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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.

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

2013-01-01

2

Diffusion microscopist simulator: a general Monte Carlo simulation system for diffusion magnetic resonance imaging.  

PubMed

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, Benoît; Le Bihan, Denis; Li-Schlittgen, Jing-Rebecca; Lin, Ching-Po; Poupon, Cyril

2013-01-01

3

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

4

Cavernous and inferior petrosal sinus sampling and dynamic magnetic resonance imaging in the preoperative evaluation of Cushing's disease.  

PubMed

The surgical management of Cushing's disease is often complicated by difficulties detecting corticotropic adenomas. Various diagnostic modalities are used when conventional magnetic resonance imaging (MRI) is negative or inconclusive. We sought to analyze our use of two such modalities in the surgical management of Cushing's disease: (1) cavernous/inferior petrosal sinus sampling (central venous sampling, CVS) for adrenocorticotropic hormone and (2) dynamic MRI (dMRI). We conducted a single-center, retrospective review of all patients with Cushing's disease treated by a single neurosurgeon with endonasal transsphenoidal surgery. Accuracy of adenoma localization with CVS and dMRI was analyzed. Ninety-one consecutive patients were included. Pathology confirmed an adenoma in 66. Preoperative dMRI and CVS were performed in 40 and 37 patients, respectively, with 20 undergoing both studies. Surgical pathology was positive for adenoma in 31 dMRI patients, 25 CVS patients, and 13 who underwent both. Among patients with pathology confirming an adenoma, dMRI identified a lesion in 96.8% and correctly lateralized the lesion in 89.7%, while CVS correctly lateralized in 52.2-65.2% (depending on location of sampling). Among patients with both studies, dMRI and CVS correctly lateralized in 76.9 and 61.5-69.2%, respectively. Accuracy of CVS improved if only patients with symmetric venous drainage were considered. In this mixed population of Cushing's disease patients, dMRI was more accurate than CVS at localizing adenomas, supporting the use of advance MRI techniques in the work-up of Cushing's disease. CVS, however, remains an important tool in the workup of Cushing's syndrome. PMID:24398617

Potts, Matthew B; Shah, Jugal K; Molinaro, Annette M; Blevins, Lewis S; Tyrrell, J Blake; Kunwar, Sandeep; Dowd, Christopher F; Hetts, Steven W; Aghi, Manish K

2014-02-01

5

Dynamic Magnetic Resonance Imaging of the Pharynx During Deglutition  

PubMed Central

Objectives To utilize dynamic magnetic resonance imaging (dMRI) to visualize the pharynx and upper esophageal segment in normal, healthy controls. Methods A 3-T scanner with a 4-channel head coil and a dual-channel neck coil was employed to obtain hsMRI images of subjects swallowing liquids and pudding. Thirty sequential images were acquired over 3300ms for each swallow. Imaging was performed in the midsagittal and axial plane at the level of the oropharynx and pharyngoesophageal segment. Axial images were then analyzed for variables related to alterations in pharyngeal and UES area during swallowing as well as temporal measures related to these structures. Results All subjects tolerated the study protocol without complaint. Changes in pharyngeal wall luminal area and temporal measurements were consistent within and between subjects. Inter- and intra-rater reliability for the measurement tool was excellent. Conclusions dMRI of the swallow sequence is both feasible and reliable and may eventually compliment currently-used diagnostic modalities as it adds substantive information.

Amin, Milan R.; Achlatis, Stratos; Lazarus, Cathy L.; Branski, Ryan C.; Storey, E. Pippa; Praminik, Bidyut; Fang, Yixin; Sodickson, Daniel

2014-01-01

6

Estimation of Error in Maximal Intensity Projection-Based Internal Target Volume of Lung Tumors: A Simulation and Comparison Study Using Dynamic Magnetic Resonance Imaging  

SciTech Connect

Purpose: To evaluate the error in four-dimensional computed tomography (4D-CT) maximal intensity projection (MIP)-based lung tumor internal target volume determination using a simulation method based on dynamic magnetic resonance imaging (dMRI). Methods and Materials: Eight healthy volunteers and six lung tumor patients underwent a 5-min MRI scan in the sagittal plane to acquire dynamic images of lung motion. A MATLAB program was written to generate re-sorted dMRI using 4D-CT acquisition methods (RedCAM) by segmenting and rebinning the MRI scans. The maximal intensity projection images were generated from RedCAM and dMRI, and the errors in the MIP-based internal target area (ITA) from RedCAM ({epsilon}), compared with those from dMRI, were determined and correlated with the subjects' respiratory variability ({nu}). Results: Maximal intensity projection-based ITAs from RedCAM were comparatively smaller than those from dMRI in both phantom studies ({epsilon} = -21.64% {+-} 8.23%) and lung tumor patient studies ({epsilon} = -20.31% {+-} 11.36%). The errors in MIP-based ITA from RedCAM correlated linearly ({epsilon} = -5.13{nu} - 6.71, r{sup 2} = 0.76) with the subjects' respiratory variability. Conclusions: Because of the low temporal resolution and retrospective re-sorting, 4D-CT might not accurately depict the excursion of a moving tumor. Using a 4D-CT MIP image to define the internal target volume might therefore cause underdosing and an increased risk of subsequent treatment failure. Patient-specific respiratory variability might also be a useful predictor of the 4D-CT-induced error in MIP-based internal target volume determination.

Cai Jing; Read, Paul W.; Baisden, Joseph M.; Larner, James M.; Benedict, Stanley H. [Department of Radiation Oncology, University of Virginia, Charlottesville, VA (United States); Sheng Ke [Department of Radiation Oncology, University of Virginia, Charlottesville, VA (United States)], E-mail: ks2mc@virginia.edu

2007-11-01

7

Pediatric magnetic resonance imaging  

SciTech Connect

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

Cohen, M.D.

1986-01-01

8

Magnetic Resonance Imaging (MRI).  

National Technical Information Service (NTIS)

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

E. Feigenbaum

1985-01-01

9

Magnetic resonance imaging  

SciTech Connect

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

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

1988-01-01

10

Magnetic Resonance Imaging (MRI)  

MedlinePLUS

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

11

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

12

Magnetic resonance-compatible-spirometry: principle, technical evaluation and application  

Microsoft Academic Search

The aim of this study was to assess the feasibility and accuracy of a novel magnetic resonance-compatible (MRc)-spirometer. The influence of body posture, magnetic resonance (MR)-setting and image acquisition on lung function was evaluated. Dynamic MR imaging (dMRI) was compared with simultaneously measured lung function. The development of the MRc-spirometer was based on a commercial spirometer and evaluated by flow-generator

M. Eichinger; M. Puderbach; H. J. Smith; R. Tetzlaff; A. Kopp-Schneider; M. Bock; J. Biederer; H. U. Kauczor

2007-01-01

13

Breast magnetic resonance imaging.  

PubMed

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

Johnson, Marlene M

2012-01-01

14

Classification of magnetic resonance images  

Microsoft Academic Search

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

Katarina Trojacanec; Gjorgji Madzarov; Dejan Gjorgjevikj; Suzana Loskovska

2010-01-01

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

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

17

Interventional cardiovascular magnetic resonance imaging  

PubMed Central

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

Raman, Venkatesh K.; Lederman, Robert J.

2008-01-01

18

Magnetic resonance imaging of cholangiocarcinoma.  

PubMed

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

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

2004-05-01

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

Basics of magnetic resonance imaging  

SciTech Connect

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

Oldendorf, W.; Oldendorf, W. Jr.

1988-01-01

21

Multidimensionally encoded magnetic resonance imaging.  

PubMed

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

Lin, Fa-Hsuan

2013-07-01

22

Magnetic resonance imaging of acquired cardiac disease.  

PubMed Central

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

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

1996-01-01

23

[Cardiac magnetic resonance imaging (MRI)].  

PubMed

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

Vignaux, Olivier

2004-07-31

24

Ferromagnetic Resonance Imaging with Magnetic Resonance Force Microscopy  

NASA Astrophysics Data System (ADS)

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

Pelekhov, Denis

2009-03-01

25

Mathematical Foundations for Magnetic Resonance Imaging.  

National Technical Information Service (NTIS)

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

S. Mansson

1995-01-01

26

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

27

Magnetic Resonance Imaging and Magnetic Resonance Angiography of Vertebrobasilar Dolichoectasia  

Microsoft Academic Search

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

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

1993-01-01

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

3D-Computerized facial reconstructions from 3D-MRI of human heads using deformable model approach  

Microsoft Academic Search

The aim of facial reconstruction is to estimate the face of an unknown individual from the shape of his\\/her skull to aid in recognition and identification. In this paper a 3D computerized facial reconstruction method from 3D-MRI of human heads is presented. It based on a model deformable approach constrained by the knowledge of soft tissues thicknesses, at a certain

Adel Kermi; S. Marniche-Kermi; M. T. Laskri

2010-01-01

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

Imaging agents for in vivo magnetic resonance and scintigraphic imaging  

DOEpatents

Methods are provided for in vivo magnetic resonance imaging and/or scintigraphic imaging of a subject using chelated transition metal and lanthanide metal complexes. Novel ligands for these complexes are provided. No Drawings

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

1991-04-23

32

Current technical development of magnetic resonance imaging  

Microsoft Academic Search

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

Stephen J. Riederer

2000-01-01

33

Homodyne detection in magnetic resonance imaging  

Microsoft Academic Search

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

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

1991-01-01

34

Magnetic resonance imaging of acetabular labral tears.  

PubMed

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

Rakhra, Kawan S

2011-05-01

35

Coronary computed tomography and magnetic resonance imaging.  

PubMed

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

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

2009-04-01

36

Coronary Computed Tomography and Magnetic Resonance Imaging  

PubMed Central

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

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

2009-01-01

37

UHF acoustic microscopic imaging of resonator motion  

Microsoft Academic Search

An important characteristic of acoustic resonator design at ultra high frequencies (UHF) is the efficiency of the device, which is affected by leakage radiation beyond the active transducer area. In order to directly measure leakage radiation, acoustic microscopic imaging of the ultrasonic resonant motion at 880 MHz has been performed with an autocompensating interferometer and heterodyne demodulation. A method of

Ken L. Telschow; Vance A. Deason; David L. Cottle

2000-01-01

38

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

39

Nuclear magnetic resonance imaging: Basic principles  

SciTech Connect

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

Young, S.W.

1985-01-01

40

Image processing for magnetic-resonance elastography  

Microsoft Academic Search

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

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

1996-01-01

41

Image analysis for magnetic resonance elastography  

Microsoft Academic Search

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

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

1996-01-01

42

Parallel Magnetic Resonance Imaging using Neural Networks  

Microsoft Academic Search

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

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

2007-01-01

43

The role of fetal magnetic resonance imaging  

Microsoft Academic Search

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

C Wright; C P Sibley; P N Baker

2010-01-01

44

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

45

Magnetic resonance imaging and magnetic resonance spectroscopic imaging of prostate cancer  

Microsoft Academic Search

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

Renata Huzjan; Evis Sala; Hedvig Hricak

2005-01-01

46

Nuclear magnetic resonance imaging of the pancreas  

SciTech Connect

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

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

1980-03-01

47

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

48

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

49

Magnetic resonance imaging of the cervix  

PubMed Central

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

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

2007-01-01

50

Magnetic Resonance Imaging of the Retina  

PubMed Central

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

Duong, Timothy Q.; Muir, Eric R.

2010-01-01

51

In vitro quantitative ((1))H and ((19))F nuclear magnetic resonance spectroscopy and imaging studies of fluvastatin™ in Lescol® XL tablets in a USP-IV dissolution cell.  

PubMed

Swellable polymeric matrices are key systems in the controlled drug release area. Currently, the vast majority of research is still focused on polymer swelling dynamics. This study represents the first quantitative multi-nuclear (((1))H and ((19))F) fast magnetic resonance imaging study of the complete dissolution process of a commercial (Lescol® XL) tablet, whose formulation is based on the hydroxypropyl methylcellulose (HPMC) polymer under in vitro conditions in a standard USP-IV (United States Pharmacopeia apparatus IV) flow-through cell that is incorporated into high field superconducting magnetic resonance spectrometer. Quantitative RARE ((1))H magnetic resonance imaging (MRI) and ((19))F nuclear magnetic resonance (NMR) spectroscopy and imaging methods have been used to give information on: (i) dissolution media uptake and hydrodynamics; (ii) active pharmaceutical ingredient (API) mobilisation and dissolution; (iii) matrix swelling and dissolution and (iv) media activity within the swelling matrix. In order to better reflect the in vivo conditions, the bio-relevant media Simulated Gastric Fluid (SGF) and Fasted State Simulated Intestinal Fluid (FaSSIF) were used. A newly developed quantitative ultra-fast MRI technique was applied and the results clearly show the transport dynamics of media penetration and hydrodynamics along with the polymer swelling processes. The drug dissolution and mobility inside the gel matrix was characterised, in parallel to the ((1))H measurements, by ((19))F NMR spectroscopy and MRI, and the drug release profile in the bulk solution was recorded offline by UV spectrometer. We found that NMR spectroscopy and 1D-MRI can be uniquely used to monitor the drug dissolution/mobilisation process within the gel layer, and the results from ((19))F NMR spectra indicate that in the gel layer, the physical mobility of the drug changes from "dissolved immobilised drug" to "dissolved mobilised drug". PMID:21911016

Zhang, Qilei; Gladden, Lynn; Avalle, Paolo; Mantle, Michael

2011-12-20

52

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

53

Magnetic Resonance Imaging (MRI) - Spine  

MedlinePLUS

... hearing aids, all of which can be damaged pins, hairpins, metal zippers and similar metallic items, which can distort MRI images removable dental work pens, pocket knives and eyeglasses body piercings ...

54

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

55

Magnetic resonance imaging of shoulder arthropathies.  

PubMed

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

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

2012-05-01

56

Functional magnetic resonance imaging in pediatrics  

PubMed Central

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

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

2005-01-01

57

Stepped impedance resonators for high-field magnetic resonance imaging.  

PubMed

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

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

2014-02-01

58

Review: Magnetic resonance imaging techniques in ophthalmology  

PubMed Central

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

Fagan, Andrew J.

2012-01-01

59

Clinical Applications of Magnetic Resonance Imaging  

PubMed Central

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

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

1992-01-01

60

Vibration criteria for a magnetic resonance imager  

NASA Astrophysics Data System (ADS)

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

Nash, Anthony

1994-10-01

61

Imaging of the dielectric resonance effect in high field magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

At a high field magnetic resonance imaging (MRI), the interactions between the RF pulse and the high permittivity samples, which cause the B1 field inhomogeneity, can no longer be negligible. We present a postprocessing method of compensating the B1 field inhomogeneity mainly caused by the dielectric resonance. The intensity of the transmitted B1 field is calculated using two spin echo images of the water phantom obtained with different flip angles 45° and 90°. Applying the proposed method, the dielectric resonance of the water in high field MRI is visualized as a quantitative map of the B1 field. The corrected image compensating the B1 field inhomogeneity was also calculated.

Mihara, Hiroaki; Iriguchi, Norio; Ueno, Shoogo

2005-05-01

62

Magnetic resonance acoustic radiation force imaging  

PubMed Central

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

McDannold, Nathan; Maier, Stephan E.

2008-01-01

63

Clinical impact of shoulder magnetic resonance imaging  

Microsoft Academic Search

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

Joseph P. Iannotti; Gerald R. Williams

1997-01-01

64

Magnetic resonance imaging of painful shoulder arthroplasty  

Microsoft Academic Search

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

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

2002-01-01

65

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

66

Dark Field Imaging of Plasmonic Resonator Arrays  

NASA Astrophysics Data System (ADS)

We present critical coupling of electromagnetic waves to plasmonic cavity arrays fabricated on Moir'e surfaces. The critical coupling condition depends on the superperiod of Moir'e surface, which also defines the coupling between the cavities. Complete transfer of the incident power can be achieved for traveling wave plasmonic resonators, which have relatively short superperiod. When the superperiod of the resonators increases, the coupled resonators become isolated standing wave resonators in which complete transfer of the incident power is not possible. Dark field plasmon microscopy imaging and polarization dependent spectroscopic reflection measurements reveal the critical coupling conditions of the cavities. We image the light scattered from SPPs in the plasmonic cavities excited by a tunable light source. Tuning the excitation wavelength, we measure the localization and dispersion of the plasmonic cavity mode. Dark field imaging has been achieved in the Kretschmann configuration using a supercontinuum white light laser equipped with an acoustooptic tunable filter. Polarization dependent spectroscopic reflection and dark field imaging measurements are correlated and found to be in agreement with FDTD simulations.

Aydinli, Atilla; Balci, Sinan; Karademir, Ertugrul; Kocabas, Coskun

2012-02-01

67

Magnetic resonance imaging of the knee  

Microsoft Academic Search

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

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

1988-01-01

68

Magnetic resonance imaging of orbital tumors  

Microsoft Academic Search

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

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

2006-01-01

69

Sports Health Magnetic Resonance Imaging Challenge  

PubMed Central

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

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

2010-01-01

70

Magnetic resonance imaging of the carpal tunnel.  

PubMed

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

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

1990-05-01

71

Magnetic Resonance Imaging of Glutamate  

PubMed Central

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

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

2011-01-01

72

Image processing for magnetic-resonance elastography  

NASA Astrophysics Data System (ADS)

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

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

1996-04-01

73

Imaging in breast cancer: Magnetic resonance spectroscopy  

PubMed Central

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

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

2005-01-01

74

Magnetic resonance imaging of renal transplants.  

PubMed

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

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

1984-12-01

75

Functional magnetic resonance imaging (FMRI) of the human brain  

Microsoft Academic Search

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

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

1994-01-01

76

PACS-based functional magnetic resonance imaging.  

PubMed

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

Erberich, Stephan G

2003-01-01

77

Nuclear magnetic resonance imaging in Marfan's syndrome.  

PubMed

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

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

1987-01-01

78

Magnetic Resonance Imaging of Dendrite Currents  

NASA Astrophysics Data System (ADS)

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

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

2011-10-01

79

Impedance magnetic resonance imaging: A method for imaging of impedance distributions based on magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

Magnetic resonance imaging (MRI) techniques have become important tools in medicine and biology. Conventional MRI, however, produces no information about the electrical properties of the body. This article proposes a new and noninvasive method for imaging electrical properties such as conductivity and impedance based on MRI techniques. The basic idea is to use the shielding effects of induced eddy currents in the body on spin precession. Two types of methods are introduced; (i) a large flip angle method, and (ii) a third coil method. The large flip angle method enhances the shielding effects of conducting tissues at the given Larmor frequency. The third coil method detects the shielding effects of conducting tissues at an arbitrary frequency. Both phantom and animal experiments have been carried out to verify this concept using a MRI system of 7.05 T with a bore size of 183 mm in diameter.

Ueno, S.; Iriguchi, N.

1998-06-01

80

Proton Magnetic Resonance Imaging of Flowing Blood.  

NASA Astrophysics Data System (ADS)

A novel technique of making angiographic images non-invasively by NMR is introduced. In order to visualize the vascular structure, flowing blood must be labeled to achieve contrast against background static tissue. In this technique, a little surface coil is used as the labeling device in addition to a whole-body NMR imager. To label the flowing blood, a magnetic field gradient is applied along the long axis of a living subject. The labeling coil over a carotid artery in the neck is fed RF at the resonant frequency of the protons under the coil. Arterial flow moves blood protons from a field below resonance (at the heart), steadily passing through resonance (at the neck) to a field high above resonance (in the head); at the end of the event blood protons are inverted, or labeled by an adiabatic fast passage. Meanwhile, protons in stationary tissue feel only a constant field and remain unaffected. Blood retains this label as it flows downstream into the head and gives a negative signal, while protons in other tissue a positive signal. Two projection images of the head, with and without labeling, are obtained and subtracted digitally. The residue of the subtraction shows moving material only since signals arising from static material are identical and are cancelled in the subtraction process. Finally, the three dimensional vascular structure is presented in a projective format onto a two dimensional plane resembling an angiogram produced with dye injection and X-rays. Pulse sequences specially designed to image moving objects are presented and discussed. Experimental results on phantoms, volunteers and patients are demonstrated. Competing techniques by NMR are reviewed and compared.

Du, Leila Ning-Zhi

1987-09-01

81

Magnetic resonance imaging assessment of cardiac function  

Microsoft Academic Search

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

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

2003-01-01

82

In vivo nuclear magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

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

Leblanc, A.

1986-05-01

83

Nuclear magnetic resonance imaging of atherosclerotic disease  

SciTech Connect

Nuclear magnetic resonance (NMR) images of 93 patients undergoing studies of the abdomen and pelvis were studied for evidence of lesions of the aorta and the iliac and femoral arteries; atherosclerotic lesions were present in 13 of them. The lesions consisted of eccentric and concentric mural thickening with luminal narrowing and discrete plaques protruding into the vessel lumen. This appearance was distinctly different from the morphology of the internal vessel surface and uniformly thin vessel wall in normal patients and volunteers under the age of 30 years. Intraluminal flow signals observed in atherosclerotic and nonatherosclerotic subjects could be distinguished from mural lesions because of their lack of contiguity with the vessel wall and variation in appearance on multiple images obtained with the first and second spin echo. This initial experience suggests a potential role for NMR in the noninvasive imaging of atherosclerotic lesions. The natural contrast between flowing blood and the vessel wall indicates a distinct advantage of NMR for vascular imaging.

Herfkens, R.J.; Higgins, C.B.; Hricak, H.; Lipton, M.J.; Crooks, L.E.; Sheldon, P.E.; Kaufman, L.

1983-07-01

84

Multiparametric magnetic resonance imaging of prostate cancer  

PubMed Central

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

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

2012-01-01

85

Magnetic resonance imaging of perianal fistulas.  

PubMed

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

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

2014-02-01

86

Magnetic resonance imaging of small bowel neoplasms  

PubMed Central

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

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

2013-01-01

87

Magnetic resonance imaging of adnexal masses.  

PubMed

Adnexal masses are common in women of all ages. A range of physiological and benign ovarian conditions that develop in women, especially in the reproductive age, and adnexal malignancies can be evaluated with magnetic resonance imaging (MRI). Management of women with adnexal masses is frequently guided by imaging findings; therefore, precise characterization of adnexal pathology should be performed whenever possible. Magnetic resonance imaging is useful in characterization of adnexal masses that are not completely evaluated by ultrasound because it can provide additional information on soft tissue composition of adnexal masses based on specific tissue relaxation times and allows multiplanar imaging at large field of view to define the origin and extent of pelvic pathology. The patients most likely to benefit from MRI are pregnant women and those who are premenopausal and have masses that have complex features on ultrasound but do not have raised cancer antigen 125 tumor marker levels. The overlap in imaging appearance among different cell type malignancies makes it difficult to predict exact histology based on MRI appearance; however, MRI has a high accuracy in differentiating benign from malignant masses. Teratomas, endometriomas, simple and hemorrhagic cysts, fibromas, exophytic or extrauterine fibroids, and hydrosalpinges can be diagnosed with high confidence. In this article, the authors review the histopathologic background and MRI features of adnexal masses and discuss the role of MRI in the differentiation of benign from malignant adnexal pathologies. PMID:17417086

Rajkotia, Kavita; Veeramani, Murugusundaram; Macura, Katarzyna J

2006-12-01

88

Metabolic tumor imaging using magnetic resonance spectroscopy.  

PubMed

The adaptability and the genomic plasticity of cancer cells, and the interaction between the tumor microenvironment and co-opted stromal cells, coupled with the ability of cancer cells to colonize distant organs, contribute to the frequent intractability of cancer. It is becoming increasingly evident that personalized molecular targeting is necessary for the successful treatment of this multifaceted and complex disease. Noninvasive imaging modalities such as magnetic resonance (MR), positron emission tomography (PET), and single-photon emission computed tomography (SPECT) are filling several important niches in this era of targeted molecular medicine, in applications that span from bench to bedside. In this review we focus on noninvasive magnetic resonance spectroscopy (MRS) and spectroscopic imaging (MRSI) and their roles in future personalized medicine in cancer. Diagnosis, the identification of the most effective treatment, monitoring treatment delivery, and response to treatment are some of the broad areas into which MRS techniques can be integrated to improve treatment outcomes. The development of novel probes for molecular imaging--in combination with a slew of functional imaging capabilities--makes MRS techniques, especially in combination with other imaging modalities, valuable in cancer drug discovery and basic cancer research. PMID:21362514

Glunde, Kristine; Bhujwalla, Zaver M

2011-02-01

89

Multi-dimensionally encoded magnetic resonance imaging  

PubMed Central

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

Lin, Fa-Hsuan

2013-01-01

90

Delayed optical images through coupled-resonator-induced transparency.  

PubMed

We propagated transverse two-dimensional images encoded on optical pulses through a frequency window of a coupled-image-resonator-induced transparency. The optical images are stored and delayed by 10.6ns, reflecting the tunable dispersion of the coupled resonator. The k-space bandwidth of the amplitude transfer function of the system is discussed in the presence of the off-resonance Fano interference effect between the two resonators. PMID:20967084

Sultana, Parvin; Takami, Akira; Matsumoto, Takahiro; Tomita, Makoto

2010-10-15

91

Automated lung segmentation in magnetic resonance images  

NASA Astrophysics Data System (ADS)

Segmentation of the lungs within magnetic resonance (MR) scans is a necessary preprocessing step in the computerized analysis of thoracic MR images. This task is complicated by potentially significant cardiac and pulmonary motion artifacts, partial volume effect, and morphological deformation from disease. We have developed an automated segmentation method to account for these complications. First, the thorax is segmented using a threshold obtained from analysis of the cumulative gray-level histogram constructed along a diagonal line through the center of the image. Next two separate lung-thresholded images are created. The first lung-thresholded image is created using histogram-based gray-level thresholding techniques applied to the segmented thorax. To include lung areas that may be adversely affected by artifact or disease, a second lung-thresholded image is created by applying a grayscale erosion operator to the first lung-thresholded image. After a rolling ball filter is applied to the lung contour to eliminate non-lung pixels from the thresholded lung regions, a logical OR operation is used to combine the two lung-thresholded images into the final segmented lung regions. Modifications to this approach were required to properly segment sections in the lung bases. In a preliminary evaluation, the automated method was applied to 10 MR scans, an observer evaluated the segmented lung regions using a five-point scale ("highly accurate segmentation" to "highly inaccurate segmentation"). Eighty-five percent of the segmented lung regions were rated as highly or moderately accurate.

Sensakovic, William F.; Armato, Samuel G., III; Starkey, Adam

2005-04-01

92

Magnetic resonance imaging of chest wall lesions.  

PubMed Central

Magnetic resonance imaging (MRI) demonstrates surface anatomy, nerves, and soft tissue pathology. Selective placement of the cursor lines in MRI displays specific anatomy. The MR images can then be used as adjunct in teaching surface anatomy to medical students and to other health professionals. Because the normal surface anatomy could be imaged at UCLA's radiology department, it was decided to image soft tissue abnormalities with MR to assist in patient care. Patients imaged were scheduled for special procedures of the chest or staging lymphangiograms. Patients were placed into categories depending on known diagnosis or interesting clinical presentation. The diagnostic categories included Hodgkin's disease, melanoma, carcinomas (eg, lung or breast), lymphedema, sarcomas, dermatological disorders, and neurological disorders. All images were orchestrated by the radiologist. This article discusses both the teaching and clinical impact on patient care. Images Figures 1A-B Figure 2 Figure 3 Figure 4 Figure 5 Figures 6A-B Figure 7 Figure 8 Figures 9A-B Figure 10

Collins, J. D.; Shaver, M.; Batra, P.; Brown, K.; Disher, A. C.

1991-01-01

93

Graph theory based algorithm for magnetic resonance brain images segmentation  

Microsoft Academic Search

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

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

2008-01-01

94

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

95

Cardiovascular Magnetic Resonance Imaging in Experimental Models  

PubMed Central

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

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

2010-01-01

96

Magnetic resonance imaging at ultrahigh fields.  

PubMed

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

Ugurbil, Kamil

2014-05-01

97

Magnetic Resonance Imaging Evaluation of Cardiac Masses  

PubMed Central

Background Cardiac tumors are extremely rare; however, when there is clinical suspicion, proper diagnostic evaluation is necessary to plan the most appropriate treatment. In this context, cardiovascular magnetic resonance imaging (CMRI) plays an important role, allowing a comprehensive characterization of such lesions. Objective To review cases referred to a CMRI Department for investigation of cardiac and paracardiac masses. To describe the positive case series with a brief review of the literature for each type of lesion and the role of cardiovascular magnetic resonance imaging in evaluation. Methods Between August 2008 and December 2011, all cases referred for CMRI with suspicion of tumor involving the heart were reviewed. Cases with positive histopathological diagnosis, clinical evolution or therapeutic response compatible with the clinical suspicion and imaging findings were selected. Results Among the 13 cases included in our study, eight (62%) had histopathological confirmation. We describe five benign tumors (myxomas, rhabdomyoma and fibromas), five malignancies (sarcoma, lymphoma, Richter syndrome involving the heart and metastatic disease) and three non-neoplastic lesions (pericardial cyst, intracardiac thrombus and infectious vegetation). Conclusion CMRI plays an important role in the evaluation of cardiac masses of non-neoplastic and neoplastic origin, contributing to a more accurate diagnosis in a noninvasive manner and assisting in treatment planning, allowing safe clinical follow-up with good reproducibility.

Braggion-Santos, Maria Fernanda; Koenigkam-Santos, Marcel; Teixeira, Sara Reis; Volpe, Gustavo Jardim; Trad, Henrique Simao; Schmidt, Andre

2013-01-01

98

Polarimetric surface plasmon resonance imaging biosensor  

NASA Astrophysics Data System (ADS)

We report the realization of a surface plasmon resonance imaging biosensor potentially capable of dynamically characterizing optical anisotropy by means of polarimetric measurements. Our approach relies on a light beam propagating through a high refractive index glass-prism (Kretschmann-Raether configuration) in order to excite a surface plasmon wave along a metal-dielectric interface. This evanescent wave probes the metal-dielectric vicinities with subnanometer sensitivity, thus resolving optical characteristics of adsorbed biomolecular targets. Fixing wavelength and angle of incidence of the beam enables real-time monitoring of adsorptions and desorptions of targets onto the whole surface of the chip, allowing for example characterization of DNA:DNA interaction kinetics with applications to genetic diagnosis. The polarimetric surface plasmon resonance imaging device uses a pyramid of high index glass and two orthogonal SPR imaging sensor arms. The interface is probed along two orthogonal directions. A signal difference in reflection between the two arms should allow us to resolve local optical anisotropy of the dielectric medium, keeping the parallel and real-time capabilities of the system. Additional information can be obtained by varying the angle of incidence of the light beam or tuning its wavelength. We believe that this type of sensor will be useful for studying collective biomolecular assemblies' conformational changes.

Duval, A.; Bardin, F.; Moreau, J.; Aide, A.; Bellemain, A.; Canva, M.

2007-07-01

99

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

100

Tools for cardiovascular magnetic resonance imaging  

PubMed Central

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.

Krishnamurthy, Ramkumar; Cheong, Benjamin

2014-01-01

101

Applications for breast magnetic resonance imaging.  

