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1

[Magnetic resonance imaging elbow anatomy].  

PubMed

Knowledge of the anatomy of the elbow joint has become intricate due to the advent of magnetic resonance imaging (MRI) techniques, as they are superior to represent the different soft tissues. This advantage allows evaluating in detail the increasingly frequent pathologic processes that occur in high performance athletes. The ideal MRI technique includes having the patient in a comfortable position, using an appropriate surface antenna and the right sequences in the appropriate planes depending on the entity. Being familiar with the normal elbow anatomy is crucial to properly identify the pathology and avoid potential diagnostic errors. PMID:22509650

Rodríguez-Ramírez, C L; Aguila-Mendoza, A

2

Normal and variant abdominal anatomy on magnetic resonance imaging.  

PubMed

The diagnostic usefulness of abdominal magnetic resonance (MR) imaging lies in the improved contrast resolution and ability to qualify several tissue characteristics of a specific organ or lesion. Our institution uses organ-specific protocols to facilitate technical reproducibility and optimize scan duration. These protocols are discussed individually in this article when applicable, noting that many build on a basic protocol with slight variations. Because most abdominal MR imaging studies are targeted toward an organ or area of interest, this article discusses the protocol strategies and relevant anatomy in a segmented/organ-specific manner. PMID:21816329

Wasnik, Ashish P; Mazza, Michael B; Lalchandani, Usha R; Liu, Peter S

2011-08-01

3

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

Microsoft Academic Search

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

Richard Kijowski; Michael Tuite; Matthew Sanford

2004-01-01

4

Anatomy of the thorax and shoulder girdle displayed by magnetic resonance imaging.  

PubMed Central

In 1971, radiographic anatomy of the human body was added to the gross anatomy course at UCLA. Radiographic contrast studies and plain anatomical displays were formulated into teaching packages for all organ systems. Residents presented each package to first-year medical students in the dissection laboratory to augment the teaching of anatomy. In November 1984, magnetic resonance imaging was instituted in the radiology department. Imaging the chest produced coronal and axial planes which displayed the muscles and soft tissues of the thorax. In 1986, the authors presented their study of MR anatomy of the chest and shoulder girdle to the American Association of Anatomists. The purpose of this presentation is to demonstrate the anatomy of the thorax and shoulder girdle as displayed by magnetic resonance, correlated with regional anatomy, with emphasis on soft tissue structures. Images Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13

Collins, J. D.; Shaver, M. L.; Batra, P.; Brown, K.

1991-01-01

5

Magnetic resonance assessment of pelvic anatomy and pelvic floor disorders after childbirth  

Microsoft Academic Search

To compare pelvic anatomy, using magnetic resonance imaging, between postpartum women with or without pelvic floor disorders.\\u000a We measured postpartum bony and soft tissue pelvic dimensions in 246 primiparas, 6–12-months postpartum. Anatomy was compared\\u000a between women with and without urinary or fecal incontinence, or pelvic organ prolapse; P?

Victoria L. Handa; Mark E. Lockhart; Kimberly S. Kenton; Catherine S. Bradley; Julia R. Fielding; Geoffrey W. Cundiff; Caryl G. Salomon; Christiane Hakim; Wen Ye; Holly E. Richter

2009-01-01

6

Anatomy and pathology of the male pelvis by magnetic resonance imaging  

Microsoft Academic Search

Magnetic resonance imaging (MRI) of the male pelvis was performed in 25 subjects: five normal voluteers; six patients with carcinoma of the bladder; nine with benign nodular hyperplasia (including five with concomitant bladder carcinoma); nine with prostatic carcinoma; and one with a lymphocele after radical prostatectomy. The display of normal anatomy is enhanced by the ability of the MRI device

H. Hricak; R. D. Williams; D. B. Spring; Moon K. L. Jr; M. W. Hedgcock; R. A. Watson; L. E. Crooks

1983-01-01

7

Human tooth pulp anatomy visualization by 3D magnetic resonance microscopy  

PubMed Central

Background Precise assessment of dental pulp anatomy is of an extreme importance for a successful endodontic treatment. As standard radiographs of teeth provide very limited information on dental pulp anatomy, more capable methods are highly appreciated. One of these is 3D magnetic resonance (MR) microscopy of which diagnostic capabilities in terms of a better dental pulp anatomy assessment were evaluated in the study. Materials and methods Twenty extracted human teeth were scanned on a 2.35 T MRI system for MR microscopy using the 3D spin-echo method that enabled image acquisition with isotropic resolution of 100 ?m. The 3D images were then post processed by ImageJ program (NIH) to obtain advanced volume rendered views of dental pulps. Results MR microscopy at 2.35 T provided accurate data on dental pulp anatomy in vitro. The data were presented as a sequence of thin 2D slices through the pulp in various orientations or as volume rendered 3D images reconstructed form arbitrary view-points. Sequential 2D images enabled only an approximate assessment of the pulp, while volume rendered 3D images were more precise in visualization of pulp anatomy and clearly showed pulp diverticles, number of pulp canals and root canal anastomosis. Conclusions This in vitro study demonstrated that MR microscopy could provide very accurate 3D visualization of dental pulp anatomy. A possible future application of the method in vivo may be of a great importance for the endodontic treatment.

Sustercic, Dusan; Sersa, Igor

2012-01-01

8

Sexual dimorphism in the human brain: evaluation of tissue volume, tissue composition and surface anatomy using magnetic resonance imaging  

Microsoft Academic Search

Magnetic resonance imaging (MRI) was used to evaluate sex differences in brain morphology by comparing measures of brain tissue volume, brain tissue composition (proportions of gray and white matter), and measures of cortical surface anatomy. A large and well-matched sample of healthy women (n=42) and healthy men (n=42) were evaluated. There was a significant gender effect on intracranial volume, males

Peg Nopoulos; Michael Flaum; Dan O’Leary; Nancy C Andreasen

2000-01-01

9

Magnetic Resonance Imaging and 3-Dimensional Analysis of External Anal Sphincter Anatomy  

PubMed Central

OBJECTIVE: To use magnetic resonance images of living women and 3-dimesional modeling software to identify the component parts and characteristic features of the external anal sphincter (EAS) that have visible separation or varying origins and insertions. METHODS: Detailed structural analysis of anal sphincter anatomy was performed on 3 pelvic magnetic resonance imaging (MRI) data sets selected for image clarity from ongoing studies involving nulliparous women. The relationships of anal sphincter structures seen in axial, sagittal, and coronal planes were examined using the 3-D Slicer 2.1b1 software program. The following were requirements for sphincter elements to be considered separate: 1) a clear and consistently visible separation or 2) a different origin or insertion. The characteristic features identified in this way were then evaluated in images from an additional 50 nulliparas for the frequency of feature visibility. RESULTS: There were 3 components of the EAS that met criteria as being “separate” structures. The main body (EAS-M) is separated from the subcutaneous external anal sphincter (SQ-EAS) by a clear division that could be observed in all (100%) of the MRI scans reviewed. The wing-shaped end (EAS-W) has fibers that do not cross the midline ventrally, but have lateral origins near the ischiopubic ramus. This EAS-W component was visible in 76% of the nulliparas reviewed. CONCLUSION: Three distinct external anal sphincter components can be identified by MRI in the majority of nulliparous women.

Hsu, Yvonne; Fenner, Dee E.; Weadock, William J.; DeLancey, John O. L.

2006-01-01

10

Anatomy and pathology of the male pelvis by magnetic resonance imaging  

SciTech Connect

Magnetic resonance imaging (MRI) of the male pelvis was performed in 25 subjects: five normal voluteers; six patients with carcinoma of the bladder; nine with benign nodular hyperplasia (including five with concomitant bladder carcinoma); nine with prostatic carcinoma; and one with a lymphocele after radical prostatectomy. The display of normal anatomy is enhanced by the ability of the MRI device to provide images in direct transverse, sagittal, and coronal planes. Sessile and pedunculated types of bladder carcinoma are readily shown due to the superior ability of MRI for soft-tissue characterization. Direct sagittal scans are advantageous for evaluation of tumors at the bladder base, and by combining two different planes of images, the extent of the neoplasm is better delineated. In the analysis of the prostate, MRI displays the gland in three dimensions and therefore allows accurate volumetric measurements. The greatest potential of MRI seems to be its ability to detect pathology confined to the gland. However, it is not yet known if a neoplastic nodule can be differentiated from chronic prostatitis. Unlike x-ray CT, metallic clips produce no streaking artifacts, giving MRI a definite advantage in the evaluation of patients after radical surgery. These observations were made on a small number of patients. If the results are confirmed with a larger number of patients, MRI will assume a prominent role in the clinical evaluation of bladder and prostate cancer.

Hricak, H. (Univ. of California, San Francisco); Williams, R.D.; Spring, D.B.; Moon, K.L., Jr.; Hedgcock, M.W.; Watson, R.A.; Crooks, L.E.

1983-12-01

11

Atlas of fetal sectional anatomy with ultrasound and magnetic resonance imaging  

SciTech Connect

Here is an atlas of sectional anatomy for the fetus featuring correlated anatomy and imaging, transverse coronal and sagittal views, a guide to development of the brain, cardiac anatomy in standard plans of study and, over 280 illustrations.

Isaacson, G.; Mintz, M.C.; Crelin, E.S.

1986-01-01

12

Differences in Femoral Notch Anatomy between Men and WomenA Magnetic Resonance Imaging Study  

Microsoft Academic Search

Background: Research has shown that variations in femoral intercondylar notch morphometry may be a predisposing factor for noncontact anterior cruciate ligament injury.Hypothesis: There are anatomic differences in the anterior cruciate ligament and femoral notch between men and women.Study Design: Descriptive anatomic study.Methods: Using magnetic resonance imaging, we performed a three-dimensional analysis of the femoral intercondylar notch morphometry to look for

William P. H. Charlton; Thomas A. St. John; Michael G. Ciccotti; Nichol Harrison; Mark Schweitzer

2002-01-01

13

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

14

Anatomy of the perineal membrane as seen in magnetic resonance images of nulliparous women  

PubMed Central

Objective Recent cadaver research demonstrates the perineal membrane’s ventral and dorsal portions and close relationship to the levator ani muscle. This study seeks to show these relationships in women by magnetic resonance (MR) images. Methods The subjects were 20 asymptomatic nulliparous women with normal pelvic examinations. MR images were acquired in multiple planes. Anatomical relationships from cadaver studies were examined in these planes. Results In the coronal plane the ventral perineal membrane forms an interconnected complex with the compressor urethrae, vestibular bulb and levator ani. The dorsal part connects the levator ani and vaginal side wall via a distinct band to the ischiopubic ramus. In the sagittal plane the parallel position of perineal membrane and levator ani are seen. Conclusion The perineal membrane’s anatomical features can be seen in women with MR. The close relationship between the perineal membrane and levator ani is evident.

BRANDON, Catherine J.; LEWICKY-GAUPP, Christina; LARSON, Kindra A.; DeLANCEY, John O.L.

2009-01-01

15

Magnetic resonance arthrography of glenohumeral lesions: anatomy and arthroscopically confirmed pathology.  

PubMed

Interpretation of magnetic resonance (MR) arthrography images of the glenohumeral ligaments is made difficult by anatomical variations and by the lack of descriptions of signs of pathology of the ligaments. In this review, we describe the normal and pathologic appearance of the glenohumeral ligaments of the shoulder. These ligaments play an important role in stabilization of the shoulder. Both 1.5 and 3 T MR units were used to acquire the MR images. The principal investigator reviewed the imaging reports and arthroscopic reports. All cases were correlated with arthroscopy. Lesions of the superior glenohumeral, middle glenohumeral, and inferior glenohumeral, including humeral avulsion of the glenoid ligament are discussed. Diagnosis of lesions of the glenohumeral ligaments remains a challenge. PMID:20947292

Boulet, Cedric; De Maeseneer, Michel; Pouliart, Nicole; De Mey, Johan; Handelberg, Frank; Shahabpour, Maryam

2010-10-14

16

Overhauser enhanced magnetic resonance imaging for tumor oximetry: Coregistration of tumor anatomy and tissue oxygen concentration  

PubMed Central

An efficient noninvasive method for in vivo imaging of tumor oxygenation by using a low-field magnetic resonance scanner and a paramagnetic contrast agent is described. The methodology is based on Overhauser enhanced magnetic resonance imaging (OMRI), a functional imaging technique. OMRI experiments were performed on tumor-bearing mice (squamous cell carcinoma) by i.v. administration of the contrast agent Oxo63 (a highly derivatized triarylmethyl radical) at nontoxic doses in the range of 2–7 mmol/kg either as a bolus or as a continuous infusion. Spatially resolved pO2 (oxygen concentration) images from OMRI experiments of tumor-bearing mice exhibited heterogeneous oxygenation profiles and revealed regions of hypoxia in tumors (<10 mmHg; 1 mmHg = 133 Pa). Oxygenation of tumors was enhanced on carbogen (95% O2/5% CO2) inhalation. The pO2 measurements from OMRI were found to be in agreement with those obtained by independent polarographic measurements using a pO2 Eppendorf electrode. This work illustrates that anatomically coregistered pO2 maps of tumors can be readily obtained by combining the good anatomical resolution of water proton-based MRI, and the superior pO2 sensitivity of EPR. OMRI affords the opportunity to perform noninvasive and repeated pO2 measurements of the same animal with useful spatial (?1 mm) and temporal (2 min) resolution, making this method a powerful imaging modality for small animal research to understand tumor physiology and potentially for human applications.

