department of Orthopedic Surgery; SUNY Upstate December 2000 Abstract Most brain imaging studies of pain are done using a two-state subtraction design

Apkarian, A. Vania

381

Functional connectivity magnetic resonance imaging classification of autism  

PubMed Central

Group differences in resting state functional magnetic resonance imaging connectivity between individuals with autism and typically developing controls have been widely replicated for a small number of discrete brain regions, yet the whole-brain distribution of connectivity abnormalities in autism is not well characterized. It is also unclear whether functional connectivity is sufficiently robust to be used as a diagnostic or prognostic metric in individual patients with autism. We obtained pairwise functional connectivity measurements from a lattice of 7266 regions of interest covering the entire grey matter (26.4 million connections) in a well-characterized set of 40 male adolescents and young adults with autism and 40 age-, sex- and IQ-matched typically developing subjects. A single resting state blood oxygen level-dependent scan of 8?min was used for the classification in each subject. A leave-one-out classifier successfully distinguished autism from control subjects with 83% sensitivity and 75% specificity for a total accuracy of 79% (P?=?1.1?×?10?7). In subjects <20 years of age, the classifier performed at 89% accuracy (P?=?5.4?×?10?7). In a replication dataset consisting of 21 individuals from six families with both affected and unaffected siblings, the classifier performed at 71% accuracy (91% accuracy for subjects <20 years of age). Classification scores in subjects with autism were significantly correlated with the Social Responsiveness Scale (P?=?0.05), verbal IQ (P?=?0.02) and the Autism Diagnostic Observation Schedule-Generic's combined social and communication subscores (P?=?0.05). An analysis of informative connections demonstrated that region of interest pairs with strongest correlation values were most abnormal in autism. Negatively correlated region of interest pairs showed higher correlation in autism (less anticorrelation), possibly representing weaker inhibitory connections, particularly for long connections (Euclidean distance >10?cm). Brain regions showing greatest differences included regions of the default mode network, superior parietal lobule, fusiform gyrus and anterior insula. Overall, classification accuracy was better for younger subjects, with differences between autism and control subjects diminishing after 19 years of age. Classification scores of unaffected siblings of individuals with autism were more similar to those of the control subjects than to those of the subjects with autism. These findings indicate feasibility of a functional connectivity magnetic resonance imaging diagnostic assay for autism. PMID:22006979

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

2011-01-01

382

Magnetic resonance imaging of rodent tumors using radiofrequency gradient echoes.  

PubMed

This paper evaluates the use of radiofrequency (RF) magnetic field gradient echoes to provide contrast in magnetic resonance (MR) images of model tumors. Decay of RF gradient echoes as a function of evolution time was measured and sensitivity of the decay to changes in blood pressure was evaluated. Previous investigators have demonstrated that static field (B0) gradient echoes provide MR image contrast which is sensitive to the rate of self-diffusion of tissue water and may also be sensitive to the rate of tissue perfusion. Gradient echoes produced by RF magnetic field gradients provide a useful alternative to the conventional B0 methods. Unlike B0 gradient echoes RF gradient echoes are relatively insensitive to local magnetic susceptibility gradients and to magnetic field gradients produced by eddy currents. Differences between the two methods may be particularly significant for studies of tumors where large concentrations of deoxyhemoglobin and other paramagnetic substances may cause significant susceptibility gradients. Mammary adenocarcinomas subcutaneously implanted in the flanks of female Fisher rats were studied. Magnetic resonance experiments were performed at 2 T. A surface coil was used to provide an RF gradient and to excite and detect signals from the tumors. The decay of echo amplitude as a function of evolution time was measured and the decay at short and long evolution times was analyzed independently to calculate two apparent diffusion coefficients (ADCs). The preparation was extremely stable and the standard error for 10 consecutive measurements of gradient echo amplitude made over 30-60 min with an RF gradient strength of 50 kHz/cm, gradient duration of 1 ms (i.e., 50 cycles/cm), and echo evolution time (td) of 1 s was generally +/- 0.8%. The ADC calculated from the decay at short evolution times was approximately 3 x 10(-5) cm2/s. The ADC calculated from the decay at longer evolution times was approximately 0.5 x 10(-5) cm2/s. Both ADCs decreased immediately following sacrifice and administration of Hydralazine. The experiments demonstrate that measurements of RF gradient echo amplitudes in tumors can be made in vivo with a high degree of reproducibility and suggest that RF gradient echo amplitudes are sensitive to acute physiological changes in tumors. This method may be useful for characterization of tumors and prediction and monitoring of effects of therapeutic agents. PMID:7968288

Karczmar, G S; River, J N; Goldman, Z; Li, J; Weisenberg, E; Lewis, M Z; Liu, K

1994-01-01

383

Preliminary study of diffusion-weighted imaging and magnetic resonance spectroscopy imaging in kimura disease.  

PubMed

In this study, we evaluated the value of diffusion-weighted imaging (DWI) and magnetic resonance (MR) spectroscopy imaging (MRSI) combined with computed tomography (CT) and conventional MR imaging (MRI) in the diagnosis of Kimura disease (KD). The clinical data and CT and MRI findings of 5 patients with KD proven by histopathologic examination were retrospectively reviewed. Diffusion-weighted imaging and MRSI were performed at 1.5 T in 3 patients with KD. Apparent diffusion coefficient (ADC) values and the choline/creatine ratio of the lesions were compared with those of the contralateral normal parotid glands. All imaging results were compared with histopathologic findings. The typical features of KD were subcutaneous lesions, continuously infiltrative parotid lesions with or without intraparotid lymphadenopathies, and reactive cervical lymphadenopathies on CT and conventional MRI. On DWI, the ADC values of all subcutaneous and infiltrative parotid lesions were higher compared to those of normal parotid glands, and the ADC values of reactive lymphadenopathies were lower compared to both. The choline/creatine levels of subcutaneous and infiltrative parotid lesions were slightly higher than those of normal parotid glands. In conclusion, DWI and MRSI offer valuable information that may be characteristic of KD, which can highly suggest the diagnosis of KD when combined with morphological imaging. PMID:25377973

Wang, Jie; Tang, Zuohua; Feng, Xiaoyuan; Zeng, Wenjiao; Tang, Weijun; Wu, Lingjie; Jin, Lixin

2014-11-01

384

High frequency resonant waveguide grating imager for assessing drug-induced cardiotoxicity  

NASA Astrophysics Data System (ADS)

We report a high-frequency resonant waveguide grating imager for assessing compound-induced cardiotoxicity. The imager sweeps the wavelength range from 823 nm to 838 nm every 3 s to identify and monitor compound-induced shifts in resonance wavelength and then switch to the intensity-imaging mode to detect the beating rhythm and proarrhythmic effects of compounds on induced pluripotent stem cell-derived cardiomyocytes. This opens possibility to study cardiovascular biology and compound-induced cardiotoxicity.