PubMed

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

Pilewskie, Melissa; Morrow, Monica

2014-07-01

102

[Magnetic resonance imaging of craniofacial pathology].  

PubMed

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

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

1986-01-01

103

Nanoplatforms for magnetic resonance imaging of cancer  

PubMed Central

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

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

2011-01-01

104

Foundations of Advanced Magnetic Resonance Imaging  

PubMed Central

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

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

2005-01-01

105

In vivo nuclear magnetic resonance imaging  

NASA Technical Reports Server (NTRS)

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

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

1984-01-01

106

Magnetic resonance imaging after exposure to microgravity  

NASA Technical Reports Server (NTRS)

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

Leblanc, Adrian

1993-01-01

107

Magnetic resonance imaging of fistula-in-ano  

Microsoft Academic Search

PURPOSE: Successful management of anal fistulas depends upon accurate assessment of the primary tract and any secondary extensions. Preoperative imaging has, to date, been disappointing. METHODS: A prospective study of 35 patients with a clinical diagnosis of fistula-in-ano was performed comparing magnetic resonance imaging with the independently documented operative findings. Magnetic resonance imaging was also compared with anal endosonography in

Peter J. Lunniss; Peter G. Barker; Abdul H. Sultan; Peter Armstrong; Rodney H. Reznek; Clive I. Bartram; Karen S. Cottam; Robin K. Phillips

1994-01-01

108

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

109

Diffusion-weighted magnetic resonance imaging of the temporal bone  

Microsoft Academic Search

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

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

2010-01-01

110

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.

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

2007-01-01

111

Functional magnetic resonance imaging: imaging techniques and contrast mechanisms.  

PubMed Central

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

Howseman, A M; Bowtell, R W

1999-01-01

112

Use of contrast agents in oncological imaging: magnetic resonance imaging  

PubMed Central

Abstract Magnetic resonance plays a leading role in the management of oncology patients, providing superior contrast resolution and greater sensitivity compared with other techniques, which enables more accurate tumor identification, characterization and staging. Contrast agents are widely used in clinical magnetic resonance imaging; approximately 40–50% of clinical scans are contrast enhanced. Most contrast agents are based on the paramagnetic gadolinium ion Gd3+, which is chelated to avoid the toxic effects of free gadolinium. Multiple factors such as molecule structure, molecule concentration, dose, field strength and temperature determine the longitudinal and transverse relaxation rates (R1 and R2, respectively) and thus the T1- and T2-relaxivities of these chelates. These T1- and T2-relaxivities, together with their pharmacokinetic properties (i.e. distribution and concentration in the area of interest), determine the radiologic efficacy of the gadolinium-based contrast agents.

Cugini, Christian; Scatto, Giuliano; Zanato, Riccardo; Fusaro, Michele; Dorigo, Alberto

2013-01-01

113

Functional magnetic resonance imaging of the lung.  

PubMed

Beyond being a substitute for X-ray, computed tomography, and scintigraphy, magnetic resonance imaging (MRI) inherently combines morphologic and functional information more than any other technology. Lung perfusion: The most established method is first-pass contrast-enhanced imaging with bolus injection of gadolinium chelates and time-resolved gradient-echo (GRE) sequences covering the whole lung (1 volume/s). Images are evaluated visually or semiquantitatively, while absolute quantification remains challenging due to the nonlinear relation of T1-shortening and contrast material concentration. Noncontrast-enhanced perfusion imaging is still experimental, either based on arterial spin labeling or Fourier decomposition. The latter is used to separate high- and low-frequency oscillations of lung signal related to the effects of pulsatile blood flow. Lung ventilation: Using contrast-enhanced first-pass perfusion, lung ventilation deficits are indirectly identified by hypoxic vasoconstriction. More direct but still experimental approaches use either inhalation of pure oxygen, an aerosolized contrast agent, or hyperpolarized noble gases. Fourier decomposition MRI based on the low-frequency lung signal oscillation allows for visualization of ventilation without any contrast agent. Respiratory mechanics: Time-resolved series with high background signal such as GRE or steady-state free precession visualize the movement of chest wall, diaphragm, mediastinum, lung tissue, tracheal wall, and tumor. The assessment of volume changes allows drawing conclusions on regional ventilation. With this arsenal of functional imaging capabilities at high spatial and temporal resolution but without radiation burden, MRI will find its role in regional functional lung analysis and will therefore overcome the sensitivity of global lung function analysis for repeated short-term treatment monitoring. PMID:24481761

Biederer, J; Heussel, C P; Puderbach, M; Wielpuetz, M O

2014-02-01

114

A desktop magnetic resonance imaging system.  

PubMed

Modern magnetic resonance imaging (MRI) systems consist of several complex, high cost subsystems. The cost and complexity of these systems often makes them impractical for use as routine laboratory instruments, limiting their use to hospitals and dedicated laboratories. However, advances in the consumer electronics industry have led to the widespread availability of inexpensive radio-frequency integrated circuits with exceptional abilities. We have developed a small, low-cost MR system derived from these new components. When combined with inexpensive desktop magnets, this type of MR scanner has the promise of becoming standard laboratory equipment for both research and education. This paper describes the development of a prototype desktop MR scanner utilizing a 0.21 T permanent magnet with an imaging region of approximately 2 cm diameter. The system uses commercially available components where possible and is programmed in LabVIEW software. Results from 3D data sets of resolution phantoms and fixed, newborn mice demonstrate the capability of this system to obtain useful images from a system constructed for approximately $13,500. PMID:11755094

Wright, Steven M; Brown, David G; Porter, Jay R; Spence, David C; Esparza, Emilio; Cole, David C; Huson, F Russell

2002-01-01

115

Magnetic resonance imaging of feline hippocampal necrosis.  

PubMed

The clinical, neuropathologic, and magnetic resonance (MR) imaging features in four cats with necrosis of the hippocampus and piriform lobe are described. All cats had acute generalized seizures and behavioral changes including aggression, salivation, polyphagia, and disorientation. Routine hematologic, serum chemistry, and cerebrospinal fluid analyses were normal. MR imaging abnormalities were restricted to the area of the hippocampus and piriform lobe. The lesions were T2-hyperintense, T1-hypointense, and were characterized by various degrees of contrast enhancement. Lesions were consistent with necrotizing encephalitis. Two cats were euthanized and underwent postmortem examination within a week after MR imaging due to the lack of response to antiepileptic drug therapy and progressive encephalopathy [corrected] The remaining two cats lived for about four months and were then euthanized because of persistent behavioral and neurologic signs; only one of these cats underwent postmortem examination with histopathologic examination. Histopathological findings were typical of severe, diffuse, bilateral symmetric necrosis, and degeneration of neurons in the hippocampus and piriform lobe, but an etiologic agent was not apparent. This apparently unique feline syndrome, now reported in Switzerland and Italy, has no known cause at this time. PMID:18720764

Schmied, Oliver; Scharf, Gernot; Hilbe, Monika; Michal, Ulrike; Tomsa, Kamil; Steffen, Frank

2008-01-01

116

Magnetic resonance imaging of glioblastoma using aptamer conjugated magnetic nanoparticles  

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

117

Magnetic Resonance Imaging of the Knee  

PubMed Central

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

Hash, Thomas W.

2013-01-01

118

Magnetic resonance imaging in pediatric stroke.  

PubMed

Pediatric stroke is a term that can be used to encompass everything from hypoxic-ischemic injury to the fetal central nervous system, and especially the premature neonate, to bland versus hemorrhagic infarction from arterial or venous causes in the infant and older child. Pediatric stroke is a chronically underrecognized and therefore underdiagnosed problem that may have significant economic implications. The risk factors for stroke in children are numerous and differ from those in adults. However, with adequate workup, the etiology can be identified in about 75% of cases. Cardiac disorders and hemoglobinopathy are the most common causes of ischemic infarction in children, whereas various congenital anomalies of the blood vessels or defects in coagulation or platelet function often are found in children with parenchymal hemorrhage. Magnetic resonance imaging provides a noninvasive method of investigating childhood stroke, aiding in both better diagnosis and management of this problem. PMID:11847499

Hunter, Jill Vanessa

2002-02-01

119

Economic costs of nuclear magnetic resonance imaging.  

PubMed

The costs of nuclear magnetic resonance (NMR) imaging have been carefully accounted during its early use at one institution. Capital requirements total $2,250,000 ($750,000 for construction and $1,500,000 for equipment). The annual operational costs are estimated at $907,000. At the current estimated patient procedure volume of 1,500 per year, an economic break-even point analysis indicates a required charge of $775 per patient procedure. This compares with the current break-even point charge for computed tomography of $342. If patient throughout can be increased to 12 procedures per day, the NMR break-even point charge would be reduced to $402. PMID:6707263

Evens, R G

1984-04-01

120

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

121

Nuclear magnetic resonance imaging of liver hemangiomas  

SciTech Connect

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

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

1985-10-01

122

Morphometric magnetic resonance imaging in psychiatry.  

PubMed

Although advances in the clinical criteria of various axis I psychiatric disorders are continually being made, there is still considerable overlap in the clinical features, and diagnosis is often challenging. As a result, there has been substantial interest in using morphometric magnetic resonance imaging to better characterize these diseases and inform diagnosis. Region of interest and voxel-based morphometry studies are reviewed herein to examine the extent to which these goals are being met across various psychiatric disorders. It is concluded based on the studies reviewed that specific patterns of regional loss, although present in certain axis I disorders, are not, as yet, diagnostically useful. However, advances in outcome and treatment monitoring show considerably more promise for rapid application in psychiatry. PMID:19363434

Fleck, David E; Nandagopal, Jayasree; Cerullo, Michael A; Eliassen, James C; DelBello, Melissa P; Adler, Caleb M; Strakowski, Stephen M

2008-04-01

123

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.

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

2012-01-01

124

Gradient and RF Coil Issues in Magnetic Resonance Imaging  

Microsoft Academic Search

Techniques are presented for new analysis of coils in magnetic resonance imaging that should lead to faster and more accurate pictures of humans. Insertable planar, cylindrical or elliptical gradient coils offer the potential for significant performance increases in magnetic resonance imaging. Using variational methods to minimize inductance and thereby optimize switching speeds, we have analyzed coils with these three geometries.

Michael Alan Martens

1991-01-01

125

Cardiac magnetic resonance imaging of a patient with an magnetic resonance imaging conditional permanent pacemaker  

PubMed Central

Cardiac magnetic resonance imaging (MRI) is increasingly used as the optimum modality for cardiac imaging. An aging population and rising numbers of patients with permanent pacemakers means many such individuals may require cardiac MRI scanning in the future. Whilst the presence of a permanent pacemaker is historically regarded as a contra-indication to MRI scanning, pacemaker systems have been developed to limit any associated risks. No reports have been published regarding the use of such devices with cardiac MRI in a clinical setting. We present the safe, successful cardiac MRI scan of a patient with an MRI-conditional permanent pacing system.

Hogarth, Andrew J.; Artis, Nigel J.; Sivananthan, U. Mohan; Pepper, Chris B.

2011-01-01

126

An efficient method for dynamic magnetic resonance imaging  

Microsoft Academic Search

Many magnetic resonance imaging applications require the acquisition of a time series of images. In conventional Fourier transform based imaging methods, each of these images is acquired independently so that the temporal resolution possible is limited by the number of spatial encodings (or data points in the Fourier space) collected, or one has to sacrifice spatial resolution for temporal resolution.

Zhi-Pei Liang; Paul C. Lauterbur

1994-01-01

127

Use of magnetic resonance imaging in pharmacogenomics.  

PubMed

Because of the large variation in the response to psychoactive medication, many studies have attempted to uncover genetic factors that determine response. While considerable knowledge exists on the large effects of genetic polymorphisms on pharmacokinetics and plasma concentrations of drugs, effects of the concentration at the target site and pharmacodynamic effects on brain functions in disease are much less known. This article reviews the role of magnetic resonance imaging (MRI) to visualize response to medication in brain behaviour circuits in vivo in humans and assess the influence of pharmacogenetic factors. Two types of studies have been used to characterize effects of medication and genetic variation. In task-related activation studies the focus is on changes in the activity of a neural circuit associated with a specific psychological process. The second type of study investigates resting state perfusion. These studies provide an assessment of vascular changes associated with bioavailability of drugs in the brain, but may also assess changes in neural activity after binding of centrally active agents. Task-related pharmacogenetic studies of cognitive function have characterized the effects in the prefrontal cortex of genetic polymorphisms of dopamine receptors (DRD2), metabolic enzymes (COMT) and in the post-synaptic signalling cascade under the administration of dopamine agonists and antagonists. In contrast, pharmacogenetic imaging with resting state perfusion is still in its infancy. However, the quantitative nature of perfusion imaging, its non-invasive character and its repeatability might be crucial assets in visualizing the effects of medication in vivo in man during therapy. PMID:23802603

Viviani, Roberto; Lehmann, Marie-Louise; Stingl, Julia C

2014-04-01

128

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

PubMed Central

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

Bresch, Erik; Narayanan, Shrikanth

2010-01-01

129

Single image signal-to-noise ratio estimation for magnetic resonance images.  

PubMed

A novel technique to quantify the signal-to-noise ratio (SNR) of magnetic resonance images is developed. The image SNR is quantified by estimating the amplitude of the signal spectrum using the autocorrelation function of just one single magnetic resonance image. To test the performance of the quantification, SNR measurement data are fitted to theoretically expected curves. It is shown that the technique can be implemented in a highly efficient way for the magnetic resonance imaging system. PMID:20703587

Sim, K S; Lai, M A; Tso, C P; Teo, C C

2011-02-01

130

Magnetic Resonance Imaging of Adhesive Capsulitis: Correlation with Clinical Staging  

Microsoft Academic Search

The purpose of this study was to evaluate non-contrast magnetic resonance imaging (MRI) findings of adhesive capsulitis and\\u000a correlate them with clinical stages of adhesive capsulitis. This will hopefully define a role for shoulder MR imaging in the\\u000a diagnosis of adhesive capsulitis as well as in potentially directing appropriate treatment. Forty-seven consecutive non-contrast\\u000a magnetic resonance imaging examinations of 46 patients

Carolyn M. Sofka; Gina A. Ciavarra; Jo A. Hannafin; Frank A. Cordasco; Hollis G. Potter

2008-01-01

131

Uncertainty analysis and visualization of diffusion tensor images  

NASA Astrophysics Data System (ADS)

Diffusion magnetic resonance imaging (dMRI) has become a popular technique to detect brain white matter structure. However, imaging noise, imaging artifacts, and modeling techniques, etc., create many uncertainties, which may generate misleading information for further analysis or applications, such as surgical planning. Therefore, how to analyze, effectively visualize, and reduce these uncertainties become very important research questions. In this dissertation, we present both rank-k decomposition and direct decomposition approaches based on spherical deconvolution to decompose the fiber directions more accurately for high angular resolution diffusion imaging (HARDI) data, which will reduce the uncertainties of the fiber directions. By applying volume rendering techniques to an ensemble of 3D orientation distribution function (ODF) glyphs, which we call SIP functions of diffusion shapes, one can elucidate the complex heteroscedastic structural variation in these local diffusion shapes. Furthermore, we quantify the extent of this variation by measuring the fraction of the volume of these shapes, which is consistent across all noise levels, the certain volume ratio . To better understand the uncertainties in white matter fiber tracks, we propose three metrics to quantify the differences between the results of diffusion tensor magnetic resonance imaging (DT-MRI) fiber tracking algorithms: the area between corresponding fibers of each bundle, the Earth Mover's Distance (EMD) between two fiber bundle volumes, and the current distance between two fiber bundle volumes. Based on these metrics, we discuss an interactive fiber track comparison visualization toolkit we have developed to visualize these uncertainties more efficiently. Physical phantoms, with high repeatability and reproducibility, are also designed with the hope of validating the dMRI techniques. In summary, this dissertation provides a better understanding about uncertainties in diffusion magnetic resonance imaging: where and how much are the uncertainties? How do we reduce these uncertainties? How can we possibly validate our algorithms?

Jiao, Fangxiang

132

Low field strength magnetic resonance imaging of the neonatal brain  

PubMed Central

Background: Magnetic resonance (MR) imaging of the neonate has been restricted by the need to transport the sick baby to the large magnetic resonance scanners and often the need for sedation or anaesthesia in order to obtain good quality images. Ultrasound is the reference standard for neonatal imaging. Objective: To establish a dedicated neonatal MR system and compare the clinical usefulness of MR imaging with ultrasound imaging. Design: Prospective double blind trial. Setting: Neonatal intensive care unit, Sheffield. Main outcome measures: Imaging reports. Patients: 134 premature and term babies. Results: In 56% of infants with pathology suspected on clinical grounds, MR provided additional useful clinical information over and above that obtained with ultrasound. Conclusion: Infants can be safely imaged by dedicated low field magnetic resonance on the neonatal intensive care unit without the need for sedation at a cost equivalent to ultrasound.

Whitby, E; Paley, M; Smith, M; Sprigg, A; Woodhouse, N; Griffiths, P

2003-01-01

133

Signal and noise estimation from magnetic resonance images  

Microsoft Academic Search

This thesis deals with the estimation of noise and signal from Magnetic Resonance (MR) images with a special reference to magnitude MR images. Furthermore, the estimation and improvement of the image signal-to-noise ratio (SNR) and an application to 3D segmentation is discussed. In order to process experimental data in a scientifically justified manner, knowledge of the underlying probability density function

Jan Sijbers

1998-01-01

134

Neural networks based segmentation of magnetic resonance images  

Microsoft Academic Search

Segmentation of the images obtained from magnetic resonance imaging (MRI) is an important step in the visualization of soft tissues in the human body. The new emerging field of artificial neural networks (ANNs) promises to provide unique solutions for the pattern classification of medical images. In this preliminary study, we report an application of Hopfield neural network (HNN) for the

Rachid Sammouda; Noboru Niki; Hiromu Nishitani

1994-01-01

135

Multispectral magnetic resonance image segmentation using LVQ neural networks  

Microsoft Academic Search

Segmentation of images obtained from magnetic resonance (MR) imaging techniques is an important step in the analysis of MR images of the human body. The multi-spectral nature of MRI has been exploited in the past to obtain better performance in the segmentation process. The new emerging field of artificial neural networks promises to provide improved solutions for the pattern classification

Javad Alirezaie; C. Nahmias; M. E. Jernigan

1995-01-01

136

Anatomic segmentation and volumetric calculations in nuclear magnetic resonance imaging  

Microsoft Academic Search

A comprehensive methodology for image segmentation is presented. Tools for differential and intensity contouring, and outline optimization are discussed, as well as the methods for automating such procedures. After segmentation, regional volumes and image intensity distributions can be determined. The methodology is applied to nuclear magnetic resonance images of the brain. Examples of the results of volumetric calculations for the

DAVID N KENNEDY; PAULINE A FILIPEK

1989-01-01

137

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

138

Bioengineered iron-oxide nanocrystals: Applications in magnetic resonance imaging  

Microsoft Academic Search

Superparamagnetic Iron-Oxide nanoparticles (SPIO) are used as magnetic resonance imaging (MRI) contrast agents in clinical and research applications, effectively increasing the imaging sensitivity of MRI. Current clinical MRI applications utilizing SPIO are limited to liver and gastrointestinal imaging, but further bioengineering will expand the capabilities of SPIO enhanced MRI. This thesis presents different methods of bioengineering SPIO contrast agents for

Brian A. Larsen

2008-01-01

139

Imaging of Electrically Detected Magnetic Resonance of a Silicon Wafer  

Microsoft Academic Search

An imaging technique of electrically detected magnetic resonance (EDMR) was newly developed. Because the EDMR signal is obtained from paramagnetic recombination centers, one may expect the image to represent the distribution of defect and\\/or impurity sites in the sample. We successfully obtained EDMR images of a light-illuminated silicon plate 8 mm in width and 15 mm in length, which was

Toshiyuki Sato; Hidekatsu Yokoyama; Hiroaki Ohya; Hitoshi Kamada

2001-01-01

140

Magnetic resonance imaging of the elbow. Part II: Abnormalities of the ligaments, tendons, and nerves  

Microsoft Academic Search

Part II of this comprehensive review on magnetic resonance imaging of the elbow discusses the role of magnetic resonance imaging in evaluating patients with abnormalities of the ligaments, tendons, and nerves of the elbow. Magnetic resonance imaging can yield high-quality multiplanar images which are useful in evaluating the soft tissue structures of the elbow. Magnetic resonance imaging can detect tears

Richard Kijowski; Michael Tuite; Matthew Sanford

2005-01-01

141

Magnetic resonance imaging in entomology: a critical review  

PubMed Central

Magnetic resonance imaging (MRI) enables in vivo imaging of organisms. The recent development of the magnetic resonance microscope (MRM) has enabled organisms within the size range of many insects to be imaged. Here, we introduce the principles of MRI and MRM and review their use in entomology. We show that MRM has been successfully applied in studies of parasitology, development, metabolism, biomagnetism and morphology, and the advantages and disadvantages relative to other imaging techniques are discussed. In addition, we illustrate the images that can be obtained using MRM. We conclude that although MRM has significant potential, further improvements to the technique are still desirable if it is to become a mainstream imaging technology in entomology. Abbreviation: CSI chemical shift imaging. The dependence of the resonance frequency of a nucleus on the chemical binding of the atom or molecule in which it is contained. (N)MRI (nuclear) magnetic resonance imaging MRM magnetic resonance microscopy Voxel A contraction for volume element, which is the basic unit of MR reconstruction; represented as a pixel in the display of the MR image.

Hart, A.G.; Bowtell, R.W.; Kockenberger, W.; Wenseleers, T.; Ratnieks, F.L.W.

2003-01-01

142

Magnetic Resonance Imaging Method For Estimating Cone Of Uncertainty  

Cancer.gov

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

143

Magnetic resonance imaging of cavernous sinus cavernous hemangiomas  

Microsoft Academic Search

Radiological findings of surgically verified cavernous hemangiomas of the cavernous sinus are presented with special reference to the appearance in magnetic resonance imaging. Differences in radiological features of the cavernous sinus cavernous hemangiomas and intracerebral cavernous hemangiomas are discussed.

Y. Katayama; T. Tsubokawa; S. Miyazaki; K. Yoshida; K. Himi

1991-01-01

144

Physiological monitoring of small animals during magnetic resonance imaging  

Microsoft Academic Search

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

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

2005-01-01

145

Physiological monitoring of small animals during magnetic resonance imaging  

Microsoft Academic Search

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

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

146

The Nobel Prize in Medicine for Magnetic Resonance Imaging  

ERIC Educational Resources Information Center

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

Fry, Charles G.

2004-01-01

147

Functional magnetic resonance imaging: Clinical applications and potential  

Microsoft Academic Search

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

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

1999-01-01

148

Detection of fungal wood decay using Magnetic Resonance Imaging  

Microsoft Academic Search

Fagus sylvatica   L.) infected with the brown rot fungus Coniophora puteana (Schum.) Karst was examined 12 and 26 days after incubation using magnetic resonance imaging. We were able to detect areas\\u000a containing free water attributed to fungal activity 12 days after incubation. Magnetic resonance imaging was found to be a\\u000a useful tool for determining early stages of fungal decay in

Ulrich Müller; Roland Bammer; Erhard Halmschlager; Rudolf Stollberger; Rupert Wimmer

2001-01-01

149

Cardiac Sarcoidosis Detected by Delayed-Hyperenhancement Magnetic Resonance Imaging  

PubMed Central

We report the case of a patient with sarcoidosis and ventricular tachycardia in whom cardiac magnetic resonance imaging provided supportive evidence of cardiac involvement by delineating regions of myocardial inflammation and fibrosis inconsistent with ischemic injury. The identification of cardiac involvement in patients with sarcoidosis is problematic, and the true incidence is unknown. Cardiac magnetic resonance imaging may help establish the actual incidence of cardiac involvement and allow further advances in monitoring and treatment options.

Nemeth, Margit A.; Muthupillai, Raja; Wilson, James M.; Awasthi, Mukta; Flamm, Scott D.

2004-01-01

150

Cardiac sarcoidosis detected by delayed-hyperenhancement magnetic resonance imaging.  

PubMed

We report the case of a patient with sarcoidosis and ventricular tachycardia in whom cardiac magnetic resonance imaging provided supportive evidence of cardiac involvement by delineating regions of myocardial inflammation and fibrosis inconsistent with ischemic injury. The identification of cardiac involvement in patients with sarcoidosis is problematic, and the true incidence is unknown. Cardiac magnetic resonance imaging may help establish the actual incidence of cardiac involvement and allow further advances in monitoring and treatment options. PMID:15061637

Nemeth, Margit A; Muthupillai, Raja; Wilson, James M; Awasthi, Mukta; Flamm, Scott D

2004-01-01

151

Computed tomography and magnetic resonance imaging of cerebral coenurosis.  

PubMed

A case of Coenurus cerebralis involving both cerebral hemispheres and the interpeduncular cistern is presented to illustrate the computed tomography (CT) and magnetic resonance imaging (MRI) features. In CT scans viable cysts appear as lucent lesions surrounded by a contrast-enhanced peripheral rim. By using multiple echo sequences the cyst content is characterized in magnetic resonance images by a cerebrospinal fluid-like intensity pattern. PMID:3576430

Pau, A; Turtas, S; Brambilla, M; Leoni, A; Rosa, M; Viale, G L

1987-06-01

152

Magnetic Resonance Imaging of Neoplasms of the Pancreatobiliary System  

Microsoft Academic Search

Magnetic resonance imaging (MRI) and magnetic resonance cholangiopancreatography (MRCP) are noninvasive imaging techniques\\u000a that can detect, characterize, and stage neoplasms of the biliary system and pancreas. In patients with suspected pancreatic\\u000a cancer, MRI\\/MRCP can help distinguish those patients who are unresectable from those who are potentially resectable. In patients\\u000a with pancreatic cysts, MRI assists in the distinction among pseudocysts, benign

Evan S. Siegelman; Wendy C. Hsu

153

Deep ultraviolet resonant Raman imaging of a cell  

NASA Astrophysics Data System (ADS)

We report the first demonstration of deep ultraviolet (DUV) Raman imaging of a cell. Nucleotide distributions in a HeLa cell were observed without any labeling at 257 nm excitation with resonant bands attributable to guanine and adenine. Obtained images represent DNA localization at nucleoli in the nucleus and RNA distribution in the cytoplasm. The presented technique extends the potential of Raman microscopy as a tool to selectively probe nucleic acids in a cell with high sensitivity due to resonance.

Kumamoto, Yasuaki; Taguchi, Atsushi; Smith, Nicholas Isaac; Kawata, Satoshi

2012-07-01

154

Real-Time Magnetic Resonance Imaging: Diagnostic and Interventional Applications  

Microsoft Academic Search

.   The advent of ultra-fast imaging techniques has extended the utility of magnetic resonance imaging (MRI) from a static and\\u000a purely diagnostic status to an imaging modality ideally suited for a number of therapeutic applications. These advances—along\\u000a with the recent development and refinement of miniature intravascular imaging catheters and MRI-compatible guidewires, balloon\\u000a catheters, and radiofrequency ablation catheters—have created an exciting

Albert C. Lardo

2000-01-01

155

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

National Technical Information Service (NTIS)

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

1984-01-01

156

Nuclear magnetic resonance (NMR) blood flow imaging  

Microsoft Academic Search

Picture element values in NMR images are dependent not only upon T⁠and Tâ relaxation times but also on the local density and velocity of hydrogen nuclei moving through the region being imaged. In 1959 the potential of non-imaging NMR for measuring blood flow was demonstrated. Recently several investigators have proposed methods for combining NMR imaging with NMR blood flow

R. R. Price; J. A. Patton; M. D. Kulkarni; D. R. Pickens; J. J. Erickson; W. H. Stephens; C. L. Partain; A. E. Jr. James

1984-01-01

157

Silicon Nanoparticles as Hyperpolarized Magnetic Resonance Imaging Agents  

PubMed Central

Magnetic resonance imaging of hyperpolarized nuclei provides high image contrast with little or no background signal. To date, in-vivo applications of pre-hyperpolarized materials have been limited by relatively short nuclear spin relaxation times. Here, we investigate silicon nanoparticles as a new type of hyperpolarized magnetic resonance imaging agent. Nuclear spin relaxation times for a variety of Si nanoparticles are found to be remarkably long, ranging from many minutes to hours at room temperature, allowing hyperpolarized nanoparticles to be transported, administered, and imaged on practical time scales. Additionally, we demonstrate that Si nanoparticles can be surface functionalized using techniques common to other biologically targeted nanoparticle systems. These results suggest that Si nanoparticles can be used as a targetable, hyperpolarized magnetic resonance imaging agent with a large range of potential applications.

Aptekar, Jacob W.; Cassidy, Maja C.; Johnson, Alexander C.; Barton, Robert A.; Lee, Menyoung; Ogier, Alexander C.; Vo, Chinh; Anahtar, Melis N.; Ren, Yin; Bhatia, Sangeeta N.; Ramanathan, Chandrasekhar; Cory, David G.; Hill, Alison L.; Mair, Ross W.; Rosen, Matthew S.; Walsworth, Ronald L.

2014-01-01

158

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.

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

2013-01-01

159

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

160

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

161

Magnetic resonance imaging of penile cancer.  

PubMed

Penile cancer is a rare neoplasm that, although rare in the developed world, has devastating physical and psychological consequences for the patient. Novel MR imaging techniques such as lymphotropic nanoparticle-enhanced MR imaging may help identify metastatic lymph node disease. This article reviews the normal penile anatomy and MR imaging techniques and features of primary and metastatic penile cancer. Recent advances in penile cancer imaging are discussed. PMID:24792677

Gupta, Sumit; Rajesh, Arumugam

2014-05-01

162

Real-Time Functional Magnetic Resonance Imaging  

Microsoft Academic Search

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

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

1995-01-01

163

Magnetic resonance imaging of vulnerable atherosclerotic plaques: current imaging strategies and molecular imaging probes.  