Krishna, Murali C.; English, Sean; Yamada, Kenichi; Yoo, John; Murugesan, Ramachandran; Devasahayam, Nallathamby; Cook, John A.; Golman, Klaes; Ardenkjaer-Larsen, Jan Henrik; Subramanian, Sankaran; Mitchell, James B.

2002-01-01

17

Feasibility of interactive magnetic resonance imaging of moving anatomy for clinical practice.  

PubMed

BACKGROUND: Real-time magnetic resonance imaging (MRI) imaging with real-time reconstruction has been available for some time. The technique acquires and presents the MRI images to the operator the instant they are acquired. However, besides guiding purposes, like catheter tracking and placement of electrodes during neurosurgery, the diagnostic value of this method is relatively unexplored. PURPOSE: To test an interactive slice-positioning system with respect to real-time MRI reconstruction for imaging of moving anatomical structures on two different scanner brands by using inexpensive computer hardware. MATERIALS AND METHODS: The MRI data were sampled using two acquisition schemes: a Cartesian sampling scheme and a radial sampling scheme based on the golden ratio. Four anatomical targets, which exhibit non-periodic movement, were identified and imaged: movement of the gastric ventricle emptying, movement of the small bowels, the articulators of a professional singer and of a 20-week old fetus. RESULTS: Informative anatomical images were obtained in different settings of moving targets. The implemented real-time system acquired, reconstructed and displayed MRI images in real time with a high frame rate using inexpensive computer hardware on two standard 1.5 T clinical MRI scanners. CONCLUSION: Our approach verified that when imaging selected moving anatomical targets, with no a priori knowledge of the movement, interactive slice positioning using real-time reconstruction may be a feasible approach for finding the optimal slice position in cases in which a standard 3D volumetric scan is impeded by movement. Future studies are needed to explore its full potential. PMID:23758759

Brix, Lau; Sørensen, Thomas S; Berber, Yasmina; Ries, Mario; Stausbøl-Grøn, Brian; Ringgaard, Steffen

2013-06-11

18

Cardiac anatomy, function and metabolism in elite cyclists assessed by magnetic resonance imaging and spectroscopy.  

PubMed

We investigated whether left ventricular hypertrophy in elite cyclists is associated with functional changes or abnormal energy metabolism. Left ventricular hypertrophy is a powerful risk factor for sudden cardiac death with different prognostic significance among the various geometric forms. Cyclists may have a combination of mixed eccentric and concentric hypertrophy. Magnetic resonance imaging was used to define left ventricular mass, geometry and function. Thirteen highly trained male cyclists and 12 healthy controls were investigated. Proton-decoupled phosphorus-31 cardiac spectroscopy was performed to assess parameters of myocardial high-energy phosphate metabolism. Left ventricular mass and end-diastolic volumes normalized for body surface area were significantly higher in cyclists (124.1 +/- 9.4 g.m-2 and 106.2 +/- 11.4 ml.m-2, respectively) than in controls (85.9 +/- 9.3 g.m-2 and 79.1 +/- 11.6 ml.m-2, respectively), (both P < 0.0001). The left ventricular mass to end-diastolic volume ratio, as a parameter of left ventricular geometry, was not significantly increased in cyclists compared to controls. Resting left ventricular ejection fraction, cardiac index, and systolic wall stress in cyclists did not differ significantly from those of controls. The phosphocreatine to adenosine triphosphate ratio was not significantly different between cyclists and controls (2.2 +/- 0.34 vs 2.2 +/- 0.17, ns). Cyclists show prominent left ventricular hypertrophy with normal geometry. The finding that the hypertrophic hearts of the cyclists had normal left ventricular function and a normal phosphocreatine to adenosine triphosphate ratio suggests that sport-induced left ventricular hypertrophy is a physiological adaptation rather than a pathophysiological response. PMID:8869870

Pluim, B M; Chin, J C; De Roos, A; Doornbos, J; Siebelink, H M; Van der Laarse, A; Vliegen, H W; Lamerichs, R M; Bruschke, A V; Van der Wall, E E

1996-08-01

19

Pocket atlas of cranial magnetic resonance imaging  

SciTech Connect

This atlas illustrates normal cerebral anatomy in magnetic resonance images. From their studies in cerebral anatomy utilizing cryomicrotome and other techniques, the authors selected more than 100 high-resolution images that represent the most clinically useful scans.

Haughton, V.M.; Daniels, D.L.

1986-01-01

20

Three-Dimensional Reconstruction of Brain Surface Anatomy Based on Magnetic Resonance Imaging Diffusion-Weighted Imaging: A New Approach  

Microsoft Academic Search

Fifty normal noninfarct patients and 12 cases with infarcts of the cerebrum were examined with routine magnetic resonance imaging and echo-planar diffusion-weighted imaging. The diffusion-weighted three-dimensional images were reconstructed with volume-rendering processing on workstation. Precentral gyrus, postcentral gyrus, superior parietal lobule, superior frontal gyrus, precentral sulcus, central sulcus, postcentral sulcus, intraparietal sulcus and superior frontal sulcus were best shown of

Xiangyang Gong; Marong Fang; Jin Wang; Jianzhong Sun; Xizheng Zhang; W. H. Kwong; David T. Yew

2004-01-01

21

Three-dimensional reconstruction of brain surface anatomy based on magnetic resonance imaging diffusion-weighted imaging: A new approach  

Microsoft Academic Search

Fifty normal noninfarct patients and 12 cases with infarcts of the cerebrum were examined with routine magnetic resonance imaging and echo-planar diffusion-weighted imaging. The diffusion-weighted three-dimensional images were reconstructed with volume-rendering processing on workstation. Precentral gyrus, post-central gyrus, superior parietal lobule, superior frontal gyrus, precentral sulcus, central sulcus, postcentral sulcus, intraparietal sulcus and superior frontal sulcus were best shown of

Xiangyang Gong; Marong Fang; Jin Wang; Jianzhong Sun; Xizheng Zhang; W. H. Kwong; David T. Yew

2004-01-01

22

High-resolution, high-throughput magnetic resonance imaging of mouse embryonic anatomy using a fast gradient-echo sequence  

Microsoft Academic Search

Embryonic development in normal and genetically modified mice is commonly analysed by histological sectioning. This procedure is time-consuming, prone to artefact, and results in the loss of three-dimensional (3D) information. Magnetic resonance imaging (MRI) of embryos has the potential of non-invasively acquiring a complete 3D data set. Published methods have used spin-echo techniques with inherently high signal-to-noise ratio (SNR); however,

Jürgen E. Schneider; Simon D. Bamforth; Stuart M. Grieve; Kieran Clarke; Shoumo Bhattacharya; Stefan Neubauer

2003-01-01

23

Ultrahigh-field magnetic resonance imaging: the clinical potential for anatomy, pathogenesis, diagnosis, and treatment planning in brain disease.  

PubMed

In this review, current (clinical) applications and possible future directions of ultrahigh-field (?7 T) magnetic resonance (MR) imaging in the brain are discussed. Ultrahigh-field MR imaging can provide contrast-rich images of diverse pathologies and can be used for early diagnosis and treatment monitoring of brain disease. These images may provide increased sensitivity and specificity. Several limitations need to be overcome before worldwide clinical implementation can be commenced. Current literature regarding clinically based ultrahigh-field MR imaging is reviewed, and limitations and promises of this technique are discussed, as well as some practical considerations for the implementation in clinical practice. PMID:22548936

van der Kolk, Anja G; Hendrikse, Jeroen; Luijten, Peter R

2012-05-01

24

Three-dimensional volume rendering of the ankle based on magnetic resonance images enables the generation of images comparable to real anatomy  

PubMed Central

We have applied high-quality medical imaging techniques to study the structure of the human ankle. Direct volume rendering, using specific algorithms, transforms conventional two-dimensional (2D) magnetic resonance image (MRI) series into 3D volume datasets. This tool allows high-definition visualization of single or multiple structures for diagnostic, research, and teaching purposes. No other image reformatting technique so accurately highlights each anatomic relationship and preserves soft tissue definition. Here, we used this method to study the structure of the human ankle to analyze tendon–bone–muscle relationships. We compared ankle MRI and computerized tomography (CT) images from 17 healthy volunteers, aged 18–30 years (mean 23 years). An additional subject had a partial rupture of the Achilles tendon. The MRI images demonstrated superiority in overall quality of detail compared to the CT images. The MRI series accurately rendered soft tissue and bone in simultaneous image acquisition, whereas CT required several window-reformatting algorithms, with loss of image data quality. We obtained high-quality digital images of the human ankle that were sufficiently accurate for surgical and clinical intervention planning, as well as for teaching human anatomy. Our approach demonstrates that complex anatomical structures such as the ankle, which is rich in articular facets and ligaments, can be easily studied non-invasively using MRI data.

Anastasi, Giuseppe; Cutroneo, Giuseppina; Bruschetta, Daniele; Trimarchi, Fabio; Ielitro, Giuseppe; Cammaroto, Simona; Duca, Antonio; Bramanti, Placido; Favaloro, Angelo; Vaccarino, Gianluigi; Milardi, Demetrio

2009-01-01

25

From Signal to Image: Magnetic Resonance Imaging Physics for Cardiac Magnetic Resonance  

Microsoft Academic Search

.   Magnetic resonance imaging (MRI) is a powerful tool which enables the visualization of anatomy and the assessment of many\\u000a physiological aspects of organ function. MRI and magnetic resonance angiography and magnetic resonance spectroscopy will play\\u000a critical roles in cardiac applications during the next millennium. Thus, it is important to have a basic understanding of\\u000a the most important physical processes

R. V. Mulkern; T. Chung

2000-01-01

26

Nuclear magnetic resonance spectroscopy  

Microsoft Academic Search

Magnetic resonance spectroscopy is a valuable method for the non-invasive investigation of metabolic processes and can now be combined with conventional magnetic resonance imaging in patients. This article gives a brief introduction into the principles and physiological and clinical applications of in vivo proton magnetic resonance spectroscopy, surveys experiences in healthy volunteers and presents exemplary results in patients suffering from

Armin Ettl; Christa Fischer-Klein; Andreas Chemelli; Albert Daxer; Stephan Felber

1994-01-01

27

Ultrahigh-field magnetic resonance imaging: the clinical potential for anatomy, pathogenesis, diagnosis and treatment planning in neck and spine disease.  

PubMed

An increase of the magnetic field strength to ultrahigh-field yields advantageous as well as disadvantageous changes in physical effects. The beneficial increase in signal/noise ratio can be leveraged into higher spatiotemporal resolution, and an exacerbation of artifacts can impede ultrahigh-field imaging. With the successful introduction of intracranial and musculoskeletal imaging at 7 T, recent advances in coil design have created opportunities for further applications of ultrahigh-field magnetic resonance (MR) imaging in other parts of the body. Initial studies in 7 T neck and spine MR imaging have revealed promising insights and new challenges, demanding further research and methodological optimization. PMID:22548937

Umutlu, Lale; Forsting, Michael; Ladd, Mark E

2012-03-15

28

Sports health magnetic resonance imaging challenge.  

PubMed

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. PMID:23015984

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

2010-11-01

29

Magnetic resonance imaging and spectroscopy  

SciTech Connect

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

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

1986-01-01

30

Cardiac Magnetic Resonance In Adults With Congenital Heart Disease  

PubMed Central

Increasing numbers of adults with congenital heart disease are referred for cardiac magnetic resonance imaging. Knowledge of the congenital heart anatomy, prior surgical interventions, and the development of an imaging focus for each individual patient plays a crucial role when performing a successful cardiac magnetic resonance imaging examination. The following manuscript focuses on cardiac magnetic resonance imaging considerations of three specific conotruncal congenital heart lesions: tetralogy of Fallot, transposition of the great arteries (TGA), and physiologically corrected TGA (c-TGA).

Valente, Anne Marie

2013-01-01

31

Versatile Magnetic Resonance Spectrometer  

Microsoft Academic Search

A Pound-Knight-Watkins marginal oscillator has been modified by the addition of a vibrating capacitor in parallel with the tuning capacitor to produce a simple circuit which may be used to observe paramagnetic resonance at low fields, nuclear magnetic resonance, and nuclear quadrupole resonance. Suggestions are made as to the type of information which may be obtained in an undergraduate laboratory

J. A. Cowen; W. H. Tanttila

1958-01-01

32

VERSATILE MAGNETIC RESONANCE SPECTROMETER  

Microsoft Academic Search

A Pound-Knight-Watkins marginal osciliator was modified by the addition ; of a vibrating capacitor in parallel with the tuning capacitor to produce a ; simple circuit which may be used to observe paramagnetic resonance at low fields, ; nuclear magnetic resonance, and nuclear quadrupole resonance. Suggestions are ; mnde as to the type of information which may be obtained in

J. A. Cowen; W. H. Tanttila

1958-01-01

33

Cross-Sectional Anatomy, Computed Tomography and Magnetic Resonance Imaging of the Thoracic Region of Common Dolphin (Delphinus delphis) and Striped Dolphin (Stenella coeruleoalba).  