Ferrie, Ann M.; Wu, Qi; Deichmann, Oberon D.; Fang, Ye

2014-05-01

385

Echo-Planar Magnetic Resonance Imaging Studies of Frontal Cortex Activation During Word Generation in Humans  

Microsoft Academic Search

Nine subjects were studied by high-speed magnetic resonance imaging while performing language-based tasks. Subjects were asked either to repeat or to generate verbs associated with nouns read by an experimenter while magnetic resonance images were obtained of the left inferior frontal lobe. The echo-planar imaging sequence was used with a gradient echo time of 70 ms to give an apparent

Gregory McCarthy; Andrew M. Blamire; Douglas L. Rothman; Rolf Gruetter; Robert G. Shulman

1993-01-01

386

Assessment of mandibular growth and response to orthopedic treatment with 3- dimensional magnetic resonance images  

Microsoft Academic Search

Introduction: Three-dimensional (3D) craniofacial images are commonly used in clinical studies in orthodon- tics to study developmental and morphologic relationships. Methods: We used 3D magnetic resonance imaging to study relationships among craniofacial components during the pubertal growth spurt and in response to Fränkel appliance therapy. The sample for this prospective study was 156 high-resolution magnetic resonance images with 1 mm

Lucia H. S. Cevidanes; Alexandre A. Franco; Guido Gerig; William R. Proffit; Dennis E. Slice; Donald H. Enlow; Helio K. Yamashita; Yong-Jik Kim; Marco A. Scanavinii; Julio W. Vigoritoj

387

Extragastrointestinal stromal tumors: Computed tomography and magnetic resonance imaging findings  

PubMed Central

Extragastrointestinal stromal tumors (EGISTs) are rare mesenchymal tumors that originate outside the gastrointestinal tract. The aim of the present study was to investigate the computed tomography (CT) and magnetic resonance imaging (MRI) features of EGISTs and analyze the correlations between radiological findings and pathological features. CT and MRI images of 24 patients with EGISTs were reviewed retrospectively. Patient demographics and tumor characteristics, including localization, size, contours, borders, cystic-necrotic components, calcification, hemorrhage, tumor vessels, attenuation and intensity, degree and pattern of enhancement, ascites, tumor invasion, lymphadenopathy and distant metastasis were recorded. Statistical analyses to compare the radiological characteristics of low- and high-grade EGISTs were performed with ?2 or Fisher’s exact tests. The mean patient age at the time of presentation was 53 years. A total of 24 EGISTs were detected, originating in the omentum (n=4), mesentery (n=19) and retroperitoneum (n=1), respectively. The EGISTs displayed a predominantly spindle cell subtype (87.5%; 21/24). The majority of the EGISTs appeared as large (>10 cm; 70.8%; 17/24), round or oval (66.7%; 16/24), cystic-solid (87.5%; 21/24) and ill-defined (66.7%; 16/24) soft-tissue masses. The EGISTs were hypodense (69.6%; 16/23) or isodense (30.4%; 7/23) on CT images, hypointense (50%; 3/6), isointense (33.3%; 2/6) or hyperintense (16.7%; 1/6) on T1-weighted imaging (T1WI), and hyperintense on T2WI (100%; 6/6) and diffusion-WI (DWI; 100%; 6/6). A total of 54.2% (13/24) of the EGISTs displayed tumor vessels. Overall, 95.8% (23/24) of the masses showed marked enhancement and 87.5% (21/24) demonstrated heterogeneous enhancement. Calcification, hemorrhage, ascites and lymphadenopathy were rare characteristics in the EGISTs. Distant metastases were present in 10 patients (41.7%). The size, borders, tumor vessels and distant metastasis correlated with high-grade EGISTs [>5 mitoses/50 high-power fields (HPFs)] (P<0.05). The results of the present study indicated that clinical and radiological features, including advanced age, a large tumor size, cystic-necrotic components, rare lymphadenopathy, a heterogeneous enhancement pattern and hepatic metastasis may aid in the diagnosis of EGISTs. Radiological characteristics, such as a large size (>10 cm), ill-defined borders, tumor vessels and distant metastasis, can provide useful information in identifying the malignant behavior of EGISTs.

ZHU, JINGQI; YANG, ZHANGWEI; TANG, GUANGYU; WANG, ZHONGQIU

2015-01-01

388

Detectability of early brain meningitis with magnetic resonance imaging  

SciTech Connect

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

Runge, V.M.; Wells, J.W.; Williams, N.M. [Univ. of Kentucky, Lexington, KY (United States)

1995-08-01

389

Use magnetic resonance imaging to assess articular cartilage  

PubMed Central

Magnetic resonance imaging (MRI) enables a noninvasive, three-dimensional assessment of the entire joint, simultaneously allowing the direct visualization of articular cartilage. Thus, MRI has become the imaging modality of choice in both clinical and research settings of musculoskeletal diseases, particular for osteoarthritis (OA). Although radiography, the current gold standard for the assessment of OA, has had recent significant technical advances, radiographic methods have significant limitations when used to measure disease progression. MRI allows accurate and reliable assessment of articular cartilage which is sensitive to change, providing the opportunity to better examine and understand preclinical and very subtle early abnormalities in articular cartilage, prior to the onset of radiographic disease. MRI enables quantitative (cartilage volume and thickness) and semiquantitative assessment of articular cartilage morphology, and quantitative assessment of cartilage matrix composition. Cartilage volume and defects have demonstrated adequate validity, accuracy, reliability and sensitivity to change. They are correlated to radiographic changes and clinical outcomes such as pain and joint replacement. Measures of cartilage matrix composition show promise as they seem to relate to cartilage morphology and symptoms. MRI-derived cartilage measurements provide a useful tool for exploring the effect of modifiable factors on articular cartilage prior to clinical disease and identifying the potential preventive strategies. MRI represents a useful approach to monitoring the natural history of OA and evaluating the effect of therapeutic agents. MRI assessment of articular cartilage has tremendous potential for large-scale epidemiological studies of OA progression, and for clinical trials of treatment response to disease-modifying OA drugs. PMID:22870497

Wang, Yuanyuan; Wluka, Anita E.; Jones, Graeme; Ding, Changhai

2012-01-01

390

Radiation therapy planning and simulation with magnetic resonance images  

NASA Astrophysics Data System (ADS)

We present a system which allows for use of magnetic resonance (MR) images as primary RT workflow modality alone and no longer limits the user to computed tomography data for radiation therapy (RT) planning, simulation and patient localization. The single steps for achieving this goal are explained in detail. For planning two MR data sets, MR1 and MR2 are acquired sequentially. For MR1 a standardized Ultrashort TE (UTE) sequence is used enhancing bony anatomy. The sequence for MR2 is chosen to get optimal contrast for the target and the organs at risk for each individual patient. Both images are naturally in registration, neglecting elastic soft tissue deformations. The planning software first automatically extracts skin and bony anatomy from MR1. The user can semi-automatically delineate target structures and organs at risk based on MR1 or MR2, associate all segmentations with MR1 and create a plan in the coordinate system of MR1. Projections similar to digitally reconstructed radiographs (DRR) enhancing bony anatomy are calculated from the MR1 directly and can be used for iso-center definition and setup verification. Furthermore we present a method for creating a Pseudo-CT data set which assigns electron densities to the voxels of MR1 based on the skin and bone segmentations. The Pseudo-CT is then used for dose calculation. Results from first tests under clinical conditions show the feasibility of the completely MR based workflow in RT for necessary clinical cases. It needs to be investigated in how far geometrical distortions influence accuracy of MR-based RT planning.