PubMed

The vulnerability or destabilization of atherosclerotic plaques has been directly linked to plaque composition. Imaging modalities, such as magnetic resonance (MR) imaging, that allow for evaluation of plaque composition at a cellular and molecular level, could further improve the detection of vulnerable plaque and may allow for monitoring the efficacy of antiatherosclerotic therapies. In this review we focus on MR imaging strategies for the detection and evaluation of atherosclerotic plaques and their composition. We highlight recent advancements in the development of MR pulse sequences, computer image analysis, and the use of commercially available MR contrast agents, such as gadopentic acid (Gd-DTPA), for plaque characterization. We also discuss molecular imaging strategies that are currently being used to design specific imaging probes targeted to biochemical and cellular markers of atherosclerotic plaque vulnerability. PMID:17729343

Briley-Saebo, Karen C; Mulder, Willem J M; Mani, Venkatesh; Hyafil, Fabien; Amirbekian, Vardan; Aguinaldo, Juan Gilberto S; Fisher, Edward A; Fayad, Zahi A

2007-09-01

164

Magnetic Resonance Imaging in Experimental Models of Brain Disorders  

Microsoft Academic Search

This review gives an overview of the application of magnetic resonance imaging (MRI) in experimental models of brain disorders. MRI is a noninvasive and versatile imaging modality that allows longitudinal and three-dimensional assessment of tissue morphology, metabolism, physiology, and function. MRI can be sensitized to proton density, T1, T2, susceptibility contrast, magnetization transfer, diffusion, perfusion, and flow. The combination of

Rick M. Dijkhuizen; Klaas Nicolay

2003-01-01

165

Fluorescence resonance energy transfer imaging by maximum likelihood estimation  

Microsoft Academic Search

Fluorescence resonance energy transfer (FRET) is a fluorescence microscope imaging process involving nonradiative energy transfer between two fluorophores (the donor and the acceptor). FRET is used to detect the chemical interactions and, in some cases, measure the distance between molecules. Existing approaches do not always well compensate for bleed-through in excitation, cross-talk in emission detection and electronic noise in image

Yupeng Zhang; Yumin Yuan; Timothy J. Holmes

2004-01-01

166

A General Survey of Chocolate Confectionery by Magnetic Resonance Imaging  

Microsoft Academic Search

Magnetic resonance imaging (MRI) has been used to survey the structure of a range of chocolate products, including tablet, straightline and countline products: typically two dimensional MRI at 2 Tesla gives 50 × 50 mm spatial resolution for a 3 mm thick slice in 8 mins. High signal intensity and excellent image contrast is obtained for nuts or other fat

Marc E. Miquel; Laurance D. Hall

1998-01-01

167

Task-specific deactivation patterns in functional magnetic resonance imaging  

Microsoft Academic Search

In general, image analysis of cognitive experiments using functional magnetic resonance imaging techniques has emphasized those regions of the brain where increases in signal intensity, with regard to the reference state, are associated with activation. Nevertheless, a number of recent papers have shown that there are areas of deactivation as well. In this study, we have used a univariate analysis

M Hutchinson; W Schiffer; S Joseffer; A Liu; R Schlosser; S Dikshit; E Goldberg; J. D Brodie

1999-01-01

168

Improvement of functional magnetic resonance images by pretreatment of data  

Microsoft Academic Search

Functional magnetic resonance images of the brains of subjects performing the finger-tapping paradigm were made using a conventional technique. Two threshold values for the pixels were obtained by analysing pixel by pixel the distributions of the means and variances of each subject's images for 20 consecutive scans, both while performing the task and while at rest. Considerable signal improvement in

Manuel Cortijo; Carmen Santisteban; Beatriz Carrero-González; Jesus Alvarado; Jesus Ruiz-Cabello

1996-01-01

169

What Have We Learned From Magnetic Resonance Imaging Studies?  

Microsoft Academic Search

e review studies that have examined the relationship between magnetic reso- nance imaging findings and clinical disability, postmortem observations, and cog- nitive dysfunction in patients with multiple sclerosis. We also review the use of magnetic resonance imaging findings as an outcome measure in clinical trials assessing the efficacy of new therapeutic agents for the treatment of multiple sclerosis. More ad-

Samia J. Khoury; Howard L. Weiner

1998-01-01

170

Magnetic resonance imaging as a tool for extravehicular activity analysis  

NASA Technical Reports Server (NTRS)

The purpose of this research is to examine the value of magnetic resonance imaging (MRI) as a means of conducting kinematic studies of the hand for the purpose of EVA capability enhancement. After imaging the subject hand using a magnetic resonance scanner, the resulting 2D slices were reconstructed into a 3D model of the proximal phalanx of the left hand. Using the coordinates of several landmark positions, one is then able to decompose the motion of the rigid body. MRI offers highly accurate measurements due to its tomographic nature without the problems associated with other imaging modalities for in vivo studies.

Dickenson, R.; Lorenz, C.; Peterson, S.; Strauss, A.; Main, J.

1992-01-01

171

Echo-Planar Imaging: Magnetic Resonance Imaging in a Fraction of a Second  

Microsoft Academic Search

Progress has recently been made in implementing magnetic resonance imaging (MRI) techniques that can be used to obtain images in a fraction of a second rather than in minutes. Echo-planar imaging (EPI) uses only one nuclear spin excitation per image and lends itself to a variety of critical medical and scientific applications. Among these are evaluation of cardiac function in

Michael K. Stehling; Robert Turner; Peter Mansfield

1991-01-01

172

Magnetic resonance imaging of brain angiogenesis after stroke  

Microsoft Academic Search

Stroke is a major cause of mortality and long-term disability worldwide. The initial changes in local perfusion and tissue\\u000a status underlying loss of brain function are increasingly investigated with noninvasive imaging methods. In addition, there\\u000a is a growing interest in imaging of processes that contribute to post-stroke recovery. In this review, we discuss the application\\u000a of magnetic resonance imaging (MRI)

Peter R. SeevinckLisette; Lisette H. Deddens; Rick M. Dijkhuizen

2010-01-01

173

Molecular Imaging of Cancer: Applications of Magnetic Resonance Methods  

PubMed Central

Cancer is a complex disease exhibiting a host of phenotypic diversities. Noninvasive multinuclear magnetic resonance imaging (MRI) and spectroscopic imaging (MRSI) provide an array of capabilities to characterize and understand several of the vascular, metabolic, and physiological characteristics unique to cancer. The availability of targeted contrast agents has widened the scope of MR techniques to include the detection of receptor and gene expression. In this paper, we have highlighted the application of several MR techniques in imaging and understanding cancer.

Gimi, Barjor; Pathak, Arvind P.; Ackerstaff, Ellen; Glunde, Kristine; Artemov, Dmitri; Bhujwalla, Zaver M.

2009-01-01

174

Mathematical modeling of the heart using magnetic resonance imaging  

Microsoft Academic Search

A hybrid three-dimensional solid mathematical model of cardiac ventricular geometry developed using magnetic resonance (MR) images of an in vivo canine heart is discussed. The modeling techniques were validated using MR images of an ex vivo heart and direct measurements of cardiac geometry and mass properties. A spin-echo MR sequence with in-plane resolution of 1.0 mm was used to image

Lawrence L. Creswell; Stephan G. Wyers; John S. Pirolo; William H. Perman; Michael W. Vannier; Michael K. Pasque

1992-01-01

175

Magnetic Resonance Image Tissue Classification Using a Partial Volume Model  

Microsoft Academic Search

We describe a sequence of low-level operations to isolate and classify brain tissue within T1-weighted magnetic resonance images (MRI). Our method first removes nonbrain tissue using a combination of anisotropic diffusion filtering, edge detection, and mathematical morphology. We compensate for image nonuniformities due to magnetic field inhomogeneities by fitting a tricubic B-spline gain field to local estimates of the image

David W. Shattuck; Stephanie R. Sandor-Leahy; Kirt A. Schaper; David A. Rottenberg; Richard M. Leahy

2001-01-01

176

Segmentation of magnetic resonance images of the thorax by backpropagation  

Microsoft Academic Search

Segmentation of images-especially medical images-is an important problem for which automatic solutions are urgently sought. In this paper, we report on work in which neural networks are trained by backpropagation to segment magnetic resonance (MR) images of the thorax, by classifying pixels as either boundary (pixels on the boundary between lung interior and surrounding tissue) or non-boundary. Networks trained on

I. Middleton; R. I. Damper

1995-01-01

177

Plasmon—resonant gold nanoparticles for cancer optical imaging  

NASA Astrophysics Data System (ADS)

Gold nanoparticles (AuNPs) interact with light and have strong and tunable surface plasmon resonance, which can be detected using multiple imaging modalities. These provide an unique opportunity for their potential applications in optical imaging for early detection of cancer. In this review, we summarized nanoparticles targeting properties for cancer, plasmon optical properties of AuNPs, application of AuNPs for cancer optical imaging. Also discussed is the safety of AuNPs.

Wang, Zhen

2013-03-01

178

Functional imaging of the central nervous system using magnetic resonance imaging and positron emission tomography.  

PubMed

There have been striking advances recently in magnetic resonance imaging and positron emission tomography (PET) imaging of the central nervous system, particularly in the area of "functional" imaging. We discuss these advances with emphasis on the similarities and differences between the PET and magnetic resonance imaging methods. In addition, we examine recent progress and controversies in the use of volume-localized nuclear magnetic resonance spectroscopy. Finally, we review the use of three-dimensional acquisition for PET studies, with an evaluation of the relative advantages and disadvantages of this modification of the PET technique. PMID:8293168

Neil, J J

1993-12-01

179

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

Hendee, William R.; Morgan, Christopher J.

1984-01-01

180

Magnetic resonance imaging in patients with panhypopituitarism  

Microsoft Academic Search

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

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

1992-01-01

181

Magnetic resonance imaging in scaphoid fractures.  

PubMed

The use of a 1.5 tesla superconducting M.R. imager and surface coil was found to enhance the ability of M.R.I. to depict the fine anatomy of the wrist. Five healthy volunteers and 28 patients with scaphoid fractures underwent M.R.I., which made possible a definitive diagnosis of scaphoid fractures at an early stage. A fresh fracture was identified by decreased or iso signal intensity on the T1-weighted image and increased signal intensity on the T2-weighted image. This increase continued until bony union was apparent on radiographs. On the T2-weighted image, high signal intensity was characteristic of fresh fractures and suggested that bony union was possible. When bony union was complete, the intensity of the signal for the scaphoid on both T1- and T2-weighted images returned to normal. M.R.I. should thus prove useful in the diagnosis of scaphoid fractures. PMID:1640140

Imaeda, T; Nakamura, R; Miura, T; Makino, N

1992-02-01

182

Magnetic Resonance Imaging: From Spin Physics to Medical Diagnosis  

Microsoft Academic Search

Two rather similar historical evolutions are evoked, each one originating in fundamental spin studies by physicists, and ending\\u000a as magnetic resonance imaging (MRI), a set of invaluable tools for clinical diagnosis in the hands of medical doctors. The\\u000a first one starts with the early work on nuclear magnetic resonance, the founding stone of the usual proton-based MRI, of which\\u000a the

Pierre-Jean Nacher

2009-01-01

183

Magnetic resonance imaging in central nervous system tuberculosis  

PubMed Central

Tuberculosis (TB) in any form is a devastating disease, which in its most severe form involves the central nervous system (CNS), with a high mortality and morbidity. Early diagnosis of CNS TB is necessary for appropriate treatment to reduce this morbidity and mortality. Routine diagnostic techniques involve culture and immunological tests of the tissue and biofluids, which are time-consuming and may delay definitive management. Noninvasive imaging modalities such as computed tomography (CT) scan and magnetic resonance imaging (MRI) are routinely used in the diagnosis of neurotuberculosis, with MRI offering greater inherent sensitivity and specificity than CT scan. In addition to conventional MRI imaging, magnetization transfer imaging, diffusion imaging, and proton magnetic resonance spectroscopy techniques are also being evaluated for better tissue characterization in CNS TB. The current article reviews the role of various MRI techniques in the diagnosis and management of CNS TB.

Trivedi, Richa; Saksena, Sona; Gupta, Rakesh K

2009-01-01

184

Basic Principles of Magnetic Resonance Imaging--An Update  

PubMed Central

Magnetic resonance (MR) imaging technology has undergone many technologic advances over the past few years. Many of these advances were stimulated by the wealth of information emerging from nuclear magnetic resonance research in the areas of new and optimal scanning methods and radio-frequency coil design. Other changes arose from the desire to improve image quality, ease siting restrictions and generally facilitate the clinical use of MR equipment. Many questions, however, remain unanswered. Perhaps the most controversial technologic question involves the optimal field strength required for imaging or spectroscopic applications or both. Other issues include safety and clinical efficacy. Technologic issues affect all aspects of MR use including the choice of equipment, examination procedure and image interpretation. Thus, an understanding of recent changes and their theoretic basis is necessary. ImagesFigure 9.

Scherzinger, Ann L.; Hendee, William R.

1985-01-01

185

Nuclear magnetic resonance (NMR) blood flow imaging  

SciTech Connect

Picture element values in NMR images are dependent not only upon T/sub 1/ and T/sub 2/ relaxation times but also on the local density and velocity of hydrogen nuclei moving through the region being imaged. In 1959 the potential of non-imaging NMR for measuring blood flow was demonstrated. Recently several investigators have proposed methods for combining NMR imaging with NMR blood flow measurements. The authors have investigated the relationships between various radiofrequency pulse sequences and flow rate and their effects on image intensity using a constant flow pump and a 0.5 Tesla Technicare Teslacon NMR imager. Dilute mixtures of ethylene glycol were used to simulate blood. Flow measurements were made in Tygon Tubing (12 mm) at variable velocities ranging from 0-35 cm/sec. The flow phantom was used to calibrate several pulse sequences relating image intensity and vascular flow velocity. Representative patient studies demonstrating blood-flow have been performed. The calibration is being extended to pulsatile flow systems.

Price, R.R.; Patton, J.A.; Kulkarni, M.D.; Pickens, D.R.; Erickson, J.J.; Stephens, W.H.; Partain, C.L.; James, A.E. Jr.

1984-01-01

186

Magnetic resonance imaging: effects of magnetic field strength  

SciTech Connect

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

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

1984-04-01

187

Renal relevant radiology: renal functional magnetic resonance imaging.  

PubMed

Because of its noninvasive nature and provision of quantitative measures of a wide variety of physiologic parameters, functional magnetic resonance imaging (MRI) shows great potential for research and clinical applications. Over the past decade, application of functional MRI extended beyond detection of cerebral activity, and techniques for abdominal functional MRI evolved. Assessment of renal perfusion, glomerular filtration, interstitial diffusion, and parenchymal oxygenation turned this modality into an essential research and potentially diagnostic tool. Variations in many renal physiologic markers can be detected using functional MRI before morphologic changes become evident in anatomic magnetic resonance images. Moreover, the framework of functional MRI opened a window of opportunity to develop novel pathophysiologic markers. This article reviews applications of some well validated functional MRI techniques, including perfusion, diffusion-weighted imaging, and blood oxygen level-dependent MRI, as well as some emerging new techniques such as magnetic resonance elastography, which might evolve into clinically useful tools. PMID:24370767

Ebrahimi, Behzad; Textor, Stephen C; Lerman, Lilach O

2014-02-01

188

Magnetic Resonance Molecular Imaging and Targeted Therapeutics  

Microsoft Academic Search

Advances in cellular and molecular biology are extending the horizons of medical imaging from gross anatomical description\\u000a toward delineation of cellular and biochemical signaling processes. The emerging fields of cellular and molecular imaging\\u000a aim to noninvasively diagnose disease based on the in vivo detection and characterization of complex pathological processes,\\u000a such as induction of inflammation or angiogenesis. Techniques have been

Anne Morawski Neubauer; Patrick Winter; Shelton Caruthers; Gregory Lanza; Samuel A. Wickline

189

Centric scan SPRITE magnetic resonance imaging  

Microsoft Academic Search

Two rapid, pure phase encode, centric scan, Single Point Ramped Imaging with T1-Enhancement (SPRITE) MRI methods are described. Each retains the benefits of the standard SPRITE method, most notably the ability to image short T2* systems, while increasing the sensitivity and generality of the technique. The Spiral-SPRITE method utilizes a modified Archimedean spiral k-space trajectory. The Conical-SPRITE method utilizes a

Meghan Halse; David J. Goodyear; Bryce MacMillan; Pavol Szomolanyi; David Matheson; Bruce J. Balcom

2003-01-01

190

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

Microsoft Academic Search

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

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

2009-01-01

191

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

Microsoft Academic Search

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

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

1999-01-01

192

Computed tomography and magnetic resonance imaging in spinal hydatidosis.  

PubMed

Computed tomography and magnetic resonance imaging in patients with spinal hydatidosis provide comprehensive evaluation of the actual extent of the disease. Paravertebral uncalcified cysts, hardly recognizable by conventional radiologic examinations, are clearly shown by both methods. Initial involvement of the spongy bone is evident in computed tomography scans, in contrast to what usually appears to be normal in plain films or tomograms. Occurrence of cysts within the spinal canal is revealed by both types of computed scans, with magnetic resonance imaging being able to provide further information on the involvement of the spinal cord. PMID:3824143

Pau, A; Simonetti, G; Tortori-Donati, P; Turtas, S; Viale, G L

1987-04-01

193

Field Map Reconstruction in Magnetic Resonance Imaging Using Bayesian Estimation  

PubMed Central

Field inhomogeneities in Magnetic Resonance Imaging (MRI) can cause blur or image distortion as they produce off-resonance frequency at each voxel. These effects can be corrected if an accurate field map is available. Field maps can be estimated starting from the phase of multiple complex MRI data sets. In this paper we present a technique based on statistical estimation in order to reconstruct a field map exploiting two or more scans. The proposed approach implements a Bayesian estimator in conjunction with the Graph Cuts optimization method. The effectiveness of the method has been proven on simulated and real data.

Baselice, Fabio; Ferraioli, Giampaolo; Shabou, Aymen

2010-01-01

194

Magnetic Resonance Imaging and Tracking of Stem Cells  

PubMed Central

To date, several stem cell labeling protocols have been developed, contributing to a fast growing and promising field of stem cell imaging by MRI (magnetic resonance imaging). Most of these methods utilize iron oxide nanoparticles (MION, SPIO, USPIO, VSIOP) for cell labeling, which provide negative (dark) signal effects on T2-weighted MR images. The following protocol describes stem cell labeling techniques with commercially available gadolinium chelates, which provide positive contrast on T1-weighted MR images, which can be advantageous for specific applications.

Nejadnik, Hossein; Castillo, Rostislav; Daldrup-Link, Heike E.

2014-01-01

195

Radiologic Imaging Modalities, Including Magnetic Resonance, for Evaluating Lymph Nodes  

PubMed Central

Although lymphography may be more accurate in assessing the extent of abdominal and pelvic Hodgkin's lymphoma, computed tomography (CT) has similar or greater overall accuracy than other imaging modalities in detecting malignant lymph nodes in the neck, chest, abdomen and pelvis. In this early stage of magnetic resonance (MR) imaging, its depiction of nodes is apparently mostly similar to that of CT. In addition, MR imaging shows the capacity to distinguish between enlarged lymph nodes caused by acute inflammation and those caused by malignant processes. ImagesFigure 1.Figure 2.Figure 3.Figure 4.Figure 5.Figure 6.

Dooms, Georges C.; Hricak, Hedvig

1986-01-01

196

Cardiomyocyte Death: Insights from Molecular and Microstructural Magnetic Resonance Imaging  

PubMed Central

Cardiomyocytes can die via necrosis, apoptosis, and autophagy. Although the molecular signals and pathways underlying these processes have been well elucidated, the pathophysiology of cardiomyocyte death remains incompletely understood. This review describes the development and application of novel imaging techniques to detect and characterize cardiomyocyte death noninvasively in vivo. It focuses on molecular and microstructural magnetic resonance images (MRIs) and their respective abilities to image cellular events such as apoptosis, inflammation, and myofiber architecture. These in vivo imaging techniques have the potential to provide novel insights into the mechanisms of cardiomyocyte death and to help guide the development of novel cardioprotective therapies.

Berry, Natalia C.

2011-01-01

197

Neonatal life support during magnetic resonance imaging.  

PubMed

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

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

2002-01-01

198

Clinical applications of magnetic resonance imaging - current status  

SciTech Connect

Magnetic resonance imaging has far-reaching real and possible clinical applications. Its usefulness has been best explored and realized in the central nervous system, especially the posterior fossa and brain stem, where most abnormalities are better identified than with computed tomography. Its lack of ionizing radiation and extreme sensitivity to normal and abnormal patterns of myelination make magnetic resonance imaging advantageous for diagnosing many neonatal and pediatric abnormalities. New, reliable cardiac gating techniques open the way for promising studies of cardiac anatomy and function. The ability to image directly in three orthogonal planes gives us new insight into staging and follow-up of pelvic tumors and other pelvic abnormalities. Exquisite soft tissue contrast, far above that attainable by other imaging modalities, has made possible the early diagnosis of traumatic ligamentous knee injury, avascular necrosis of the hip and diagnosis, treatment planning and follow-up of musculoskeletal neoplasms. 59 references, 9 figures.

Cammoun, D.; Hendee, W.R.; Davis, K.A.

1985-12-01

199

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

200

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

201

Brain Magnetic Resonance Imaging with Contrast Dependent on Blood Oxygenation  

NASA Astrophysics Data System (ADS)

Paramagnetic deoxyhemoglobin in venous blood is a naturally occurring contrast agent for magnetic resonance imaging (MRI). By accentuating the effects of this agent through the use of gradient-echo techniques in high fields, we demonstrate in vivo images of brain microvasculature with image contrast reflecting the blood oxygen level. This blood oxygenation level-dependent (BOLD) contrast follows blood oxygen changes induced by anesthetics, by insulin-induced hypoglycemia, and by inhaled gas mixtures that alter metabolic demand or blood flow. The results suggest that BOLD contrast can be used to provide in vivo real-time maps of blood oxygenation in the brain under normal physiological conditions. BOLD contrast adds an additional feature to magnetic resonance imaging and complements other techniques that are attempting to provide positron emission tomography-like measurements related to regional neural activity.

Ogawa, S.; Lee, T. M.; Kay, A. R.; Tank, D. W.

1990-12-01

202

Patterned Resonance Plasmonic Microarrays for High-Performance SPR Imaging  

PubMed Central

We report a novel optical platform based on SPR generation and confinement inside a defined 3-dimensional microwell geometry that leads to background resonance-free SPR images. The array shows an exceptionally high signal-to-noise ratio (S/N>80) for imaging analysis and subnanometric thickness resolution. An angular sensitivity of 1 degree/0.01 RIU has been achieved and the signal to background ratio (S/B) improves to 20, one order of magnitude higher than best literature results. The design proves effective for probing supported lipid membrane arrays in real time with a thickness resolution of 0.24 nm and allows for imaging analysis of microfluidic circuits where resonant spots are separated by only one pixel (~ 7 ?m). The high image quality and unique chip geometry open up new avenues for array screening and biomicrofluidics using SPRi detection.

Abbas, Abdennour; Linman, Matthew J.; Cheng, Quan

2011-01-01

203

Magnetic resonance imaging of neural circuits  

Microsoft Academic Search

A major goal of modern MRI research is to be able to image neural circuits in the central nervous system. Critical to this mission is the ability to describe a number of important parameters associated with neural circuits. These parameters include neural architecture, functional activation of neural circuits, anatomical and functional connectivity of neural circuits, and factors that might alter

Alan P Koretsky; Jeff Duyn

2008-01-01

204

Maximum Likelihood Estimators in Magnetic Resonance Imaging  

Microsoft Academic Search

Images of the MRI signal intensity are normally constructed by taking the magnitude of the complex-valued data. This results in a biased estimate of the true signal intensity. We consider this as a prob- lem of parameter estimation with a nuisance parameter. Using several standard techniques for this type of problem, we derive a variety of es- timators for the

M. Dylan Tisdall; M. Stella Atkins; R. A. Lockhart

2007-01-01

205

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

206

[Magnetic resonance imaging of the mediastinal vessels in pediatric patients].  

PubMed

The appearance of new and better magnetic resonance imaging (MRI) techniques have made the MRI a very important imaging method for the evaluation of thoracic vessels in pediatrics. The 3D angio-MRI using GD is capable of clearly demonstrating the morphology of the aorta and pulmonary vessels. The MRI may significantly reduce the number of angiographies needed and, in some patients, may even provide additional information to the angiography. PMID:17910864

Hernández, R J; Sáez, F

2007-01-01

207

Magnetic resonance imaging vs. computed tomography: advantages and disadvantages.  

PubMed

Magnetic resonance imaging (MRI) of the head and spine exceeds the sensitivity of computed tomography (CT) in detecting parenchymal lesions of the brain and spinal cord. MRI should be employed as a screening examination, particularly in patients suspected of having demyelinating diseases. CT continues to be the imaging technique of choice in evaluation of trauma, accurately depicting bony abnormalities and intracranial hemorrhage in evaluation of the spinal column and suspected disc herniation and in uncooperative patients. PMID:3905153

Earnest, F; Baker, H L; Kispert, D B; Laws, E R

1985-01-01

208

Magnetic resonance imaging of vaginal and vulval pathology  

Microsoft Academic Search

There are a number of conditions affecting the vagina and vulva that can be optimally assessed with the use of high-resolution\\u000a magnetic resonance imaging (MRI). This paper gives a suggested protocol for MRI technique and sequences for imaging the pelvis\\u000a and perineum and reviews the MRI appearances of many of the common pathologies affecting the vagina and vulva. Congenital\\u000a anomalies,

N. Griffin; L. A. Grant; E. Sala

2008-01-01

209

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

210

Biological magnetic resonance imaging using laser-polarized 129Xe  

Microsoft Academic Search

As currently implemented, magnetic resonance imaging (MRI) relies on the protons of water molecules in tissue to provide the NMR signal. Protons are, however, notoriously difficult to image in some biological environments of interest, notably the lungs1 and lipid bilayer membranes such as those in the brain2. Here we show that 129Xe gas can be used for high-resolution MRI when

M. S. Albert; G. D. Cates; B. Driehuys; W. Happer; B. Saam; C. S. Springer; A. Wishnia

1994-01-01

211

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.

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

2012-01-01

212

Assessment of coronary artery stenosis by magnetic resonance imaging.  

PubMed Central

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

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

1996-01-01

213

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

214

New approach for analyzing magnetic resonance elastography images  

Microsoft Academic Search

A new method for evaluating Magnetic Resonance Elastography (MRE) wave images is introduced, which consists of both local frequency estimation (LFE) and simulation of wave patterns by a coupled harmonic oscillator (CHO) approach. It is shown that i) LFE performs improved reconstruction by use of Gauss filters and ii) CHO calculations can help to refine the resulting wave speed or

Ingolf Sack; Gerd Buntkowsky; Johannes Bernarding; Thomas Tolxdorff; Juergen Braun

2001-01-01

215

Magnetic resonance imaging in obstructive M?llerian anomalies  

PubMed Central

Herlyn-Werner-Wunderlich (HWW) syndrome is a very rare congenital anomaly of the urogenital tract involving Müllerian ducts and Wolffian structures. It is characterized by the triad of didelphys uterus, obstructed hemivagina, and ipsilateral renal agenesis. Magnetic resonance imaging (MRI) is a sensitive, non-invasive diagnostic modality for demonstrating anatomic variation and associated complications.

Sen, Kamal Kumar; Balasubramaniam, Dhivya; Kanagaraj, Vikrant

2013-01-01

216

Volume measurement of multiple sclerosis lesions with magnetic resonance images  

Microsoft Academic Search

The ability to visualise multiple selerosis lesions in vivo with magnetic resonance imaging suggests and important role in monitoring the course of the disease. In order to help the long-term assessment of prospective treatments, a semi-automated technique for measuring lesion volume has been developed to provide a quantitative index of disease progression. Results are presented from a preliminary study with

D. A. G. Wicks; P. S. Tofts; D. H. Miller; G. H. Boulay; A. Feinstein; R. P. Sacares; I. Harvey; R. Brenner; W. I. McDonald

1992-01-01

217

RECONSTRUCTION OF HUMAN LUNG MORPHOLOGY MODELS FROM MAGNETIC RESONANCE IMAGES  

EPA Science Inventory

Reconstruction of Human Lung Morphology Models from Magnetic Resonance Images T. B. Martonen (Experimental Toxicology Division, U.S. EPA, Research Triangle Park, NC 27709) and K. K. Isaacs (School of Public Health, University of North Carolina, Chapel Hill, NC 27514) ...

218

17O magnetic resonance imaging of the human brain.  

PubMed

Here we show the first example of in vivo oxygen-17 (17O) magnetic resonance imaging of the human in natural abundance. Two-dimensional fast multi-planar gradient recalled 90 deg echo (FMPGR/90) pulse sequence and three-dimensional projection reconstruction pulse sequence methods were used. PMID:15727263

Fiat, Daniel; Hankiewicz, Janusz; Liu, Siyuan; Trbovic, Sinisa; Brint, Steven

2004-12-01

219

Evaluation of Skin Tumors by Magnetic Resonance Imaging  

Microsoft Academic Search

In vivo magnetic resonance imaging (MRI) is a powerful noninvasive technique in medical diagnosis; however, its application to analyze skin disorders is still at initial stages. To check whether MRI can be used as a noninvasive tool to analyze skin tumors, we carried out MRI of mice after treatment with benzo[a]pyrene (BP), a well known carcinogen. MRI was done on

Moganty R Rajeswari; Aklank Jain; Ashok Sharma; Dinesh Singh; N R Jagannathan; Uma Sharma; M N Degaonkar

2003-01-01

220

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

221

Multispectral magnetic resonance image segmentation using neural networks  

Microsoft Academic Search

The design, implementation, and preliminary testing of a computer system for automatic multispectral magnetic resonance imaging analysis is presented. The modular structure of the system permits easy comparison between various classification algorithms. The classification accuracy of traditional statistical pattern-recognition algorithms is compared to the results that can be obtained with neural networks of different topologies. Quantitative (confusion matrices) as well

Mehmed Ozkan; Hendrick G. Sprenkels; Benoit M. Dawant

1990-01-01

222

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

223

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

224

Measuring Cerebral Blood Flow Using Magnetic Resonance Imaging Techniques  

Microsoft Academic Search

Magnetic resonance imaging techniques measuring CBF have developed rapidly in the last decade, resulting in a wide range of available methods. The most successful approaches are based either on dynamic tracking of a bolus of a paramagnetic contrast agent (dynamic susceptibility contrast) or on arterial spin labeling. This review discusses their principles, possible pitfalls, and potential for absolute quantification and

Fernando Calamante; David L. Thomas; Gaby S. Pell; Jonna Wiersma; Robert Turner

1999-01-01

225

Functional magnetic resonance imaging in medicine and physiology  

Microsoft Academic Search

Magnetic resonance imaging (MRI) is a well-established diagnostic tool that provides detailed information about macroscopic structure and anatomy. Recent advances in MRI allow the noninvasive spatial evaluation of various biophysical and biochemical processes in living systems. Specifically, the motion of water can be measured in processes such as vascular flow, capillary flow, diffusion, and exchange. In addition, the concentrations of

C. T. W. Moonen; P. C. M. van Zijl; J. A. Frank; D Le Bihan; E. D. Becker

1990-01-01

226

Magnetic Resonance Imaging in Multiple Myeloma: Diagnostic and Clinical Implications  

Microsoft Academic Search

Purpose Magnetic resonance imaging (MRI) permits the detection of diffuse and focal bone marrow infiltration in the absence of osteopenia or focal osteolysis on standard metastatic bone surveys (MBSs). Patients and Methods Both baseline MBS and MRI were available in 611 of 668 myeloma patients who were treated uniformly with a tandem autologous transplantation-based protocol and were evaluated to determine

Ronald Walker; Bart Barlogie; Jeffrey Haessler; Guido Tricot; Elias Anaissie; John D. Shaughnessy Jr; Joshua Epstein; Rudy van Hemert; Eren Erdem; Antje Hoering; John Crowley; Ernest Ferris; Klaus Hollmig; Frits van Rhee; Maurizio Zangari; Mauricio Pineda-Roman; Abid Mohiuddin; Shmuel Yaccoby; Jeffrey Sawyer; Edgardo J. Angtuaco

2010-01-01

227

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

228

In vivo microelectrode track reconstruction using magnetic resonance imaging  

Microsoft Academic Search

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

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

1998-01-01

229

Quantitative Serum Proteomics from Surface Plasmon Resonance Imaging  

Microsoft Academic Search

The detection and quantification of specific proteins in complex mixtures is a major challenge for proteomics. For example, the development of disease-related biomarker panels will require fast and efficient methods for obtaining multiparameter protein profiles. We established a high throughput, label-free method for analyzing serum using surface plasmon resonance imaging of antibody microar- rays. Microarrays were fabricated using standard pin

Christopher Lausted; Zhiyuan Hu; Leroy Hood

2008-01-01

230

Nuclear magnetic resonance imaging of the kidney: renal masses  

Microsoft Academic Search

Fifteen patients with a variety of renal masses were examined by nuclear magnetic resonance (NMR), computed tomography, ultrasound, and intravenous urography. NMR clearly differentiated between simple renal cysts and other renal masses. On spin echo images, the simple renal cyst appeared as a round or slightly oval, homogeneous low-intensity mass with characteristically long T1 and T2 values. The thickness of

H. Hricak; R. D. Williams; K. L. Jr. Moon; A. A. Moss; C. Alpers; L. E. Crooks; L. Kaufman

1983-01-01

231

Automatic Contour Propagation in Cine Cardiac Magnetic Resonance Images  

Microsoft Academic Search

We have developed a method for automatic contour propagation in cine cardiac magnetic resonance images. The method consists of a new active contour model that tries to maintain a constant contour environment by matching gray values in profiles perpendicular to the contour. Consequently, the contours should maintain a constant position with respect to neighboring anatomical structures, such that the resulting

Gilion Hautvast; Steven Lobregt; Marcel Breeuwer; Frans A. Gerritsen

2006-01-01

232

Magnetic Resonance Imaging of Short T 2 Components in Tissue  

Microsoft Academic Search

The most widely used clinical magnetic resonance imaging techniques for the diagnosis of parenchymal disease employ heavily T2-weighted sequences to detect an increase or decrease in the signal from long T2 components in tissue. Tissues also contain short T2 components that are not detected or only poorly detected with conventional sequences. These components are the majority species in tendons, ligaments,

P. D. Gatehouse; G. M. Bydder

2003-01-01

233

Three-Dimensional Magnetic Resonance Imaging of Velopharyngeal Structures  

ERIC Educational Resources Information Center

Purpose: To report the feasibility of using a 3-dimensional (3D) magnetic resonance imaging (MRI) protocol for examining velopharyngeal structures. Using collected 3D MRI data, the authors investigated the effect of sex on the midsagittal velopharyngeal structures and the levator veli palatini (levator) muscle configurations. Method: Ten Caucasian…

Bae, Youkyung; Kuehn, David P.; Sutton, Bradley P.; Conway, Charles A.; Perry, Jamie L.