PubMed

The aim of this study was to provide a detailed anatomical description of the thoracic region features in normal common (Delphinus delphis) and striped dolphins (Stenella coeruleoalba) and to compare anatomical cross-sections with computed tomography (CT) and magnetic resonance imaging (MRI) scans. CT and MRI were used to scan 7 very fresh by-caught dolphin cadavers: four common and three striped dolphins. Diagnostic images were obtained from dolphins in ventral recumbency, and after the examinations, six dolphins were frozen (-20°C) and sliced in the same position. As well as CT and MRI scans, cross-sections were obtained in the three body planes: transverse (slices of 1 cm thickness), sagittal (5 cm thickness) and dorsal (5 cm thickness). Relevant anatomical features of the thoracic region were identified and labelled on each section, obtaining a complete bi-dimensional atlas. Furthermore, we compared CT and MRI scans with anatomical cross-sections, and results provided a complete reference guide for the interpretation of imaging studies of common and striped dolphin's thoracic structures. PMID:23711289

Alonso-Farré, J M; Gonzalo-Orden, M; Barreiro-Vázquez, J D; Ajenjo, J M; Barreiro-Lois, A; Llarena-Reino, M; Degollada, E

2013-05-27

34

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

35

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

36

Nuclear magnetic resonance gyroscope  

SciTech Connect

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

Grover, B.C.

1984-02-07

37

Magnetic Resonance Imaging  

NSDL National Science Digital Library

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

VU Bioengineering RET Program, School of Engineering,

38

Nuclear Magnetic Resonance.  

National Technical Information Service (NTIS)

Nuclear Magnetic Resonance (NMR) is a new technique which has been introduced into the medical diagnostic imaging field. NMR is a method of imaging the body by exposing it to low-energy magnetic and radio-frequency fields. This process yields bio-chemical...

D. Watkins N. Netherton

1983-01-01

39

Resonant and non-resonant magnetic scattering  

SciTech Connect

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

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

1991-12-31

40

Resonant and non-resonant magnetic scattering  

SciTech Connect

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

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

1991-01-01

41

Clinical magnetic resonance imaging  

SciTech Connect

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

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

1988-01-01

42

Magnetic Resonance Annual, 1985  

SciTech Connect

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

Kressel, H.Y.

1985-01-01

43

Magnetic resonance fingerprinting.  

PubMed

Magnetic resonance is an exceptionally powerful and versatile measurement technique. The basic structure of a magnetic resonance experiment has remained largely unchanged for almost 50?years, being mainly restricted to the qualitative probing of only a limited set of the properties that can in principle be accessed by this technique. Here we introduce an approach to data acquisition, post-processing and visualization--which we term 'magnetic resonance fingerprinting' (MRF)--that permits the simultaneous non-invasive quantification of multiple important properties of a material or tissue. MRF thus provides an alternative way to quantitatively detect and analyse complex changes that can represent physical alterations of a substance or early indicators of disease. MRF can also be used to identify the presence of a specific target material or tissue, which will increase the sensitivity, specificity and speed of a magnetic resonance study, and potentially lead to new diagnostic testing methodologies. When paired with an appropriate pattern-recognition algorithm, MRF inherently suppresses measurement errors and can thus improve measurement accuracy. PMID:23486058

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

2013-03-14

44

Nuclear magnetic resonance gyroscopes  

Microsoft Academic Search

Nuclear magnetic resonance gyroscopes (NMRGs) detect rotation as a shift in the Larmor precession frequency of nuclear spins. A review of the open literature on NMRGs is presented, which includes an introduction to the spectroscopic techniques that enable NMRGs and a discussion of the design details for several specific NMRGs that have been built.

E. A. Donley

2010-01-01

45

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

46

Anatomical Brain Magnetic Resonance Imaging of Typically Developing Children and Adolescents  

ERIC Educational Resources Information Center

|Methodological issues relevant to magnetic resonance imaging studies of brain anatomy are discussed along with the findings on the neuroanatomic changes during childhood and adolescence. The development of the brain is also discussed.|

Giedd, Jay N.; Lalonde, Francois M.; Celano, Mark J.; White, Samantha L.; Wallace, Gregory L.; Lee, Nancy R.; Lenroot, Rhoshel K.

2009-01-01

47

High field magnetic resonance  

US Patent & Trademark Office Database

A magnetic resonance system is disclosed. The system includes a transceiver having a multichannel receiver and a multichannel transmitter, where each channel of the transmitter is configured for independent selection of frequency, phase, time, space, and magnitude, and each channel of the receiver is configured for independent selection of space, time, frequency, phase and gain. The system also includes a magnetic resonance coil having a plurality of current elements, with each element coupled in one to one relation with a channel of the receiver and a channel of the transmitter. The system further includes a processor coupled to the transceiver, such that the processor is configured to execute instructions to control a current in each element and to perform a non-linear algorithm to shim the coil.

2010-09-21

48

Nuclear magnetic resonance contrast agents  

DOEpatents

This invention relates to the field of nuclear magnetic resonance imaging and nuclear magnetic resonance spectroscopy, also known simply as magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS). MRI and MRS are particularly useful in medical research and diagnosis. MRI may be used in addition to x-ray imaging. This invention concerns a family of contrast agents for use in magnetic resonance imaging and a method of enhancing the contrast of magnetic resonance images of an object by incorporating a contrast agent of this invention into the object prior to forming the images or during formation of the images. A contrast agent of this invention is a paramagnetic lanthanide hexaazamacrocyclic molecule, where a basic example has the formula LnC{sub 16}H{sub 14}N{sub 6}. Important applications of the invention are in medical diagnosis, treatment, and research, where images of portions of a human body are formed by means of magnetic resonance techniques. 2 figs.

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

1989-01-24

49

Magnetic Resonance and Computed Tomographic Image-Directed Stereotaxy for Animal Research  

Microsoft Academic Search

Current stereotactic frames for animal experimentation presume normal intracranial anatomy for atlas-directed probe placement. This is an invalid assumption for animal brain tumor models, where distortions of cerebral anatomy make image-directed stereotaxy necessary. To address this need, an accurate and reproducible magnetic resonance and computed tomographic compatible image-directed stereotactic apparatus for animal experimentation is presented.

Robert J. Maciunas; Robert L. Galloway

1989-01-01

50

Magnetic Resonance Facility (Fact Sheet)  

SciTech Connect

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

Not Available

2012-03-01

51

Micro-magnetic resonance imaging of avian embryos  

PubMed Central

Chick embryos are useful models for probing developmental mechanisms including those involved in organogenesis. In addition to classic embryological manipulations, it is possible to test the function of molecules and genes while the embryo remains within the egg. Here we define conditions for imaging chick embryo anatomy and for visualising living quail embryos. We focus on the developing limb and describe how different tissues can be imaged using micro-magnetic resonance imaging and this information then synthesised, using a three-dimensional visualisation package, into detailed anatomy. We illustrate the potential for micro-magnetic resonance imaging to analyse phenotypic changes following chick limb manipulation. The work with the living quail embryos lays the foundations for using micro-magnetic resonance imaging as an experimental tool to follow the consequences of such manipulations over time.

Li, Xiaojing; Liu, Jia; Davey, Megan; Duce, Suzanne; Jaberi, Neema; Liu, Gang; Davidson, Gemma; Tenent, Seaneen; Mahood, Ruth; Brown, Phoebe; Cunningham, Craig; Bain, Andrew; Beattie, Kevin; McDonald, Laura; Schmidt, Katy; Towers, Matthew; Tickle, Cheryll; Chudek, Sandy

2007-01-01

52

[Myelin and nuclear magnetic resonance].  

PubMed

MRI is one of the most important tools for the investigation of white matter diseases of the central nervous system. Other techniques based on the magnetic resonance phenomena (magnetization transfer imaging, diffusion imaging, magnetic resonance spectroscopy) have joined MRI to better caracterize certain diseases, understand their pathophysiology and follow their evolution. PMID:18033031

Tourbah, A; Dormont, D; Galanaud, D; Sedel, F; Lyon-Caen, O

2007-10-01

53

Magnetic resonance enterography.  

PubMed

Magnetic resonance (MR) enterography is a targeted examination of the gastrointestinal tract, particularly the small intestine, without nasojejunal intubation (in which case it is referred to as MR enteroclysis). Until recently, MR imaging of the small bowel could not reliably compete with the high-quality small bowel images generated by computed tomography (CT). Now, however, MR enterography is not only a feasible alternative to CT, but may provide superior diagnostic information, specifically with regard to differentiating active, inflammatory disease from chronic, fibrostenotic disease. MR enterography is no longer merely adequate and radiation-free; it is an essential part of the imaging armamentarium. PMID:23182510

Grand, David J; Beland, Michael; Harris, Adam

2013-01-01

54

nuclear magnetic resonance gyroscope  

SciTech Connect

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

Karwacki, F. A.; Griffin, J.

1985-04-02

55

Nuclear Magnetic Resonance (NMR) Guidelines.  

National Technical Information Service (NTIS)

Nuclear Magnetic Resonance (NMR) is a medical diagnostic imaging technique that applies the atomic principles of magnetic spin to visualize and analyze disease states in bodily tissues. NMR differs from the radiological devices in that (a) it does not uti...

R. Halpern

1983-01-01

56

Magnetic resonance cell  

SciTech Connect

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

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

1984-05-01

57

PTK787\\/ZK 222584, a Specific Vascular Endothelial Growth Factor-Receptor Tyrosine Kinase Inhibitor, Affects the Anatomy of the Tumor Vascular Bed and the Functional Vascular Properties as Detected by Dynamic Enhanced Magnetic Resonance Imaging 1  

Microsoft Academic Search

Antiangiogenic therapy is a promising new strategy of inhibiting tumor growth and formation of metastases. Recently, a number of compounds with different effects on tumor endothelial cells have entered clinical trials and revealed the need for diagnostic methods to detect their biological activity. Dynamic enhanced magnetic resonance imaging (dyMRI) is used in most clinical trials with antiangiogenic active compounds. We

Joachim Drevs; Ralph Muller-Driver; Christine Wittig; Stefan Fuxius; Norbert Esser; Harald Hugenschmidt; Moritz A. Konerding; Peter R. Allegrini; Jeanette Wood; Jurgen Hennig; Clemens Unger

2002-01-01

58

Magnetic Field Issues in Magnetic Resonance Imaging  

Microsoft Academic Search

Advances in Magnetic Resonance Imaging depend on the capability of the available hardware. Specifically, for the main magnet configuration, using derivative constraints, we can create a static magnetic field with reduced levels of inhomogeneity over a prescribed imaging volume. In the gradient coil, the entire design for the axial elliptical coil, and the mathematical foundation for the transverse elliptical coil

Labros Spiridon Petropoulos

1993-01-01

59

Travelling-wave nuclear magnetic resonance.  

PubMed

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

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

2009-02-19

60

Magnetic resonance venography and liver transplant complications  

PubMed Central

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

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

2013-01-01

61

Magnetic resonance venography and liver transplant complications.  

PubMed

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

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

2013-09-28

62

Secondary resonance magnetic force microscopy  

NASA Astrophysics Data System (ADS)

In this study, we have developed secondary resonance magnetic force microscopy (SR-MFM) for imaging alternating magnetic fields from a sample surface at the secondary resonant frequency of the magnetic cantilever at the same time as the topographic image. SR-MFM images of alternating magnetic fields diverging from the main pole in a driving perpendicular magnetic recording head are presented, and the divergence and convergence of the fields are discussed. The spatial resolution of SR-MFM is estimated to be 18 nm this is 2.5 times smaller than that of conventional MFM.

Tanaka, Suguru; Azuma, Yasuo; Majima, Yutaka

2012-04-01

63

Field Concentrator Based Resonant Magnetic Sensor  

Microsoft Academic Search

A novel resonant magnetic sensor based on the combination of a mechanical resonator and a magnetic field concentrator with two gaps is reported. In contrast to previous Lorentz force based resonant magnetic sensors, a high sensitivity is achieved without modulated driving current and complex feedback electronics. Furthermore, compared to magnetic moment based resonant magnetic sensors, the new concept requires no

S. Brugger; P. Simon; O. Paul

2006-01-01

64

Cranial and spinal magnetic resonance imaging: A guide and atlas  

SciTech Connect

This atlas provides a clinical guide to interpreting cranial and spinal magnetic resonance images. The book includes coverage of the cerebrum, temporal bone, and cervical, thoracic, and lumbar spine, with more than 400 scan images depicting both normal anatomy and pathologic findings. Introductory chapters review the practical physics of magnetic resonance (MR) imaging, offer guidelines for interpreting cranial MR scans, and provide coverage of each anatomic region of the cranium and spine. For each region, scans accompanied by captions, show normal anatomic sections matched with MR images. These are followed by MR scans depicting various disease states.

Daniels, D.L.; Haughton, V.M.

1987-01-01

65

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

66

Nuclear magnetic resonance contrast agents  

DOEpatents

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

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

1997-12-30

67

Nuclear magnetic resonance contrast agents  

DOEpatents

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

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

1997-01-01

68

Nuclear magnetic resonance spectrometry  

SciTech Connect

This review covers the published literature from July 1983 to August 1985 although some citations of other work are also included. As noted in earlier reviews it is impossible to summarize 2 years of NMR literature in so short a space. However, it is hoped that the books, reviews, and various citations will be a useful guide to the reader. The publication Spectroscopy (PO Box 50, Springfield, OR 97477; H. W. Lafferty, Ed.) has recently commenced and promises to be of interest and utility in various areas of spectroscopy, including NMR. Noninvasive Medical Imaging, an international journal published by Verlag Chemie GmbH (Federal Republic of Germany) and Reviews of Magnetic Resonance in Medicine published by Pergamon Press cover specialized application of NMR. The American Chemical Society has introduced an audiocassette course on Fourier Transform NMR Spectroscopy. An extensive C13 NMR Data Base has been made available by Science Information Services, Inc., Larchmont, NY, and City Software, Milwaukee, WI has introduced The NMR Simulator for the IBM PC. 342 references, 2 tables.