Boettger, Thomas; Nyholm, Tufve; Karlsson, Magnus; Nunna, Chandrasekhar; Celi, Juan Carlos

2008-03-01

391

Sublingual Epidermoid Cyst Presenting with Distinctive Magnetic Resonance Imaging Findings  

PubMed Central

A case of sublingual epidermoid cyst presenting distinctive magnetic resonance imaging (MRI) findings is described. A 39-year-old man presented to our hospital with a three months progressive left submandibular swelling, difficulty moving his tongue, and snoring. Preoperative evaluation with MRI and fine needle aspiration cytology (FNAC) revealed that the heterogeneous cystic lesion contained the squamous cells, which is compatible with ectodermal tissue. The mass was located above the mylohyoid muscle and spread to the pharyngeal space. By considering the size, infection history, patient age, and location, the cyst was completely resected under general anesthesia via cervical approach without any complication. Histopathologically, the cyst wall was lined by stratified squamous epithelium with no skin appendage, suggesting an epidermoid cyst. Ultrasound (US), MRI and FNAC were very useful of the preoperative diagnosis for oral and sublingual lesion. The postoperative course was uneventful and without recurrence after 24 months. This case showed that epidermoid cysts formed the rarely heterogeneous cystic tumor and it underlined usefulness of preoperative diagnosis, such as US, MRI and FNAC for oral and sublingual tumor. PMID:25332766

Yoshida, Naohiro; Kodama, Kozue; Iino, Yukiko

2014-01-01

392

Genetically encoded reporters for hyperpolarized xenon magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

Magnetic resonance imaging (MRI) enables high-resolution non-invasive observation of the anatomy and function of intact organisms. However, previous MRI reporters of key biological processes tied to gene expression have been limited by the inherently low molecular sensitivity of conventional 1H MRI. This limitation could be overcome through the use of hyperpolarized nuclei, such as in the noble gas xenon, but previous reporters acting on such nuclei have been synthetic. Here, we introduce the first genetically encoded reporters for hyperpolarized 129Xe MRI. These expressible reporters are based on gas vesicles (GVs), gas-binding protein nanostructures expressed by certain buoyant microorganisms. We show that GVs are capable of chemical exchange saturation transfer interactions with xenon, which enables chemically amplified GV detection at picomolar concentrations (a 100- to 10,000-fold improvement over comparable constructs for 1H MRI). We demonstrate the use of GVs as heterologously expressed indicators of gene expression and chemically targeted exogenous labels in MRI experiments performed on living cells.

Shapiro, Mikhail G.; Ramirez, R. Matthew; Sperling, Lindsay J.; Sun, George; Sun, Jinny; Pines, Alexander; Schaffer, David V.; Bajaj, Vikram S.

2014-07-01

393

Functional magnetic resonance imaging of autism spectrum disorders  

PubMed Central

This review presents an overview of functional magnetic resonance imaging findings in autism spectrum disorders (ASDs), Although there is considerable heterogeneity with respect to results across studies, common themes have emerged, including: (i) hypoactivation in nodes of the “social brain” during social processing tasks, including regions within the prefrontal cortex, the posterior superior temporal sulcus, the amygdala, and the fusiform gyrus; (ii) aberrant frontostriatal activation during cognitive control tasks relevant to restricted and repetitive behaviors and interests, including regions within the dorsal prefrontal cortex and the basal ganglia; (iii) differential lateralization and activation of language processing and production regions during communication tasks; (iv) anomalous mesolimbic responses to social and nonsocial rewards; (v) task-based long-range functional hypoconnectivity and short-range hyper-connectivity; and (vi) decreased anterior-posterior functional connectivity during resting states. These findings provide mechanistic accounts of ASD pathophysiology and suggest directions for future research aimed at elucidating etiologic models and developing rationally derived and targeted treatments. PMID:23226956

Dichter, Gabriel S.

2012-01-01

394

Myocardial strains from 3D displacement encoded magnetic resonance imaging  

PubMed Central

Background The ability to measure and quantify myocardial motion and deformation provides a useful tool to assist in the diagnosis, prognosis and management of heart disease. The recent development of magnetic resonance imaging methods, such as harmonic phase analysis of tagging and displacement encoding with stimulated echoes (DENSE), make detailed non-invasive 3D kinematic analyses of human myocardium possible in the clinic and for research purposes. A robust analysis method is required, however. Methods We propose to estimate strain using a polynomial function which produces local models of the displacement field obtained with DENSE. Given a specific polynomial order, the model is obtained as the least squares fit of the acquired displacement field. These local models are subsequently used to produce estimates of the full strain tensor. Results The proposed method is evaluated on a numerical phantom as well as in vivo on a healthy human heart. The evaluation showed that the proposed method produced accurate results and showed low sensitivity to noise in the numerical phantom. The method was also demonstrated in vivo by assessment of the full strain tensor and to resolve transmural strain variations. Conclusions Strain estimation within a 3D myocardial volume based on polynomial functions yields accurate and robust results when validated on an analytical model. The polynomial field is capable of resolving the measured material positions from the in vivo data, and the obtained in vivo strains values agree with previously reported myocardial strains in normal human hearts. PMID:22533791

2012-01-01

395

The role of intraoperative magnetic resonance imaging in glioma surgery  

PubMed Central

For patients with gliomas, the goal of surgery is to maximize the extent of tumor resection while avoiding injury to functional tissue. The hope is to improve patients’ survival and maintain the highest quality of life as possible. However, because of the infiltrative nature of gliomas these two goals often oppose each other so a compromise must be met. Many tools have been developed to help with this challenge of glioma surgery. Over the past two decades, intraoperative-magnetic resonance imaging (iMRI) has emerged as an increasingly important modality to enhance surgical safety while providing the surgeon with updated information to guide their resection. Here the authors review the studies that demonstrate a positive correlation between extent of resection (EOR) and overall survival (OS), although the data is clearer in patients with low-grade gliomas (LGG) and still somewhat controversial in those with higher-grade tumors. We will then review some of the studies that support the role of iMRI and how it has impacted glioma surgery by increasing the EOR. The value of iMRI usage in regards to overall patient outcome can be extrapolated through its effect on EOR. Overall, available data support the safe use of iMRI and as an effective adjunct in glioma surgery. PMID:23230537