2011-01-01

234

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

235

Electrical conductivity imaging by magnetic resonance electrical impedance tomography (MREIT).  

PubMed

Magnetic resonance electrical impedance tomography (MREIT) is a recently developed imaging technique that combines MRI and electrical impedance tomography (EIT). In MREIT, cross-sectional electrical conductivity images are reconstructed from the internal magnetic field density data produced inside an electrically conducting subject when an electrical current is injected into the subject. In this work the results of an electrical conductivity imaging experiment are presented, along with some practical considerations regarding MREIT. The MREIT experiment was performed with a 0.3 Tesla MRI system on a phantom made of two compartments with different electrical conductivities. The current density inside the phantom was measured by the MR current density imaging (MRCDI) technique. The measured current density was then used for conductivity image reconstruction by the J-substitution algorithm. The conductivity phantom images obtained with an injection current of 28mA showed conductivity errors of about 25.5%. PMID:14523975

Oh, Suk H; Han, Jae Y; Lee, Soo Y; Cho, Min H; Lee, Byung I; Woo, Eung J

2003-10-01

236

Imaging of electrically detected magnetic resonance of a silicon wafer.  

PubMed

An imaging technique of electrically detected magnetic resonance (EDMR) was newly developed. Because the EDMR signal is obtained from paramagnetic recombination centers, one may expect the image to represent the distribution of defect and/or impurity sites in the sample. We successfully obtained EDMR images of a light-illuminated silicon plate 8 mm in width and 15 mm in length, which was cut from a silicon wafer (n-type, 100 Omega cm), under ESR irradiation at a frequency of 890 MHz (wavelength, 340 mm). The reproducibility of the EDMR image obtained from a sample was amply satisfactory. When the oxidized surface of the silicon was removed, the EDMR signal disappeared. Although the EDMR signal reappeared when the surface of the sample became reoxidized, the EDMR image obtained was slightly different from the earlier one. This finding shows that the EDMR image obtained from the sample shows the distribution of defects at the Si/SiO(2) interface. PMID:11700087

Sato, T; Yokoyama, H; Ohya, H; Kamada, H

2001-11-01

237

Imaging of Electrically Detected Magnetic Resonance of a Silicon Wafer  

NASA Astrophysics Data System (ADS)

An imaging technique of electrically detected magnetic resonance (EDMR) was newly developed. Because the EDMR signal is obtained from paramagnetic recombination centers, one may expect the image to represent the distribution of defect and/or impurity sites in the sample. We successfully obtained EDMR images of a light-illuminated silicon plate 8 mm in width and 15 mm in length, which was cut from a silicon wafer ( n-type, 100 ? cm), under ESR irradiation at a frequency of 890 MHz (wavelength, 340 mm). The reproducibility of the EDMR image obtained from a sample was amply satisfactory. When the oxidized surface of the silicon was removed, the EDMR signal disappeared. Although the EDMR signal reappeared when the surface of the sample became reoxidized, the EDMR image obtained was slightly different from the earlier one. This finding shows that the EDMR image obtained from the sample shows the distribution of defects at the Si/SiO 2 interface.

Sato, Toshiyuki; Yokoyama, Hidekatsu; Ohya, Hiroaki; Kamada, Hitoshi

2001-11-01

238

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.

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

2008-01-01

239

Magnetic resonance imaging of the optic nerves and chiasm  

SciTech Connect

Magnetic resonance imaging (MR) of the optic nerves and chiasm was compared with computed tomography (CT) in 4 healthy volunteers, 4 patients without orbital or chiasmal abnormalities, and 4 patients with tumor (anterior clinoid meningioma in 2, optic nerve glioma in 1, and optic nerve sheath meningioma in 1). MR was found to be effective in demonstrating the optic nerves and related structures, particularly the intracanalicular portion of the nerve which is difficult to see with CT. Best results were achieved with partial saturation recovery (SR) images. As axial views cannot always distinguish the ethmoid sinus tissue from the optic nerve, it may be necessary to employ both axial and coronal images.

Daniels, D.L.; Herfkins, R.; Gager, W.E.; Meyer, G.A.; Koehler, P.R.; Williams, A.L.; Haughton, V.M.

1984-07-01

240

Real-time Magnetic Resonance Imaging Guidance for Cardiovascular Procedures  

PubMed Central

Magnetic resonance imaging (MRI) of the cardiovascular system has proven to be an invaluable diagnostic tool. Given the ability to allow for real-time imaging, MRI guidance of intraoperative procedures can provide superb visualization which can facilitate a variety of interventions and minimize the trauma of the operations as well. In addition to the anatomic detail, MRI can provide intraoperative assessment of organ and device function. Instruments and devices can be marked to enhance visualization and tracking. All of which is an advance over standard x-ray or ultrasonic imaging.

Horvath, Keith A.; Li, Ming; Mazilu, Dumitru; Guttman, Michael A.; McVeigh, Elliot R.

2008-01-01

241

Magnetic resonance imaging of convection in laser-polarized xenon  

NASA Technical Reports Server (NTRS)

We demonstrate nuclear magnetic resonance (NMR) imaging of the flow and diffusion of laser-polarized xenon (129Xe) gas undergoing convection above evaporating laser-polarized liquid xenon. The large xenon NMR signal provided by the laser-polarization technique allows more rapid imaging than one can achieve with thermally polarized gas-liquid systems, permitting shorter time-scale events such as rapid gas flow and gas-liquid dynamics to be observed. Two-dimensional velocity-encoded imaging shows convective gas flow above the evaporating liquid xenon, and also permits the measurement of enhanced gas diffusion near regions of large velocity variation.

Mair, R. W.; Tseng, C. H.; Wong, G. P.; Cory, D. G.; Walsworth, R. L.

2000-01-01

242

Advanced techniques in pediatric abdominopelvic oncologic magnetic resonance imaging.  

PubMed

Advances in the treatment of pediatric abdominopelvic malignancies have increased survival drastically. Imaging is critical in initial tumor characterization/staging, assessment of treatment response, and surveillance following therapy. Magnetic resonance imaging (MRI) is playing an increasing role in the care of these patients due to its lack of ionizing radiation, superior contrast resolution and the ability to characterize tumors based on tissue characteristics (e.g., T1 and T2 relaxation times). Modern MR techniques also allow for assessment of tumors based on functional characteristics. This article is focused on emerging MRI technologies and potential applications in the imaging of pediatric abdominopelvic malignancies. PMID:24183528

Smith, Ethan A

2013-11-01

243

Myxoid adrenocortical adenoma: magnetic resonance imaging and pathology correlation.  

PubMed

We report a case of a 74-year-old female with myxoid adrenocortical adenoma which showed different magnetic resonance imaging findings compared to those of a typical adrenocortical adenoma. The myxoid change in the adrenocortical adenoma is a rare form of degeneration. It presents a considerable diagnostic challenge to both radiologists and clinicians because it can mimic other adrenal tumor types on imaging. The MRI findings of the presented case included a high signal intensity on T2-weighted images similar to that of fluid and delayed progressive enhancement. PMID:24643431

Kim, Tae Un; Kim, Suk; Lee, Jun Woo; Lee, Nam Kyung; Ha, Hong Koo; Park, Won Young

2014-01-01

244

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

245

Optically trapped atomic resonant devices for narrow linewidth spectral imaging  

NASA Astrophysics Data System (ADS)

This thesis focuses on the development of atomic resonant devices for spectroscopic applications. The primary emphasis is on the imaging properties of optically thick atomic resonant fluorescent filters and their applications. In addition, this thesis presents a new concept for producing very narrow linewidth light as from an atomic vapor lamp pumped by a nanosecond pulse system. This research was motivated by application for missile warning system, and presents an innovative approach to a wide angle, ultra narrow linewidth imaging filter using a potassium vapor cell. The approach is to image onto and collect the fluorescent photons emitted from the surface of an optically thick potassium vapor cell, generating a 2 GHz pass-band imaging filter. This linewidth is narrow enough to fall within a Fraunhefer dark zone in the solar spectrum, thus make the detection solar blind. Experiments are conducted to measure the absorption line shape of the potassium resonant filter, the quantum efficiency of the fluorescent behavior, and the resolution of the fluorescent image. Fluorescent images with different spatial frequency components are analyzed by using a discrete Fourier transform, and the imaging capability of the fluorescent filter is described by its Modulation Transfer Function. For the detection of radiation that is spectrally broader than the linewidth of the potassium imaging filter, the fluorescent image is seen to be blurred by diffuse fluorescence from the slightly off resonant photons. To correct this, an ultra-thin potassium imaging filter is developed and characterized. The imaging property of the ultra-thin potassium imaging cell is tested with a potassium seeded flame, yielding a resolution image of ˜ 20 lines per mm. The physics behind the atomic resonant fluorescent filter is radiation trapping. The diffusion process of the resonant photons trapped in the atomic vapor is theoretically described in this thesis. A Monte Carlo method is used to simulate the absorption and fluorescence. The optimum resolution of the fluorescent image is predicted by simulation. Radiation trapping is also shown to be useful for the generation of ultra-narrow linewidth light from an atomic vapor flash lamp. A 2 nanosecond, high voltage pulse is used to excite low pressure mercury vapor mixed with noble gases, producing high intensity emission at the mercury resonant line at 253.7 nm. With a nanosecond pumping time and high electrical current, the radiation intensity of the mercury discharge is increased significantly compared to a normal glow discharge lamp, while simultaneously suppressing the formation of an arc discharge. By avoiding the arc discharge, discrete spectral lines of mercury were kept at narrow bandwidth. Due to radiation trapping, the emission linewidth from the nanosecond mercury lamp decreases with time and produces ultra-narrow linewidth emission 100 ns after of the excitation, this linewidth is verified by absorption measurements through low pressure mercury absorption filter. The lamp is used along with mercury absorption filters for spectroscopic applications, including Filtered Rayleigh Scattering with different CO2 pressures and Raman scattering from methanol.

Qian, Lipeng

246

Magnetic Resonance Imaging by Synergistic Diffusion-Diffraction Patterns  

NASA Astrophysics Data System (ADS)

Inferring on the geometry of an object from its frequency spectrum is highly appealing since the object could then be imaged noninvasively or from a distance (as famously put by Kac, “can one hear the shape of a drum?”). In nuclear magnetic resonance of porous systems, the shape of the drum is represented by the pore density function that bears all the information on the collective pore microstructure. So far, conventional magnetic resonance imaging (MRI) could only detect the pore autocorrelation function, which inherently obscures fine details on the pore structure. Here, for the first time, we report on a unique imaging mechanism arising from synergistic diffusion-diffractions that directly yields the pore density function. This mechanism offers substantially higher spatial resolution compared to conventional MRI while retaining all fine details on the collective pore morphology. Thus, using these unique synergistic diffusion-diffractions, the “shape of the drum” can be inferred.

Shemesh, Noam; Westin, Carl-Fredrik; Cohen, Yoram

2012-02-01

247

Magnetic resonance imaging using linear magneto-inductive waveguides  

NASA Astrophysics Data System (ADS)

Magneto-inductive waveguides are arrays of magnetically coupled, lumped element resonators, which support slow waves at radio frequency. Their use in internal magnetic resonance imaging (MRI), where they may provide an intrinsically safe method of signal detection and transmission, is described. A catheter-based receiver formed from a thin-film printed circuit mounted on a tubular scaffold using heat-shrink tubing is demonstrated, and its electrical response and imaging sensitivity are explained in terms of the excitation and propagation of magneto-inductive waves. The theoretical predictions are confirmed using the results of electrical measurement and 1H MRI at 1.5 T, and imaging is achieved over a total length greater than 1.5 m using a single receiver.

Syms, R. R. A.; Young, I. R.; Ahmad, M. M.; Rea, M.

2012-12-01

248

SEVEN TOPICS IN FUNCTIONAL MAGNETIC RESONANCE IMAGING  

PubMed Central

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

BANDETTINI, PETER A.

2010-01-01

249

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

ERIC Educational Resources Information Center

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

Seedhouse, Steven J.; Hoffmann, Markus M.

2008-01-01

250

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.

Akki, Ashwin; Gupta, Ashish

2013-01-01

251

[Magnetic resonance tomography and hybrid imaging in rheumatology].  

PubMed

In rheumatologic diseases magnet resonance imaging (MRI) is capable of depicting early inflammatory changes which are frequently missed by other imaging modalities. New MRI protocols and hardware, primarily whole-body MRI and low-field extremity MRI facilitate the use of MRI in rheumatology patients. The increasing number of functional MRI techniques provide additional molecular information on the tissue composition, e.g. cartilage quality. These molecular MRI techniques enable new ways for early disease detection and therapy monitoring. Hybrid imaging modalities, such as MRI-SPECT (single photon mmission tomography) and MRI-PET (positron emission tomography) provide a new level of molecular imaging in rheumatology by adding the advantages of the combined modalities. This article provides an up-to-date overview of new MRI techniques and innovative hybrid imaging modalities and summarizes the first available results of these procedures in rheumatologic applications. PMID:23446460

Buchbender, C; Schneider, M; Ostendorf, B

2013-03-01

252

Sacrococcygeal chordoma: Magnetic resonance imaging and computed tomography  

SciTech Connect

Magnetic resonance imaging (MRI) was compared to computed tomography (CT) in four cases of sacrococcygeal chordoma. Both techniques yielded important anatomic information and represented important advances over early radiologic imaging methods. MRI provided superior contrast with surrounding soft tissues because of the prolonged T1 and T2 times of the tumors. The direct sagittal images obtained by MRI were valuable in determining the extent of lesions. Either MRI or direct CT coronal images were needed for the demonstration of tumor involving the sacral nerve roots. It was not possible to reliably distinguish between tumor adherent to bowel wall and bowel wall invasion by either technique. It is concluded that MRI is at least equal to CT for demonstration of these lesions and seems likely to become the imaging method of choice.

Rosenthal, D.I.; Scott, J.A.; Mankin, H.J.; Wismer, G.L.; Brady, T.J.

1985-07-01

253

ROUTINE THREE-DIMENSIONAL MAGNETIC RESONANCE IMAGING OF JOINTS  

PubMed Central

Due to its high spatial resolution and excellent tissue contrast, magnetic resonance (MR) imaging has become the most commonly used imaging method to evaluate joints. Most musculoskeletal MR imaging is performed using two-dimensional fast spin-echo sequences. However, three-dimensional sequences have also been used for joint imaging and have the advantage of acquiring thin continuous slices through joints which reduces the effects of partial volume averaging. With recent advances in MR technology, three-dimensional sequences with isotropic resolution have been developed. These sequences allow high quality multi-planar reformat images to be obtained following a single acquisition, thereby eliminating the need to repeat sequences with identical tissue contrast in different planes. Preliminary results on the diagnostic performance of three-dimensional isotropic resolution sequences are encouraging. However, additional studies are needed to determine whether these sequences can replace currently used two-dimensional fast spin-echo sequences for providing comprehensive joint assessment in clinical practice.

Kijowki, Richard; Gold, Garry E.

2011-01-01

254

Reproducibility of magnetic resonance perfusion imaging.  

PubMed

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 K(trans) from DCE-MRI showed comparable reproducibility (mean wCV, 5.13% for Gd-DTPA, 8.06% for P792). ICC of K(trans) showed high intra-subject reproducibility (ICC = 0.999/0.995) and inter-subject heterogeneity (ICC = 0.774). Histograms of K(trans) 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

255

Intraoperative magnetic resonance imaging-conditional robotic devices for therapy and diagnosis.  

PubMed

Magnetic resonance imaging presents high-resolution preoperative scans of target tissue and allows for the availability of intraoperative real-time images without the exposure of patients to ionizing radiation. This has motivated scientists and engineers to integrate medical robotics with the magnetic resonance imaging modality to allow robot-assisted, image-guided diagnosis and therapy. This article provides a review of the state-of-the-art medical robotic systems available for use in conjunction with intraoperative magnetic resonance imaging. The robot functionalities and mechanical designs for a wide range of magnetic resonance imaging interventions are presented, including their magnetic resonance imaging compatibility, actuation, kinematics and the mechanical and electrical designs of the robots. Classification and comparative study of various intraoperative magnetic resonance image guided robotic systems are provided. The robotic systems reviewed are summarized in a table in detail. Current technologies for magnetic resonance imaging-conditional robotics are reviewed and their potential future directions are sketched. PMID:24534419

Fisher, Taylor; Hamed, Abbi; Vartholomeos, Panagiotis; Masamune, Ken; Tang, Guoyi; Ren, Hongliang; Tse, Zion T H

2014-03-01

256

Resonant Mode Reduction in Radiofrequency Volume Coils for Ultrahigh Field Magnetic Resonance Imaging.  

PubMed

In a multimodal volume coil, only one mode can generate homogeneous Radiofrequency (RF) field for Magnetic Resonance Imaging. The existence of other modes may increase the volume coil design difficulties and potentially decreases coil performance. In this study, we introduce common-mode resonator technique to high and ultrahigh field volume coil designs to reduce the resonant mode while maintain the homogeneity of the RF field. To investigate the design method, the common-mode resonator was realized by using a microstrip line which was split along the central to become a pair of parallel transmission lines within which common-mode currents exist. Eight common-mode resonators were placed equidistantly along the circumference of a low loss dielectric cylinder to form a volume coil. Theoretical analysis and comparison between the 16-strut common-mode volume coil and a conventional 16-strut volume coil in terms of RF field homogeneity and efficiency was performed using Finite-Difference Time-Domain (FDTD) method at 298.2 MHz. MR imaging experiments were performed by using a prototype of the common-mode volume coil on a whole body 7 Tesla scanner. FDTD simulation results showed the reduced number of resonant modes of the common-mode volume coil over the conventional volume coil, while the RF field homogeneity of the two type volume coils was kept at the same level. MR imaging of a water phantom and a kiwi fruit showing the feasibility of the proposed method for simplifying the volume coil design is also presented. PMID:22081791

Pang, Yong; Xie, Zhentian; Li, Ye; Xu, Duan; Vigneron, Daniel; Zhang, Xiaoliang

2011-07-28

257

Regression Models for Identifying Noise Sources in Magnetic Resonance Images  

PubMed Central

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

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

2009-01-01

258

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

Microsoft Academic Search

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

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

259

Segmentation of magnetic resonance images to construct human head model for diffuse optical imaging  

Microsoft Academic Search

The brain activation image obtained by diffuse optical tomography (DOT) is obtained by solving inverse problem using the spatial sensitivity profile (SSP). The SSP can be obtained from the analysis of the light propagation using threedimensional head models. The head model is based upon segmented magnetic resonance (MR) image and there are several types of software based on binarization for

Kazuki Kurihara; Hiroshi Kawaguchi; Yosuke Takahashi; Takayuki Obata; Eiji Okada

2011-01-01

260

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

Microsoft Academic Search

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

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

2008-01-01

261

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.

2012-01-01

262

Magnetic Resonance Imaging Mapping of Brain Function Human Visual Cortex  

PubMed Central

Belliveau JW, Kwong KK, Kennedy DN, Baker JR, Stern CE, Benson R, Chesler DA, Weisskoff RM, Cohen MS, Tootell RBH, Fox PT, Brady TJ, Rosen BR. Magnetic resonance imaging mapping of brain function: human visual cortex. Invest Radiol 1992;27:SS9–S65. Magnetic resonance imaging (MRI) studies of human brain activity are described. Task-induced changes in brain cognitive state were measured using high-speed MRI techniques sensitive to changes in cerebral blood volume (CBV), blood flow (CBF), and blood oxygenation. These techniques were used to generate the first functional MRI maps of human task activation, by using a visual stimulus paradigm. The methodology of MRI brain mapping and results from the investigation of the functional organization and frequency response of human primary visual cortex (Vl) are presented.

BELLIVEAU, J.W.; KWONG, K.K.; KENNEDY, D.N.; BAKER, J.R.; STERN, C.E.; BENSON, R.; CHESLER, D.A.; WEISSKOFF, R.M.; COHEN, M.S.; TOOTELL, R.B.H.; FOX, P.T.; BRADY, T.J.; ROSEN, B.R.

2014-01-01

263

Transcranial magnetic stimulation assisted by neuronavigation of magnetic resonance images  

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

264

Molecular magnetic resonance imaging with targeted contrast agents  

Microsoft Academic Search

Magnetic resonance imaging (MRI) produces high-resolution three-dimensional maps delineating morphological features of the specimen. Differential contrast in soft tissues depends on endogenous differences in water content, relaxation times, and\\/or diffusion characteristics of the tissue of interest. The specificity of MRI can be further increasedbyexogenouscontrastagents(CA)suchasgadoliniumchelates,whichhavebeensuccessfullyusedforimaging of hemodynamic parameters including blood perfusion and vascular permeability. Development of targeted MR CA directed to

Dmitri Artemov

2003-01-01

265

NUCLEAR MAGNETIC RESONANCE IMAGING OF WATER CONTENT IN THE SUBSURFACE  

Microsoft Academic Search

This report contains the experimental, theoretical and numerical studies performed under Department of Energy (DOE) Agreement Number DE-FG07-96ER14732 entitled ''Surface Nuclear Magnetic Resonance for Imaging Subsurface Water.'' DOE and Department of Defense (DOD) complexes and test ranges are situated in widely varying climatic conditions from the desert southwest to the humid east. The mission of the Office of Environmental Restoration

Hendrickx; Jan M. H

1999-01-01

266

Magnetic resonance imaging of the internal auditory canal  

SciTech Connect

Three patients with exclusively or predominantly intracanalicular neuromas and 5 with presumably normal internal auditory canals were examined with prototype 1.4- or 1.5-tesla magnetic resonance (MR) scanners. MR images showed the 7th and 8th cranial nerves in the internal auditory canal. The intracanalicular neuromas had larger diameter and slightly greater signal strength than the nerves. Early results suggest that minimal enlargement of the nerves can be detected even in the internal auditory canal.

Daniels, D.L.; Herfkins, R.; Koehler, P.R.; Millen, S.J.; Shaffer, K.A.; Williams, A.L.; Haughton, V.M.

1984-04-01

267

Phase and sensitivity of receiver coils in magnetic resonance imaging  

PubMed Central

Receiver coil response is a major cause of nonuniformities in magnetic resonance images. The spatial dependence of the sensitivity and phase of single-saddle receiver coils has been investigated quantitatively by calculating the H1 field and comparing the results with measurements of a uniform phantom. Agreement between the measurements and calculations is excellent. A method is developed which corrects for both the nonuniform sensitivity and the phase shifts introduced by receiver coils.

McVeigh, E. R.; Bronskill, M. J.; Henkelman, R. M.

2007-01-01

268

Magnetic resonance imaging: effects of magnetic field strength  

Microsoft Academic Search

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

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

1984-01-01

269

Electron Paramagnetic Resonance Imaging of Oxidative Stress in Renal Disease  

Microsoft Academic Search

The importance of analyzing the kinetics of reactive oxygen species or related substances in vivo is increasing. Electron paramagnetic resonance (EPR) is currently a powerful method for in vivo, non-invasive analysis of oxidative stress. We have applied EPR imaging for murine renal ischemia-reperfusion injury, as a model of acute renal damage, and NF-E2-related factor 2 (Nrf2)-deficient mice, a model for

Aki Hirayama; Sohji Nagase

2006-01-01

270

Model-based simulation of dynamic magnetic resonance imaging signals  

Microsoft Academic Search

This paper presents a model-based method to efficiently simulate dynamic magnetic resonance imaging signals. Using an analytical spatiotemporal object model, the method can approximate time-varying k-space signals such as those from objects in motion and\\/or during dynamic contrast enhancement. Both rigid-body and non-rigid-body motions can be simulated using the proposed method. In addition, it can simulate data with arbitrary data

Jim X. Ji; Yuttapong Jiraraksopakun

2008-01-01

271

Muscle cross-section measurement by magnetic resonance imaging  

Microsoft Academic Search

Summary  Muscle cross-section areas were measured by magnetic resonance imaging (MRI) in the thigh of a human cadaver,. the results being compared with those obtained by photography of corresponding anatomic macroslices. A close correlation was found between MRI and photographic evaluation, differences between the methods ranging from nil to 9.5%, depending on the scan position and the muscle groups. In vivo

Ralph Beneke; JiJrg Neuerburg; Klaus Bohndorf

1991-01-01

272

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

273

Computed tomography and magnetic resonance imaging findings in ophthalmoplegic migraine.  

PubMed

A patient with ophthalmoplegic migraine is described, and his computed tomography and magnetic resonance imaging findings are discussed. According to our results, triad migraine, third nerve palsy, and focal enhancement of an enlarged third cranial nerve at the root exit zone should be considered pathognomonic of the disease, and further examinations should be avoided. Pathogenetic theories of the disease are discussed, and we suggest a new pathogenetic theory. PMID:20472197

Miglio, Laura; Feraco, Paola; Tani, Giovanni; Ambrosetto, Paolo

2010-06-01

274

Exploiting Temporal Information in Functional Magnetic Resonance Imaging Brain Data  

Microsoft Academic Search

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

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

2005-01-01

275

Functional magnetic resonance imaging of the human brain  

Microsoft Academic Search

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

Seong-Gi Kim; Kamil Ugurbil

1997-01-01

276

Wavelet-based Rician noise removal for magnetic resonance imaging  

Microsoft Academic Search

It is well known that magnetic resonance magnitude image data obey a Rician distribution. Unlike additive Gaussian noise, Rician “noise” is signal-dependent, and separating signal from noise is a difficult task. Rician noise is especially problematic in low signal-to-noise ratio (SNR) regimes where it not only causes random fluctuations, but also introduces a signal-dependent bias to the data that reduces

Robert D. Nowak

1999-01-01

277

Imaging local electrochemical current via surface plasmon resonance.  

PubMed

We demonstrated an electrochemical microscopy technique based on the detection of variations in local electrochemical current from optical signals arising from surface plasmon resonance. It enables local electrochemical measurements (such as voltammetry and amperometry) with high spatial resolution and sensitivity, because the signal varies with current density rather than current. The imaging technique is noninvasive, scanning-free, and fast, and it constitutes a powerful tool for studying heterogeneous surface reactions and for analyzing trace chemicals. PMID:20223983

Shan, Xiaonan; Patel, Urmez; Wang, Shaopeng; Iglesias, Rodrigo; Tao, Nongjian

2010-03-12

278

Surface charge switching nanoparticles for magnetic resonance imaging.  

PubMed

In this study, polypeptide-based nanoparticles [constituted using poly(l-lysine) coupled with deoxycholic acid (DOCA) and conjugated with 2,3-dimethylmaleic acid (DMA)] have high tumor selectivity once electrostatically switched by the acidic milieu of solid tumors. These nanoparticles exhibited a significantly increased in vitro cellular uptake and high accumulation in the acidic tumor site in vivo. Consequently, Fe3O4-loaded nanoparticles enabled high contrast magnetic resonance (MR) imaging of the tumor in vivo. PMID:24858382

Lee, Dong Jin; Oh, Young Taik; Lee, Eun Seong

2014-08-25

279

Experiences with functional magnetic resonance imaging at 1 tesla  

Microsoft Academic Search

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

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

1998-01-01

280

Functional magnetic resonance imaging in renal artery stenosis  

Microsoft Academic Search

Renal artery stenosis (RAS) is the leading cause of secondary hypertension. Magnetic resonance (MR) imaging and in particular\\u000a MR angiography have evolved into important diagnostic tools for the detection and grading of RAS due to the lack of ionizing\\u000a radiation and nephrotoxic contrast agent. This review describes state-of-the-art MR angiographic techniques and introduces\\u000a the reader to current concepts of RAS

S. O. Schoenberg; J. R. Rieger; H. J. Michaely; H. Rupprecht; W. Samtleben; M. F. Reiser

2006-01-01

281

Hemodynamic Assessment of Carotid Stenosis by Functional Magnetic Resonance Imaging  

Microsoft Academic Search

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

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

2008-01-01

282

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

283

Magnetic Resonance Imaging of Stroke in the Rat  

PubMed Central

Magnetic resonance imaging (MRI) is now a routine neuroimaging tool in the clinic. Throughout all phases of stroke from acute to chronic, MRI plays an important role to diagnose, evaluate and monitor the cerebral tissue undergoing stroke. This review provides a description of various MRI methods and an overview of selected MRI studies, with an embolic stroke model of rat, performed in the MRI laboratory of Department of Neurology, Henry Ford Hospital, Detroit, Michigan, US.