Wasson, J.R.

1986-04-01

69

Multimodal Magnetic Resonance Imaging for Brain Disorders: Advances and Perspectives  

Microsoft Academic Search

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

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

2008-01-01

70

Orthopaedic Magnetic Resonance Imaging Challenge  

PubMed Central

Apophyseal avulsion injuries of the hip and pelvis are frequent athletic injuries in children and adolescents, most commonly associated with explosive movement or sprinting. This article details typically encountered apophyseal injuries and their appearance on magnetic resonance imaging.

Kjellin, Ingrid; Stadnick, Michael E.; Awh, Mark H.

2010-01-01

71

Fluorine-19 Nuclear Magnetic Resonance.  

National Technical Information Service (NTIS)

Several series of diadducts of titanium tetrafluoride were studied with high resolution fluorine-19 nuclear magnetic resonance spectroscopy. These consisted of studies with aromatic amine oxides, amides and sulfoxides as bases. Mixed diadducts of TiF4 wit...

R. O. Ragsdale

1971-01-01

72

Metabolic brain imaging by magnetic resonance  

Microsoft Academic Search

Novel magnetic resonance methods have been developed to noninvasively measure biochemical compounds in the human brain as guided by magnetic resonance imaging. Together, these methods are referred to as magnetic resonance spectroscopy (MRS) and can be divided into three major categories: single voxel MRS, magnetic resonance spectroscopic imaging and dynamic MRS, which is a novel adaption of the first method.

Edward J Novotny Jr

2006-01-01

73

Magnetic resonance imaging of the knee.  

PubMed

Magnetic resonance imaging (MRI) is an accepted non-invasive modality for evaluation of soft tissue pathology without exposure to ionizing radiation. Current applications demonstrate excellent visualization of the anatomy and pathology of various organs. Preliminary studies in the knee reveal fine resolution of anatomy and pathology involving the meniscus. The purpose of this study is to determine a prospective correlation between MRI scans and actual meniscal pathology as documented at the time of arthroscopy. MRI scans were obtained in 155 patients, on 156 knees (one patient with bilateral scans), with 86 patients (87 knees) eventually undergoing diagnostic and operative videoarthroscopy performed by the same surgeon (DWJ). All images were obtained on the same high-resolution 1.5 Tesla GE Signa Magnetic Resonance Scanner with the same radiologist performing all readings (PEB). The knees were studied in the coronal and sagittal plane using a spin echo sequence and 5 mm slice thicknesses. The menisci were described as having Grade 1, 2, or 3 changes, with Grade 3 reserved for complete tears. Using arthroscopy as the diagnostic standard, the accuracy of MRI in diagnosing medial and lateral meniscal tears was 93.1% and 96.6%, respectively with a Grade 3 MRI reading. For tears of the ACL, the accuracy was 96.6% as confirmed at arthroscopy. Five tears of the PCL were also documented by MRI and correlated with clinical evaluation. Other abnormalities seen were articular cartilage and osteochondral defects, bone tumors, tibial plateau fractures, Baker's cysts, and meniscal cysts. The MRI scan is a highly accurate, noninvasive modality for documentation of meniscal pathology as well as cruciate ligament tears in the knee. PMID:3344877

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

74

Magnetic Resonance Force Microscope Development  

SciTech Connect

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

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

1999-06-03

75

Applied peritoneal anatomy.  

PubMed

The peritoneal cavity is a complex anatomical structure with multiple attachments and connections. These are better understood with reference to the embryological development of this region. Armed with this knowledge, the diagnosis and assessment of a wide range of common intra-abdominal diseases becomes straightforward. This article will review and simplify the terminology, complex embryological development, and anatomy of the peritoneum, peritoneal attachments, and the reflections forming the peritoneal boundaries. Normal anatomy will be described using schematic diagrams with corresponding computed tomography (CT) and magnetic resonance imaging (MRI) images, including CT peritoneograms. The relevance of intra- and extra-peritoneal anatomy to common pathological processes will be demonstrated. PMID:23149392

Patel, R R; Planche, K

2012-11-10

76

Influence of X Chromosome and Hormones on Human Brain Development: A Magnetic Resonance Imaging and Proton Magnetic Resonance Spectroscopy Study of Turner Syndrome  

Microsoft Academic Search

Background: Women with Turner syndrome (TS; 45,X) lack a normal second X chromosome, and many are prescibed exogenous sex and growth hormones (GH). Hence, the allow its an opportunity to investigate genetic and endocrine influences on brain development. Methods: We examined brain anatomy and metabolism in 27 adult monosomic TS women and 21 control subjects with volumetric magnetic resonance imaging

William J. Cutter; Eileen M. Daly; Dene M. W. Robertson; Xavier A. Chitnis; Therese A. M. J. van Amelsvoort; Andrew Simmons; Virginia W. K. Ng; Benjamin S. Williams; Phillip Shaw; Gerard S. Conway; David H. Skuse; David A. Collier; Michael Craig; Declan G. M. Murphy

2006-01-01

77

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

78

Interventional Cardiovascular Magnetic Resonance Imaging  

PubMed Central

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

Saikus, Christina E.; Lederman, Robert J.

2010-01-01

79

Superconducting magnets for whole body magnetic resonance imaging  

Microsoft Academic Search

Superconducting magnets have achieved preeminence in the magnetic resonance imaging (MRI) industry. Further growth in this market will depend on reducing system costs, extending medical applications, and easing the present siting problem. New magnet designs from Oxford address these issues. Compact magnets are economical to build and operate. Two 4 Tesla whole body magnets for research in magnetic resonance spectroscopy

M. F. Murphy

1989-01-01

80

Clinical Applications of Cardiac Magnetic Resonance Imaging After Repair of Tetralogy of Fallot  

Microsoft Academic Search

.   In the past 15 years, cardiovascular magnetic resonance (MR) has evolved into an imaging technique that provides adequate,\\u000a and in part unique, information on residual problems in the follow-up of patients operated for tetralogy of Fallot. Spin-echo\\u000a or gradient-echo cine magnetic resonance imaging allow detailed assessment of intracardiac and large vessel anatomy, which\\u000a is particularly helpful in Fallot patients

W. A. Helbing; A. de Roos

2000-01-01

81

Prognostic value of magnetic resonance imaging in the management of fistula-in-ano  

Microsoft Academic Search

PURPOSE: Magnetic resonance imaging of fistula-in-ano has been shown to predict surgical anatomy accurately and identify complex features. In addition, fistula complexity has been correlated with poor outcome after surgical intervention. We investigated whether preoperative magnetic resonance imaging could predict clinical outcome after surgery for fistulous disease better than clinical examination under anesthetic. METHODS: Seventy patients with clinically suspected fistula-in-ano

K. S. Chapple; J. A. Spencer; A. C. J. Windsor; D. Wilson; J. Ward; N. S. Ambrose

2000-01-01

82

Magnetic resonance apparatus  

DOEpatents

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

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

1982-01-01

83

Magnetic resonance imaging in medicine  

Microsoft Academic Search

Over the past twenty years, magnetic resonance imaging (MRI) has become one of the most important imaging modalities available to clinical medicine. It offers great technical flexibility, and is free of the hazards associated with ionizing radiation. In addition to its role as a routine imaging technique with a growing range of clinical applications, the pace of development in MRI

Stephen F. Keevil

2001-01-01

84

Magnetic resonance of a single molecular spin  

Microsoft Academic Search

Magnetic-resonance spectroscopy on single molecules represents the ultimate limit in sensitivity of electron spin resonance: the detection of a single molecular spin. This is achieved by combining single molecule spectroscopy and optically detected magnetic resonance. Experimental results on pentacene in p-terphenyl both in zero-field and in the presence of a weak magnetic field demonstrate that magnetic-resonance spectroscopy on single molecules

Jürgen Köhler

1999-01-01

85

Magnetic Resonance Spectroscopy and Magnetic Resonance Imaging Findings in Krabbe's Disease  

Microsoft Academic Search

Two twins with late infantile globoid cell leukodystrophy or Krabbe's disease were studied with conventional magnetic resonance imaging (MRI) and proton magnetic resonance spectroscopy. Brain MRI demonstrated brain atrophy with extensive bilateral symmetric abnormal T2 signal in the posterior periventricular white matter, parietal lobes, corona radiata, centrum semiovale, and splenium of the corpus callosum. Magnetic resonance imaging-guided proton magnetic resonance

Maria K. Zarifi; A. Aria Tzika; Loukas G. Astrakas; Tina Young Poussaint; Douglas C. Anthony; Basil T. Darras

2001-01-01

86

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

87

Magnetic Resonance Reporter Gene Imaging  

PubMed Central

Molecular imaging has undergone an explosive advancement in recent years, due to the tremendous research efforts made to understand and visualize biological processes. Molecular imaging by definition assesses cellular and molecular processes in living subjects, with the targets of following metabolic, genomic, and proteomic events. Furthermore, reporter gene imaging plays a central role in this field. Many different approaches have been used to visualize genetic events in living subjects, such as, optical, radionuclide, and magnetic resonance imaging. Compared with the other techniques, magnetic resonance (MR)-based reporter gene imaging has not occupied center stage, despite its superior three-dimensional depictions of anatomical details. In this article, the authors review the principles and applications of various types of MR reporter gene imaging technologies and discuss their advantages and disadvantages.

Lee, Sheen-Woo; Lee, Sang-Hoon; Biswal, Sandip

2012-01-01

88

Visualization of the cardiac venous system using cardiac magnetic resonance.  

PubMed

We sought to investigate the value of cardiac magnetic resonance to depict cardiac venous anatomy. For cardiac resynchronization therapy the lead for the left ventricle is usually placed by transvenous approach into a tributary of the coronary sinus (CS). Knowledge of the anatomy and variations of the cardiac venous system may facilitate the positioning of the left ventricle lead. The cardiac magnetic resonance examinations of 23 subjects (16 volunteers and 7 patients) were retrospectively analyzed. All examinations were performed using navigator-gated whole-heart steady-state free precession coronary artery imaging after administration of intravascular contrast agents (gadofosveset in volunteers; Gadomer-17 in patients). The cardiac venous system was visualized in all subjects. The most frequent anatomical variant observed (in 12 subjects [52%]) was a connection of the small cardiac vein to the CS at the crux cordis. In 10 subjects (44%) the small veins entered the right atrium independently from the CS, and the posterior interventricular vein was connected to the CS at the crux cordis. Only one subject had a disconnection between the CS and posterior interventricular vein, which entered into the right atrium independently. The mean distance of the posterior vein of the left ventricle and the left marginal vein to the ostium of the CS was 15.2+/-4.7 mm and 49.7+/-14.1 mm, respectively. In conclusion, the anatomy of the cardiac venous system and its anatomical variability can be described using cardiac magnetic resonance. Its preimplantation visualization may help to facilitate the implant procedure and to reduce fluoroscopy time. PMID:18237610

Chiribiri, Amedeo; Kelle, Sebastian; Götze, Stephan; Kriatselis, Charalampos; Thouet, Thomas; Tangcharoen, Tarinee; Paetsch, Ingo; Schnackenburg, Bernhard; Fleck, Eckart; Nagel, Eike

2007-12-21

89

Human Cerebral Cortex: Localization, Parcellation, and Morphometry with Magnetic Resonance Imaging  

Microsoft Academic Search

We describe a system of parcellation of the human brain that is based on the functional anatomy of the cerebral cortex and that is applied to the analysis of magnetic resonance images. This system is designed to support investigations of hemispheric asymmetries and quantitative lesion localization studies in cognitive neuroscience. The system of cortical subdivision is a neural systems oriented

J. Rademacher; A. M. Galaburda; D. N. Kennedy; P. A. Filipek; V. S. Caviness

1992-01-01

90

Hemispheric lateralization at different levels of human auditory word processing: a functional magnetic resonance imaging study  

Microsoft Academic Search

We used functional magnetic resonance imaging to disentangle the functional anatomy of brain systems involved in the processing of auditory word form and meaning. Three monitoring tasks on auditory stimuli, aimed at phonetic, lexical and semantic processing, were used. We found no lateralization of temporal lobe activations, when word processing was contrasted versus the complex phonetic task. Bilateral middle temporal

Roland Zahn; Walter Huber; Eva Drews; Stephan Erberich; Timo Krings; Klaus Willmes; Michael Schwarz

2000-01-01

91

Magnetic resonance imaging of the retina: A brief historical and future perspective  

PubMed Central

This invited review starts with a brief introduction of retinal anatomy and magnetic resonance imaging techniques with contrast to optics, followed by a history and future perspective on MRI applications to investigate the retinas of rodents, non-human primates and humans.

Duong, Timothy Q.

2011-01-01

92

Functional Evaluation of Pulmonary Circulation: With Special Emphasis on Magnetic Resonance Imaging  

Microsoft Academic Search

Complete assessment of the pulmonary circulation should include not only the anatomy of the pulmonary arteries and veins but also the functional and hemodynamic consequences of the pathology. The available tools for the pulmonary vascular assessment include: catheterization with x-ray angiography, echocardiography, magnetic resonance (MR), computed tomography (CT), and radioisotope scintigraphy. As each has its own advantages and disadvantages, proper

Shi-Joon Yoo; Lars Grosse-Wortmann

93

Spatiotemporal spiral magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

This paper addresses the problem of Magnetic Resonance (MR) imaging of moving targets using spiral scan echo planar data collection. A system model is developed to interpret the readouts of repeated spiral excitations via two separate time variables, the slow-time and fast-time. This mathematical model is used to construct an inversion for forming the time progression of the target image. A method for increasing the repetition rate of the spiral data collection is presented. Results are provided.