Liang, Danny; Schulder, Michael

2012-01-01

396

In vivo microelectrode track reconstruction using magnetic resonance imaging  

PubMed Central

To obtain more precise anatomical information about cortical sites of microelectrode recording and microstimulation experiments in alert animals, we have developed a non-invasive, magnetic resonance imaging (MRI) technique for reconstructing microelectrode tracks. We made microelectrode penetrations in the brains of anesthetized rats and marked sites along them by depositing metal, presumably iron, with anodic monophasic or biphasic current from the tip of a stainless steel microelectrode. The metal deposits were clearly visible in the living animal as approximately 200 ?m wide hypointense punctate marks using gradient echo sequences in a 4.7T MRI scanner. We confirmed the MRI findings by comparing them directly to the postmortem histology in which the iron in the deposits could be rendered visible with a Prussian blue reaction. MRI-visible marks could be created using currents as low as 1 ?A (anodic) for 5 s, and they remained stable in the brains of living rats for up to nine months. We were able to make marks using either direct current or biphasic current pulses. Biphasic pulses caused less tissue damage and were similar to those used by many laboratories for functional microstimulation studies in the brains of alert monkeys. PMID:9667395

Fung, S.H.; Burstein, D.; Born, R.T.

2010-01-01

397

Achromatic synesthesias - a functional magnetic resonance imaging study.  

PubMed

Grapheme-color synesthetes experience consistent, automatic and idiosyncratic colors associated with specific letters and numbers. Frequently, these specific associations exhibit achromatic synesthetic qualities (e.g. white, black or gray). In this study, we have investigated for the first time the neural basis of achromatic synesthesias, their relationship to chromatic synesthesias and the achromatic congruency effect in order to understand not only synesthetic color but also other components of the synesthetic experience. To achieve this aim, functional magnetic resonance imaging experiments were performed in a group of associator grapheme-color synesthetes and matched controls who were stimulated with real chromatic and achromatic stimuli (Mondrians), and with letters and numbers that elicited different types of grapheme-color synesthesias (i.e. chromatic and achromatic inducers which elicited chromatic but also achromatic synesthesias, as well as congruent and incongruent ones). The information derived from the analysis of Mondrians and chromatic/achromatic synesthesias suggests that real and synesthetic colors/achromaticity do not fully share neural mechanisms. The whole-brain analysis of BOLD signals in response to the complete set of synesthetic inducers revealed that the functional peculiarities of the synesthetic brain are distributed, and reflect different components of the synesthetic experience: a perceptual component, an (attentional) feature binding component, and an emotional component. Additionally, the inclusion of achromatic experiences has provided new evidence in favor of the emotional binding theory, a line of interpretation which constitutes a bridge between grapheme-color synesthesia and other developmental modalities of the phenomenon. PMID:24845620

Melero, H; Ríos-Lago, M; Peña-Melián, A; Álvarez-Linera, J

2014-09-01

398

Magnetic Resonance Imaging Traits in Siblings Discordant for Alzheimer Disease  

PubMed Central

BACKGROUND Magnetic resonance imaging (MRI) can aid clinical assessment of brain changes potentially correlated with Alzheimer disease (AD). MRI traits may improve our ability to identify genes associated with AD-outcomes. We evaluated semi-quantitative MRI measures as endophenotypes for genetic studies by assessing their association with AD in families from the Multi-Institutional Research in Alzheimer Genetic Epidemiology (MIRAGE) Study. METHODS Discordant siblings from multiple ethnicities were ascertained through a single affected proband. Semi-quantitative MRI measures were obtained for each individual. The association between continuous/ordinal MRI traits and AD were analyzed using generalized estimating equations. Medical history and Apolipoprotein E (APOE)?4 status were evaluated as potential confounders. RESULTS Comparisons of 214 affected and 234 unaffected subjects from 229 sibships revealed that general cerebral atrophy, white matter hyperintensities (WMH), and mediotemporal atrophy differed significantly between groups (each at P < .0001) and varied by ethnicity. Age at MRI and duration of AD confounded all associations between AD and MRI traits. Among unaffected sibs, the presence of at least one APOE?4 allele and MRI infarction was associated with more WMH after adjusting for age at MRI. CONCLUSION The strong association between MRI traits and AD suggests that MRI traits may be informative endophenotypes for basic and clinical studies of AD. In particular, WMH may be a marker of vascular disease that contributes to AD pathogenesis. PMID:18808654

Cuenco, Karen T.; Green, Robert C.; Zhang, J.; Lunetta, Kathryn; Erlich, Porat M.; Cupples, L. Adrienne; Farrer, Lindsay A.; DeCarli, Charles; Baldwin, C. T.; Auerbach, S.; Akomolafe, A.; Freedman, Lorin; Ofili, E.; Chui, H.; DeCarli, C.; Duara, R.; Foroud, T.; Farlow, M.; Friedland, R.; Go, R.; Kurz, A.; Obisesan, T.; Petrovitch, H.; White, L.; Relkin, N.; Sabbagh, M.; Sadovnick, D.; Tsolaki, M.

2009-01-01

399

[Cardiac magnetic resonance imaging of acute myocardial infarction].  

PubMed

Area at risk, infarct area, the size of no-reflow phenomenon and finally left ventricular function determine immediate and long-term outcome in patients with acute myocardial infarction (AMI). Cardiac magnetic resonance imaging is a gold standard technique for evaluation of left ventricular volumes and function and therefore has evolved into an important diagnostic tool in the assessment of patients with AMI. Increased free water content in the infracted myocardium prolongs the T2-relaxation time. Differences in T2-relaxation time are clinically useful for detection of area of risk whereas first-pass technique is useful for the assessment of areas with perfusion deficit at rest. Myocardial necrosis appears hyper-enhanced in comparison to the normal myocardium after contrast injection with delayed enhancement (DE) technique. Experimental and clinical studies indicate that extent of DE closely correlates with infarct size and predicts functional recovery of postinfarcted myocardium. The hypo-enhanced zone usually located in the core of hyper-enhanced region indicates microvascular obstruction (MVO) and corresponds with the area of no-reflow as defined by histopathology. The presence of MVO is associated with impaired functional recovery after AMI. PMID:22134999

Zalewski, Jaros?aw

2010-01-01

400

Combined magnetic resonance, fluorescence, and histology imaging strategy in a human breast tumor xenograft model  

PubMed Central

Applications of molecular imaging in cancer and other diseases frequently require combining in vivo imaging modalities, such as magnetic resonance and optical imaging, with ex vivo optical, fluorescence, histology, and immunohistochemical (IHC) imaging, to investigate and relate molecular and biological processes to imaging parameters within the same region of interest. We have developed a multimodal image reconstruction and fusion framework that accurately combines in vivo magnetic resonance imaging (MRI) and magnetic resonance spectroscopic imaging (MRSI), ex vivo brightfield and fluorescence microscopic imaging, and ex vivo histology imaging. Ex vivo brightfield microscopic imaging was used as an intermediate modality to facilitate the ultimate link between ex vivo histology and in vivo MRI/MRSI. Tissue sectioning necessary for optical and histology imaging required generation of a three-dimensional (3D) reconstruction module for 2D ex vivo optical and histology imaging data. We developed an external fiducial marker based 3D reconstruction method, which was able to fuse optical brightfield and fluorescence with histology imaging data. Registration of 3D tumor shape was pursued to combine in vivo MRI/MRSI and ex vivo optical brightfield and fluorescence imaging data. This registration strategy was applied to in vivo MRI/MRSI, ex vivo optical brightfield/fluorescence, as well as histology imaging data sets obtained from human breast tumor models. 3D human breast tumor data sets were successfully reconstructed and fused with this platform. PMID:22945331

Jiang, Lu; Greenwood, Tiffany R.; Amstalden van Hove, Erika R.; Chughtai, Kamila; Raman, Venu; Winnard, Paul T.; Heeren, Ron; Artemov, Dmitri; Glunde, Kristine

2014-01-01

401

Should magnetic resonance imaging or computed tomography be the primary brain imaging modality in the transient ischemic attack clinic?  