Michael, CHOPP; Lian, LI; Li, ZHANG; Zheng-gang, ZHANG; Qing-jiang, LI; Quan, JIANG

2014-01-01

284

Organic radical contrast agents for magnetic resonance imaging.  

PubMed

We report a molecular design that provides an intravenously injectable organic radical contrast agent (ORCA) for which the molecular (1)H water relaxivity (r(1)) is ca. 5 mM(-1) s(-1). The ORCA is based on spirocyclohexyl nitroxide radicals and poly(ethylene glycol) chains conjugated to a fourth-generation polypropylenimine dendrimer scaffold. The metal-free ORCA has a long shelf life and provides selectively enhanced magnetic resonance imaging in mice for over 1 h. PMID:22974177

Rajca, Andrzej; Wang, Ying; Boska, Michael; Paletta, Joseph T; Olankitwanit, Arnon; Swanson, Michael A; Mitchell, Deborah G; Eaton, Sandra S; Eaton, Gareth R; Rajca, Suchada

2012-09-26

285

Music Onset Detection Based on Resonator Time Frequency Image  

Microsoft Academic Search

This paper describes a new method for music onset detection. The novelty of the approach consists mainly of two elements: the time-frequency processing and the detection stages. The resonator time frequency image (RTFI) is the basic time-frequency analysis tool. The time-frequency processing part is in charge of transforming the RTFI energy spectrum into more natural energy- change and pitch-change cues

Ruohua Zhou; Marco Mattavelli; Giorgio Zoia

2008-01-01

286

Magnetic Resonance Imaging and Pituitary Function in Children with Panhypopituitarism  

Microsoft Academic Search

Background: To explore the relationship between magnetic resonance imaging (MRI) findings and multiple pituitary-target hormones in patients with panhypopituitarism or multiple pituitary hormone deficiency (MPHD). Methods: 125 patients with MPHD (102 boys, MPHD group) and 90 age-, sex- and Tanner stage-matched normal children (control group) were enrolled. 96 of the patients with MPHD underwent MRI scans of the hypothalamic-pituitary area.

Guimei Li; Peng Shao; Xiaojun Sun; Qian Wang; Lijuan Zhang

2010-01-01

287

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

288

Resonant imaging of carotenoid pigments in the human retina  

NASA Astrophysics Data System (ADS)

We have generated high spatial resolution images showing the distribution of carotenoid macular pigments in the human retina using Raman spectroscopy. A low level of macular pigments is associated with an increased risk of developing age-related macular degeneration, a leading cause of irreversible blindness. Using excised human eyecups and resonant excitation of the pigment molecules with narrow bandwidth blue light from a mercury arc lamp, we record Raman images originating from the carbon-carbon double bond stretch vibrations of lutein and zeaxanthin, the carotenoids comprising human macular pigments. Our Raman images reveal significant differences among subjects, both in regard to absolute levels as well as spatial distribution within the macula. Since the light levels used to obtain these images are well below established safety limits, this technique holds promise for developing a rapid screening diagnostic in large populations at risk for vision loss from age-related macular degeneration.

Gellermann, Werner; Emakov, Igor V.; McClane, Robert W.

2002-06-01

289

Matching pursuit data acquisition in magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

The matching pursuit (MP) algorithm developed by S. Mallat and Z. Zhang is applied to magnetic resonance (MR) imaging. Since matching pursuit is a greedy algorithm to find waveforms which are the best match for an object-signal, the signal can be decomposed with a few iterations. In this paper, we propose an application of the MP algorithm to the MR imaging to reduce imaging time. Inner products of residual signals and selected waveforms in the MP algorithm are derived from the MR signals by excitation of RF pulses which are Fourier transforms of selected waveforms. Results from computer simulations demonstrate that the imaging time is reduced by using the MP algorithm and further a progressive reconstruction can be achieved.

Ro, Yong M.; Neff, Ralph A.; Zakhor, Avideh

1997-05-01

290

Artifacts from dental casting alloys in magnetic resonance imaging.  

PubMed

The potential advantage of magnetic resonance imaging (MRI) has been limited by artifacts due to the presence of metallic materials. For quantitative evaluation of the magnitude of artifacts from dental casting alloys and implant materials in MR imaging, 11 dental casting or implant materials were imaged by means of 1.5 T MRI apparatus with three different sequences. Mean and standard deviation of water signal intensity (SI) around the sample in the region of interest (1200 mm(2)) were determined, and the coefficient of variation was compared for evaluation of the homogeneity of the SI. A variety of artifacts with different magnitudes was observed. Only one of the samples, composed mainly of Pd, In, and Sb, showed no artifacts in all imaging sequences. We concluded that selection of specific dental casting alloys according to their elemental compositions could minimize the metal artifacts in MRI; however, titanium alloys currently pose a problem with respect to causing MRI artifacts. PMID:12885843

Shafiei, F; Honda, E; Takahashi, H; Sasaki, T

2003-08-01

291

Bulk and surface sensitivity of a resonant waveguide grating imager  

NASA Astrophysics Data System (ADS)

We report the assessment of the sensitivity of a microplate-compatible resonant waveguide grating imager. The sensitivity to bulk refractive index changes was determined using a serial dilution of glycerol solution with the help of a refractometer. The surface sensitivity was examined using layer-by-layer polyelectrolyte films in conjunction with optical waveguide lightmode spectroscopy and characterized by the binding of acetazolamide to immobilized carbonic anhydrase under microfluidics. The results suggest that the imager has a limit of detection down to 2.2 × 10-6 for refractive index change and 0.078 ng/cm2 for the adsorbed mass.

Orgovan, Norbert; Kovacs, Boglarka; Farkas, Eniko; Szabó, Bálint; Zaytseva, Natalya; Fang, Ye; Horvath, Robert

2014-02-01

292

Image force microscopy of molecular resonance: A microscope principle  

PubMed Central

We demonstrate a technique in microscopy which extends the domain of atomic force microscopy to optical spectroscopy at the nanometer scale. We show that molecular resonance of feature sizes down to the single molecular level can be detected and imaged purely by mechanical detection of the force gradient between the interaction of the optically driven molecular dipole and its mirror image in a platinum coated scanning probe tip. This microscopy and spectroscopy technique is extendable to frequencies ranging from radio to infrared and the ultraviolet.

Rajapaksa, I.; Uenal, K.; Wickramasinghe, H. Kumar

2010-01-01

293

Magnetic resonance imaging for the ophthalmologist: A primer  

PubMed Central

Magnetic resonance imaging (MRI) and computerized tomography (CT) have added a new dimension in the diagnosis and management of ocular and orbital diseases. Although CT is more widely used, MRI is the modality of choice in select conditions and can be complimentary to CT in certain situations. The diagnostic yield is best when the ophthalmologist and radiologist work together. Ophthalmologists should be able to interpret these complex imaging modalities as better clinical correlation is then possible. In this article, we attempt to describe the basic principles of MRI and its interpretation, avoiding confusing technical terms.

Simha, Arathi; Irodi, Aparna; David, Sarada

2012-01-01

294

Magnetic resonance imaging of gel-cast ceramic composites  

SciTech Connect

Magnetic resonance imaging (MRI) techniques are being employed to aid in the development of advanced near-net-shape gel-cast ceramic composites. MRI is a unique nondestructive evaluation tool that provides information on both the chemical and physical properties of materials. In this effort, MRI imaging was performed to monitor the drying of porous green-state alumina - methacrylamide-N.N`-methylene bisacrylamide (MAM-MBAM) polymerized composite specimens. Studies were performed on several specimens as a function of humidity and time. The mass and shrinkage of the specimens were also monitored and correlated with the water content.

Dieckman, S.L.; Balss, K.M.; Waterfield, L.G. [and others

1997-04-01

295

Spectrally Resolved Magnetic Resonance Imaging of the XenonBiosensor  

SciTech Connect

Due to its ability to non-invasively record images, as well as elucidate molecular structure, nuclear magnetic resonance is the method of choice for applications as widespread as chemical analysis and medical diagnostics. Its detection threshold is, however, limited by the small polarization of nuclear spins in even the highest available magnetic fields. This limitation can, under certain circumstances, be alleviated by using hyper-polarized substances. Xenon biosensors make use of the sensitivity gain of hyperpolarized xenon to provide magnetic resonance detection capability for a specific low-concentration target. They consist of a cryptophane cage, which binds one xenon atom, and which has been connected via a linker to a targeting moiety such as a ligand or antibody. Recent work has shown the possibility of using the xenon biosensor to detect small amounts of a substance in a heterogeneous environment by NMR. Here, we demonstrate that magnetic resonance (MR) provides the capability to obtain spectrally and spatially resolved images of the distribution of immobilized biosensor, opening the possibility for using the xenon biosensor for targeted imaging.

Hilty, Christian; Lowery, Thomas; Wemmer, David; Pines, Alexander

2005-07-15

296

Magnetic resonance imaging: effects of magnetic field strength.  

PubMed

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

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

1984-04-01

297

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

298

Ferromagnetic resonance imaging of Co films using magnetic resonance force microscopy  

SciTech Connect

Magnetic resonance force microscope (MRFM) technique has been applied to the study of spatial imaging in thin Co ferromagnetic film. A novel approach is proposesd to improve spatial resolution in MRFM, which is limited by the broad width of Co ferromagnetic resonance (FMR) line. The authors introduce a selective local field with a small yittrium iron garnet (YIG) grain. They have performed MRFM detected FMR on a sample consisting of two sections of Co films laterally separated by {approximately}20 {micro}m. The experimental results demonstrate the scanning imaging capabilities of MRFM. The results can be understood qualitatively by means of the calculated magnetic field and field gradient profiles generated by the YIG shere.

Suh, B.J.; Hammel, P.C.; Zhang, Z. [Los Alamos National Lab., NM (United States); Midzor, M.M.; Roukes, M.L. [California Inst. of Tech., Pasadena, CA (United States); Childress, J.R. [Univ. of Florida, Gainsville, FL (United States)

1998-07-01

299

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

300

Using high-Tc superconducting resonator for enhancement of diffusion tensor imaging  

Microsoft Academic Search

Here, a report on diffusion tensor imaging (DTI) using a 125.3 MHz high-temperature superconducting (HTS) surface resonator for magnetic resonance imaging (MRI) is presented. A 40 mm in diameter Bi2Sr2Ca2Cu3Ox (Bi-2223) tape surface resonator was built. Using a HTS surface resonator at 77 K than a similar copper surface resonator at 300 K, the capacity to save the accuracy of

In-Tsang Lin; Hong-Chang Yang; Jyh-Horng Chen

2011-01-01

301

Magnetic resonance imaging pattern recognition in hypomyelinating disorders.  

PubMed

Hypomyelination is observed in the context of a growing number of genetic disorders that share clinical characteristics. The aim of this study was to determine the possible role of magnetic resonance imaging pattern recognition in distinguishing different hypomyelinating disorders, which would facilitate the diagnostic process. Only patients with hypomyelination of known cause were included in this retrospective study. A total of 112 patients with Pelizaeus-Merzbacher disease, hypomyelination with congenital cataract, hypomyelination with hypogonadotropic hypogonadism and hypodontia, Pelizaeus-Merzbacher-like disease, infantile GM1 and GM2 gangliosidosis, Salla disease and fucosidosis were included. The brain scans were rated using a standard scoring list; the raters were blinded to the diagnoses. Grouping of the patients was based on cluster analysis. Ten clusters of patients with similar magnetic resonance imaging abnormalities were identified. The most important discriminating items were early cerebellar atrophy, homogeneity of the white matter signal on T(2)-weighted images, abnormal signal intensity of the basal ganglia, signal abnormalities in the pons and additional T(2) lesions in the deep white matter. Eight clusters each represented mainly a single disorder (i.e. Pelizaeus-Merzbacher disease, hypomyelination with congenital cataract, hypomyelination with hypogonadotropic hypogonadism and hypodontia, infantile GM1 and GM2 gangliosidosis, Pelizaeus-Merzbacher-like disease and fucosidosis); only two clusters contained multiple diseases. Pelizaeus-Merzbacher-like disease was divided between two clusters and Salla disease did not cluster at all. This study shows that it is possible to separate patients with hypomyelination disorders of known cause in clusters based on magnetic resonance imaging abnormalities alone. In most cases of Pelizaeus-Merzbacher disease, hypomyelination with congenital cataract, hypomyelination with hypogonadotropic hypogonadism and hypodontia, Pelizaeus-Merzbacher-like disease, infantile GM1 and GM2 gangliosidosis and fucosidosis, the imaging pattern gives clues for the diagnosis. PMID:20881161

Steenweg, Marjan E; Vanderver, Adeline; Blaser, Susan; Bizzi, Alberto; de Koning, Tom J; Mancini, Grazia M S; van Wieringen, Wessel N; Barkhof, Frederik; Wolf, Nicole I; van der Knaap, Marjo S

2010-10-01

302

Magnetic resonance imaging pattern recognition in hypomyelinating disorders  

PubMed Central

Hypomyelination is observed in the context of a growing number of genetic disorders that share clinical characteristics. The aim of this study was to determine the possible role of magnetic resonance imaging pattern recognition in distinguishing different hypomyelinating disorders, which would facilitate the diagnostic process. Only patients with hypomyelination of known cause were included in this retrospective study. A total of 112 patients with Pelizaeus–Merzbacher disease, hypomyelination with congenital cataract, hypomyelination with hypogonadotropic hypogonadism and hypodontia, Pelizaeus–Merzbacher-like disease, infantile GM1 and GM2 gangliosidosis, Salla disease and fucosidosis were included. The brain scans were rated using a standard scoring list; the raters were blinded to the diagnoses. Grouping of the patients was based on cluster analysis. Ten clusters of patients with similar magnetic resonance imaging abnormalities were identified. The most important discriminating items were early cerebellar atrophy, homogeneity of the white matter signal on T2-weighted images, abnormal signal intensity of the basal ganglia, signal abnormalities in the pons and additional T2 lesions in the deep white matter. Eight clusters each represented mainly a single disorder (i.e. Pelizaeus–Merzbacher disease, hypomyelination with congenital cataract, hypomyelination with hypogonadotropic hypogonadism and hypodontia, infantile GM1 and GM2 gangliosidosis, Pelizaeus–Merzbacher-like disease and fucosidosis); only two clusters contained multiple diseases. Pelizaeus–Merzbacher-like disease was divided between two clusters and Salla disease did not cluster at all. This study shows that it is possible to separate patients with hypomyelination disorders of known cause in clusters based on magnetic resonance imaging abnormalities alone. In most cases of Pelizaeus–Merzbacher disease, hypomyelination with congenital cataract, hypomyelination with hypogonadotropic hypogonadism and hypodontia, Pelizaeus–Merzbacher-like disease, infantile GM1 and GM2 gangliosidosis and fucosidosis, the imaging pattern gives clues for the diagnosis.

Steenweg, Marjan E.; Vanderver, Adeline; Blaser, Susan; Bizzi, Alberto; de Koning, Tom J.; Mancini, Grazia M. S.; van Wieringen, Wessel N.; Barkhof, Frederik; Wolf, Nicole I.

2010-01-01

303

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

304

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.

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

2005-01-01

305

Retrorectal tumors in adults: Magnetic resonance imaging findings  

PubMed Central

AIM: To retrospectively evaluate the magnetic resonance imaging (MRI) features of adult retrorectal tumors and compare with histopathologic findings. METHODS: MRI features of 21 patients with preoperative suspicion of retrorectal tumors were analyzed based on the histopathological and clinical data. RESULTS: Fourteen benign cystic lesions appeared hypointense on T1-weighted images, and hyperintense on T2-weighted images with regular peripheral rim. Epidermoid or dermoid cysts were unilocular, and tailgut cysts were multilocular. Presence of intracystic intermediate signal intensity was observed in one case of tailgut cyst with a component of adenocarcinoma. Six solid tumors were malignant lesions and showed heterogeneous intensity on MRI. Mucinous adenocarcinomas showed high signal intensity on T2-weighted and mesh-like enhancing areas on fat-suppressed T2-weighted images. There was a fistula between the mass and anus with an internal opening in mucinous adenocarcinomas arising from anal fistula. Gastrointestinal stromal tumors displayed low signal intensity on T1-weighted images, and intermediate to high signal intensity on T2-weighted images. Central necrosis could be seen as a high signal on T2-weighted images. CONCLUSION: MRI is a helpful technique to define the extent of the retrorectal tumor and its relationship to the surrounding structures, and also to demonstrate possible complications so as to choose the best surgical approach.

Yang, Bo-Lin; Gu, Yun-Fei; Shao, Wan-Jin; Chen, Hong-Jin; Sun, Gui-Dong; Jin, Hei-Ying; Zhu, Xin

2010-01-01

306

Single Acquisition Quantitative Single Point Electron Paramagnetic Resonance Imaging  

PubMed Central

Purpose Electron paramagnetic resonance imaging (EPRI) has emerged as a promising non-invasive technology to dynamically image tissue oxygenation. Due to its extremely short spin-spin relaxation times, EPRI benefits from a single-point imaging (SPI) scheme where the entire FID signal is captured using pure phase encoding. However, direct T2*/pO2 quantification is inhibited due to constant magnitude gradients which result in time-decreasing FOV. Therefore, conventional acquisition techniques require repeated imaging experiments with differing gradient amplitudes (typically 3), which results in long acquisition time. Methods In this study, gridding was evaluated as a method to reconstruct images with equal FOV to enable direct T2*/pO2 quantification within a single imaging experiment. Additionally, an enhanced reconstruction technique that shares high spatial k-space regions throughout different phase encoding time delays was investigated (k-space extrapolation). Results The combined application of gridding and k-space extrapolation enables pixelwise quantification of T2* from a single acquisition with improved image quality across a wide range of phase encoding delay times. The calculated T2*/pO2 does not vary across this time range. Conclusion By utilizing gridding and k-space extrapolation, accurate T2*/pO2 quantification can be achieved within a single dataset to allow enhanced temporal resolution (by a factor of 3).

Jang, Hyungseok; Subramanian, Sankaran; Devasahayam, Nallathamby; Saito, Keita; Matsumoto, Shingo; Krishna, Murali C; McMillan, Alan B

2013-01-01

307

Magnetic resonance imaging signatures of vascular pathology in multiple sclerosis.  

PubMed

Venous vascular contributing factors to multiple sclerosis (MS) have been known for some time. Only recently has the scope of their potential role become more apparent with the theory of chronic cerebrospinal venous insufficiency (CCSVI). As research expands to further explore the role of vascular pathology in the MS population, it is expedient to review the evidence from an imaging perspective. In this paper, we review the current state-of-the-art methods using magnetic resonance imaging (MRI) as applied to imaging MS patients and CCSVI. This includes evaluating imaging signatures of vascular structure and flow as well as brain iron content. Upon review of the literature, we find that extracranial venous anomalies including stenosis, venous malformations, and collateralization of flow in the major veins of the neck have been observed to be prevalent in the MS population. Abnormal flow has been reported in MS patients both in major vessels using phase-contrast flow quantification and in the brain using perfusion-weighted imaging. We discuss the role of quantitative flow imaging and its potential in assessing possible biomarkers for abnormal flow. Finally, it has been suggested that the presence of high iron content may indirectly indicate progression of existing vascular pathology. To that end, we review the use of susceptibility-weighted imaging in monitoring iron in the thalamus, basal ganglia, and MS lesions. PMID:22971468

Utriainen, David; Trifan, Gabriela; Sethi, Sean; Elias, Saba; Hewett, Joseph; Feng, Wei; Haacke, E Mark

2012-10-01

308

Magnetic resonance imaging of the pelvic floor: from clinical to biomechanical imaging.  

PubMed

This article reviews the current role of magnetic resonance imaging in the study of the pelvic floor anatomy and pelvic floor dysfunction. The application of static and dynamic magnetic resonance imaging in the clinical context and for biomechanical simulation modeling is assessed, and the main findings are summarized. Additionally, magnetic resonance-based diffusion tensor imaging is presented as a potential tool to evaluate muscle fiber morphology. In this article, focus is set on pelvic floor muscle damage related to urinary incontinence and pelvic organ prolapse, sometimes as a consequence of vaginal delivery. Modeling applications that evaluate anatomical and physiological properties of pelvic floor are presented to further illustrate their particular characteristics. Finally, finite element method is described as a method for modeling and analyzing pelvic floor structures' biomechanical performance, based on material and behavioral properties of the tissues, and considering pressure loads that mimic real-life conditions such as active contraction or Valsalva maneuver. PMID:24030164

Brandão, Sofia; Da Roza, Thuane; Parente, Marco; Ramos, Isabel; Mascarenhas, Teresa; Natal Jorge, Renato M

2013-12-01

309

In vivo motion analysis of forearm rotation utilizing magnetic resonance imaging  

Microsoft Academic Search

Objective. To analyse in vivo normal forearm rotation utilizing the image processing method on axial magnetic resonance imaging.Design. Rotatory motion and translation of the radius and rotation of the ulna were analysed in vivo, utilizing features of the bone image; axial centre of gravity and axis of the bone.Methods. Axial magnetic resonance images at the proximal, middle and distal portion

T. Nakamura; Y. Yabe; Y. Horiuchi; N. Yamazaki

1999-01-01

310

Incidental pancreatic cysts: role of magnetic resonance imaging.  

PubMed

The widespread adoption of multidetector computed tomography and magnetic resonance imaging (MRI) for evaluation of intraabdominal pathology has resulted to a steady increase in the number of incidentally discovered pancreatic cysts in clinical practice during the last decades. The differential diagnosis of these cysts is broad including pseudocysts, serous cystic neoplasms, mucinous cystic neoplasms, and intraductal papillary mucinous neoplasms. The MRI has an important role both in the initial characterization of incidentally detected pancreatic cysts and the follow-up of these lesions and has become an integral part of the diagnostic algorithm for pancreatic cysts at many institutions. The inherent soft-tissue contrast of magnetic resonance cholangiopancreatography provides the vehicle for providing a specific diagnosis in many pancreatic cysts. Furthermore, an MRI-based characterization of pancreatic cysts allows for selection of those cysts that are more likely to benefit from endoscopic ultrasound and fine-needle aspiration for analysis of the fluid contents. Moreover, small asymptomatic incidental pancreatic cysts without concerning MRI features such as internal septae and/or nodularity may be safely followed with serial imaging. The lack of risk associated to repeated exposure to ionizing radiation and its ability to characterize pancreatic cysts are strong arguments for selecting MRI as the preferred imaging modality for following up these lesions. However, the recommendations for imaging follow-up continue to evolve, and several of the proposed guidelines are reviewed in this manuscript. PMID:24690615

Pinho, Daniella F; Rofsky, Neil M; Pedrosa, Ivan

2014-04-01

311

Evaluation of muscle injury using magnetic resonance imaging  

NASA Technical Reports Server (NTRS)

The objective of this study was to investigate spin echo T2 relaxation time changes in thigh muscles after intense eccentric exercise in healthy men. Spin echo and calculated T2 relaxation time images of the thighs were obtained on several occasions after exercise of one limb; the contralateral limb served as control. Muscle damage was verified by elevated levels of serum creatine kinase (CK). Thirty percent of the time no exercise effect was discernible on the magnetic resonance (MR) images. In all positive MR images (70%) the semitendinosus muscle was positive, while the biceps femoris, short head, and gracilis muscles were also positive in 50% and 25% of the total cases, respectively. The peak T2 relaxation time and serum CK were correlated (r = 0.94, p<0.01); temporal changes in muscle T2 relaxation time and serum CK were similar, although T2 relaxation time remained positive after serum CK returned to background levels. We conclude that magnetic resonance imaging can serve as a useful tool in the evaluation of eccentric exercise muscle damage by providing a quantitative indicator of damage and its resolution as well as the specific areas and muscles.

LeBlanc, A. D.; Jaweed, M.; Evans, H.

1993-01-01

312

Linear constraint minimum variance beamformer functional magnetic resonance inverse imaging  

PubMed Central

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

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

2011-01-01

313

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.

Cronin, Edmond M; Wilkoff, Bruce L

2012-01-01

314

New developments in magnetic resonance imaging of the nail unit.  

PubMed

The evolution of dedicated magnetic resonance imaging (MRI) musculoskeletal equipment allows new sequences and better images of the nail unit. The use of MRI has modified the imaging strategies used in treating inflammatory arthritis. In the case of psoriatic arthritis (PsA), the MRI study of the nail unit identifies nail involvement, which appears as an initial lesion for the induction of distal phalanx damage and consequently of distal interphalangeal joint arthritis. All patients with psoriasis, even in the absence of a clinically evident onychopathy, show characteristic MRI changes in the nail. This evidence could have a practical diagnostic value, because MRI study of the nail could document diagnosis in patients with undifferentiated spondyloarthropathies who have a barely evident psoriasis. We discuss the advantages and problems related to the use of low-field and high-field MRI in the study of the nail unit of patients with PsA. PMID:22751592

Soscia, Ernesto; Sirignano, Cesare; Catalano, Onofrio; Atteno, Mariangela; Costa, Luisa; Caso, Francesco; Peluso, Rosario; Bruner, Vincenzo; Aquino, Maria Maddalena; Del Puente, Antonio; Salvatore, Marco; Scarpa, Raffaele

2012-07-01

315

Applications of magnetic resonance imaging in food science.  

PubMed

The physical and chemical changes that occur in foods during growth, harvest, processing, storage, preparation, and consumption are often very difficult to measure and quantify. Magnetic resonance imaging (MRI) is a pioneering technology, originally developed in the medical field, that is now being used in a large number of disciplines to study a wide variety of materials and processes. In food science, MRI techniques allow the interior of foods to be imaged noninvasively and nondestructively. These images can then be quantified to yield information about several processes and material properties, such as mass and heat transfer, fat and ice crystallization, gelation, water mobidity, composition and volume changes, food stability and maturation, flow behavior, and temperature. This article introduces the fundamental principles of MRI, presents some of the recent advances in MRI technology, and reviews some of the current applications of MRI in food science research. PMID:8740439

Schmidt, S J; Sun, X; Litchfield, J B

1996-04-01

316

Tracking immune cells in vivo using magnetic resonance imaging  

PubMed Central

The increasing complexity of in vivo imaging technologies, coupled with the development of cell therapies, has fuelled a revolution in immune cell tracking in vivo. Powerful magnetic resonance imaging (MRI) methods are now being developed that use iron oxide- and 19F-based probes. These MRI technologies can be used for image-guided immune cell delivery and for the visualization of immune cell homing and engraftment, inflammation, cell physiology and gene expression. MRI-based cell tracking is now also being applied to evaluate therapeutics that modulate endogenous immune cell recruitment and to monitor emerging cellular immunotherapies. These recent uses show that MRI has the potential to be developed in many applications to follow the fate of immune cells in vivo.

Ahrens, Eric T.; Bulte, Jeff W. M.

2013-01-01

317

The role of magnetic resonance imaging in acute transverse myelitis.  

PubMed

Eighteen adult patients presenting with acute transverse myelitis (ATM) were evaluated using magnetic resonance imaging. Only 7 had abnormal scans showing an area of increased signal intensity within the cord solely on T2 weighted images; T1 weighted images were normal. The MRI abnormality did not correlate with the cause of the transverse myelitis, the extent of maximum neurological deficit, or the prognosis. A scan performed more than 5 days after the onset of disease was most likely to be positive. Even though the prognostic value of MRI in ATM may be limited, it remains a valuable technique for ruling out other causes of noncompressive spinal cord lesions, such as hemorrhage, vascular malformation, or tumor. PMID:1423048

Austin, S G; Zee, C S; Waters, C

1992-11-01

318

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

319

Neuroenteric cysts of the brain-comprehensive magnetic resonance imaging  

PubMed Central

Neuroenteric cysts are developmental cysts that should be differentiated from other, more common non-neoplastic cysts as well as cystic neoplasms. While these lesions may have varied imaging findings, T1 hyperintense prepontine lesion due to mucinous/proteinaceous content is characteristic. Location and imaging characteristics aid in formulating the correct diagnosis of neuroepithelial/neuroenteric cysts. Magnetic resonance spectroscopy (MRS) has the specific finding of N-Acetyl Aspartate (NAA)-like peak at 2.02 ppm which is not seen in other cystic lesions. In this study, we aim to discuss the imaging findings of these lesions on conventional and advanced MRI findings and provide radiologic-pathologic correlation. We also briefly describe the pathogenesis, embryology and radiological differential diagnoses of these cysts.

Hingwala, Divyata R; Radhakrishnan, Neelima; Kesavadas, Chandrasekharan; Thomas, Bejoy; Kapilamoorthy, Tirur Raman; Radhakrishnan, Vishnupuri V

2013-01-01

320

Cardiac magnetic resonance imaging in Alstr?m syndrome  

PubMed Central

Background A case series of the cardiac magnetic resonance imaging findings in seven adult Alström patients. Methods Seven patients from the National Specialist Commissioning Group Centre for Alström Disease, Torbay, England, UK, completed the cardiac magnetic resonance imaging protocol to assess cardiac structure and function in Alström cardiomyopathy. Results All patients had some degree of left and right ventricular dysfunction. Patchy mid wall gadolinium delayed enhancement was demonstrated, suggesting an underlying fibrotic process. Some degree of cardiomyopathy was universal. No evidence of myocardial infarction or fatty infiltration was demonstrated, but coronary artery disease cannot be completely excluded. Repeat scanning after 18 months in one subject showed progression of fibrosis and decreased left ventricular function. Conclusion Adult Alström cardiomyopathy appears to be a fibrotic process causing impairment of both ventricles. Serial cardiac magnetic resonance scanning has helped clarify the underlying disease progression and responses to treatment. Confirmation of significant mutations in the ALMS1 gene should lead to advice to screen the subject for cardiomyopathy, and metabolic disorders.

Loudon, Margaret A; Bellenger, Nicholas G; Carey, Catherine M; Paisey, Richard B

2009-01-01

321

Molecular Imaging in Cardiovascular Magnetic Resonance Imaging: Current Perspective and Future Potential  

PubMed Central

The development of novel imaging agents and techniques is allowing some biological events to be imaged in vivo with magnetic resonance imaging (MRI) at the cellular and subcellular level. In this paper, the use of novel gadolinium chelates and superparamagnetic iron oxide nanoparticles for molecular MRI of the cardiovascular system is extensively reviewed. The physical properties of these imaging agents and the pulse sequences best suited to their visualization are extensively discussed. The application of molecular MRI in diseases of the vasculature and myocardium is then reviewed. The clinical experience to date, as well as the promise and potential impact of molecular MRI, is extensively discussed.

Sosnovik, David E.

2008-01-01

322

Magnetic resonance imaging of the rhesus monkey brain: use for stereotactic neurosurgery  

Microsoft Academic Search

Standard stereotactic procedures rely upon external cranial landmarks and standardized atlases for localization of subcortical neural regions. Magnetic resonance imaging permits the visualization of the neural structure of the brain in vivo. A stereotactic instrument compatible with a magnetic resonance unit was constructed and together with magnetic resonance imaging a procedure was developed that overcomes the limitations and inaccuracies of

R. C. Saunders; T. G. Aigner; J. A. Frank

1990-01-01

323

Evaluation of myocardial viability with cardiac magnetic resonance imaging.  