Soumekh, Mehrdad

1999-05-01

94

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

95

Magnetic resonance imaging in glenohumeral instability  

PubMed Central

The glenohumeral joint is the most commonly dislocated joint of the body and anterior instability is the most common type of shoulder instability. Magnetic resonance (MR) imaging, and more recently, MR arthrography, have become the essential investigation modalities of glenohumeral instability, especially for pre-procedure evaluation before arthroscopic surgery. Injuries associated with glenohumeral instability are variable, and can involve the bones, the labor-ligamentous components, or the rotator cuff. Anterior instability is associated with injuries of the anterior labrum and the anterior band of the inferior glenohumeral ligament, in the form of Bankart lesion and its variants; whereas posterior instability is associated with reverse Bankart and reverse Hill-Sachs lesion. Multidirectional instability often has no labral pathology on imaging but shows specific osseous changes such as increased chondrolabral retroversion. This article reviews the relevant anatomy in brief, the MR imaging technique and the arthrographic technique, and describes the MR findings in each type of instability as well as common imaging pitfalls.

Jana, Manisha; Gamanagatti, Shivanand

2011-01-01

96

SQUID-Detected Magnetic Resonance Imaging in Microtesla Magnetic Fields  

Microsoft Academic Search

We describe studies of nuclear magnetic resonance (NMR) spectroscopy and magnetic resonance imaging (MRI) of liquid samples at room temperature in microtesla magnetic fields. The nuclear spins are prepolarized in a strong transient field. The magnetic signals generated by the precessing spins, which range in frequency from tens of Hz to several kHz, are detected by a low-transition temperature dc

R. McDermott; N. Kelso; S. K. Lee; M. MöBetale; M. Mück; W. Myers; B. ten Haken; H. C. Seton; A. H. Trabesinger; A. Pines; J. Clarke

2004-01-01

97

PTK787/ZK 222584, a specific vascular endothelial growth factor-receptor tyrosine kinase inhibitor, affects the anatomy of the tumor vascular bed and the functional vascular properties as detected by dynamic enhanced magnetic resonance imaging.  

PubMed

Antiangiogenic therapy is a promising new strategy of inhibiting tumor growthand formation of metastases. Recently, a number of compounds with different effects on tumor endothelial cells have entered clinical trials and revealed the need for diagnostic methods to detect their biological activity. Dynamic enhanced magnetic resonance imaging (dyMRI) is used in most clinical trials with antiangiogenic active compounds. We evaluated this method by using PTK787/ZK 222584, a specific inhibitor of the VEGF-receptor tyrosine kinases, which showed antitumoral and antiangiogenic activity in a murine renal cell carcinoma (RENCA) model. After intrarenal application of RENCA cells, mice developed a primary tumor and metastases to the lung and abdominal lymph nodes. After daily oral therapy for 21 days with either PTK787/ZK 222584 at a dose of 50 mg/kg or vehicle, primary tumors of all animals were analyzed by dyMRI. Gadolinium-DOTA (Dotarem) was used as a contrast agent to detect vessel permeability and contrast agent extravasation, whereas intravascular iron oxide nanoparticles (Endorem) were used to detect partial tumor blood volume. Additionally, vessel density, architecture, diameter, and blood flow velocity were investigated by appropriate methods. Surprisingly, no changes in extravasation occurred under treatment with PTK787/ZK 222584 as compared with the control group, whereas a significant decrease in vessel permeability occurred. Furthermore, an increase in partial blood volume was found in the PTK787/ZK 222584-treated group, although vessel density was reduced as seen by histology. Using the corrosion cast technique, reduction in vessel density was significant but not very pronounced and predominantly attributable to the loss of microvessels only. This finding correlated with a shift to large vessel diameters in the primary tumors of PTK787/ZK 222584-treated animals and with reduction of blood flow velocity in the tumor feeding renal artery. From these findings, we conclude that the treatment with PTK787/ZK 222584 primarily reduces the number of tumor microvessels, accompanied by a hemodynamic dilation of the remaining vessels. This dilation could influence the result of dyMRI such that no change in extravasation or even an increase in partial tumor blood volume could be observed. PMID:12124335

Drevs, Joachim; Müller-Driver, Ralph; Wittig, Christine; Fuxius, Stefan; Esser, Norbert; Hugenschmidt, Harald; Konerding, Moritz A; Allegrini, Peter R; Wood, Jeanette; Hennig, Jürgen; Unger, Clemens; Marmé, Dieter

2002-07-15

98

Bistable electron magnetic resonance in solids  

Microsoft Academic Search

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

Didier Gourier; Laurent Binet; Olivier Guillot-Noël

2004-01-01

99

Neuronal current distribution imaging using magnetic resonance  

Microsoft Academic Search

A new functional magnetic resonance imaging (fMRI) technique to visualize the distribution of neuronal currents in the human brain was developed Measurements of the internal magnetic field deformation caused by an electric current dipole in a phantom were performed using a method based on the microscopic magnetic resonance imaging technique. The minimal value of the current dipole moment detected by

Hirotake Kamei; Keiji Iramina; K. Yoshikawa; Shoogo Ueno

1999-01-01

100

Clinical assessment of ischemia and malignancy with magnetic resonance spectroscopy  

Microsoft Academic Search

Summary form only given. Using recent developments in construction of high field magnets, magnetic resonance spectroscopy has been integrated with magnetic resonance imaging for clinical use. Magnetic resonance (MR) spectra can be obtained from an image-defined volume of interest using a variety of magnetic resonance localization techniques. Recently, magnetic resonance spectroscopic imaging techniques have been developed which fully combine MR

M. W. Weiner

1988-01-01

101

Localized ferromagnetic resonance using Magnetic Resonance Force Microscopy  

Microsoft Academic Search

Magnetic Resonance Force Microscopy (MRFM) is a novel approach to scanned probe imaging, combining the advantages of Magnetic Resonance Imaging (MRI) with Scanning Probe Microscopy (SPM) [1]. It has extremely high sensitivity that has demonstrated detection of individual electron spins [2] and small numbers of nuclear spins [3]. Here we describe our MRFM experiments on Ferromagnetic thin film structures. Unlike

Jongjoo Kim

2008-01-01

102

Magnetic Resonance Spectroscopy in Biological Systems.  

National Technical Information Service (NTIS)

These notes give a general view of the various methods of magnetic resonance spectroscopy and of their possible applications to biological and medical problems. After analyzing the fundamental NMR and EPR techniques, double resonance (ENDOR), pulsed NMR a...

E. Tiezzi

1971-01-01

103

Magnetic Resonance Force Microscopy with Magnetic Tiped Cantilevers  

NASA Astrophysics Data System (ADS)

Magnetic resonance force microscopy has been performed, until recently, by attaching the sample under study to a fragile microcantilever. Increasing the resolution, force-sensitivity and practicality of the technique, demands both reducing the size of the magnetic particle and measuring magnetic resonance as an excitation of magnetic-tip cantilevers. To lift the sample-on-cantilever restriction we have succesfully attached and controllably magnetized a micron-size Alnico particle to the end of a commercial Si cantilever. We will describe the techniques and protocols used to magnetize and characterize the magnetic particles as well as the mechanical detection of electron spin resonance with these probes.

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

1998-03-01

104

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

105

Pharmacological Stress Cardiovascular Magnetic Resonance  

PubMed Central

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

Chotenimitkhun, Runyawan; Hundley, W. Gregory

2013-01-01

106

Superconducting magnets for whole body magnetic resonance imaging  

SciTech Connect

Superconducting magnets have achieved preeminence in the magnetic resonance imaging (MRI) industry. Further growth in this market will depend on reducing system costs, extending medical applications, and easing the present siting problem. New magnet designs from Oxford address these issues. Compact magnets are economical to build and operate. Two 4 Tesla whole body magnets for research in magnetic resonance spectroscopy (MRS) are now in operation. Active-Shield magnets, by drastically reducing the magnetic fringe fields, will allow MRI systems with superconducting magnets to be located in previously inaccessible sites.

Murphy, M.F.

1989-03-01

107

MAGNETIC RESONANCE ELASTOGRAPHY: A REVIEW  

PubMed Central

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

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

2011-01-01

108

Magnetic Resonance Imaging System Based on Earth's Magnetic Field  

Microsoft Academic Search

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

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

2004-01-01

109

A mechanical analog of nuclear magnetic resonance  

NSDL National Science Digital Library

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

Masters, Mark F.

2013-02-13

110

Advances in mechanical detection of magnetic resonance  

PubMed Central

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

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

2008-01-01

111

Magnetic resonance arthrography of the upper extremity.  

PubMed

Although magnetic resonance arthrography is not indicated for every clinical scenario, capsular distention can significantly improve visualization of intra-articular pathologic conditions. With attention to technique, intraarticular injection can be completed successfully with little patient discomfort. This article provides details of the technique for injection of the shoulder, the elbow, and the wrist for optimization of magnetic resonance imaging. PMID:23472588

Lomasney, Laurie M; Choi, Haemi; Jayanthi, Neeru

2012-12-20

112

Existence of resonances in magnetic scattering  

NASA Astrophysics Data System (ADS)

The Schrödinger operator with a compactly supported magnetic field is shown to produce infinitely many resonances, in any odd dimension[greater-or-equal, slanted]3. The proof is based on the Poisson formula for resonances and properties of the magnetic heat invariants.

Hitrik, Michael

2002-11-01

113

Advances in Magnetic Resonance Electrical Impedance Mammography  

Microsoft Academic Search

Magnetic Resonance Electrical Impedance Mammography (MREIM) is a new imaging technique under development by Wollin Ventures, Inc. in conjunction with the H. Lee Moffitt Cancer Center & Research Institute. MREIM addresses the problem of low specificity of magnetic resonance mammography and high false-positive rates, which lead to unnecessary biopsies. Because cancerous tissue has a higher electrical conductivity than benign tissue,

Nataliya Kovalchuk

2008-01-01

114

Chemical Principles Revisited. Proton Magnetic Resonance Spectroscopy.  

ERIC Educational Resources Information Center

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

McQuarrie, Donald A.

1988-01-01

115

Magnetic Field Issues in Magnetic Resonance Imaging.  

NASA Astrophysics Data System (ADS)

Advances in Magnetic Resonance Imaging depend on the capability of the available hardware. Specifically, for the main magnet configuration, using derivative constraints, we can create a static magnetic field with reduced levels of inhomogeneity over a prescribed imaging volume. In the gradient coil, the entire design for the axial elliptical coil, and the mathematical foundation for the transverse elliptical coil have been presented. Also, the design of a self-shielded cylindrical gradient coil with a restricted length has been presented. In order to generate gradient coils adequate for head imaging without including the human shoulders in the design, asymmetric cylindrical coils in which the gradient center is shifted axially towards the end of a finite cylinder have been introduced and theoretical as well as experimental results have been presented. In order to eliminate eddy current effects in the design of the non-shielded asymmetric gradient coils, the self-shielded asymmetric cylindrical gradient coil geometry has been introduced. Continuing the development of novel geometries for the gradient coils, the complete set of self-shielded cylindrical gradient coils, which are designed such that the x component of the magnetic field varies linearly along the three traditional gradient axes, has been presented. In order to understand the behavior of the rf field inside a dielectric object, a mathematical model is briefly presented. Although specific methods can provide an indication of the rf behavior inside a loosely dielectric object, finite element methodology is the ultimate approach for modeling the human torso and generating an accurate picture for the shape of the rf field inside this dielectric object. For this purpose we have developed a 3D finite element model, using the Coulomb gauge condition as a constraint. Agreement with the heterogeneous multilayer planar model has been established, while agreement with theoretical results from the spherical model and experimental results from the cylindrical model at 170 M H z is very good and provides an encouraging sign for using this finite element approach for modeling the rf inside the human body. (Abstract shortened by UMI.).

Petropoulos, Labros Spiridon

116

Magnetic resonance imaging: Basic principles  

SciTech Connect

This book has been revised to reflect the past three years' technological developments and to meet the everyday needs of radiologists and clinicians who use MRI in routine practice. Among the new features are a lucid explanation of the gray scale and its significance; a complete atlas of normal MRI anatomy; and head-to-foot illustrations of pathologic MRI findings.

Young, S.W.

1987-01-01

117

Magnetic resonance of a single molecular spin  

NASA Astrophysics Data System (ADS)

THE introduction of optical detection methods for observing magnetic resonance transitions in metastable paramagnetic states1-4 has contributed enormously to our understanding of the properties of photoexcited molecules in condensed phases. In such experiments the luminescence intensity is recorded as a function of the frequency of an applied microwave field. At resonance with transitions between sublevels of a metastable paramagnetic state, the lifetime of the metastable state is altered and a consequent change in the luminescence intensity is observed. Here we report the observation of such optically detected magnetic resonance transitions for the triplet state of a single pentacene molecule embedded in a p-terphenyl host crystal. This result has been obtained by combining the conventional optical detection technique for observing magnetic resonance transitions1-4 with the new single-molecule optical detection methods developed recently5,6. This observation opens the way for magnetic resonance studies in condensed phases with single-molecule sensitivity.

Köhler, J.; Disselhorst, J. A. J. M.; Donckers, M. C. J. M.; Groenen, E. J. J.; Schmidt, J.; Moerner, W. E.