PubMed Central

Objective The Royal College of Physicians and National Institute of Clinical Excellence have recommended that magnetic resonance imaging should be the modality of choice for cerebral imaging in transient ischemic attack patients. However, implementation of this is often difficult. Therefore, it is important to know whether magnetic resonance imaging contributes significantly to early clinical management in transient ischemic attack patients. Design A retrospective case-notes review of 65 consecutive patients seen by one neurology trainee (with consultant review), in a neurovascular service where computed tomography has been the primary cerebral imaging modality. Setting Outpatient TIA/Neurovascular clinic at Imperial College hospital. Participants 65 consecutive patients seen by one neurology trainee (with consultant review). Main outcome measure We recorded the preliminary clinical diagnosis, details of investigations performed and whether or not patients had a magnetic resonance imaging brain scan subsequently, the number followed up in clinic and the final diagnosis. Results Of the 65 cases seen, 55% were classified initially as transient ischemic attack/stroke mimics. Of the 29 cases (45%) that were classified as transient ischemic attack, all had computed tomography scans, 12 had magnetic resonance imaging scans subsequently and 14 were followed up several weeks later. Of the 36 cases classified as stroke mimics, 27 had computed tomography scans immediately and 31 had carotid Dopplers, six subsequently had magnetic resonance imaging scans and 14 were followed up in clinic. Only two patients had their diagnosis revised on the basis of the magnetic resonance imaging. Conclusions Our study suggests that magnetic resonance imaging brain changes the diagnosis in a relatively small percentage of cases. A good history and examination remain paramount in the assessment of patients presenting to the transient ischemic attack clinic, particularly when more than 50% of cases referred are transient ischemic attack/stroke mimics. PMID:25408918

Ganesalingam, Jeban

2014-01-01

402

Focal Cortical Dysplasia Segmentation in 3D Magnetic Resonance Images of the Human Brain  

Microsoft Academic Search

In this work we present an image processing pipeline for automatic segmentation of focal cortical dysplasia lesions in 3D magnetic resonance images of the human brain. Dys- plasia lesions are a common cause of refractory epilepsy, especially in children, and their treatment often involve sur- gical intervention. To achieve this pipeline we developed several new image processing techniques, procedures and

Felipe P. G. Bergo; Alexandre X. Falc

403

Compromising abnormalities of the brachial plexus as displayed by magnetic resonance imaging  

Microsoft Academic Search

Magnetic resonance images (MRI) of brachial plexus anatomy bilaterally, not possible by plain radiographs or CT, were presented to the Vascular Surgery, Neurology, and the Neurosurgery departments. Patients were requested for MRI of their brachial plexus. They were referred for imaging and the imaging results were presented to the faculty and housestaff. Our technique was accepted and adopted to begin

James D. Collins; Marla L. Shaver; Anthony C. Disher; Theodore Q. Miller

1995-01-01

404

High-resolution magnetic resonance imaging of the wrist: normal anatomy  

Microsoft Academic Search

Magnetic resonance imaging (MRI) provided adequate depiction of carpal soft tissue structures in normal volunteers, as well as accurate anatomic correlation with cadaveric specimens. Using a high field strength system and surface coil techniques, the intricate anatomy of the wrist was best defined on long TR short TE images. However, from a practical view, T1 weighted images (TR 600 ms,

Lori L. Baker; Paul C. Hajek; Ann Björkengren; Robert Galbraith; David J. Sartoris; Richard H. Gelberman; Donald Resnick

1987-01-01

405

A method for foetal heart rate monitoring during magnetic resonance imaging using Doppler ultrasound  

Microsoft Academic Search

A means of monitoring foetal heart rate (FHR) during magnetic resonance imaging (MRI) is presented. Foetal heart rate was measured using a modified standard Doppler ultrasound based monitor. The transducer and lead from the monitor required alteration to reduce interference and distortion in the MR images to acceptable levels. These changes enabled high quality images to be produced with insignificant

Simon A Shakespeare; Rachel J Moore; John A Crowe; Penny A Gowland; Barrie R Hayes-Gill

1999-01-01

406

Geometric Analysis and Symbol Calculus: Fourier Transform Magnetic Resonance Imaging and Wavelets  

Microsoft Academic Search

Due to its unequalled advantages, the magnetic resonance imaging (MRI) modality has truly revolutionized the diagnosis and evaluation of pathology. Because many morphological anatomic details that may not be visualized by other high tech imaging methods can now be readily shown by diagnostic MRI, it has already become the standard modality by which all other clinical imaging techniques are measured.

Walter Schempp

1997-01-01

407

[Magnetic resonance imaging in juvenile idiopathic arthritis: peculiarities of imaging children].  

PubMed

The term juvenile idiopathic arthritis (JIA) encompasses a heterogeneous group of arthritides with no known cause that begin before the age of 16 years and persist for at least 6 weeks. In recent decades, imaging techniques have acquired a fundamental role in the diagnosis and follow-up of JIA, owing to the unification of the different criteria for classification, which has strengthened the research in this field, and to the development of disease-modifying antirheumatic drugs. In this article, we briefly explain what JIA is. Moreover, we describe the role and limitations of plain-film radiography, ultrasonography, and magnetic resonance imaging (MRI). Finally, we review the MRI protocol and findings, and we comment on the differential diagnosis. PMID:23337696

Navallas, M; Rebollo Polo, M; Riaza, L; Muchart López, J; Maristany, T

2013-09-01

408

In vivo Off-Resonance Saturation Magnetic Resonance Imaging of AvB3-Targeted Superparamagnetic Nanoparticles  

E-print Network

of cancer (Fig. 1A). Polymeric micelles are a new class of self-assembled nanoparticles with a core expres- sion of these diseases. Here, we combine an ultrasensitive design of superparamagnetic polymeric micelles (SPPM) and an off-resonance saturation (ORS) method to enhance the imaging efficacy of tumor