PubMed

Assessment of myocardial viability is of clinical and scientific significance. Traditionally, the detection of myocardial viability (either stunning or hibernation) has been used in aiding diagnosis before revascularization, especially in high-risk patients. There is a considerable body of observational evidence showing substantial improvement after revascularization in patients with significant left ventricular dysfunction and myocardial viability. Recent randomized evidence has questioned the benefit of viability testing but must be interpreted with caution. Dobutamine stress echocardiography, nuclear imaging, and cardiovascular magnetic resonance are the mainstays of viability testing and provide information on contractile function, cellular metabolism, and myocardial fibrosis, respectively. Larger, multicenter trials with outcome data are needed to define the nature of viability testing and, particularly, cardiovascular magnetic resonance in moderate-to-severe ischemic cardiomyopathy. PMID:22014488

Grover, Suchi; Srinivasan, Govindarajan; Selvanayagam, Joseph B

2011-01-01

324

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

325

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

326

High pressure magnetic resonance imaging with metallic vessels  

NASA Astrophysics Data System (ADS)

High pressure measurements in most scientific fields rely on metal vessels given the superior tensile strength of metals. We introduce high pressure magnetic resonance imaging (MRI) measurements with metallic vessels. The developed MRI compatible metallic pressure vessel concept is very general in application. Macroscopic physical systems are now amenable to spatially resolved nuclear magnetic resonance (NMR) study at variable pressure and temperature. Metallic pressure vessels not only provide inherently high tensile strengths and efficient temperature control, they also permit optimization of the MRI RF probe sensitivity. An MRI compatible pressure vessel is demonstrated with a rock core holder fabricated using non-magnetic stainless steel. Water flooding through a porous rock under pressure is shown as an example of its applications. High pressure NMR spectroscopy plays an indispensable role in several science fields. This work will open new vistas of study for high pressure material science MRI and MR.

Han, Hui; Ouellette, Matthew; MacMillan, Bryce; Goora, Frederic; MacGregor, Rodney; Green, Derrick; Balcom, Bruce J.

2011-12-01

327

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

328

Breast imaging technology: Application of magnetic resonance imaging to angiogenesis in breast cancer  

PubMed Central

Magnetic resonance imaging (MRI) techniques enable vascular function to be mapped with high spatial resolution. Current methods for imaging in breast cancer are described, and a review of recent studies that compared dynamic contrast-enhanced MRI with histopathological indicators of tumour vascular status is provided. These studies show correlation between in vivo dynamic contrast measurements and in vitro histopathology. Dynamic contrast enhanced MRI is also being applied to assessment of the response of breast tumours to treatment.

Leach, Martin O

2001-01-01

329

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.

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

2012-01-01

330

Review of Magnetic Resonance Imaging with Application to Neural Tissue Tractography  

Microsoft Academic Search

Magnetic resonance imaging (MRI) provides an exquisitely probe of neural tissue structure in vivo. In this paper, the foundations and characteristics of different imaging approaches are reviewed, such as diffusion tensor imaging (DTI), Q-space imaging (QSI), high angular resolution diffusion imaging (HARDI) and Q-ball imaging (QBI), and so on. Wherein, the basic theory, visualization, and reconstruction technology of DTI and

Jie Zhou; Shan Jiang; Meiyun Zhang; Jie Lin

2008-01-01

331

New approach for analyzing magnetic resonance elastography images  

NASA Astrophysics Data System (ADS)

A new method for evaluating Magnetic Resonance Elastography (MRE) wave images is introduced, which consists of both local frequency estimation (LFE) and simulation of wave patterns by a coupled harmonic oscillator (CHO) approach. It is shown that i) LFE performs improved reconstruction by use of Gauss filters and ii) CHO calculations can help to refine the resulting wave speed or elasticity map by taking local attenuation, reflection, and diffraction into account. The performance of new LFE and CHO calculations is demonstrated by MRE experiments on a gel phantom as well as by simulations of shear waves in a brain phantom, such as for potential in-vivo MRE-experiments.

Sack, Ingolf; Buntkowsky, Gerd; Bernarding, Johannes; Tolxdorff, Thomas; Braun, Juergen

2001-06-01

332

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

333

Langevin equation approach to diffusion magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

The normal phase diffusion problem in magnetic resonance imaging (MRI) is treated by means of the Langevin equation for the phase variable using only the properties of the characteristic function of Gaussian random variables. The calculation may be simply extended to anomalous diffusion using a fractional generalization of the Langevin equation proposed by Lutz [E. Lutz, Phys. Rev. E 64, 051106 (2001)] pertaining to the fractional Brownian motion of a free particle coupled to a fractal heat bath. The results compare favorably with diffusion-weighted experiments acquired in human neuronal tissue using a 3 T MRI scanner.

Cooke, Jennie M.; Kalmykov, Yuri P.; Coffey, William T.; Kerskens, Christian M.

2009-12-01

334

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

335

Medial temporal cortices in ex vivo magnetic resonance imaging.  

PubMed

This review focuses on the ex vivo magnetic resonance imaging (MRI) modeling of medial temporal cortices and associated structures, the entorhinal verrucae and the perforant pathway. Typical in vivo MRI has limited resolution due to constraints on scan times and does not show laminae in the medial temporal lobe. Recent studies using ex vivo MRI have demonstrated lamina in the entorhinal, perirhinal, and hippocampal cortices. These studies have enabled probabilistic brain mapping that is based on the ex vivo MRI contrast, validated to histology, and subsequently mapped onto an in vivo spherically warped surface model. Probabilistic maps are applicable to other in vivo studies. PMID:23881818

Augustinack, Jean C; van der Kouwe, André J W; Fischl, Bruce

2013-12-15

336

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.

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

2009-01-01

337

The use of magnetic resonance imaging in the obstetric patient.  

PubMed

Objective: To review the biological effects and safety of magnetic resonance imaging (MRI) in the obstetric patient and to review procedural issues, indications, and contraindications for obstetrical MRI. Outcomes: This guideline is intended to reassure patients and clinicians of the safety of MRI in pregnancy and to provide a framework for its use. Evidence: Published literature was retrieved through searches of PubMed or Medline in 2013 using controlled vocabulary and key words (e.g., MRI, safety, pregnancy). Results were restricted to systematic reviews, randomized control trials/controlled clinical trials, and observational studies published in English and in French. There were no date restrictions. Searches were updated on a regular basis and incorporated in the guideline to July 2013. Grey (unpublished) literature was identified through searching the websites of health technology assessment and health technology-related agencies, clinical practice guideline collections, clinical trial registries, and national and international medical specialty societies. Values: The quality of evidence in this document was rated using the criteria described in the Report of the Canadian Task Force on Preventive Health Care (Table). Benefits, harms, and costs: This article is intended to reassure obstetric care providers that if used in an appropriate manner without the use of contrast agents, MRI in the obstetrical patient is safe for mother and fetus in the second and third trimesters. Because obstetrical MRI is expensive and has limited availability in Canada, this clinical guideline is intended to encourage the judicious use of this resource. Summary Statements 1. Fetal magnetic resonance imaging is safe at 3.0 tesla or less during the second and third trimesters. (II-2) 2. It is safe to continue breastfeeding after receiving a gadolinium contrast agent. (III) Recommendations 1. Use of magnetic resonance imaging during the first trimester of pregnancy should be restricted to maternal indications for which the information is considered clinically imperative. Inadvertent exposure to magnetic resonance imaging during the first trimester has not been associated with any long-term sequelae and should not raise clinical concern. (III-C) 2. Gadolinium contrast may be used in pregnant women when the benefits outweigh the potential risks. (III-C). PMID:24798674

Patenaude, Yves; Pugash, Denise; Lim, Kenneth; Morin, Lucie; Lim, Kenneth; Bly, Stephen; Butt, Kimberly; Cargill, Yvonne; Davies, Gregory; Denis, Nanette; Hazlitt, Gail; Morin, Lucie; Naud, Kentia; Ouellet, Annie; Salem, Shia

2014-04-01

338

Magnetic resonance imaging in Löfgren's syndrome: demonstration of periarthritis.  

PubMed

In Löfgren's syndrome, pain and swelling commonly involves the ankle joints. In this prospective case series, the magnetic resonance imaging findings of ankle joint involvement are described. Extensive subcutaneous and soft tissue oedema was commonly seen around the ankles. Bone, cartilage, ligaments and tendons were typically uninvolved. Small amounts of joint and tenosynovial fluid were present without evidence of synovial thickening or synovitis. The fluid is probably reactive to adjacent inflammation in the para-articular soft tissues and probably not representing a primary site of involvement. These findings demonstrate that the arthritis in Löfgren's syndrome stems primarily from periarthritis. This is consistent with prior descriptions using ultrasonography. PMID:16897117

Anandacoomarasamy, Ananthila; Peduto, Anthony; Howe, Graydon; Manolios, Nicholas; Spencer, David

2007-04-01

339

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.

Bauman, Grzegorz; Eichinger, Monika

2012-01-01

340

Automated Brain Extraction from T2-weighted Magnetic Resonance Images  

PubMed Central

Purpose To develop and implement an automated and robust technique to extract brain from T2-weighted images. Materials and Methods Magnetic resonance imaging (MRI) was performed on 75 adult volunteers to acquire dual fast spin echo (FSE) images with fat-saturation technique on a 3T Philips scanner. Histogram-derived thresholds were derived directly from the original images followed by the application of regional labeling, regional connectivity, and mathematical morphological operations to extract brain from axial late-echo FSE (T2-weighted) images. The proposed technique was evaluated subjectively by an expert and quantitatively using Bland-Altman plot and Jaccard and Dice similarity measures. Results Excellent agreement between the extracted brain volumes with the proposed technique and manual stripping by an expert was observed based on Bland-Altman plot and also as assessed by high similarity indices (Jaccard: 0.9825± 0.0045; Dice: 0.9912 ±0.0023). Conclusion Brain extraction using proposed automated methodology is robust and the results are reproducible.

Datta, Sushmita; Narayana, Ponnada A.

2011-01-01

341

Off-center magnetic resonance imaging with permanent magnets  

NASA Astrophysics Data System (ADS)

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

Abele, Manlio G.; Rusinek, Henry

2008-04-01

342

Intensity Inhomogeneity Correction of Magnetic Resonance Images using Patches  

PubMed Central

This paper presents a patch-based non-parametric approach to the correction of intensity inhomogeneity from magnetic resonance (MR) images of the human brain. During image acquisition, the inhomogeneity present in the radio-frequency coil, is usually manifested on the reconstructed MR image as a smooth shading effect. This artifact can significantly deteriorate the performance of any kind of image processing algorithm that uses intensities as a feature. Most of the current inhomogeneity correction techniques use explicit smoothness assumptions on the inhomogeneity field, which sometimes limit their performance if the actual inhomogeneity is not smooth, a problem that becomes prevalent in high fields. The proposed patch-based inhomogeneity correction method does not assume any parametric smoothness model, instead, it uses patches from an atlas of an inhomogeneity-free image to do the correction. Preliminary results show that the proposed method is comparable to N3, a current state of the art method, when the inhomogeneity is smooth, and outperforms N3 when the inhomogeneity contains non-smooth elements.

Roy, Snehashis; Carass, Aaron; Bazin, Pierre-Louis; Prince, Jerry L.

2014-01-01

343

Magnetic resonance imaging in neonates with total asphyxia.  

PubMed

Magnetic resonance (MR) findings in cases of total asphyxia, whose lesions are mainly in the brainstem and deep nuclei, have not been clarified. In this study, we investigated MR images in neonates with total asphyxia. MR images of six infants (three males and three females; gestational age, 35-39 weeks; birth weights, 1880-3572 g) with total asphyxia were examined. In all subjects, neonatal cortical MR lesions were limited to the hippocampus with highlighting on T1-weighted imaging (T1-WI). The neonatal MR lesions of the cerebral white matter were limited to the white matter between the insula and putamen in four infants, and were diffusely involved in two infants. The ventral lateral nucleus of the thalamus was hyperintense on T1-WI in all of the subjects. Other nuclei in the thalamus, the globus pallidus and the putamen were involved in neonatal MR images of all subjects. High intensity areas on T2- weighted imaging were observed at the dorsal areas in the midbrain, pons and medulla oblongata in all or most of the subjects at the neonatal period. Also, high intensity areas on T1-WI were observed in the tegmentum of the pons and the midbrain in five cases. Neonates with total asphyxia had lesions mainly in the tegmentem of the brainstem, thalamus, putamen and globus palludus. Some of the infants had extensive lesions of the white matter. PMID:22583740

Sugiura, Hiroshi; Kouwaki, Masanori; Kato, Tohru; Ogata, Tsutomu; Sakamoto, Rie; Ieshima, Atsushi; Yokochi, Kenji

2013-01-01

344

Signal and noise estimation from magnetic resonance images  

NASA Astrophysics Data System (ADS)

This thesis deals with the estimation of noise and signal from Magnetic Resonance (MR) images with a special reference to magnitude MR images. Furthermore, the estimation and improvement of the image signal-to-noise ratio (SNR) and an application to 3D segmentation is discussed. In order to process experimental data in a scientifically justified manner, knowledge of the underlying probability density function (PDF) is indispensable. Therefore, the PDF's of raw as well as processed (i.e., magnitude and phase) MR data are derived to serve as a basis for solving of various estimation problems. The estimation problems include estimation of noise and signal from MR data. Conventional estimation techniques are compared to the Maximum Likelihood (ML) estimation method where use is made of the specific PDF characterizing the MR data. It is shown that conventional estimation methods often yield biased results. In addition, it is shown how the knowledge of the proper PDF can be used to systematic errors during estimation. Applications discussed include the estimation of T1 and T2 maps. Also, an efficient and accurate method for the estimation and improvement of the image SNR is proposed, based on the cross-correlation of two realizations of the same image. Finally, a new segmentation technique is described, which was developed for precise and accurate volume quantization from 3D MR data. Several applications are discussed.

Sijbers, Jan

345

Quantitative Magnetic Resonance Imaging of 3-He Gas Transport  

NASA Astrophysics Data System (ADS)

In magnetic resonance (MR) imaging the use of laser-polarized 3-He dramatically increases detection sensitivity and facilitates gas visualization. Here, the potential use of 3-He MR imaging for quantifying gas transport in the respiratory tract of laboratory rodents is examined by studying laminar flow in a straight pipe with a diameter comparable to the rat trachea (˜ 3.2 mm). At physiological flow rates (˜ 4 ml/s), laminar-like features are observed in 2D images of axial diffusion, and the structure of observed flow lamina differs significantly from predictions based on the Navier-Stokes equations. To reconcile these results, we formulate a statistical model of gas transport that accounts for Brownian motion on the imaging time scale. The model uses the 2D solution to the diffusion equation to describe how diffusing gas molecules sample the stationary flow field. The effects on MR measurements are then formulated in terms of the mean flow velocity, higher order correlation functions, and the details of data acquisition. Comparison between modeling and experiment shows that MR imaging results are accurately predicted for different gas mixtures and acquisition conditions. The model is generally applicable to any flow conduit, resulting in a quantitative basis for noninvasive gas transport studies.

Jacob, Richard E.; Minard, Kevin R.

2007-03-01

346

A probabilistic neural network based image segmentation network for magnetic resonance images  

Microsoft Academic Search

A network structure for segmenting magnetic resonance medical images is proposed. The incorporation of a probabilistic neural network structure into the segmentation process allows decisions regarding the characterization of each pixel to be made in a probabilistic manner, thus reducing the effect of an incorrect decision early in the process on the final segmentation result. The probabilistic neural network facilitates

M. Morrison; Y. Attikiouzel

1992-01-01

347

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

Microsoft Academic Search

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

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

2001-01-01

348

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

349

Direct Neural Imaging using Ultra-Low Field Magnetic Resonance  

NASA Astrophysics Data System (ADS)

An enduring challenge in neuroscience is the accurate in vivo mapping of neural activity with high spatial and temporal resolution. A method being developed by our group tries to meet this challenge by using Ultra-Low Field (ULF) MRI. Other groups have attempted direct neural imaging (DNI) using high field MRI. However, the use of ULF presents two advantages. First, the susceptibility artifact at high fields, which masks the DNI signal, is negligible at low fields. Second, the reduced Larmor frequency at ULF may overlap with the frequency spectrum of the neural magnetic field, resonantly enhancing the MRI signal. In this presentation, I will first show our custom-built ULF MRI setups that have successfully produced ULF anatomical images. I will then highlight the numerous studies we have done to investigate the feasibility of DNI with these systems, including both experimental and theoretical studies.

Maskaly, Karlene; Espy, Michelle; Flynn, Mark; Gomez, John; Kraus, Robert; Matlashov, Andrei; Mosher, John; Newman, Shaun; Owens, Tuba; Peters, Mark; Sandin, J.; Schultz, Larry; Urbaitis, Algis; Volegov, Petr; Zotev, Vadim

2009-03-01

350

Cardiovascular Magnetic Resonance Imaging of Myocardial Infarction, Viability, and Cardiomyopathies  

PubMed Central

Cardiovascular magnetic resonance provides the opportunity for a truly comprehensive evaluation of patients with a history of MI, with regards to characterizing the extent of disease, impact on LV function and degree of viable myocardium. The use of contrast-enhanced CMR for first-pass perfusion and late gadolinium enhancement is a powerful technique for delineating areas of myocardial ischemia and infarction. Using a combination of T2-weighted and contrast-enhanced CMR images, information about the acuity of an infarct can be obtained. There is an extensive amount of literature using contrast-enhanced CMR to predict myocardial functional recovery with revascularization in patients with ischemic cardiomyopathies. In addition, CMR imaging in patients with cardiomyopathies can distinguish between ischemic and non-ischemic etiologies, with the ability to further characterize the underlying pathology for non-ischemic cardiomyopathies.

West, Amy M.; Kramer, Christopher M.

2010-01-01

351

Magnetic resonance imaging of acute symptomatic Schmorl's node formation.  

PubMed

The intraspongious herniation of intervertebral disk material into the endplate of a vertebral body was first described by Schmorl in 1927. Any process which weakens the cartilaginous endplate or the subchondral cancellous bone may predispose to the development of Schmorl's nodes. These include Scheuermann's disease, infection, metabolic disorders, neoplastic disorders, and degenerative disease. In the young individual, however, trauma may precipitate an acute focal and symptomatic endplate herniation by the well-hydrated and delineated nucleus pulposus. Magnetic resonance imaging (MRI) is the most sensitive imaging method for the detection of intervertebral disk disease and, thus, has facilitated the diagnosis of traumatic Schmorl's nodes. MRI was very helpful in diagnosing an acute, traumatic, symptomatic Schmorl's node when plain film radiographs and nuclear medicine bone scan were unremarkable. PMID:1754491

Walters, G; Coumas, J M; Akins, C M; Ragland, R L

1991-10-01

352

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

353

Simultaneous Magnetic Resonance Imaging and Consolidation Measurement of Articular Cartilage  

PubMed Central

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.

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

2014-01-01

354

Statistical reconstruction algorithms for continuous wave electron spin resonance imaging.  

PubMed

Electron spin resonance imaging (ESRI) is an important branch of ESR that deals with heterogeneous samples ranging from semiconductor materials to small live animals and even humans. ESRI can produce either spatial images (providing information about the spatially dependent radical concentration) or spectral-spatial images, where an extra dimension is added to describe the absorption spectrum of the sample (which can also be spatially dependent). The mapping of oxygen in biological samples, often referred to as oximetry, is a prime example of an ESRI application. ESRI suffers frequently from a low signal-to-noise ratio (SNR), which results in long acquisition times and poor image quality. A broader use of ESRI is hampered by this slow acquisition, which can also be an obstacle for many biological applications where conditions may change relatively quickly over time. The objective of this work is to develop an image reconstruction scheme for continuous wave (CW) ESRI that would make it possible to reduce the data acquisition time without degrading the reconstruction quality. This is achieved by adapting the so-called "statistical reconstruction" method, recently developed for other medical imaging modalities, to the specific case of CW ESRI. Our new algorithm accounts for unique ESRI aspects such as field modulation, spectral-spatial imaging, and possible limitation on the gradient magnitude (the so-called "limited angle" problem). The reconstruction method shows improved SNR and contrast recovery vs. commonly used back-projection-based methods, for a variety of simulated synthetic samples as well as in actual CW ESRI experiments. PMID:23644350

Kissos, Imry; Levit, Michael; Feuer, Arie; Blank, Aharon

2013-06-01

355

Narrow band deformable registration of prostate magnetic resonance imaging, magnetic resonance spectroscopic imaging, and computed tomography studies  

SciTech Connect

Purpose: Endorectal (ER) coil-based magnetic resonance imaging (MRI) and magnetic resonance spectroscopic imaging (MRSI) is often used to obtain anatomic and metabolic images of the prostate and to accurately identify and assess the intraprostatic lesions. Recent advancements in high-field (3 Tesla or above) MR techniques affords significantly enhanced signal-to-noise ratio and makes it possible to obtain high-quality MRI data. In reality, the use of rigid or inflatable endorectal probes deforms the shape of the prostate gland, and the images so obtained are not directly usable in radiation therapy planning. The purpose of this work is to apply a narrow band deformable registration model to faithfully map the acquired information from the ER-based MRI/MRSI onto treatment planning computed tomography (CT) images. Methods and Materials: A narrow band registration, which is a hybrid method combining the advantages of pixel-based and distance-based registration techniques, was used to directly register ER-based MRI/MRSI with CT. The normalized correlation between the two input images for registration was used as the metric, and the calculation was restricted to those points contained in the narrow bands around the user-delineated structures. The narrow band method is inherently efficient because of the use of a priori information of the meaningful contour data. The registration was performed in two steps. First, the two input images were grossly aligned using a rigid registration. The detailed mapping was then modeled by free form deformations based on B-spline. The limited memory Broyden-Fletcher-Goldfarb-Shanno algorithm (L-BFGS), which is known for its superior performance in dealing with high-dimensionality problems, was implemented to optimize the metric function. The convergence behavior of the algorithm was studied by self-registering an MR image with 100 randomly initiated relative positions. To evaluate the performance of the algorithm, an MR image was intentionally distorted, and an attempt was then made to register the distorted image with the original one. The ability of the algorithm to recover the original image was assessed using a checkerboard graph. The mapping of ER-based MRI onto treatment planning CT images was carried out for two clinical cases, and the performance of the registration was evaluated. Results: A narrow band deformable image registration algorithm has been implemented for direct registration of ER-based prostate MRI/MRSI and CT studies. The convergence of the algorithm was confirmed by starting the registration experiment from more than 100 different initial conditions. It was shown that the technique can restore an MR image from intentionally introduced deformations with an accuracy of approximately 2 mm. Application of the technique to two clinical prostate MRI/CT registrations indicated that it is capable of producing clinically sensible mapping. The whole registration procedure for a complete three-dimensional study (containing 256 x 256 x 64 voxels) took less than 15 min on a standard personal computer, and the convergence was usually achieved in fewer than 100 iterations. Conclusions: A deformable image registration procedure suitable for mapping ER-based MRI data onto planning CT images was presented. Both hypothetical tests and patient studies have indicated that the registration is reliable and provides a valuable tool to integrate the ER-based MRI/MRSI information to guide prostate radiation therapy treatment.

Schreibmann, Eduard [Department of Radiation Oncology, Stanford University School of Medicine Stanford, CA (United States); Xing Lei [Department of Radiation Oncology, Stanford University School of Medicine Stanford, CA (United States)]. E-mail: lei@reyes.stanford.edu

2005-06-01

356

Magnetic resonance imaging of the shoulder in patients with rheumatoid arthritis  

Microsoft Academic Search

To evaluate the ability of magnetic resonance imaging (MRI) to detect shoulder abnormalities 18 patients (36 shoulders) with rheumatoid arthritis (RA) and shoulder complaints were studied. Osseous abnormalities of the glenoid and humeral head were readily detected with MRI. The imaging planes used were not suitable for the evaluation of acromioclavicular joint involvement. Magnetic resonance imaging depicted soft tissue abnormalities

G J Kieft; B A Dijkmans; J L Bloem; H M Kroon

1990-01-01

357

Phantom design for the validation of diffusion magnetic resonance imaging in brain white matter  

Microsoft Academic Search

Diffusion magnetic resonance imaging is a non-invasive imag- ing technique that can measure the self-diffusion of water molecules in all directions. This imaging modality enables the visualization of brain white matter, which consists of neuronal fibers and is responsible for the regula- tion of the human nerve system. To determine the accuracy and precision of diffusion magnetic resonance in vivo,

Els Fieremans; Yves De Deene; Ignace Lemahieu

358

Advances in magnetic resonance imaging: cine MRI and flow velocity mapping  

Microsoft Academic Search

Magnetic resonance imaging is a powerful tool for evaluating the variety of abnormalities that occur in congenital heart disease. Specific morphological queries regarding arterial and venous connections, thoracic and visceral situs, valvar relationships and great vessel anatomy can be answered in great detail with standard spin-echo imaging techniques. The continuing technological development of magnetic resonance imaging, however, has allowed analysis

Scott D. Flamm; Douglas S. Moodie

1997-01-01

359

Flow-sensitive four-dimensional magnetic resonance imaging: flow patterns in ascending aortic aneurysms  

Microsoft Academic Search

Objective: Pathological aortic flow patterns differ significantly from haemodynamics within the healthy aorta. Development and impact of pathological flow is largely unknown and might affect pathogenesis and the progression of thoracic aortic diseases. This study presents pathological blood-flow patterns within a series of six patients suffering from ascending aortic aneurysms investigated with high-detail flow-sensitive, four-dimensional (4D)-MRI and three-dimensional (3D) computer-aided

Ernst Weigang; Fabian A. Kari; Friedhelm Beyersdorf; Maximilian Luehr; Christian D. Etz; Alex Frydrychowicz; Andreas Harloff; Michael Markl

2008-01-01

360

Neuropathologic correlates of magnetic resonance imaging in multiple sclerosis.  

PubMed

The advent of magnetic resonance imaging (MRI) has revolutionized concepts of the pathogenesis of multiple sclerosis (MS). Magnetic resonance imaging provides the ability to delineate the evolution of the disease process over time; captured static snapshots can then be used in pathologic correlations studies. Certain patterns in the 2- or 3-dimensional MRI sphere correlate very well with similar patterns of histopathology. A multimodality approach that makes use of numerous MRI techniques can lead to significant insights into the nature of the changes in the CNS. MRI-pathology correlation studies in MS are being performed using newer MRI techniques as they become available. Such correlations and basic histopathologic studies have shown abnormalities in MS far beyond the well-documented changes in the plaque and have brought into question the dogma that MS is an initially inflammatory nondegenerative disease. This review briefly outlines technical considerations in MRI-pathology correlative studies and describes the past and current status of our ability to correlate focal and diffuse changes on the MRI with neuropathologic findings in MS patients. PMID:22892523

Moore, G R Wayne; Laule, Cornelia

2012-09-01

361

The physics of functional magnetic resonance imaging (fMRI)  

NASA Astrophysics Data System (ADS)

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

Buxton, Richard B.

2013-09-01

362

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

363

Magnetic resonance imaging of interstitial laser photocoagulation in brain.  

PubMed

Magnetic resonance (MR) imaging can be used to monitor the development of thermal lesions induced in tissue using interstitial laser photocoagulation (ILP). A potential application for ILP is the treatment of surgically inaccessible brain tumors. For the successful clinical application of MR-monitored ILP, it is necessary to relate MR images of ILP lesions to the actual induced lesions. In this preliminary study we performed ILP in the normal brains of anesthetized cats by delivering interstitially 1.0, 1.5, and 2.0 W of continuous-wave Nd:YAG laser energy (1,064 nm) for 1,000 s via a plane-cut 400 microns core optical fiber. At 48 h post-irradiation the lesions consisted of four sharply demarcated concentric zones of thermal damage. Lesion diameter increased linearly with delivered power. T2-weighted proton spin-echo images acquired during ILP showed a region of complete or near signal loss that underestimated the actual lesion at 48 h. Gadolinium-enhanced T1-weighted spin-echo images acquired immediately post-irradiation showed the actual lesion precisely. PMID:1573967

Tracz, R A; Wyman, D R; Little, P B; Towner, R A; Stewart, W A; Schatz, S W; Pennock, P W; Wilson, B C

1992-01-01

364

The role of magnetic resonance imaging in scaphoid fractures.  

PubMed

Fractures of the scaphoid are the most common surgically treated carpal fracture, and early diagnosis is critical to minimize complications including osteonecrosis. If the initial radiographs after the injury are inconclusive, early magnetic resonance imaging (MRI) provides an immediate diagnosis to allow for proper management. This has been shown to be cost effective both in direct measureable costs and likely in difficult-to-measure indirect costs related to lost productivity. In the cases in which no scaphoid fracture is present, MRI provides alternate diagnoses such as identification of other fractures (eg, other carpals and distal radius), osseous contusions, and soft tissue injuries (preferably ? 1.5T). When MRI is contraindicated, computed tomography (CT) is a reasonable alternative after the initial and repeat negative radiographs. MRI is the best imaging modality for assessing osteonecrosis of the proximal pole in a scaphoid nonunion. Unfortunately, the most useful imaging sequences remain controversial. My institution relies on the noncontrast T1-weighted images for the primary diagnosis of osteonecrosis with dynamic contrast enhancement used in a supplemental fashion. PMID:24079527

Murthy, Naveen S

2013-10-01

365

Magnetic resonance-guided positron emission tomography image reconstruction.  

PubMed

The resolution of positron emission tomography (PET) images is limited by the physics of positron-electron annihilation and instrumentation for photon coincidence detection. Model-based methods that incorporate accurate physical and statistical models have produced significant improvements in reconstructed image quality when compared with filtered backprojection reconstruction methods. However, it has often been suggested that by incorporating anatomical information, the resolution and noise properties of PET images could be further improved, leading to better quantitation or lesion detection. With the recent development of combined MR-PET scanners, we can now collect intrinsically coregistered magnetic resonance images. It is therefore possible to routinely make use of anatomical information in PET reconstruction, provided appropriate methods are available. In this article, we review research efforts over the past 20 years to develop these methods. We discuss approaches based on the use of both Markov random field priors and joint information or entropy measures. The general framework for these methods is described, and their performance and longer-term potential and limitations are discussed. PMID:23178087

Bai, Bing; Li, Quanzheng; Leahy, Richard M

2013-01-01

366

Fluorescence resonance energy transfer imaging by maximum likelihood estimation  

NASA Astrophysics Data System (ADS)

Fluorescence resonance energy transfer (FRET) is a fluorescence microscope imaging process involving nonradiative energy transfer between two fluorophores (the donor and the acceptor). FRET is used to detect the chemical interactions and, in some cases, measure the distance between molecules. Existing approaches do not always well compensate for bleed-through in excitation, cross-talk in emission detection and electronic noise in image acquisition. We have developed a system to automatically search for maximum-likelihood estimates of the FRET image, donor concentration and acceptor concentration. It also produces other system parameters, such as excitation/emission filter efficiency and FRET conversion factor. The mathematical model is based upon a Poisson process since the CCD camera is a photon-counting device. The main advantage of the approach is that it automatically compensates for bleed-through and cross-talk degradations. Tests are presented with synthetic images and with real data referred to as positive and negative controls, where FRET is known to occur and to not occur, respectively. The test results verify the claimed advantages by showing consistent accuracy in detecting FRET and by showing improved accuracy in calculating FRET efficiency.