1993-05-01

118

An atlas of radiological anatomy  

Microsoft Academic Search

This book contains a wealth of radiologic images of normal human anatomy; plain radiographs, contrast-enhanced radiographs, and computed tomography (CT) scans. There are 18 pages of magnetic resonance (MR) images, most on the brain and spinal cord, so that there are only two pages on MR imaging of the heart and two pages on abdominal and pelvic MR imaging. Twelve

J. Weir; P. Abrahams

1986-01-01

119

Petal resonator surface coil in spectroscopy by magnetic resonance  

NASA Astrophysics Data System (ADS)

In this work, we present a radio frequency resonator surface coil for Magnetic Resonance Imaging and Spectroscopy based on the magnetron device. We named our RF coil: Petal Resonator Surface (PERES) coil. This resonator coil consists of eight coil petals connected symmetrically all around a central single-loop coil. We previously tested this coil prototype n a General Electric 1.5 T imager and successfully acquired brain images. Based on these encouraging results, we used our coil design on the same MR imager to generate brain spectra. Finally, a MR spectrum of a healthy brain is presented. .

Hidalgo, S.; Rodriguez, A.; Rojas, R.; Sanchez, J.; Reynoso, G.; Barrios, F. A.

2001-10-01

120

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

121

Other magnetic resonance imaging techniques.  

PubMed

Relatively new developments in MRI, such as functional MRI (fMRI), magnetic resonance spectroscopy (MRS) and diffusion tensor imaging (DTI) are rapidly developing into imaging modalities that will become clinically available in the near future. They have in common that their signal is somewhat easier to interpret than structural MRI: fMRI mirrors excess cerebral blood flow, in many cases representing brain activity, MRS gives the average volume concentrations of specific chemical compounds, and DTI reflects "directedness" of micro-anatomical structures, of particular use in white matter where fiber bundle disruption can be detected with great sensitivity. While structural changes in MRI have been disappointing in giving a diagnosis of sufficient sensitivity and specificity, these newer methods hold out hope for elucidating pathological changes and differentiating patient groups more rigorously. This paper summarizes promising research results that will yet have to be translated into real life clinical studies in larger groups of patients (e.g. memory clinic patients). Where available, we have tried to summarize results comparing different types of dementia. PMID:21843379

Ebmeier, Klaus P; Filippini, Nicola; Heise, Verena; Sexton, Claire E

2011-09-01

122

Detecting spin perturbations using magnetic resonance imaging  

US Patent & Trademark Office Database

Implementations and examples of systems, apparatus and techniques for using magnetic resonance imaging to measure spin perturbations. In one implementation, a sample containing nuclear spins is magnetized using a principle magnetic field generated external to the sample. A periodic pulse sequence is applied to the sample. The pulse sequence includes multiple radio frequency (rf) pulses and multiple recovery times between the rf pulses. The pulse sequence is configured to generate, in the presence of a magnetic field perturbation, a sequence of multiple different steady states of magnetization in the sample during each period of the pulse sequence. A magnetic resonance signal acquired from the sample is processed to identify characteristics of a magnetic field perturbation in the sample. In some implementations, processing the signal to identify characteristics of a magnetic field perturbation in the sample includes processing the signal to identify characteristics of an electric current in the sample.

2012-08-21

123

Magnetic Resonance at Short Distances  

SciTech Connect

The magnetic interactions between a fermion and an antifermion of opposite electric or color charges in the $^{1}S_{0}^{-+}$ and $^{3}P_{0}^{++}$ states with $J=0$ are very attractive and singular near the origin and may allow the formation of new bound and resonance states at short distances. In the two body Dirac equations formulated in constraint dynamics, the short-distance attraction for these states for point particles leads to a quasipotential that behaves near the origin as $-\\alpha ^{2}/r^{2}$, where $ \\alpha $ is the coupling constant. Representing this quasipotential at short distances as $\\lambda (\\lambda +1)/r^{2}$ with $\\lambda =(-1+\\sqrt{1-4\\alpha ^{2}})/2$, both $^{1}S_{0}^{-+}$ and $^{3}P_{0}^{++}$ states admit two types of eigenstates with drastically different behaviors for the radial wave function $u=r\\psi $. One type of states, with $u$ growing as $r^{\\lambda +1}$ at small $r$, will be called usual states. The other type of states with $u$ growing as $r^{-\\lambda }$ will be called peculiar states. Both of the usual and peculiar eigenstates have admissible behaviors at short distances. Remarkably, the solutions for both sets of $^{1}S_{0}$ states can be written out analytically. The usual bound $^{1}S_{0}$ states possess attributes the same as those one usually encounters in QED and QCD, with bound state energies explicitly agreeing with the standard perturbative results through order $\\alpha ^{4}$. In contrast, the peculiar bound $^{1}S_{0}$ states, yet to be observed, not only have different behaviors at the origin, but also distinctly different bound state properties (and scattering phase shifts). For the peculiar $^{1}S_{0}$ ground state of fermion-antifermion pair with fermion rest mass $m$, the root-mean-square radius is approximately $1/m$, binding energy is approximately $(2-\\sqrt{2})m$, and rest mass approximately $\\sqrt{2}m$. On the other hand, the $(n+1)$${}^{1}S_{0}$ peculiar state with principal quantum number $(n+1)$ is nearly degenerate in energy and approximately equal in size with the $n$$^{1}S_{0}$ usual states. For the $ {}^{3}P_{0}$ states, the usual solutions lead to the standard bound state energies and no resonance, but resonances have been found for the peculiar states whose energies depend on the description of the internal structure of the charges, the mass of the constituent, and the coupling constant. The existence of both usual and peculiar eigenstates in the same system leads to the non-self-adjoint property of the mass operator and two non-orthogonal complete sets. As both sets of states are physically admissible, the mass operator can be made self-adjoint with a single complete set of admissible states by introducing a new peculiarity quantum number and an enlarged Hilbert space that contains both the usual and peculiar states in different peculiarity sectors. Whether or not these newly-uncovered quantum-mechanically acceptable peculiar $^{1}S_{0}$ bound states and $^{3}P_{0}$ resonances for point fermion-antifermion systems correspond to physical states remains to be further investigated.

Crater, H. W. [University of Tennessee Space Institute; Wong, Cheuk-Yin [ORNL

2012-01-01

124

Velocity-Encoded Magnetic Resonance Image Assessment of Regional Aortic Flow in Coarctation Patients  

Microsoft Academic Search

Background. During primary coarctation repair, collat- eral blood vessels contribute significantly to distal per- fusion. We sought to determine if velocity-encoded cine magnetic resonance imaging (VENC-MRI) could provide insight into anatomy and hemodynamics of collateral flow in patients with unrepaired coarctation. Methods. Sixteen patients (median age, 6.2 years; range, 1 to 18) with discrete coarctation (65% severe, 29% mild- moderate)

Tiffany J. Riehle; John N. Oshinski; Marijn E. Brummer; Jennifer Favaloro-Sabatier; William T. Mahle; Derek A. Fyfe; Kirk R. Kanter; W. James Parks

2006-01-01

125

Evaluation of Hydatid Disease of the Heart with Magnetic Resonance Imaging  

SciTech Connect

Two patients with cardiac involvement of hydatid disease are presented: one with hydatid cyst of the interventricular septum and pulmonary arteries and the other with multiple pulmonary cysts associated with intracardiac and pericardial cysts. The ability of magnetic resonance imaging (MRI) to provide a global view of cardiac anatomy in any plane with high contrast between flowing blood and soft tissue ensures it an important role in the diagnosis and preoperative assessment of hydatid disease of the heart.

Kotoulas, Grigoris K.; Magoufis, George L.; Gouliamos, Athanasios D.; Athanassopoulou, Alexandra K.; Roussakis, Arcadios C.; Koulocheri, Dimitra P.; Kalovidouris, Angelos; Vlahos, Labros [Department of Radiology, CT-MRI Unit, Areteion Hospital, University of Athens, 76 Vas. Sophias Ave., GR-115 28 Athens (Greece)

1996-05-15

126

Cardiovascular magnetic resonance imaging of hypoplastic left heart syndrome in children  

Microsoft Academic Search

Cardiovascular magnetic resonance imaging (CMR) plays an important complementary role to echocardiography and conventional\\u000a angiography in the evaluation of hypoplastic left heart syndrome. This imaging modality is particularly useful for assessing\\u000a cardiovascular postsurgical changes, extracardiac vascular anatomy, ventricular and valvular function, and a variety of complications.\\u000a The purpose of this article is to provide a contemporary review of the role

Jonathan R. Dillman; Adam L. Dorfman; Anil K. Attili; Prachi P. Agarwal; Aaron Bell; Gisela C. Mueller; Ramiro J. Hernandez

2010-01-01

127

Miniature Magnet for Electron Spin Resonance Experiments  

ERIC Educational Resources Information Center

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

Rupp, L. W.; And Others

1976-01-01

128

Magnetic Resonance Imaging Studies of Process Rheology.  

National Technical Information Service (NTIS)

The objective of this program is to develop magnetic resonance imaging and numerical modeling methods which will provide for improved methods of flow analysis as well as an improved understanding of the flow behavior of solid particle filled polymeric sus...

D. T. Wadiac G. A. Lo J. C. Crowley R. Van De Griend S. W. Sinton

1988-01-01

129

JAMA Patient Page: Magnetic Resonance Imaging  

MedlinePLUS

... Radiology; National Library of Medicine; International Society for Magnetic Resonance in Medicine; National Heart, Lung, and Blood Institute; Radiological Society of North America The JAMA Patient Page is a public ...

130

Miniature Magnet for Electron Spin Resonance Experiments  

ERIC Educational Resources Information Center

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

Rupp, L. W.; And Others

1976-01-01

131

Magnetic Earth Ionosphere Resonant Frequencies (MEIRF) Project.  

National Technical Information Service (NTIS)

The West Virginia State College Community College Division NASA Magnetic Earth Ionosphere Resonant Frequencies (MEIRF) study is described. During this contract period, the two most significant and professionally rewarding events were the presentation of t...

C. Spaniol

1993-01-01

132

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

133

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

134

Magnetic Resonance Spectroscopy of Breast Disease.  

National Technical Information Service (NTIS)

We have developed a unique magnetic resonance imaging multi voxel pulse sequence producing spectroscopic images of key metabolites found in breast cancer, and validated our work with in vitro spectra and pathology. We have shown that choline peaks are oft...

D. M. Ikeda

2001-01-01

135

Magnetic Resonance Spectroscopy of Breast Cancer.  

National Technical Information Service (NTIS)

We have developed a unique magnetic resonance imaging multi voxel pulse sequence unaffected by intravenous contrast producing spectroscopic images of key metabolites (choline) found in breast cancer, and validated our work in 22 breast lesions with in vit...

D. M. Ikeda

2002-01-01

136

Can magnetic resonance imaging differentiate undifferentiated arthritis?  

PubMed Central

A high sensitivity for the detection of inflammatory and destructive changes in inflammatory joint diseases makes magnetic resonance imaging potentially useful for assigning specific diagnoses, such as rheumatoid arthritis and psoriatic arthritis in arthritides, that remain undifferentiated after conventional clinical, biochemical and radiographic examinations. With recent data as the starting point, the present paper describes the current knowledge on magnetic resonance imaging in the differential diagnosis of undifferentiated arthritis.

?stergaard, Mikkel; Duer, Anne; H?rslev-Petersen, Kim

2005-01-01

137

A Primer on Functional Magnetic Resonance Imaging  

Microsoft Academic Search

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

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

2007-01-01

138

Resonant Magnetic Field Sensor With Frequency Output  

Microsoft Academic Search

This paper presents a novel type of resonant magnetic field sensor exploiting the Lorentz force and providing a frequency output. The mechanical resonator, a cantilever structure, is embedded as the frequency-determining element in an electrical oscillator. By generating an electrical current proportional to the position of the cantilever, a Lorentz force acting like an additional equivalent spring is exerted on

Robert Sunier; Tobias Vancura; Yue Li; Kay-Uwe Kirstein; Henry Baltes; Oliver Brand

2006-01-01

139

Force-Detected Nuclear Magnetic Resonance Probe  

NASA Astrophysics Data System (ADS)

Magnetic resonance force microscopy (MRFM) entails measuring the force on spins in a sample by a nearby magnetic grain as they are cyclically flipped by RF radiation in the presence of a background magnetic field. The sample is glued to a cantilever, which acts as the force detector. We have constructed a compact, LHe-cooled MRFM probe which fits in a 1'' tube, minimizing thermal drift, and allowing testing in storage dewars. The RF field is generated by a 700 ?m diameter coil in a tuned and matched tank circuit. Joule and RF heating control sample temperature. The sample is mounted on a silicon-nitride cantilever, and its magnetization is modulated at the cantilever resonance frequency by interrupted adiabatic rapid passage. Probe performance is demonstrated by measuring a 10 fN magnetic resonance signal from a sample of Nd doped Ca^19F_2.

Harrell, Lee E.; Thurber, Kent; Fainchtein, Raul; Marohn, John A.; Smith, Doran D.