Gao, Jinming

409

Magnetic resonance imaging for adaptive cobalt tomotherapy: A proposal  

PubMed Central

Magnetic resonance imaging (MRI) provides excellent soft tissue contrast for oncology applications. We propose to combine a MRI scanner with a helical tomotherapy (HT) system to enable daily target imaging for improved conformal radiation dose delivery to a patient. HT uses an intensity-modulated fan-beam that revolves around a patient, while the patient slowly advances through the plane of rotation, yielding a helical beam trajectory. Since the use of a linear accelerator to produce radiation may be incompatible with the pulsed radiofrequency and the high and pulsed magnetic fields required for MRI, it is proposed that a radioactive Cobalt-60 (60Co) source be used instead to provide the radiation. An open low field (0.25 T) MRI system is proposed where the tomotherapy ring gantry is located between two sets of Helmholtz coils that can generate a sufficiently homogenous main magnetic field. It is shown that the two major challenges with the design, namely acceptable radiation dose rate (and therefore treatment duration) and moving parts in strong magnetic field, can be addressed. The high dose rate desired for helical tomotherapy delivery can be achieved using two radiation sources of 220TBq (6000Ci) each on a ring gantry with a source to axis-of-rotation distance of 75 cm. In addition to this, a dual row multi-leaf collimator (MLC) system with 15 mm leaf width at isocentre and relatively large fan beam widths between 15 and 30 mm per row shall be employed. In this configuration, the unit would be well-suited for most pelvic radiotherapy applications where the soft tissue contrast of MRI will be particularly beneficial. Non-magnetic MRI compatible materials must be used for the rotating gantry. Tungsten, which is non-magnetic, can be used for primary collimation of the fan-beam as well as for the MLC, which allows intensity modulated radiation delivery. We propose to employ a low magnetic Cobalt compound, sycoporite (CoS) for the Cobalt source material itself. Rotational delivery is less susceptible to problems related to the use of a low energy megavoltage photon source while the helical delivery reduces the negative impact of the relatively large penumbra inherent in the use of Cobalt sources for radiotherapy. On the other hand, the use of a 60Co source ensures constant dose rate with gantry rotation and makes dose calculation in a magnetic field as easy as the range of secondary electrons is limited. The MR-integrated Cobalt tomotherapy unit, dubbed ‘MiCoTo,’ uses two independent physical principles for image acquisition and treatment delivery. It would offer excellent target definition and will allow following target motion during treatment using fast imaging techniques thus providing the best possible input for adaptive radiotherapy. As an additional bonus, quality assurance of the radiation delivery can be performed in situ using radiation sensitive gels imaged by MRI. PMID:21206640

Kron, Tomas; Eyles, David; John, Schreiner L; Battista, Jerry

2006-01-01

410

Orthogonal resonators for pulse in vivo electron paramagnetic imaging at 250 MHz  

NASA Astrophysics Data System (ADS)

A 250 MHz bimodal resonator with a 19 mm internal diameter for in vivo pulse electron paramagnetic resonance (EPR) imaging is presented. Two separate coaxial cylindrical resonators inserted one into another were used for excitation and detection. The Alderman-Grant excitation resonator (AGR) showed the highest efficiency among all the excitation resonators tested. The magnetic field of AGR is confined to the volume of the detection resonator, which results in highly efficient use of the radio frequency power. A slotted inner single loop single gap resonator (SLSG LGR), coaxial to the AGR, was used for signal detection. The resulting bimodal resonator (AG/LGR) has two mutually orthogonal magnetic field modes; one of them has the magnetic field in the axial direction. The resonator built in our laboratory achieved 40 dB isolation over 20 MHz bandwidth with quality factors of detection and excitation resonators of 36 and 11 respectively. Considerable improvement of the B1 homogeneity and EPR image quality in comparison with reflection loop-gap resonator of similar size and volume was observed.

Sundramoorthy, Subramanian V.; Epel, Boris; Halpern, Howard J.

2014-03-01

411

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

NASA Astrophysics Data System (ADS)

This dissertation discusses the production of highly nonequilibrium nuclear spin polarization, referred to as hyperpolarization or hp, in the nuclear spin I = 9/2 noble gas isotope krypton-83 using spin exchange optical pumping (SEOP). This nonequilibrium polarization yields nuclear magnetic resonance (NMR) signals that are enhanced three or more orders of magnitude above those of thermally polarized krypton and enables experiments that would otherwise be impossible. Krypton-83 possesses a nuclear electric quadrupole moment that dominates the longitudinal (T1) relaxation due to coupling of the quadrupole moment to fluctuating electric field gradients generated by distortions to the spherical symmetry of the electronic environment. Relaxation slows polarization buildup and limits the maximum signal intensity but makes krypton-83 a sensitive probe of its environment. The gas-phase krypton-83 longitudinal relaxation rate increases linearly with total gas density due to binary collisions. Density independent relaxation, caused by the formation of krypton-krypton van der Waals molecules and surface adsorption, also contributes to the observed rate. Buffer gases suppress van der Waals molecule mediated relaxation by breaking apart the weakly bound krypton dimers. Surface relaxation is gas composition independent and therefore more difficult to suppress. However, this relaxation mechanism makes hp krypton-83 sensitive to important surface properties including surface-to-volume ratio, surface chemistry, and surface temperature. The presence of surfaces with high krypton adsorption affinities (i.e. hydrophobic surfaces) accelerates the relaxation times and can produce T1 contrast in hp krypton-83 magnetic resonance imaging (MRI). Tobacco smoke deposited on surfaces generates strong T1 contrast allowing the observation of smoke deposition with spatial resolution. Conversely, water adsorption on surfaces significantly lengths the T1 times due competitive surface adsorption. Finally, this work demonstrates that hp krypton-83 MRI of intact, excised lungs is feasible. No attempts have been made to observe pathology specific contrast, but this work represents the first steps in developing hp krypton into a useful biomedical tool. Although the signal must be improved for biomedical applications, additional enhancements of up to 180 times greater than the currently obtained signal are possible through improved SEOP, and another order of magnitude increase can be obtained through isotopic enrichment.

Cleveland, Zackary I.

412

Multislice proton magnetic resonance spectroscopic imaging in X-linked adrenoleukodystrophy.  