Zhang, Yupeng; Yuan, Yumin; Holmes, Timothy J.

2004-06-01

367

Magnetic resonance imaging of microvessels using iron-oxide nanoparticles  

NASA Astrophysics Data System (ADS)

The visualization of microstructures including blood vessels with an inner overall cross-sectional area below approximately 200 ?m remains beyond the capabilities of current clinical imaging modalities. But with magnetic resonance (MR) imaging, magnetic entities cause susceptibility artifacts in the images by disrupting the homogeneous magnetic field in a much larger scale than their actual size. As validated in this paper through simulation and in-vitro experiments, these artifacts can serve as a source of contrast, enabling microvessels with an inner diameter below the spatial resolution of any medical imaging modalities to be visualized using a clinical MR scanner. For such experiments, micron-sized agglomerations of iron-oxide (Fe3O4) nanoparticles were injected in microchannels with internal diameters of 200 and 50 ?m equivalent to a narrower artery or a larger arteriole, and down to a smaller arteriole, respectively. The results show the feasibility of the proposed method for micro-particle detection and the visualization of microvessels using a 1.5 T clinical MR scanner. It was confirmed that the method is reproducible and accurate at the sub-pixel level.

Olamaei, N.; Cheriet, F.; Martel, S.

2013-03-01

368

Biological magnetic resonance imaging using laser-polarized 129Xe  

NASA Astrophysics Data System (ADS)

As currently implemented, magnetic resonance imaging (MRI) relies on the protons of water molecules in tissue to provide the NMR signal. Protons are, however, notoriously difficult to image in some biological environments of interest, notably the lungs1 and lipid bilayer membranes such as those in the brain2. Here we show that 129Xe gas can be used for high-resolution MRI when the nuclear-spin polarization of the atoms is increased by laser optical pumping and spin exchange3-6. This process produces hyperpolarized 129Xe, in which the magnetization is enhanced by a factor of about 105. By introducing hyperpolarized 129Xe into mouse lungs we have obtained images of the lung gas space with a speed and a resolution better than those available from proton MRI1,7 or emission tomography8,9. As xenon (a safe general anaesthetic) is rapidly and safely trans-ferred from the lungs to blood and thence to other tissues8,9, where it is concentrated in lipid10-15 and protein13,15-18 components, images of the circulatory system, the brain and other vital organs can also be obtained. Because the magnetic behaviour of 129Xe is very sensi-tive to its environment, and is different from that of 1H2O, MRI using hyperpolarized 129Xe should involve distinct and sensitive mechanisms for tissue contrast.

Albert, M. S.; Cates, G. D.; Driehuys, B.; Happer, W.; Saam, B.; Springer, C. S.; Wishnia, A.

1994-07-01

369

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

370

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.

Deddens, Lisette H.

2010-01-01

371

Multiparametric magnetic resonance imaging in the detection of prostate cancer.  

PubMed

Prostate cancer is the most common malignancy in men, but only about 10?% of patients die from that cancer. Recent studies suggest that not all patients benefit from a radical therapeutic approach. When prostate cancer is suspected, magnetic resonance imaging (MRI) can make an important contribution to cancer localization within the prostate. Many studies show that T2-weighted morphologic imaging should be supplemented by multiparametric MRI techniques including diffusion-weighted imaging, contrast-enhanced sequences, and MR spectroscopy. This approach detects aggressive prostate cancer with high sensitivity and specificity. The findings of multiparametric MRI additionally contribute information to the assessment of cancer aggressiveness. The use of these multiparametric MRI techniques will gain an increasing role in the clinical management of prostate cancer patients. They can help in establishing a definitive diagnosis with a minimum of invasiveness and may also contribute to optimal individualized treatment. This review article presents the different techniques of multiparametric MRI and discusses their contribution to the detection of prostate cancer. Moreover, this review outlines an objective approach to image interpretation and structured reporting of MRI findings using the PI-RADS criteria. The review concludes with an outline of approaches to prostate biopsy on the basis of MRI (transrectal ultrasound, direct MRI guidance of tissue sampling, and MRI-ultrasound fusion biopsy) and emerging future uses of MRI in the planning of focal treatment options and in the active surveillance of patients diagnosed with prostate cancer. PMID:24452493

Durmus, T; Baur, A; Hamm, B

2014-03-01

372

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

373

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

374

High Frequency Electromagnetic Fields in Magnetic Resonance Imaging.  

NASA Astrophysics Data System (ADS)

Radiofrequency (RF) electromagnetic fields are widely used in Nuclear Magnetic Resonance Imaging. The signal-to-noise of the image increases as the frequency of the RF does and, for that reason, high frequency systems (~64MHz) are currently being used, and still higher frequencies (170MHz) are being considered for the future. However, this could be both inconvenient and dangerous. As the frequency of the field increases, there is less field penetration into matter, due to conductivity effects. Information from a given spatial point in the object under imaging strongly depends on the value that the RF magnetic field takes at that location and sometimes it is required that the field takes prescribed values at all points in a given region of the sample. This is in contradiction with the boundary conditions of the problem (the problem is inconsistently overconstrained), unless sufficiently low frequencies are used. When high frequencies are used, a correction scheme or, at least, a knowledge of the image non-uniformity due to penetration effects is needed. On the other hand, the heat deposited inside the object also increases with frequency. The knowledge of the heat absorbed by the object is important in that it sets upper bounds on the frequency to be used or the duty cycle if irreversible changes in the sample are to be avoided. In this work we study such problem analytically, numerically, and experimentally for a variety of body shapes and field distributions. We find that 170 MHz is an approximate upper bound for the Magnetic Resonance Imaging frequency in order for it to be safely used in medical applications; different sequences were simulated in the leg and the brain in order to obtain the power deposition under them, spin echo and FLASH sequences show that the power deposited up to 170 MHz does not exceed international safety regulations of 2 W/Kg locally and 0.4 W/Kg on the average. This will not be the case any longer if 3D fast imaging is implemented at 170 MHz. We evaluate the numerical approaches and find that the one based on the use of the vector potential rather than fields and/or currents is optimal. (Abstract shortened with permission of author.).

Zypman Niechonski, Fredy Ruben

375

Enhancing magnetic resonance imaging tumor detection with fluorescence intensity and lifetime imaging  

PubMed Central

Early detection is important for many solid cancers but the images provided by ultrasound, magnetic resonance imaging (MRI), and computed tomography applied alone or together, are often not sufficient for decisive early screening?diagnosis. We demonstrate that MRI augmented with fluorescence intensity (FI) substantially improves detection. Early stage murine pancreatic tumors that could not be identified by blinded, skilled observers using MRI alone, were easily identified with MRI along with FI images acquired with photomultiplier tube detection and offset laser scanning. Moreover, we show that fluorescence lifetime (FLT) imaging enables positive identification of the labeling fluorophore and discriminates it from surrounding tissue autofluorescence. Our data suggest combined-modality imaging with MRI, FI, and FLT can be used to screen and diagnose early tumors.

Erten, Ahmet; Hall, David; Hoh, Carl; Tran Cao, Hop S.; Kaushal, Sharmeela; Esener, Sadik; Hoffman, Robert M.; Bouvet, Michael; Chen, James; Kesari, Santosh; Makale, Milan

2010-01-01

376

Monitoring water accumulation in a glacier using magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

Tête Rousse is a small polythermal glacier located in the Mont Blanc area (French Alps) at an altitude of 3100 to 3300 m. Recent accumulation of melt water in the glacier was assumed to occur, but such accumulation had yet to be confirmed. Using Surface Nuclear Magnetic Resonance imaging (3-D-SNMR), we showed that the temperate part of the Tête Rousse glacier contains two separate water-filled caverns (central and upper caverns). In 2009, the central cavern contained about 55 000 m3 of water. Since 2010, the cavern is drained every year. Using 3-D-SNMR, we monitored the changes caused by this pumping in the water distribution within the glacier body. Twice a year, we carried out magnetic resonance imaging of the entire glacier and estimated the volume of water accumulated in the central cavern. Our results show the changes in cavern geometry and recharge rate: in two years, the central cavern lost about 73% of its initial volume, but 65% were lost in one year after the first pumping. We also observed that, after being drained, the cavern was recharged at an average rate of 20 to 25 m3 d-1 over the winter months and 120 to 180 m3 d-1 in summer. These observations illustrate how ice and water may refill englacial volume being emptied by artificial draining. Comparison of the 3-D-SNMR results with those obtained by drilling and pumping showed a very good correspondence, confirming the high reliability of 3-D-SNMR imaging.

Legchenko, A.; Vincent, C.; Baltassat, J. M.; Girard, J. F.; Thibert, E.; Gagliardini, O.; Descloitres, M.; Gilbert, A.; Garambois, S.; Chevalier, A.; Guyard, H.

2013-05-01

377

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.

Novikov, Alexander

2010-01-01

378

Medical image diagnostics based on computer-aided flow analysis using magnetic resonance images.  

PubMed

Most of the cardiac abnormalities have an implication on hemodynamics and affect cardiovascular health. Diagnostic imaging modalities such as computed tomography and magnetic resonance imaging provide excellent anatomical information on myocardial structures, but fail to show the cardiac flow and detect heart defects in vivo condition. The computerized technique for fluid motion estimation by pixel intensity tracking based on magnetic resonance signals represents a promising technique for functional assessment of cardiovascular disease, as it can provide functional information of the heart in addition to analysis of its anatomy. Cardiovascular flow characteristics can be measured in both normal controls and patients with cardiac abnormalities such as atrial septal defect, thus, enabling identification of the underlying causes of these flow phenomena. This review paper focuses on an overview of a flow analysis scheme based on computer-aided evaluation of magnetic resonance intensity images, in comparison with other commonly used medical imaging modalities. Details of the proposed technique are provided with validations being conducted at selected abnormal cardiovascular patients. It is expected that this new technique can potentially extend applications for characterizing cardiovascular defects and their hemodynamic behavior. PMID:22575846

Wong, Kelvin K L; Sun, Zhonghua; Tu, Jiyuan; Worthley, Stephen G; Mazumdar, Jagannath; Abbott, Derek

2012-10-01

379

[Magnetic resonance imaging in the study of acoustic neurinoma].  

PubMed

Exploration of acoustic neurinoma, the most frequent benign tumor of posterior fossa, now includes magnetic resonance imaging, and an C.G.R. supraconductor apparatus (0.5 Tesla) has been in use since March 1986. This equipment provides high resolution frontal sections, not only of posterior fossa but of the two pontocerebellar angles and even the contents of the two IAC (thin, contiguous 4 mm sections in 256 x 256 matrix). A total of 43 patients were examined, 37 with surgically confirmed acoustic neurinoma and 2 with tumor recurrence. The neurinoma appears on the first echo as a hyposignal in relation to brain stem in sequences predominant in T1 and as a hypersignal in relation to peripontic CSF in sequences predominant in T2. Short sequences predominant in Tl (partial saturation or short ET and RT spin-echos) appear to be most effective for detection of acoustic neurinoma. Comparison of MRI and CT scan imaging showed that firstly, all cases detected by conventional scanography were correctly analyzed by MRI, with superiority for MRI for preoperative screening due to the frontal sections obtained without interference and, secondly, the non-invasive confirmation of diagnosis in doubtful or negative cases requiring computerized gaz meatocisternography. No false negative or false positive results were reported in our series or those documented in the literature using this new imaging technique, but high performance apparatus is necessary (thin sections ans powerful principal magnetic field of at least 0.5 resla). Improvements in this method could be obtained by the availability of more rapid programmes, the use of surface coils and the injection of paramagnetic substances (galodinium chelates) presently under study. NMR imaging is a reliable and non-invasive imaging method capable of replacing the scanner for study of acoustic neurinoma as soon as more apparatuses become available. PMID:3357149

Sarrat, P; Bouchet, J M; Cannoni, M; Pech, A; Bernard, P

1988-02-01

380

Bacteria tracking by in vivo magnetic resonance imaging  

PubMed Central

Background Different non-invasive real-time imaging techniques have been developed over the last decades to study bacterial pathogenic mechanisms in mouse models by following infections over a time course. In vivo investigations of bacterial infections previously relied mostly on bioluminescence imaging (BLI), which is able to localize metabolically active bacteria, but provides no data on the status of the involved organs in the infected host organism. In this study we established an in vivo imaging platform by magnetic resonance imaging (MRI) for tracking bacteria in mouse models of infection to study infection biology of clinically relevant bacteria. Results We have developed a method to label Gram-positive and Gram-negative bacteria with iron oxide nano particles and detected and pursued these with MRI. The key step for successful labeling was to manipulate the bacterial surface charge by producing electro-competent cells enabling charge interactions between the iron particles and the cell wall. Different particle sizes and coatings were tested for their ability to attach to the cell wall and possible labeling mechanisms were elaborated by comparing Gram-positive and -negative bacterial characteristics. With 5-nm citrate-coated particles an iron load of 0.015 ± 0.002 pg Fe/bacterial cell was achieved for Staphylococcus aureus. In both a subcutaneous and a systemic infection model induced by iron-labeled S. aureus bacteria, high resolution MR images allowed for bacterial tracking and provided information on the morphology of organs and the inflammatory response. Conclusion Labeled with iron oxide particles, in vivo detection of small S. aureus colonies in infection models is feasible by MRI and provides a versatile tool to follow bacterial infections in vivo. The established cell labeling strategy can easily be transferred to other bacterial species and thus provides a conceptual advance in the field of molecular MRI.

2013-01-01

381

[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

382

Bioengineered iron-oxide nanocrystals: Applications in magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

Superparamagnetic Iron-Oxide nanoparticles (SPIO) are used as magnetic resonance imaging (MRI) contrast agents in clinical and research applications, effectively increasing the imaging sensitivity of MRI. Current clinical MRI applications utilizing SPIO are limited to liver and gastrointestinal imaging, but further bioengineering will expand the capabilities of SPIO enhanced MRI. This thesis presents different methods of bioengineering SPIO contrast agents for MRI applications. In particular, chemical methods are developed to manipulate contrast agent size via aggregation, modify contrast agent surface encapsulation, and biofunctionalize contrast agents for new applications. Contrast agent sizes from 15 nm to 100 nm are synthesized by nanoparticle aggregation, yielding a new method to incrementally size contrast agent sizing for specific applications. Mono- and Diethoxy silane surface chemistries are applied to SPIO to develop quasi-monolayer biocompatible contrast agent surface encapsulations. Finally, biofunctionalization enables two new applications of SPIO contrast agents, as a new MRI-based method to detect inflammation in vivo, and as a bifunctional MRI contrast agent and nanoparticle antigen delivery system.

Larsen, Brian A.

383

Confocal UV and resonance Raman microscopic imaging of pharmaceutical products.  

PubMed

Chemical imaging using confocal Raman microscopy is a useful analytical tool in drug development because of its ability to spatially image active ingredients and excipients in dosage forms and relate their distribution to product performance. While Raman spectra are highly specific for individual components of a formulation, most Raman microscopic mapping experiments require extensive experimental time. Laser wavelengths in the near-infrared range are used to suppress fluorescence but reduce sensitivity because of the inverse quadratic dependence of Raman scattering on laser wavelength. Compact, simple ultraviolet (UV) laser designs now allow for confocal UV Raman microscopy to be performed using a versatile instrument also capable of conventional Raman microscopy and epifluorescence imaging analyses. This study presents the results of UV Raman microscopy analyses using 266 nm laser irradiation of four pharmaceutical compositions of interest, including two types of tablets containing low doses of active ingredients (in the 0.2% w/w range), an amorphous dispersion containing 1% w/w of a small molecule drug, and an enteric coated layered peptide formulation. Resonance Raman enhancements are observed for four of the active ingredients studied in these formulations. The spectroscopic properties of the materials used in this study are also assessed by diffuse reflectance UV-visible spectroscopy, fluorescence spectroscopy, and conventional bulk Fourier transform Raman spectroscopy using 1064 nm laser irradiation. Confocal UV Raman microscopy was found to offer good sensitivity and allowed for rapid microscopic mapping of drugs and excipients at low concentrations in pharmaceutical formulations. PMID:24050305

Vogt, Frederick G; Strohmeier, Mark

2013-11-01

384

Magnetic resonance imaging and computer reconstruction of the velopharyngeal mechanism.  

PubMed

Further research is needed to fully understand the mechanics of the levator veli palatini muscle in coordination with surrounding structures in individuals born with a cleft palate. The purpose of this study was to combine magnetic resonance imaging (MRI) and three-dimensional computer modeling and animation to study the velopharyngeal mechanism in infants with and without a cleft palate. Two infants with a normal velopharyngeal anatomy (subjects 1 and 2) and 2 infants with a cleft lip and palate (subjects 3 and 4) were scheduled to receive a whole-head MRI for clinical reasons unrelated to the current study. This study demonstrated a successful method for combining MRI and three-dimensional computer technology to study the velopharyngeal mechanism in infants with and infants without a cleft palate. Subject 1 displayed a levator muscle sling arrangement that was shaped like a narrow U, whereas subject 2 had a wider U-shaped muscle arrangement. Subject 4 exhibited smaller angles of origin in the oblique coronal compared with that of subject 1. Both subjects with a normal anatomy showed steeper muscles compared with those of both subjects with a cleft palate. The current study enhances the body of literature in the area of MRI by acquiring MR images from infants before and after primary palatoplasty and combining the imaging with three-dimensional computer technology. The angles of the levator muscle may prove to be a significant factor in velar elevation for normal speech. PMID:19816343

Perry, Jamie L; Kuehn, David P

2009-09-01

385

Magnetic resonance pore imaging, a tool for porous media research  

NASA Astrophysics Data System (ADS)

The internal structure of porous materials is of importance in many areas such as medicine, chemical engineering, and petrophysics. While diffraction methods such as x ray are widely used to study the internal pore space, these methods suffer from the loss of the phase information in the detected signals. Recently, an advanced diffusive diffraction NMR method was proposed [F. B. Laun , Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.107.048102 107, 048102 (2011)] which is predicted to preserve the phase information, thus overcoming this severe limitation of diffraction methods in general. Here we provide experimental confirmation that the suggested approach is indeed able to acquire the diffractive signal including its phase which allows the direct image reconstruction of the pore space, averaged over all pores. We furthermore prove that this approach may combine the advantages of magnetic resonance imaging, namely, its robust and straightforward image reconstruction via a Fourier transformation with the much improved spatial resolution of pulsed gradient spin echo NMR.

Hertel, Stefan; Hunter, Mark; Galvosas, Petrik

2013-03-01

386

Orbital cavernous hemangiomas: ultrasound and magnetic resonance imaging evaluation.  

PubMed

Cavernous hemangioma is the most common intraorbital lesion in adults. The aim of our study was to evaluate the magnetic resonance imaging (MRI) and ultrasound (US) characteristics of cavernous hemangioma and their role in the differential diagnosis of orbital tumors. Eight patients with orbital cavernous hemangiomas, five women and three men with a mean age of 48 years were examined in a period of six years. All patients underwent MRI examination and four patients were also evaluated by US. In all cases MRI depicted a well-defined intraconal tumor. The lesions were homogeneous, isointense to muscle on T1-weighted sequence and hyperintense to muscle on T2-weighted sequence in six patients. In one patient the mass was isointense on T1WI with heterogeneous signal intensity on T2WI and in one patient the lesion had heterogeneous signal intensity on both T1- and T2-weighted sequences. After intravenous contrast medium administration, the tumors showed initial inhomogeneous enhancement with progressive accumulation of contrast material on delayed images in seven patients and initial homogeneous enhancement in one patient. On ultrasonography, the orbital masses appeared slightly hyperechoic, heterogeneous with small areas of slow blood flow. The analysis of imaging characteristics of a well-defined intraconal lesion in an adult patient with painless progressive proptosis can be highly suggestive of the diagnosis of cavernous hemangioma. PMID:24148341

Diamantopoulou, A; Damianidis, Ch; Kyriakou, V; Kotziamani, N; Emmanouilidou, M; Goutsaridou, F; Tsitouridis, I

2010-03-01

387

Reporter protein-targeted probes for magnetic resonance imaging.  

PubMed

Contrast agents for magnetic resonance imaging are frequently employed as experimental and clinical probes. Drawbacks include low signal sensitivity, fast clearance, and nonspecificity that limit efficacy in experimental imaging. In order to create a bioresponsive MR contrast agent, a series of four Gd(III) complexes targeted to the HaloTag reporter were designed and synthesized. HaloTag is unique among reporter proteins for its specificity, versatility, and the covalent interaction between substrate and protein. In similar systems, these properties produce prolonged in vivo lifetimes and extended imaging opportunities for contrast agents, longer rotational correlation times, and increases in relaxivity (r(1)) upon binding to the HaloTag protein. In this work we report a new MR contrast probe, 2CHTGd, which forms a covalent bond with its target protein and results in a dramatic increase in sensitivity. A 6-fold increase in r(1), from 3.8 to 22 mM(-1) s(-1), is observed upon 2CHTGd binding to the target protein. This probe was designed for use with the HaloTag protein system which allows for a variety of substrates (specific for MRI, florescence, or protein purification applications) to be used with the same reporter. PMID:21942425

Strauch, Renee C; Mastarone, Daniel J; Sukerkar, Preeti A; Song, Ying; Ipsaro, Jonathan J; Meade, Thomas J

2011-10-19

388

Reporter Protein-Targeted Probes for Magnetic Resonance Imaging  

PubMed Central

Contrast agents for magnetic resonance imaging are frequently employed as experimental and clinical probes. Drawbacks include low signal sensitivity, fast clearance and non-specificity that limit efficacy in experimental imaging. In order to create a bio-responsive MR contrast agent, a series of four Gd(III) complexes targeted to the HaloTag reporter were designed and synthesized. HaloTag is unique among reporter proteins for its specificity, versatility, and the covalent interaction between substrate and protein. In similar systems, these properties produce prolonged in vivo lifetimes and extended imaging opportunities for contrast agents, longer rotational correlation times, and increases in relaxivity (r1) upon binding to the HaloTag protein. In this work we report a new MR contrast probe, 2CHTGd, which forms a covalent bond with a target protein and results in a dramatic increase in sensitivity. A 6-fold increase in r1, from 3.8 mM?1s?1 to 22 mM?1s?1, is observed upon 2CHTGd binding to the target protein. This probe was designed for use with the HaloTag protein system which allows for a variety of substrates (specific for MRI, florescence, or protein purification applications) to be used with the same reporter.

Strauch, Renee C.; Mastarone, Daniel J.; Sukerkar, Preeti A.; Song, Ying; Ipsaro, Jonathan J.; Meade, Thomas J.

2011-01-01

389

Development of Cell Type-Specific Contrast Agents for Magnetic Resonance Imaging of Breast Tumors.  

National Technical Information Service (NTIS)

Magnetic Resonance Imaging is an emerging diagnostic tool for breast cancer that provides high-resolution three-dimensional images of tissues. A significant increase of specificity of detection of cancerous lesions could be achieved by use of tumor specif...

A. Chestukhin

2008-01-01

390

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

National Technical Information Service (NTIS)

This research develops an automated method for segmenting Magnetic Resonance (MR) brain images based on Pulse Coupled Neural Networks (PCNN). The method developed and presented uses a PCNN to both filter and segment MR brain images. The technique begins b...

S. L. Abrahamson

1996-01-01

391

Combining magnetic resonance imaging and ultrawideband radar: A new concept for multimodal biomedical imaging  

NASA Astrophysics Data System (ADS)

Due to the recent advances in ultrawideband (UWB) radar technologies, there has been widespread interest in the medical applications of this technology. We propose the multimodal combination of magnetic resonance (MR) and UWB radar for improved functional diagnosis and imaging. A demonstrator was established to prove the feasibility of the simultaneous acquisition of physiological events by magnetic resonance imaging and UWB radar. Furthermore, first in vivo experiments have been carried out, utilizing this new approach. Correlating the reconstructed UWB signals with physiological signatures acquired by simultaneous MR measurements, representing respiratory and myocardial displacements, gave encouraging results which can be improved by optimization of the MR data acquisition technique or the use of UWB antenna arrays to localize the motion in a focused area.

Thiel, F.; Hein, M.; Schwarz, U.; Sachs, J.; Seifert, F.

2009-01-01

392

Nonlinear split-ring metamaterial slabs for magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

This work analyzes the ability of split-ring metamaterial slabs with zero/high permeability to reject/confine the radiofrequency magnetic field in magnetic resonance imaging systems. Split-ring slabs are designed and fabricated to work in a 1.5 T system. Nonlinear elements consisting of pairs of crossed diodes are inserted in the split-rings, so that the slab permeability can be switched between a value close to unity when interacting with the strong field of the transmitting coil, and zero or high values when interacting with the weak field produced by protons in tissue. Experiments are shown where these slabs locally increase the signal-to-noise-ratio.

Lopez, Marcos A.; Freire, Manuel J.; Algarin, Jose M.; Behr, Volker C.; Jakob, Peter M.; Marqués, Ricardo

2011-03-01

393

Magnetic resonance imaging of endometrial and cervical cancer.  

PubMed

In this article we review the current and developing roles of magnetic resonance imaging (MRI) in endometrial and cervical cancer. In endometrial cancer, the purpose of MRI is to stage the primary tumor and in particular to identify myometrial and cervical invasion and extra-uterine disease, thereby informing preoperative surgical planning. MRI is also used to safely select young patients suitable for fertility-preserving medical management. In cervical cancer, MRI has an established role in local staging and in assessing proximal extension of tumors in young women for feasibility of fertility-preserving surgery. It is used to plan radiotherapy for primary tumors in cervical cancer and particularly for conformal radiotherapy to deliver optimal doses to the tumor sites, while limiting unwanted exposure of bowel and other pelvic organs. In both cancers, MRI is used for diagnosing nodal disease, surveillance, detection of recurrence, and evaluation of complications secondary to treatment. PMID:18837902

Sahdev, Anju; Reznek, Rodney H

2008-09-01

394

Chemical Exchange Saturation Transfer Contrast Agents for Magnetic Resonance Imaging  

PubMed Central

Magnetic resonance imaging (MRI) contrast agents have become an important tool in clinical medicine. The most common agents are Gd3+-based complexes that shorten bulk water T1 by rapid exchange of a single innersphere water molecule with bulk solvent water. Current gadolinium agents lack tissue specificity and typically do not respond to their chemical environment. Recently, it has been demonstrated that MR contrast may be altered by an entirely different mechanism based on chemical exchange saturation transfer (CEST). CEST contrast can originate from exchange of endogenous amide or hydroxyl protons or from exchangeable sites on exogenous CEST agents. This has opened the door for the discovery of new classes of responsive agents ranging from MR gene reporter molecules to small molecules that sense their tissue environment and respond to biological events.

Sherry, A. Dean; Woods, Mark

2009-01-01

395

Resting state functional magnetic resonance imaging in Parkinson's disease.  

PubMed

Neuroimaging advances over the past several decades have provided increased understanding of the structural and functional brain changes that occur with Parkinson's disease (PD). Examination of resting state functional magnetic resonance imaging (rs-fMRI) provides a noninvasive method that focuses on low-frequency spontaneous fluctuations in the blood-oxygenation-level-dependent signal that occurs when an individual is at rest. Several analysis methods have been developed and used to explore how PD affects resting state activity and functional connectivity, and the purpose of this review is to highlight the critical advances made thus far. Some discrepancies in the rs-fMRI and PD literature exist, and we make recommendations for consideration in future studies. The rs-fMRI technique holds promise for investigating brain changes associated with the motor and nonmotor symptoms of PD, and for revealing important variations across large-scale networks of the brain in PD. PMID:24744021

Prodoehl, Janey; Burciu, Roxana G; Vaillancourt, David E

2014-06-01

396

The Accuracy of Magnetic Resonance Imaging in Radical Prostatectomy  

PubMed Central

Aims The aim of this study was to examine the accuracy of standard magnetic resonance imaging (MRI) in the localised staging of prostate cancer in those who had undergone radical prostatectomy. Patients and Methods The cohort consisted of 110 patients who had undergone MRI for staging of prostate cancer and subsequently underwent radical prostatectomy. T stage was analysed both on MRI and from the specimen following radical surgery. Results Of the patients 57% of patients had their disease up-staged following radical surgery from preoperative MRI findings. Of those patients who had their disease up-staged following surgery, nearly 50% of patients had gone from organ confined disease at time of MRI to extra-prostatic involvement from the surgical specimen. Conclusion We have reported that MRI has a wide range of accuracy. Given developments in MRI technologies further work should be pursued to help in the staging of this disease for which decision to treat is difficult.

Qayyum, T.; Willder, J.M.; McArdle, P.A.; Horgan, P.G.; Edwards, J.; Underwood, M.A.

2013-01-01

397

Assessment of gray matter heterotopia by magnetic resonance imaging  

PubMed Central

AIM: To evaluate magnetic resonance imaging (MRI) features of different types of gray matter heterotopia. METHODS: Between June 2005 and December 2009, the medical records and MRI studies of patients with gray matter heterotopia were reviewed. The MRI morphologic findings of heterotopia were recorded along with the presence and type of associated cranial malformations. Available clinical and electrophysiological data were also recorded. RESULTS: 20 patients were included in the study. Their ages ranged from 9 mo to 39 years with a mean age of 15 years. All patients suffered from epileptic seizures. According to the location of heterotopia, patients were classified into three groups: subependymal (12), subcortical (5) and band (3) heterotopia. CONCLUSION: MRI was useful in diagnosing and differentiating between various types of gray matter heterotopia. The severity of clinical manifestations of heterotopia was related to the location and pattern of heterotopia. Determination of heterotopia type and its extent is useful for management planning and predicting prognosis.

Donkol, Ragab H; Moghazy, Khaled M; Abolenin, Alaeddin

2012-01-01

398

Molecular-level functional magnetic resonance imaging of dopaminergic signaling.  

PubMed

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

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

2014-05-01

399

[Magnetic resonance imaging in the diagnosis of retrotracheal pulmonary artery].  

PubMed

The authors report the case of a 3-month-old infant with a history of interventricular septal defect with pulmonary arterial hypertension. This child had pulmonary symptomatology (dyspnea, recurrent bronchitis, acute attacks of asphyxia) which it was possible to link to a retrotracheal left pulmonary artery by magnetic resonance imaging (MRI). Classical investigations (upper GI barium series and chest X-ray) were suggestive of a bronchogenic cyst type abnormal pulmonary structure. Angiography confirmed the MRI diagnosis. In this case the infant also had tracheal lesions (lower tracheal hypoplasia) which required further evaluation by fibroscopy and bronchography. Thus MRI shows itself to be a useful investigation in the study of basic vascular abnormalities. PMID:2024907

Livolsi, A; Donato, L; Kastler, B; Willard, D; Geisert, J

1991-01-01

400

Functional Magnetic Resonance Imaging - Implications for Detection of Schizophrenia  

PubMed Central

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

Demirci, Oguz; Calhoun, Vince D

2010-01-01

401

Utility of Magnetic Resonance Imaging in Cardiac Venous Anatomic Variants  

SciTech Connect

The incidence of persistent left superior venacava (PLSVC) is approximately 0.5% in the general population; however,the coexistent absence of the right SVC has a reported incidence in tertiary centers of 0.1%. The vast majority of reports are limited to pediatric cardiology. Likewise, sinus of Valsalva aneurysm is a rare congenital anomaly, with a reported incidence of 0.1-3.5% of all congenital heart defects. We present a 71-year-old patient undergoing preoperative evaluation for incidental finding of aortic root aneurysm,and found to have all three in coexistence. Suggestive findings were demonstrated on cardiac catheterization and definitive diagnosis was made by magnetic resonance imaging. The use of MRI for the diagnosis of asymptomatic adult congenital heart disease will be reviewed.