2000-03-01

140

Functional Magnetic Resonance Imaging in Nursing Research  

Microsoft Academic Search

Functional magnetic resonance imaging (fMRI) is a powerful noninvasive neuroimaging technique nurse scientists can use to investigate the structure and cognitive capacities of the brain. A strong magnetic field and intermittent high-frequency pulses cause protons in body tissues to release energy, which can be recorded and processed into images that are sensitive to specific tissue characteristics. Although temporal and spatial

L. Clark Johnson; Todd L. Richards; Kristen H. Archbold; Carol A. Landis

2006-01-01

141

Magnetic resonance measurements of polar sea ice  

Microsoft Academic Search

A Nuclear Magnetic Resonance (NMR) sensor system has been developed to measure the brine fraction profile of polar sea ice. The system is based on a 0.3 T Halbach permanent magnet array and has significantly more sensitivity than earlier Earth's field NMR systems deployed in Antarctica. Brine fraction experiments were performed in November 2009 near Ross Island, Antarctica and the

Robin Dykstra; Achim Gadke

2011-01-01

142

Helmholtz superconducting receivers for magnetic resonance microscopy  

Microsoft Academic Search

The use of coupled high temperature superconductor (HTS) coil arrays in construction of low noise volume imaging probes for magnetic resonance is investigated. Two probes designed to image different sample volumes were developed in collaboration with Conductus Inc. The design objectives were (1)a robust vacuum system, (2)increased signal to noise performance over copper imaging probes, and (3)improved magnetic field homogeneity

Sarah Elizabeth Hurlston

2000-01-01

143

Radiation therapy planning and simulation with magnetic resonance images  

NASA Astrophysics Data System (ADS)

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

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

2008-04-01

144

Nanoscale Fourier-Transform Magnetic Resonance Imaging  

NASA Astrophysics Data System (ADS)

We report a method for nanometer-scale pulsed nuclear magnetic resonance imaging and spectroscopy. Periodic radio-frequency pulses are used to create temporal correlations in the statistical polarization of a solid organic sample. The spin density is spatially encoded by applying a series of intense magnetic field gradient pulses generated by focusing electric current through a nanometer-scale metal constriction. We demonstrate this technique using a silicon nanowire mechanical oscillator as a magnetic resonance sensor to image H1 spins in a polystyrene sample. We obtain a two-dimensional projection of the sample proton density with approximately 10-nm resolution.

Nichol, John M.; Naibert, Tyler R.; Hemesath, Eric R.; Lauhon, Lincoln J.; Budakian, Raffi

2013-07-01

145

Magnetic resonance based noninvasive RF nerve stimulator.  

PubMed

A noninvasive method of stimulating the nerve by applying radiofrequency has been presented. The design is based on the concept of magnetic resonance based power transfer. A comparison between electric field on the nerve at the frequency of 450-550 KHz with vacuum placed under a human tissue and the case where it is replaced with a resonant and non-resonant structure was analysed. Calculations were performed by using Ansoft HFSS. Power savings of 7.15% was observed when resonant structures were used, compared to vacuum. Theoretical calculation and simulation of fields were presented. PMID:23367443

Ganesh Bharadwaj, C V; Yuanjin, Zheng

2012-01-01

146

HOSPITAL PHYSICS: Magnetic resonance imaging and spectroscopy  

NASA Astrophysics Data System (ADS)

Nuclear Magnetic Resonance (NMR) was first described in the scientific literature 50 years ago when Bloch and Purcell, working independently, showed how certain nuclei placed in a magnetic field absorbed energy in the radiofrequency range and re-emitted this energy during their transition back to the relaxed state (Bloch 1946, Purcell 1946). This phenomenon has since revolutionized medical imaging with its application in Magnetic Resonance Imaging (MRI) and in vivo Magnetic Resonance Spectroscopy (MRS). MRI produces pictures of `slices' through the human body with exquisite detail and contrast without the use of radiation, while in vivo MRS provides chemical information from selected areas in a similarly non-invasive way. This article describes some of the principles involved in the two techniques.

Andrews, Caroline; Simmons, Andrew; Williams, Steve

1996-03-01

147

Magnetically-excited flexural plate wave resonator  

SciTech Connect

A flexural plate wave (FPW) resonator was constructed by patterning current lines on a silicon nitride membrane suspended on a rectangular silicon frame. Eigenmodes of the rectangular membrane were excited using Lorentz forces generated between alternating surface currents and a static in-plane magnetic field. The magnetic field strength required for these devices can be achieved with small permanent magnets ({approx} 1 cm{sup 3}). Preferential coupling to a particular membrane mode was achieved by positioning current lines along longitudinal mode antinodes. An equivalent-circuit model was derived that characterizes the input impedance of a one-port device and the transmission response of a two-port device over a range of frequencies near a single membrane resonance. Experiments were performed to characterize the effects of varying magnetic field, ambient gas, gas pressure, and input power. To the authors` knowledge, this is the first experimental demonstration of a resonant FPW device.

Martin, S.J.; Butler, M.A.; Spates, J.J.; Schubert, W.K.; Mitchell, M.A. [Sandia National Labs., Albuquerque, NM (United States). Microsensor Research and Development Dept.

1997-08-01

148

Solution nuclear magnetic resonance spectroscopy.  

PubMed

Solution nuclear magnetic resonance (NMR) spectroscopy has come a long way in characterizing the structure and function of biological molecules since the first one-dimensional spectrum of protein was recorded about 30 years ago. To date (September 1, 2012), there are 9,521 solution NMR structures in the Protein Data Bank, compared to 74,009 determined by crystallographic methods. Unlike X-ray and electron microscopy (EM) methods, which are based on the concepts of Fourier optics and image reconstruction, structure determination by NMR involves measuring structural restraints and finding structural solutions that satisfy the restraints. Although the NMR approach is much less direct in a physical sense, it has proven itself over the years to be capable of de novo structure determination at high precision. Moreover, the method is highly versatile and can be used in a variety of ways for addressing mechanistic questions. NMR measurements of protein internal dynamics and protein-protein or protein-ligand interaction are directly relevant to function in vivo because the molecules are often in physiological buffer conditions. The method can also be applied to investigate protein-folding intermediates, conformational changes, as well as intrinsically unfolded proteins. Recently, along with X-ray and EM, solution NMR has entered a state of rapid growth for structural studies of membrane proteins, already demonstrating its feasibility in de novo structure determination of membrane-embedded ion channels and receptors. As the hardware advances rapidly, especially in cryogenic probes that have much higher sensitivity, the sample concentration required for solution NMR investigation is decreasing, hopefully soon to a concentration level at which nonspecific protein aggregation is no longer an issue. After three decades of improvement in spectrometer technology, NMR pulse experiments, isotope labeling schemes, and structure determination software, we believe that solution NMR will truly enter the production phase in the next decade to answer biological questions of high impact, and to become more versatile than ever in complementing X-ray and EM in investigating protein structure and function. PMID:23132077

Chou, James J; Sounier, Remy

2013-01-01

149

Nuclear magnetic resonance apparatus for pulsed high magnetic fields  

NASA Astrophysics Data System (ADS)

A nuclear magnetic resonance apparatus for experiments in pulsed high magnetic fields is described. The magnetic field pulses created together with various magnet coils determine the requirements such an apparatus has to fulfill to be operated successfully in pulsed fields. Independent of the chosen coil it is desirable to operate the entire experiment at the highest possible bandwidth such that a correspondingly large temporal fraction of the magnetic field pulse can be used to probe a given sample. Our apparatus offers a bandwidth of up to 20 MHz and has been tested successfully at the Hochfeld-Magnetlabor Dresden, even in a very fast dual coil magnet that has produced a peak field of 94.2 T. Using a medium-sized single coil with a significantly slower dependence, it is possible to perform advanced multi-pulse nuclear magnetic resonance experiments. As an example we discuss a Carr-Purcell spin echo sequence at a field of 62 T.

Meier, Benno; Kohlrautz, Jonas; Haase, Jürgen; Braun, Marco; Wolff-Fabris, Frederik; Kampert, Erik; Herrmannsdörfer, Thomas; Wosnitza, Joachim

2012-08-01

150

Magnetic Resonance Imaging and Magnetic Resonance Cholangiopancreatography of Intraductal Papillary Mucinous Tumor of the Pancreas  

Microsoft Academic Search

- lary mucinous tumor (IPMT) of the pancreas on magnetic resonance imaging (MRI) and magnetic resonance cholangiopancreatography (MRCP) and to propose a guide for its optimal management based on the characteristic imaging findings. Sixteen patients with pathologically-proven IPMT are included in the study. All patients under - went MRI and MRCP. The imaging features were retrospectively reviewed and correlated with

Chih-hui Lee; Ta-sen Yeh; Jeng-Hwei Tseng

2006-01-01

151

Prolonged survival and serial magnetic resonance imaging/magnetic resonance spectroscopy changes in infantile Krabbe disease.  

PubMed

Krabbe disease may present during infancy, late infancy, or adulthood. Earlier-onset disease is associated with shorter survival times. We present a case of infantile onset Krabbe disease with prolonged survival, initial intracranial optic nerves and optic chiasm hypertrophy, and serial changes on cranial magnetic resonance imaging and magnetic resonance spectroscopy. PMID:22964446

Udow, Sean; Bunge, Martin; Ryner, Lawrence; Mhanni, Aizeddin A; Salman, Michael S

2012-10-01

152

Magnetic resonance of a single molecular spin  

NASA Astrophysics Data System (ADS)

Magnetic-resonance spectroscopy on single molecules represents the ultimate limit in sensitivity of electron spin resonance: the detection of a single molecular spin. This is achieved by combining single molecule spectroscopy and optically detected magnetic resonance. Experimental results on pentacene in p-terphenyl both in zero-field and in the presence of a weak magnetic field demonstrate that magnetic-resonance spectroscopy on single molecules adds on to the specificity of single-molecule spectroscopy. It proved possible to identify single molecules which contain 13C nuclei in natural abundance and to observe the splitting of the electron spin resonance line resulting from the hyperfine intercation of a single molecular spin with a single 13C nuclear spin. From the Zeeman effect the orientation of the symmetry axes of individual molecules with respect to the direction of the external magnetic field is obtained. This allows to compare the orientation of individual molecules with their substitutional-site specific transition frequencies depending on the quality of the host crystal.

Köhler, Jürgen

1999-03-01

153

Magnetic material arrangement in oriented termites: a magnetic resonance study  

NASA Astrophysics Data System (ADS)

Temperature dependence of the magnetic resonance is used to study the magnetic material in oriented Neocapritermes opacus (N.o.) termite, the only prey of the migratory ant Pachycondyla marginata (P.m.). A broad line in the g=2 region, associated to isolated nanoparticles shows that at least 97% of the magnetic material is in the termite's body (abdomen+thorax). From the temperature dependence of the resonant field and from the spectral linewidths, we estimate the existence of magnetic nanoparticles 18.5+/-0.3nm in diameter and an effective magnetic anisotropy constant, Keff between 2.1 and 3.2×104erg/cm3. A sudden change in the double integrated spectra at about 100K for N.o. with the long body axis oriented perpendicular to the magnetic field can be attributed to the Verwey transition, and suggests an organized film-like particle system.

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

2004-06-01

154

The Diversity of Nuclear Magnetic Resonance Spectroscopy  

NASA Astrophysics Data System (ADS)

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

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

155

Euclidean resonance in a magnetic field  

NASA Astrophysics Data System (ADS)

An analogy is found between Wigner resonant tunneling and tunneling across a static potential barrier in a static magnetic field. Whereas in the process of Wigner tunneling an electron encounters a classically allowed region where a discrete energy level coincides with its energy, in the magnetic field the potential barrier is constant in the direction of tunneling. Along the tunneling path, certain regions are formed where, in the classical language, the kinetic energy of the motion perpendicular to tunneling is negative. These regions play the role of potential wells, where a discrete energy level can coincide with the electron energy. This phenomenon, which occurs at a certain magnetic field, is called Euclidean resonance and substantially depends on the shape of the potential forces in the direction perpendicular to tunneling. Under conditions of Euclidean resonance, a long-distance underbarrier motion is possible, which can be observed in experiments.

Ivlev, B.

2007-08-01

156

Focal renal masses: magnetic resonance imaging  

SciTech Connect

Thirty patients with focal renal masses were evaluated on a .12-Tesla resistive magnetic resonance unit using partial saturation and spin echo pulse sequence. Fifteen patients had cystic lesions, nine patients had renal cell carcinoma, two had metastatic lesions, one had an angiomyolipoma, and three had focal bacterial infection. Renal cell carcinomas demonstrated areas of increased signal using a partial saturation sequence. Magnetic resonance imaging accurately detected perinephric extension and vascular invasion in all patients. Metastatic disease to the kidney was uniformly low in signal, in contrast to primary renal cell carcinoma; an angiomyolipoma demonstrated very high signal intensity. Two masses resulting from acute focal bacterial nephritis were uniformly low in signal. Magnetic resonance imaging appears to be an accurate way of detecting, identifying, and staging focal renal masses.

Choyke, P.L.; Kressel, H.Y.; Pollack, H.M.; Arger, P.M.; Axel, L.; Mamourian, A.C.

1984-08-01

157

Magnetic Microparticle Aggregation For Viscosity Determination By Magnetic Resonance  

PubMed Central

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

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

2009-01-01

158

Granular convection observed by magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

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

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

1995-03-01

159

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

2012-02-16

160

Diffusion-weighted magnetic resonance imaging.  

PubMed

Diffusion-weighted magnetic resonance imaging is a specialized technique that measures the degree of diffusion of water molecules within extracellular space and between intracellular and extracellular space. Diffusion-weighted imaging signal is high (bright) when diffusion is restricted, as occurs in cytotoxic damage from ischemia, inflammation, trauma, or tumor. This technique, now available on most magnetic resonance imaging units, is especially helpful in detecting early ischemic stroke and multiple sclerosis and in differentiating arachnoid cyst from epidermoid tumor and brain abscess from neoplasm. PMID:12131474

Mukherji, Suresh K; Chenevert, Thomas L; Castillo, Mauricio

2002-06-01

161

Magnetic Resonance Imaging (MRI) Safety  

MedlinePLUS

... The powerful magnetic field aligns atomic particles called protons that are present in most of the body's tissues. The applied radio waves then cause these protons to produce signals that are picked up by ...