PubMed

Multislice proton magnetic resonance spectroscopic imaging permits metabolic analysis of brain tissue in vivo by data acquisition in four oblique axial slices, each 15-mm thick and divided into 0.8-ml single-volume elements. We applied this technique to the systematic study of 25 patients with adrenoleukodystrophy: 3 with the severe childhood or adult cerebral form of the disease, 5 with adrenomyeloneuropathy, 12 with no demonstrable neurological involvement, and 5 women heterozygous for adrenoleukodystrophy who had some degree of neurological disability. Abnormalities on magnetic resonance spectroscopic imaging included a reduction in N-acetyl aspartate, an increase in choline-containing compounds, and at times, an increase in lactate. Five patients showed abnormalities in the presence of normal-appearing magnetic resonance images, and in 8 other patients the alterations on spectroscopic images were more severe than those demonstrable by magnetic resonance imaging. Correlation with clinical course suggests that an increase in the choline-containing compounds is associated with an active demyelinative process, whereas such compounds are not elevated in lesions that are stable. We conclude that magnetic resonance spectroscopic imaging is a more sensitive indicator of early neurological involvement than is magnetic resonance imaging, and that the character of abnormalities detected by the former technique may serve as a gauge of the degree of activity of the demyelinating process and as a guide to the selection and evaluation of therapeutic approaches. PMID:7944292

Kruse, B; Barker, P B; van Zijl, P C; Duyn, J H; Moonen, C T; Moser, H W

1994-10-01

413

Incidental extraspinal findings on magnetic resonance imaging of intervertebral discs  

PubMed Central

Introduction We aimed to evaluate pathological extraspinal findings and congenital anomalies/anatomical variations that were incidentally detected on the magnetic resonance imaging (MRI) scans of intervertebral discs, to find the frequencies of these incidental findings, and to emphasise the clinical importance of them. Material and methods A retrospective study including 1031 consecutive patients (730 females and 301 males, with a median age of 46 years) was conducted by evaluating a total of 1106 MRI examinations of intervertebral discs. Examinations were performed with a 1.5 T MRI unit. Incidental findings were classified as pathological findings and congenital anomalies/anatomical variations. Results The percentages of incidental extraspinal pathological findings and congenital anomalies/anatomical variations were 16.6% (95% confidence interval (CI): 14.4–18.8) and 3.7% (95% CI: 2.6–4.3), respectively. The percentage of incidental extraspinal pathological findings on cervical spinal MRI was 25.7% (95% CI: 20.1–31.7), thyroid nodules being the most common incidental findings. On thoracic spinal MRI (n = 19), inferior pole thyroid nodules were demonstrated as incidental extraspinal pathological findings, with a percentage of 10.5% (95% CI: 9.6–11.5). On lumbar spinal MRI, incidental pathological findings were detected with a percentage of 14.2% (95% CI: 11.9–16.6), while the percentage of congenital anomalies/anatomical variations was 4.8% (95% CI: 3.4–6.3). Eventually, 6.5% (95% CI: 2.6–9.4) of all cases with incidental extraspinal pathological findings underwent surgery. Conclusions On MRI examination of intervertebral discs, paying attention to incidentally detected pathological extraspinal findings and congenital anomalies/anatomical variations is very important due to the fact that they can alter the treatment of the patient or affect the patient's life. PMID:25276162

Ayaz, Umit Yasar; Turanl?, Sevim; Saltas, Hakan; Karabacak, Osman Raif; Damar, Cagr?; Hekimoglu, Baki

2014-01-01

414

Studies in nonlinear optics and functional magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

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

Dai, Tehui

415

Microwave and RF heating under noninvasive temperature measurement using magnetic resonance imaging scanner  

Microsoft Academic Search

Recent development of Magnetic Resonance Imaging (MRI) equipment enables Interventional Radiology (IVR) as diagnosis and treatment under MRI usage. In this paper, a new methodology for Magnetic Resonance (MR) scanner to apply not only diagnostic equipment but for treatment one is discussed. The temperature measuring procedure under MR is to measure phase shift of T1, which is the longitudinal relaxation

Yoshio Nikawa; Akira Ishikawa

2011-01-01

416

Laser resonators of a mirror and corner cube reflector Analysis by the imaging method  

Microsoft Academic Search

Zhou et al. (1982) have discussed the modes of a laser resonator, consisting of a mirror and a retroreflecting corner cube. A resonator of the considered type is inherently insensitive to the tilt of the corner cube. The present investigation is, therefore, concerned with the simulation of a model of a cavity which involves one real and one image mirror.

I.-C. Kuo; Ton Ko

1984-01-01

417

Highly Parallel Magnetic Resonance Imaging with a Fourth Gradient Channel for Compensation of RF Phase Patterns  

E-print Network

A fourth gradient channel was implemented to provide slice dependent RF coil phase compensation for arrays in dual-sided or "sandwich" configurations. The use of highly parallel arrays for single echo acquisition magnetic resonance imaging allows...

Bosshard, John 1983-

2012-08-20

418

Phase-based regional oxygen metabolism in magnetic resonance imaging at high field  

E-print Network

Venous oxygen saturation (Yv) in cerebral veins and the cerebral metabolic rate of oxygen (CMRO?) are important indicators for brain function and disease. Phase-susceptibility measurements in magnetic resonance imaging ...

Fan, Audrey Peiwen

2010-01-01

419

Non-invasive magnetic resonance imaging-guided focused ultrasound treatment for uterine fibroids – early experience  

Microsoft Academic Search

ObjectiveTo describe early results regarding efficacy and safety of magnetic resonance imaging-guided focused ultrasound surgery (MRgFUS) for the treatment of uterine leiomyomas among a population of Japanese women.

Yutaka Morita; Naoki Ito; Hiromi Hikida; Sawako Takeuchi; Kouji Nakamura; Hirofumi Ohashi

2008-01-01

420

Nuclear magnetic resonance imaging and analysis for determination of porous media properties  

E-print Network

Advanced nuclear magnetic resonance (NMR) imaging methodologies have been developed to determine porous media properties associated with fluid flow processes. This dissertation presents the development of NMR experimental and analysis methodologies...

Uh, Jinsoo

2007-04-25

421

Magnetic resonance spectroscopic imaging with 2D spectroscopy for the detection of brain metabolites  

E-print Network

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

Kok, Trina

2012-01-01

422

T2*-weighted magnetic resonance imaging used to detect coagulative necrosis in tissue  

E-print Network

to prevent unnecessary collateral damage to surrounding healthy tissue. This research focuses on using T2*-weighted FLASH magnetic resonance imaging to detect irreversible changes in i . n vitro bovine liver tissue and tissuesimulating polyacrylamide gel...

Van Hyfte, John Bruce

2012-06-07

423

A magnetic resonance imaging study of autism: normal fourth ventricle size and absence of pathology.  

PubMed

Magnetic resonance imaging did not diagnose neuropathology in 15 autistic patients. Measurements of the midsagittal area and volume of the fourth ventricle did not differ between these patients and matched control subjects. PMID:2929757

Garber, H J; Ritvo, E R; Chiu, L C; Griswold, V J; Kashanian, A; Freeman, B J; Oldendorf, W H

1989-04-01

424

Accelerating magnetic resonance imaging by unifying sparse models and multiple receivers  

E-print Network

Magnetic resonance imaging (MRI) is an increasingly versatile diagnostic tool for a variety of medical purposes. During a conventional MRI scan, samples are acquired along a trajectory in the spatial Fourier transform ...

Weller, Daniel (Daniel Stuart)

2012-01-01

425

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

PubMed Central

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

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

2014-01-01

426

HST.583 Functional Magnetic Resonance Imaging: Data Acquisition and Analysis, Fall 2006  

E-print Network

This team taught, multidisciplinary course covers the fundamentals of magnetic resonance imaging relevant to the conduct and interpretation of human brain mapping studies. The challenges inherent in advancing our knowledge ...