Eckart, Robert E. [Brooke Army Medical Center, 3851 Roger Brooke Drive, Fort Sam Houston, Texas 78234-6200, Cardiology Service (United States)], E-mail: Robert.Eckart@amedd.army.mil; Leitch, W. Shad [Brooke Army Medical Center, 3851 Roger Brooke Drive, Fort Sam Houston, Texas 78234-6200, Internal Medicine (United States); Shry, Eric A. [Brooke Army Medical Center, 3851 Roger Brooke Drive, Fort Sam Houston, Texas 78234-6200, Cardiology Service (United States); Krasuski, Richard A. [Wilford Hall Air Force Medical Center, Texas, Cardiology Service (United States); Lane, Michael J. [Brooke Army Medical Center, 3851 Roger Brooke Drive, Fort Sam Houston, Texas 78234-6200, Department of Radiology (United States); Leclerc, Kenneth M. [Brooke Army Medical Center, 3851 Roger Brooke Drive, Fort Sam Houston, Texas78234-6200, Cardiology Service (United States)

2003-06-15

402

Magnetic resonance imaging of aortic disease: preliminary results  

SciTech Connect

Fourteen patients with a variety of aortic diseases were evaluated with magnetic resonance imaging (MRI). These included abdominal aortic aneurysms (eight cases), aortoiliac aneurysm (one), thoracoabdominal aneurysm (one), aortic dissections (four), and Takayasu arteritis (one). The size and extent of aneurysms, the presence of thrombus or atherosclerotic debris, the relation to renal and iliac arteries, and the effect of aneurysms on adjacent structures were readily demonstrated by MRI. The size of the residual lumen in a variety of vascular diseases and abnormal blood flow patterns could be assessed. These early results indicated that MRI achieved precise and complete assessment of a number of aortic abnormalities without the administration of any type of contrast material. Thus, early experience suggests that an important application of MRI will be as a totally noninvasive and reliable method for evaluating aortic disease.

Amparo, E.G.; Higgins, C.B.; Hoddick, W.; Hricak, H.; Kerlan, R.K.; Ring, E.J.; Kaufman, L.; Hedgecock, M.W.

1984-12-01

403

Unsupervised fuzzy segmentation of 3D magnetic resonance brain images  

NASA Astrophysics Data System (ADS)

Unsupervised fuzzy methods are proposed for segmentation of 3D Magnetic Resonance images of the brain. Fuzzy c-means (FCM) has shown promising results for segmentation of single slices. FCM has been investigated for volume segmentations, both by combining results of single slices and by segmenting the full volume. Different strategies and initializations have been tried. In particular, two approaches have been used: (1) a method by which, iteratively, the furthest sample is split off to form a new cluster center, and (2) the traditional FCM in which the membership grade matrix is initialized in some way. Results have been compared with volume segmentations by k-means and with two supervised methods, k-nearest neighbors and region growing. Results of individual segmentations are presented as well as comparisons on the application of the different methods to a number of tumor patient data sets.

Velthuizen, Robert P.; Hall, Lawrence O.; Clarke, Laurence P.; Bensaid, Amine M.; Arrington, J. A.; Silbiger, M. L.

1993-07-01

404

Resonant photo-thermal conversion for sub-terahertz imaging  

NASA Astrophysics Data System (ADS)

An original design of generic interest is proposed for fast imaging, in the field of sub-terahertz frequencies, by means of resonant coupling between an ultra-thin photo-thermal converter and a metallic grid upstream an infrared camera. The material is a sheet of polyimide material with a high content of absorptive carbon inclusions. We make use of the large difference between the IR and THz wavelengths in a quarter-wave planar geometry, to ensure a highly efficient and stable conversion process. A complete setup has been implemented for demonstration purposes, using the beam from a Gunn diode at 110 GHz. Experimental results are in good agreement with the predictions from the numerical model, which helps to validate the concept and the requirements for geometrical adjustment.

Jolly, Alain; Chassagne, Bruno; Jolly, Jean-Claude

2013-01-01

405

Informing brain connectivity with optogenetic functional magnetic resonance imaging.  

PubMed

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

Lee, Jin Hyung

2012-10-01

406

Electron beam imaging and spectroscopy of plasmonic nanoantenna resonances  

NASA Astrophysics Data System (ADS)

Nanoantennas are metal structures that provide strong optical coupling between a nanoscale volume and the far field. This coupling is mediated by surface plasmons, oscillations of the free electrons in the metal. Increasing the control over the resonant plasmonic field distribution opens up a wide range of applications of nanoantennas operating both in receiving and transmitting mode. This thesis presents how the dispersion and confinement of surface plasmons in nanoantennas are resolved and further engineered. Fabrication of nanostructures is done using focused ion beam milling (FIB) in metallic surfaces. We demonstrate that patterning in single-crystal substrates allows us to precisely control the geometry in which plasmons are confined. The nanoscale properties of the resonant plasmonic fields are resolved using a new technique developed in this thesis: angle- and polarization controlled cathodoluminescence (CL) imaging spectroscopy. The use of a tightly focused electron beam allows us to probe the optical antenna properties with deep subwavelength resolution. We show using this technique that nanoantennas consisting of 500-1200 nm long polycrystalline Au nanowires support standing plasmon waves. We directly observe the plasmon wavelengths which we use to derive the dispersion relation of guided nanowire plasmons. A 590-nm-long ridge-shaped nanoantenna was fabricated using FIB milling on a single-crystal Au substrate, demonstrating a level of control over the fabrication impossible with polycrystalline metals. CL experiments show that the ridge supports multiple-order resonances. The confinement of surface plasmons to the ridge is confirmed by boundary-element-method (BEM) calculations. The resonant modes in plasmonic whispering gallery cavities consisting of a FIB-fabricated circular groove are resolved. We find an excellent agreement between boundary element method calculations and the measured CL emission from the ring-shaped cavities. The calculations show that the ring supports resonances with increasing azimuthal or radial order. The smallest cavity fits only one wavelength in its circumference. We theoretically show that in these cavities, spontaneous emission can be enhanced over a broad spectral band due to the small modal volume of the plasmon resonances. A Purcell factor >2000 was found. We further study the mode symmetries and coupling of the ring resonances using far-field excitation, fluorescence, angle-resolved cathodoluminescence and photoelectron emission microscopy. We demonstrate spectral reshaping of emitters, mode-specific angular emission patterns, and a mode-selective excitation by incoming light, and we directly resolve the modal fields at high resolution. In the next chapter, we present metal-insulator-metal plasmon waveguides in which we engineer the dispersion to reach a refractive index of zero. Using spatially- and angle-resolved CL we directly observe the spatial mode profiles and determine the dispersion relation of plasmon modes. At the cutoff frequency, the emission pattern corresponds to that of a line dipole antenna demonstrating the entire waveguide is in phase (n=0). A strongly enhanced density of optical states is directly observed at cutoff from the enhanced CL intensity. Finally, we present 5 possible applications: a localized surface plasmon sensor, a plasmon ring laser, template stripping technique, an in-situ monitor of ionoluminescence and cathodoluminescence in a FIB system and a single-photon source.

Vesseur, E. J. R.

2011-07-01

407

Strain-encoded (SENC) harmonic phase imaging for fast magnetic resonance elastography  

NASA Astrophysics Data System (ADS)

A new method is proposed for imaging the elasticity of tissue using magnetic resonance (MR). Using an external actuator to deform the tissue, local strains way according to local elasticity. The method produces images shows the distribution of strains with different grades of intensity; thus, revealing the underlying elasticity distribution. The advantages of the method are that imaging is much faster than other magnetic resonance elastography (MRE) techniques, there is no need for complicated computations, and it produces high-resolution images.

Osman, Nael F.

2001-05-01

408

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.

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

2013-01-01

409

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

410

Concurrent multiscale imaging with magnetic resonance imaging and optical coherence tomography  

PubMed Central

Abstract. 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

2013-01-01

411

Magnetic resonance spectroscopy imaging characteristics of cerebral Blastomycosis  

PubMed Central

Background: Blastomycosis is a dimorphic fungus that is endemic to the midwest and southwestern United States. Involvement of the central nervous system (CNS) is thought to only represent 5-10% of cases of disseminated Blastomycosis. Case Description: A 54-year-old Caucasian female presented to the Neurosurgery service with a 1-day history of progressive right sided hemiparesis. Magnetic resonance imaging (MRI) demonstrated a 2 × 4 cm heterogeneous intracranial mass lesion involving the left motor cortex and extending into the ipsilateral parietal lobe. Single-voxel magnetic resonance spectroscopy (MRS) over the enhancing area demonstrated diminished N-acetyl aspartate (NAA) to creatine ratio (1.10), normal choline to NAA ratio (0.82), normal choline to creatine ratio (0.9), and a diminished myoinositol to creatine ratio (0.39). There appeared to be peaks between 3.6 and 3.8 ppm over the enhancing area that were not present in the contralateral normal brain and thought to represent a “trehalose” peak. Due to worsening symptoms and uncertain preoperative diagnosis, the patient underwent a left fronto-parietal craniotomy for open surgical biopsy with possible resection approximately one month after presentation. Pathological analysis confirmed the diagnosis of Blastomycosis. Conclusion: We present the second documented case of intracranial Blastomycosis with MRS imaging. There appears to be a characteristic peak between 3.6 and 3.8 ppm that is thought to represent a “trehalose” peak. This peak is rather specific to fungi and can be helpful in differentiating fungal abscesses from pyogenic abscesses and malignant neoplasms.

Vachhani, Jay A.; Lee, William C.; Desanto, Jeffrey R.; Tsung, Andrew J.

2014-01-01

412

Magnetic resonance imaging of myocardial fibrosis in hypertrophic cardiomyopathy.  

PubMed

Myocardial fibrosis can occur in patients who have hypertrophic cardiomyopathy in the absence of epicardial coronary disease. In such patients, myocardial fibrosis has been linked to a poorer prognosis than in those without fibrosis. Gadolinium-DTPA delayed-enhancement magnetic resonance imaging (de-MRI) accurately identifies regions of myocardial fibrosis. We used de-MRI to screen for myocardial fibrosis in 8 patients with nonobstructive hypertrophic cardiomyopathy that had been diagnosed by 2-dimensional echocardiography. After localization of the heart and acquisition of electrocardiographically gated cine images, gadolinium-DTPA (0.2 mmol/kg) was administered to the patient. Fifteen minutes later, de-MRI images were obtained using a T1-weighted, inversion-recovery fast, low-angle shot sequence. Images were gated to end-diastole and obtained during a single breath-hold. The inversion time was modified iteratively to obtain maximal nulling of the signal from the ventricular myocardium. Regions of myocardium with abnormally high signals (>300% of remote normal myocardium) were designated as fibrotic. Eight patients with hypertrophic cardiomyopathy underwent de-MRI. The mean age was 52 years, the mean left ventricular mass was 201 grams, and the mean ejection fraction was 0.68. In the 6 patients with recent clinical deterioration, de-MRI showed clearly delineated areas of myocardial fibrosis; no such areas were seen in the 2 asymptomatic patients. We conclude that patients with symptomatic hypertrophic cardiomyopathy display regions of abnormal signal intensity on de-MRI that likely represent fibrosis. This technique may provide useful information in the evaluation of such patients and warrants further study. PMID:12224720

Wilson, James M; Villareal, Rollo P; Hariharan, Ramesh; Massumi, Ali; Muthupillai, Raja; Flamm, Scott D

2002-01-01

413

Magnetic Resonance Imaging of Myocardial Fibrosis in Hypertrophic Cardiomyopathy  

PubMed Central

Myocardial fibrosis can occur in patients who have hypertrophic cardiomyopathy in the absence of epicardial coronary disease. In such patients, myocardial fibrosis has been linked to a poorer prognosis than in those without fibrosis. Gadolinium-DTPA delayed-enhancement magnetic resonance imaging (de-MRI) accurately identifies regions of myocardial fibrosis. We used de-MRI to screen for myocardial fibrosis in 8 patients with nonobstructive hypertrophic cardiomyopathy that had been diagnosed by 2-dimensional echocardiography. After localization of the heart and acquisition of electrocardiographically gated cine images, gadolinium-DTPA (0.2 mmol/kg) was administered to the patient. Fifteen minutes later, de-MRI images were obtained using a T1-weighted, inversion-recovery, fast, low-angle shot sequence. Images were gated to end-diastole and obtained during a single breath-hold. The inversion time was modified iteratively to obtain maximal nulling of the signal from the ventricular myocardium. Regions of myocardium with abnormally high signals (>300% of remote normal myocardium) were designated as fibrotic. Eight patients with hypertrophic cardiomyopathy underwent de-MRI. The mean age was 52 years, the mean left ventricular mass was 201 grams, and the mean ejection fraction was 0.68. In the 6 patients with recent clinical deterioration, de-MRI showed clearly delineated areas of myocardial fibrosis; no such areas were seen in the 2 asymptomatic patients. We conclude that patients with symptomatic hypertrophic cardiomyopathy display regions of abnormal signal intensity on de-MRI that likely represent fibrosis. This technique may provide useful information in the evaluation of such patients and warrants further study. (Tex Heart Inst J 2002;29:176–80)

Wilson, James M.; Villareal, Rollo P.; Hariharan, Ramesh; Massumi, Ali; Muthupillai, Raja; Flamm, Scott D.

2002-01-01

414

PTFOS: Flexible and Absorbable Intracranial Electrodes for Magnetic Resonance Imaging  

PubMed Central

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

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

2012-01-01

415

Functional imaging as an indicator of diagnostic information in cardiac magnetic-resonance images  

NASA Astrophysics Data System (ADS)

Magnetic Resonance (MR) images of the human heart provide three dimensional geometric information about the location of cardiac structures throughout the cardiac cycle. Analysis of this four dimensional data set allows detection of abnormal cardiac function related to the presence of coronary artery disease. To assist in this analysis, quantitative measurements of cardiac performance are made from the MR data including ejection fractions, regional wall motion and myocardial wall thickening. Analysis of cardiac performance provided by quantitative analysis of MR data can be aided by computer graphics presentation techniques. Two and three dimensional functional images are computed to indicate regions of abnormality based on the previous methods. The two dimensional images are created using color graphics overlays on the original MR image to represent performance. Polygon surface modeling techniques are used to represent data which is three dimensional, such as blood pool volumes. The surface of these images are color encoded by regional ejection fraction, wall motion or wall thickening. A functional image sequence is constructed at each phase of the cardiac cycle and displayed as a movie loop for review by the physician. Selection of a region on the functional image allows visual interpretation of the original MR images, graphical plots of cardiac function and tabular results. Color encoding is based on absolute measurements and comparison to standard normal templates of cardiac performance.

Klingler, Joseph W.; Andrews, Lee T.; Begeman, Michael S.; Zeiss, Jacob; Leighton, Richard F.

1990-08-01

416

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

417

Acromial shapes and extension of rotator cuff tears: Magnetic resonance imaging evaluation  

Microsoft Academic Search

Magnetic resonance imaging makes it possible to inspect the status of the rotator cuff and the shape of the acromion. To clarify the relationship between acromial shapes and rotator cuff tears, we evaluated magnetic resonance images obtained in 192 shoulders. We classified the acromial shapes into 3 types: type I (flat), type II (curved), and type III (hooked). Among a

Mako Hirano; Junji Ide; Katsumasa Takagi

2002-01-01

418

Three-Dimensional Magnetic Resonance Imaging of the Inner Ear in Idiopathic Sudden Sensorineural Hearing Loss  

Microsoft Academic Search

Five patients with idiopathic sudden sensorineural hearing loss (ISSHL) were examined by a combination of high-resolution computed tomography and special magnetic resonance imaging techniques. By three-dimensional constructive interference in steady state magnetic resonance imaging excellent visualization of the membranous labyrinth was obtained. No fibrous or osseous obliteration of the intralabyrinthine fluid spaces was observed in all investigated temporal bones. The

F. W. J. Albers; K. M. N. P. Demuynck; J. W. Casselman

1994-01-01

419

Magnetic resonance imaging of the brain in a cohort of extremely preterm infants  

Microsoft Academic Search

To define magnetic resonance imaging (MRI) appearances of the brain in extremely preterm infants between birth and term, a sequential cohort of infants born at a gestational age <30 weeks was studied with a dedicated neonatal magnetic resonance scanner. Images of infants (n = 41) with a median gestational age of 27 weeks (range 23 to 29 weeks) were initially

Elia F. Maalouf; Philip J. Duggan; Mary A. Rutherford; Serena J. Counsell; Alison M. Fletcher; Malcolm Battin; Frances Cowan; A. David Edwards

1999-01-01

420

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

Microsoft Academic Search

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

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

2004-01-01

421

Tibial meniscal dynamics using three-dimensional reconstruction of magnetic resonance images  

Microsoft Academic Search

The human knee joint represents a complex biome chanical system of which the menisci are an integral component. At present, little data exists describing the meniscal kinematics of the intact knee. Accordingly, a three-dimensional reconstruction magnetic resonance image model was used to explore this issue.Five fresh cadaveric knees were examined by mag netic resonance imaging throughout a full range of

William O. Thompson; F. Leland Thaete; Freddie H. Fu; Scott F. Dye

1991-01-01

422

GENERIC BRAIN ACTIVATION MAPPING IN FUNCTIONAL MAGNETIC RESONANCE IMAGING: A NONPARAMETRIC APPROACH  

Microsoft Academic Search

We report a novel method to identify brain regions generically activated by periodic experimental design in functional magnetic resonance imaging data. This involves: 1) registering each of N individual functional magnetic resonance imaging datasets in a standard space; 2) computing the median standardised power of response to the experimental design; 3) testing median standardised power at each voxel against its

M. J. BRAMMER; E. T. BULLMORE; A. SIMMONS; S. C. R. WILLIAMS; P. M. GRASBYJ; R. J. HOWARD; P. W. R. WOODRUFF; S. RABE-HESKETH

1997-01-01

423

Patterns of disease activity in multiple sclerosis: clinical and magnetic resonance imaging study  

Microsoft Academic Search

OBJECTIVE--To compare the abnormalities shown by magnetic resonance imaging of the brain in three clinically distinct groups of patients with multiple sclerosis, and to correlate the extent of abnormality with the degree of clinical disability in the three groups. DESIGN--All patients underwent magnetic resonance imaging and full neurological examination, and their disability was scored according to the expanded Kurtzke disability

A J Thompson; A G Kermode; D G MacManus; B E Kendall; D P Kingsley; I F Moseley; W I McDonald

1990-01-01

424

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

425

Development of a Clinical Functional Magnetic Resonance Imaging Service  

PubMed Central

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

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

2013-01-01

426

Physiological modulations in arterial spin labeling perfusion magnetic resonance imaging.  

PubMed

The purpose of this study is to evaluate cardiac and respiratory modulations in the signals of arterial spin labeling (ASL) perfusion magnetic resonance imaging (MRI) using RETROICOR, an image domain based retrospective correction method. Systematic comparisons were conducted for tagging schemes, pulsed (PASL) versus frequency-modulated continuous (CASL) methods, and the use of background suppression (BGS). Results showed that cardiac pulsation accounted for more signal fluctuation in PASL than in CASL (two-tailed paired Student's t-test, p < 10(-3)), whereas no significant difference was found in the effect of respiratory motion ( p=0.55) on the two tagging schemes studied. For PASL, significantly more improvement was achieved by the inclusion of cardiac pulsation than respiratory motion in RETROICOR ( p < 0.01). On the contrary, the inclusion of respiratory motion offers more improvement for CASL ( p < 0.02). BGS effectively improved the temporal signal-to-noise ratio (tSNR) as previous studies reported, but no significant difference was measured in the spectral power of physiological modulations relative to the entire spectrum of PASL signals before and after the superimposition of BGS ( p=0.63 for cardiac component, p=0.67 for respiratory component). Thus, we conclude that BGS reduces noise without spectral selectivity, and the improvements of tSNR from RETROICOR and BGS are additive. CASL with a labeling duration at a multiple of an R-R interval can be used to minimize signal fluctuation originating from cardiac pulsation. PMID:19150788

Wu, Wen-Chau; Edlow, Brian L; Elliot, Mark A; Wang, Jiongjiong; Detre, John A

2009-05-01

427

Molecular nanomagnets as contrast agents for Magnetic Resonance Imaging  

NASA Astrophysics Data System (ADS)

Magnetic resonance imaging (MRI) is a non-invasive technique used in medicine to produce high quality images of human body slices. In order to enhance the contrast between different organs or to reveal altered portions of them such necrosis or tumors, the administration of a contrast agent is highly convenient. Currently Gd-DTPA, a paramagnetic complex, is the most widely administered compound. In this context, we have assayed molecular nanomagnets as MRI contrast agents. The complex [(tacn)_6Fe_8(?_3-O)_2(?_2-OH)_12]Br_8·9H_2O^1(Fe8 in brief) has been evaluated and shorter relaxation times, T1 and T_2, have been obtained for Fe8 than those obtained for the commercial Gd-DTPA. No toxic effects have been observed at concentrations up to 1 mM of Fe8 in cultured cells. Phantom studies with T_1-weighted MRI at 9.4 Tesla suggest that Fe8 can have potentiality as T_1-contrast agent. ^1Wieghardt K Angew Chem Intl Ed Engl 23 1 (1984) 77

Rodríguez, Elisenda; Roig, Anna; Molins, Elies; Arús, Carles; Cabañas, Miquel; Quintero, María Rosa; Cerdán, Sebastián; Sanfeliu, Coral

2003-03-01

428

A localized surface plasmon resonance imaging instrument for multiplexed biosensing.  

PubMed

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 multichannel 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

2013-05-01

429

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.

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

2013-01-01

430

[Diagnosis. Radiological study. Ultrasound, computed tomography and magnetic resonance imaging].  

PubMed

Because of its low cost, availability in primary care and ease of interpretation, simple X-ray should be the first-line imaging technique used by family physicians for the diagnosis and/or follow-up of patients with osteoarthritis. Nevertheless, this technique should only be used if there are sound indications and if the results will influence decision-making. Despite the increase of indications in patients with rheumatological disease, the role of ultrasound in patients with osteoarthritis continues to be limited. Computed tomography (CT) is of some -although limited- use in osteoarthritis, especially in the study of complex joints (such as the sacroiliac joint and facet joints). Magnetic resonance imaging (MRI) has represented a major advance in the evaluation of joint cartilage and subchondral bone in patients with osteoarthritis but, because of its high cost and diagnostic-prognostic yield, this technique should only be used in highly selected patients. The indications for ultrasound, CT and MRI in patients with osteoarthritis continue to be limited in primary care and often coincide with situations in which the patient may require hospital referral. Patient safety should be bourne in mind. Patients should be protected from excessive ionizing radiation due to unnecessary repeat X-rays or inadequate views or to requests for tests such as CT, when not indicated. PMID:24467957

Gallo Vallejo, Francisco Javier; Giner Ruiz, Vicente

2014-01-01

431

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.

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

2012-01-01

432

Nuclear magnetic resonance imaging and spectroscopy of human brain function.  

PubMed Central

The techniques of in vivo magnetic resonance (MR) imaging and spectroscopy have been established over the past two decades. Recent applications of these methods to study human brain function have become a rapidly growing area of research. The development of methods using standard MR contrast agents within the cerebral vasculature has allowed measurements of regional cerebral blood volume (rCBV), which are activity dependent. Subsequent investigations linked the MR relaxation properties of brain tissue to blood oxygenation levels which are also modulated by consumption and blood flow (rCBF). These methods have allowed mapping of brain activity in human visual and motor cortex as well as in areas of the frontal lobe involved in language. The methods have high enough spatial and temporal sensitivity to be used in individual subjects. MR spectroscopy of proton and carbon-13 nuclei has been used to measure rates of glucose transport and metabolism in the human brain. The steady-state measurements of brain glucose concentrations can be used to monitor the glycolytic flux, whereas subsequent glucose metabolism--i.e., the flux into the cerebral glutamate pool--can be used to measure tricarboxylic acid cycle flux. Under visual stimulation the concentration of lactate in the visual cortex has been shown to increase by MR spectroscopy. This increase is compatible with an increase of anaerobic glycolysis under these conditions as earlier proposed from positron emission tomography studies. It is shown how MR spectroscopy can extend this understanding of brain metabolism. Images Fig. 1 Fig. 2 Fig. 3

Shulman, R G; Blamire, A M; Rothman, D L; McCarthy, G

1993-01-01

433

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

NASA Astrophysics Data System (ADS)

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.

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

2009-10-01

434

Evaluation of Renal Growth by Magnetic Resonance Imaging and Computerized Tomography Volumes  

Microsoft Academic Search

PurposeMagnetic resonance imaging (MRI) and computerized tomography (CT) are commonly used to image complex medical conditions but limited data have been reported concerning normal renal volumetric measurement with these imaging techniques. We examined whether normative renal growth curves could be constructed from data derived from these imaging modalities, and from these curves assessed normal and abnormal renal development.

ROMAN HEUER; GRAHAM SOMMER; LINDA D. SHORTLIFFE

2003-01-01

435

Comparison of magnetic resonance imaging and computed tomography in suspected lesions in the posterior cranial fossa.  

PubMed Central

OBJECTIVE--To compare computed tomography and magnetic resonance imaging in investigating patients suspected of having a lesion in the posterior cranial fossa. DESIGN--Randomised allocation of newly referred patients to undergo either computed tomography or magnetic resonance imaging; the alternative investigation was performed subsequently only in response to a request from the referring doctor. SETTING--A regional neuroscience centre serving 2.7 million. PATIENTS--1020 Patients recruited between April 1986 and December 1987, all suspected by neurologists, neurosurgeons, or other specialists of having a lesion in the posterior fossa and referred for neuroradiology. The groups allocated to undergo computed tomography or magnetic resonance imaging were well matched in distributions of age, sex, specialty of referring doctor, investigation as an inpatient or an outpatient, suspected site of lesion, and presumed disease process; the referring doctor's confidence in the initial clinical diagnosis was also similar. INTERVENTIONS--After the patients had been imaged by either computed tomography or magnetic resonance (using a resistive magnet of 0.15 T) doctors were given the radiologist's report and a form asking if they considered that imaging with the alternative technique was necessary and, if so, why; it also asked for their current diagnoses and their confidence in them. MAIN OUTCOME MEASURES--Number of requests for the alternative method of investigation. Assessment of characteristics of patients for whom further imaging was requested and lesions that were suspected initially and how the results of the second imaging affected clinicians' and radiologists' opinions. RESULTS--Ninety three of the 501 patients who initially underwent computed tomography were referred subsequently for magnetic resonance imaging whereas only 28 of the 493 patients who initially underwent magnetic resonance imaging were referred subsequently for computed tomography. Over the study the number of patients referred for magnetic resonance imaging after computed tomography increased but requests for computed tomography after magnetic resonance imaging decreased. The reason that clinicians gave most commonly for requesting further imaging by magnetic resonance was that the results of the initial computed tomography failed to exclude their suspected diagnosis (64 patients). This was less common in patients investigated initially by magnetic resonance imaging (eight patients). Management of 28 patients (6%) imaged initially with computed tomography and 12 patients (2%) imaged initially with magnetic resonance was changed on the basis of the results of the alternative imaging. CONCLUSIONS--Magnetic resonance imaging provided doctors with the information required to manage patients suspected of having a lesion in the posterior fossa more commonly than computed tomography, but computed tomography alone was satisfactory in 80% of cases...

Teasdale, G. M.; Hadley, D. M.; Lawrence, A.; Bone, I.; Burton, H.; Grant, R.; Condon, B.; Macpherson, P.; Rowan, J.

1989-01-01

436

Segmentation of magnetic resonance images to construct human head model for diffuse optical imaging  

NASA Astrophysics Data System (ADS)

The brain activation image obtained by diffuse optical tomography (DOT) is obtained by solving inverse problem using the spatial sensitivity profile (SSP). The SSP can be obtained from the analysis of the light propagation using threedimensional head models. The head model is based upon segmented magnetic resonance (MR) image and there are several types of software based on binarization for segmentation of MR head images. We segmented superficial tissues which effect the light propagation in human head from MR images acquired with FATSAT and FIESTA pulse sequences by using region growing algorithm and morphological operation to facilitate the construction of the individual head models for DOT. The pixel intensity distribution of these images has appropriate characteristics to extract the superficial tissues by using algorithm based on binarization. The result of extraction was compared with the extraction from T2-weighted image which is commonly used to extract superficial tissues. The result of extraction from FATSAT or FIESTA image agree well with ground truth determined by manual segmentation.

Kurihara, Kazuki; Kawaguchi, Hiroshi; Takahashi, Yosuke; Obata, Takayuki; Okada, Eiji

2011-06-01

437

Contrast enhancement of extradural compressive material on magnetic resonance imaging.  

PubMed

Gadolinium-enhancement of compressive extradural material is detected occasionally with magnetic resonance (MR) imaging in dogs. Our goal was to characterize contrast enhancement of extradural compressive material associated with intervertebral disc herniation, and to evaluate the association between enhancement and histopathologic findings and the onset of clinical signs. Ninety-three dogs with a total of 99 lesions diagnosed as intervertebral disc herniation on MR imaging were assessed. Images were evaluated for lesion location, type of herniation, degree of compression, intramedullary T2-weighted (T2W) intensities, and contrast enhancement. In 23 dogs, surgically removed compressive material was evaluated histopathologically for hemorrhage, inflammation, neovascularization, fibroplasia, fibrosis, mineralization, necrosis, and chronicity. Contrast enhancement of extradural compressive material, meninges, and both the compressive materials and meninges was present in 51.5%, 39.4%, and 17.2% of lesions, respectively. Extradural enhancement occurred more frequently in extrusions than protrusions (P = 0.001). Meningeal enhancement and more severe neurologic deficits were significantly associated with a shorter duration of clinical signs (P = 0.04 and 0.01, respectively). Intramedullary T2W hyperintensities, present with 44.4% of lesions, were associated with more severe neurologic deficits (P = 0.001). Lesions with extradural enhancement were more often considered subacute to chronic in duration and more frequently associated with hemorrhage compared with nonenhancing material; however, no statistically significant association was established between contrast enhancement and histopathologic findings. Contrast enhancement of extradural compressive material and the meninges was found to be common with intervertebral disc herniation, and should not be interpreted as a specific sign of a mass lesion such as neoplasia. PMID:21322382

Suran, Jantra Ngosuwan; Durham, Amy; Mai, Wilfried; Seiler, Gabriela S

2011-01-01