Gollub, Randy L.

427

Multimodal neuroimaging with simultaneous electroencephalogram and high-field functional magnetic resonance imaging  

E-print Network

Simultaneous recording of electroencephalogram (EEG) and functional magnetic resonance imaging (tMRI) is an important emerging tool in functional neuroimaging with the potential to reveal new mechanisms for brain function ...

Purdon, Patrick L. (Patrick Lee), 1974-

2005-01-01

428

DIABETIC RETINOPATHY UPDATE Magnetic resonance imaging of the retina: A brief  

E-print Network

DIABETIC RETINOPATHY UPDATE Magnetic resonance imaging of the retina: A brief historical and future to investigate the retinas of rodents, non-human primates and humans. ª 2011 King Saud University. Production) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138 4. MRI of the retina

Duong, Timothy Q.

429

Stray Field Magnetic Resonance Imaging: A Non-Destructive Means for Internal Imaging of Planetary Rock Samples  

NASA Astrophysics Data System (ADS)

The ability to quickly scan and image rocks internally would be a huge advantage for Mars and other Planetary, Lunar and primitive body missions. A technique known as Stray Field Magnetic Resonance Imaging is described that would make this a reality.

Bonetti, J. A.; Manohara, H. M.; Holmes, W. A.

2012-06-01

430

Compressive Sensing Ensemble Average Propagator Estimation via 1 Spherical Polar Fourier Imaging  

E-print Network

a dense 3D sampling. Q-Ball Imaging (QBI) [16, 9] and Diffusion Orientation Transform (DOT) [13] are two.Cheng@inria.fr Abstract. In diffusion MRI (dMRI) domain, many High Angular Resolution Diffusion Imaging (HARDI) methods) was proposed to represent diffusion signal using Spherical Polar Fourier (SPF) ba- sis without specific

Boyer, Edmond

431

Investigation of cardiomyopathy using cardiac magnetic resonance imaging part 1: Common phenotypes  

PubMed Central

Cardiac magnetic resonance imaging (CMRI) has emerged as a useful tertiary imaging tool in the investigation of patients suspected of many different types of cardiomyopathies. CMRI sequences are now of a sufficiently robust quality to enable high spatial and temporal resolution image acquisition. This has led to CMRI becoming an effective non-invasive imaging gold standard for many cardiomyopathies. In this 2-part review, we outline the typical sequences used to image cardiomyopathy, and present the imaging spectrum of cardiomyopathy. Part 1 focuses on the current classification of cardiomyopathy, basic CMRI sequences used in evaluating cardiomyopathy and the imaging spectrum of common phenotypes. PMID:22558489

McDermott, Shaunagh; O'Neill, Ailbhe C; Ridge, Carole A; Dodd, Jonathan D

2012-01-01

432

Interventional magnetic resonance imaging cryotherapy of uterine fibroid tumors: Preliminary observation  

Microsoft Academic Search

Objective: The purpose of this study was to identify alternatives to hysterectomy. We have developed a transabdominal interventional magnetic resonance imaging-guided cryoablation procedure and report this novel approach. Study Design: This represents the preliminary and first report of a prospective Institutional Review Board-approved protocol to study interventional magnetic resonance imaging-guided cryoablation of uterine fibroid tumors. Women were selected on the

Bryan D. Cowan; Patrick E. Sewell; Jeffery C. Howard; Richard M. Arriola; Lynda G. Robinette

2002-01-01

433

Application of nuclear magnetic resonance imaging and spectroscopy to fluids in porous media  

E-print Network

APPLICATION OF NUCLEAR MAGNETIC RESONANCE IMAGING AND SPECTROSCOPY TO FLUIDS IN POROUS MEDIA A Thesis by SHANTHI SREE MANDAVA Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements... for the degree of MASTER OF SCIENCE May 1991 Major Subject: Chemical Engineering APPLICATION OF NUCLEAR MAGNETIC RESONANCE IMAGING AND SPECTROSCOPY TO FLUIDS IN POROUS MEDIA A Thesis by SHANTHI SREE MANDAVA Approved as to style and content by: A. Ted...

Mandava, Shanthi Sree

2012-06-07

434

Functional magnetic resonance imaging of symptom provocation in obsessive-compulsive disorder  

Microsoft Academic Search

BACKGROUND: The new technique of functional magnetic resonance imaging was used to investigate the mediating neuroanatomy of obsessive-compulsive disorder symptoms. METHODS: Ten patients with obsessive-compulsive disorder and 5 normal subjects were studied via functional magnetic resonance imaging during control and provoked conditions. Data analysis entailed parametric and nonparametric statistical mapping. RESULTS: Statistical maps (nonparametric; P < 10(-3)) showed activation for

H. C. Breiter; S. L. Rauch; K. K. Kwong; J. R. Baker; R. M. Weisskoff; D. N. Kennedy; A. D. Kendrick; T. L. Davis; A. Jiang; M. S. Cohen; C. E. Stern; J. W. Belliveau; L. Baer; R. L. O'Sullivan; C. R. Savage; M. A. Jenike; B. R. Rosen

1996-01-01

435

Recent innovations in the development of magnetic resonance imaging conditional pacemakers and implantable cardioverter-defibrillators.  

PubMed

The first generation of magnetic resonance conditional pacemakers and implantable cardioverter-defibrillators has finally arrived in clinical practice after many years of development. These devices have been optimized to properly function within magnetic fields of 1.5 T and ensure safe operation in controlled environments. Further progress is needed to develop a new generation of magnetic resonance imaging (MRI) conditional devices that can operate in higher powered MRI machines (3 T) which produce clearer images. PMID:22298178

Lobodzinski, S Suave

2012-01-01

436

Early clinical experience with high-field 1.5 Tesla magnetic resonance imaging.  

PubMed

Despite early concerns regarding potential tissue attenuation of signal and lack of inherent contrast, magnetic resonance imaging at 1.5 Tesla has proved to be a valuable extension of magnetic resonance imaging. In this report, we review our initial experience in imaging of the central nervous system, abdomen, chest and pelvis. In the central nervous system, exquisite morphologic detail has been demonstrated. This has added both in terms of sensitivity and specificity to neuroradiologic diagnosis. In the chest and abdomen, despite problems with respiratory and cardiac motion, good morphologic detail can be obtained. In the thorax, our work has demonstrated the ability of magnetic resonance imaging to clearly define the relationship of masses to the hilum and mediastinum. Imaging of the great vessels with magnetic resonance imaging has also proved useful. In the abdomen, magnetic resonance imaging has been useful in looking at the extent of masses identified, in characterizing focal liver masses, and in staging a variety of neoplasms. The high contrast resolution and the ability to image in a variety of planes is particularly helpful in the pelvis. In the male pelvis our work has primari