162

Advances in Magnetic Resonance Electrical Impedance Mammography  

NASA Astrophysics Data System (ADS)

Magnetic Resonance Electrical Impedance Mammography (MREIM) is a new imaging technique under development by Wollin Ventures, Inc. in conjunction with the H. Lee Moffitt Cancer Center & Research Institute. MREIM addresses the problem of low specificity of magnetic resonance mammography and high false-positive rates, which lead to unnecessary biopsies. Because cancerous tissue has a higher electrical conductivity than benign tissue, it may serve as a biomarker for differentiation between malignant and benign lesions. The MREIM principle is based on measuring both magnetic resonance and electric properties of the breast by adding a quasi-steady-state electric field to the standard magnetic resonance breast image acquisition. This applied electric field produces a current density that creates an additional magnetic field that in turn alters the native magnetic resonance signal in areas of higher electrical conductivity, corresponding to cancerous tissue. This work comprises MREIM theory, computer simulations, and experimental developments. First, a general overview and background review of tissue modeling and electrical-impedance imaging techniques are presented. The experimental part of this work provides a description of the MREIM apparatus and the imaging results of a custom-made breast phantom. This phantom was designed and developed to mimic the magnetic resonance and electrical properties of the breast. The theoretical part of this work provides an extension to the initial MREIM theoretical developments to further understand the MREIM effects. MREIM computer simulations were developed for both idealized and realistic tumor models. A method of numerical calculation of electric potential and induced magnetic field distribution in objects with irregular boundaries and anisotropic conductivity was developed based on the Finite Difference Method. Experimental findings were replicated with simulations. MREIM effects were analyzed with contrast diagrams to show the theoretical perceptibility as a function of the acquisition parameters. An important goal was to reduce the applied current. A new protocol for an MREIM sequence is suggested. This protocol defines parameters for the applied current synchronized to a specific magnetic resonance imaging sequence. A simulation utilizing this protocol showed that the MREIM effect is detectable for a 3-mm-diameter tumor with a current density of 0.5 A/m2, which is within acceptable limits.

Kovalchuk, Nataliya

163

Superconducting microwave resonators in magnetic fields  

NASA Astrophysics Data System (ADS)

Microwave resonators with high quality factors have enabled many recent breakthroughs with superconducting qubits and photon detectors. Vortices trapped in a superconducting resonator due to insufficient shielding or pulsed control fields constitute one potential loss mechanism that can lead to reduced quality factors. We have developed a straightforward method for enhancing the pinning, and thus reducing the excess loss from vortices trapped by field-cooling by over an order of magnitude, in Al resonators using nanofabricated surface pinning. We have also studied resonators in the absence of field-cooling, where magnetic fields applied below the transition temperature of the superconductor can still influence the behavior, by producing reversible shifts in the resonance frequency for small fields and by injecting vortices into the films at larger fields.

Song, C.; Defeo, M. P.; Yu, K.; Xiao, B.; Bhupathi, P.; Plourde, B. L. T.

2010-03-01

164

Video: Proton Nuclear Magnetic Resonance (NMR)  

NSDL National Science Digital Library

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

2011-06-03

165

Tumor Detection by Nuclear Magnetic Resonance  

Microsoft Academic Search

Spin echo nuclear magnetic resonance measurements may be used as a method for discriminating between malignant tumors and normal tissue. Measurements of spin-lattice (T1) and spin-spin (T2) magnetic relaxation times were made in six normal tissues in the rat (muscle, kidney, stomach, intestine, brain, and liver) and in two malignant solid tumors, Walker sarcoma and Novikoff hepatoma. Relaxation times for

Raymond Damadian

1971-01-01

166

Magnetic resonance of ferrite nanoparticles  

Microsoft Academic Search

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

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

1998-01-01

167

Localized ferromagnetic resonance using Magnetic Resonance Force Microscopy  

NASA Astrophysics Data System (ADS)

Magnetic Resonance Force Microscopy (MRFM) is a novel approach to scanned probe imaging, combining the advantages of Magnetic Resonance Imaging (MRI) with Scanning Probe Microscopy (SPM) [1]. It has extremely high sensitivity that has demonstrated detection of individual electron spins [2] and small numbers of nuclear spins [3]. Here we describe our MRFM experiments on Ferromagnetic thin film structures. Unlike ESR and NMR, Ferromagnetic Resonance (FMR) is defined not only by local probe field and the sample structures, but also by strong spin-spin dipole and exchange interactions in the sample. Thus, imaging and spatially localized study using FMR requires an entirely new approach. In MRFM, a probe magnet is used to detect the force response from the sample magnetization and it provides local magnetic field gradient that enables mapping of spatial location into resonance field. The probe field influences on the FMR modes in a sample, thus enabling local measurements of properties of ferromagnets. When sufficiently intense, the inhomogeneous probe field defines the region in which FMR modes are stable, thus producing localized modes. This feature enables FMRFM to be important tool for the local study of continuous ferromagnetic samples and structures. In our experiments, we explore the properties of the FMR signal as the strength of the local probe field evolves from the weak to strong perturbation limit. This underlies the important new capability of Ferromagnetic resonance imaging, a powerful new approach to imaging ferromagnet. The new developed FMR imaging technique enables FMR imaging and localized FMR spectroscopy to combine spectroscopy and lateral information of ferromagnetic resonance images [4][5]. Our theoretical approach agrees well with spatially localized spectroscopy and imaging results. This approach also allows analysis and reconstruction of FMR modes in a sample. Finally we consider the effect of strong probe fields on FMR modes. In this regime the probe field significantly modifies the FMR modes. In particular we observe the complete local suppression of the FMR mode under the probe. This provides as a new tool for local study of continuous ferromagnetic thin films and microstructures.

Kim, Jongjoo

168

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

169

Magnetic Resonance Imaging (MRI): Brain  

MedlinePLUS

... test that uses a magnetic field and radio waves to produce detailed images of the brain and the brain stem. An MRI differs from ... hospitals and radiology centers. During the exam, radio waves manipulate ... pinpoint problems in the brain and the brain stem when the scan focuses ...

170

Magnetic resonance investigation of magnetic-labeled baker's yeast cells  

NASA Astrophysics Data System (ADS)

In this study, the interaction of DMSA-coated magnetite nanoparticles (5 and 10nm core-size) with Saccharomyces cerevisae was investigated using magnetic resonance (MR) and transmission electron microscopy (TEM). The TEM micrographs revealed magnetite nanoparticles attached externally to the cell wall. The MR data support the strong interaction among the nanoparticles supported by the cells. A remarkable shift in the resonance field was used as signature of particle attachment to the cell wall.

Godoy Morais, J. P. M.; Azevedo, R. B.; Silva, L. P.; Lacava, Z. G. M.; Báo, S. N.; Silva, O.; Pelegrini, F.; Gansau, C.; Buske, N.; Safarik, I.; Safarikova, M.; Morais, P. C.

2004-05-01

171

Imaging Intelligence with Proton Magnetic Resonance Spectroscopy  

ERIC Educational Resources Information Center

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

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

2009-01-01

172

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

173

Respiratory gating of magnetic resonance images  

Microsoft Academic Search

When compared to most other high resolution imaging modalities (i.e. CT), magnetic resonance (MR) requires significantly more time for data acquisition. The average MR scan time ranges from 2 to 6 minutes. Cardiac and respiratory motion cause large artifacts and significantly reduce the resolution of internal structures. Thus, a method for gating MR acquisition with the respiratory cycle was developed.

J. A. Clanton; V. M. Runge; A. E. Jr. James

1984-01-01

174

Magnetic resonance imaging of the elbow  

Microsoft Academic Search

Magnetic resonance imaging (MRI) provides useful information regarding the elbow joint. Many abnormalities seen in the elbow are a result of trauma, often from sports such as baseball and tennis. Elbow problems are frequently related to the medial tension-lateral compression phenomenon where repeated valgus stress produces flexor-pronator strain, ulnar collateral ligament sprain, ulnar traction spurring, and ulnar neuropathy. The lateral

Lynne S. Steinbach; Russell C. Fritz; Phillip F. J. Tirman; Martin Uffman

1997-01-01

175

Analytical Methods for Characterizing Magnetic Resonance Probes  

PubMed Central

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

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

2012-01-01

176

Resonant mechanical magnetic sensor in standard CMOS  

Microsoft Academic Search

A novel micromechanical magnetic sensor has been built and tested. The field is detected by measuring the vibration amplitude of a mechanical Lorentz force oscillator. This device is made from a standard 2-?m CMOS fabrication process with a post-processing etch step to undercut and release the sensor. When operated at the resonant frequency of the mechanical system, a sensitivity of

Beverley Eyre; Kristofer S. J. Pister; William Kaiser

1998-01-01

177

Magnetic resonance imaging in obstructive Müllerian anomalies.  

PubMed

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. PMID:24082660

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

2013-04-01

178

Nuclear Magnetic Resonance Technology for Medical Studies.  

ERIC Educational Resources Information Center

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

Budinger, Thomas F.; Lauterbur, Paul C.

1984-01-01

179

Magnetic resonance imaging in motor neuron disease  

Microsoft Academic Search

Magnetic resonance imaging (MRI) of the brain was evaluated in 20 patients with motor neuron disease (MND) and in a control group of 11 healthy people. Bilateral increased signal areas of various sizes in the centrum semiovale, corona radiata, internal capsule, pedunculi of midbrain, pons, medulla and even in the frontal lobe, topographically related with the corticospinal tract, were found

M. L. Sales Luís; A. Hormigo; C. Maurício; M. M. Alves; R. Serrão

1990-01-01

180

Intraoperative Magnetic Resonance Imaging Safety Considerations  

Microsoft Academic Search

Patient safety considerations are a priority for perioperative nurses. In the intraoperative magnetic resonance imaging (MRI) chamber, additional safety precautions for both patients and staff members must be taken. This article provides a brief overview of the intraoperative MRI environment and details safety considerations for surgical staff members and patients. AORN J 77 (March 2003) 590–592.

Lori Russell

2003-01-01

181

Sample spinner for nuclear magnetic resonance spectrometer  

SciTech Connect

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

Stejskal, E.O.

1984-05-01

182

Magnetic Resonance Imaging in Biomedical Engineering  

NASA Astrophysics Data System (ADS)

The basic principles of magnetic resonance imaging covering physical principles and basic imaging techniques will be presented as a strong tool in biomedical engineering. Several applications of MRI in biomedical research practiced at the MRI laboratory of the FBMI CTU including other laboratory instruments and activities are introduced.

Ka?par, Jan; Hána, Karel; Smr?ka, Pavel; Brada, Ji?í; Beneš, Ji?í; Šunka, Pavel

2007-11-01

183

Nuclear magnetic resonance in rare earth metals  

Microsoft Academic Search

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

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

1979-01-01

184

Small Animal Imaging with Magnetic Resonance Microscopy  

Microsoft Academic Search

Small animal magnetic resonance microscopy (MRM) has evolved significantly from testing the boundaries of imag- ing physics to its expanding use today as a tool in nonin- vasive 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

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

2008-01-01

185

Magnetic resonance studies of dissolving particulate solids  

Microsoft Academic Search

Magnetic resonance methods have been used to elucidate the internal pore structure of particulate solids, in particular detergent tablets. Such information is essential to a comprehensive understanding of the dissolution characteristics of these materials and how this property is related to processing conditions during tablet formation. In particular 3-D images of porosity are produced and 2-D self-diffusion maps are acquired

M. L. Johns; L. F. Gladden

2003-01-01

186

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

187

Nuclear Magnetic Resonance Technology for Medical Studies  

Microsoft Academic Search

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

Thomas F. Budinger; Paul C. Lauterbur

1984-01-01

188

Nuclear magnetic resonance technology for medical studies  

Microsoft Academic Search

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

T. F. Budinger; P. C. Lauterbur

1984-01-01

189

Magnetic resonance imaging of pelvic organ prolapse  

Microsoft Academic Search

Magnetic resonance imaging (MRI) of pelvic organ prolapse is technically feasible and has several advantages when compared with fluoroscopic cystoproctography. Organ descent and the supportive structures of the pelvic floor can be assessed with MRI. The role of MRI in evaluating patients with pelvic floor dysfunction is evolving, and there have been many developments in the past few years. The

H. K. Pannu; Russell H. Morgan

2002-01-01

190

Advances in emission tomography and magnetic resonance  

Microsoft Academic Search

This paper will review recent technical improvements in emission tomography (PET and SPECT) as well as new approaches in magnetic resonance in vivo studies (MRI and MRS). These advances now enable more detailed studies of dementia and heart disease as well as improved methods to diagnose and treat cancer. Forms of dementia (Parkinson's and Alzheimer's disease) can now be quantitatively

T. F. Budinger

2008-01-01

191

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

192

Nuclear magnetic resonance in plant science research  

Microsoft Academic Search

In vivo nuclear magnetic resonance (NMR) spectroscopy and NMR imaging are noninvasive techniques with the potential to investigate a wide range of biochemical and physiological problems in living systems. The extent to which this potential has been realized in plant tissues is discussed with reference to recent applications to a number of systems, including root tissues and plant cell suspensions.

R. G. Ratcliffe

1991-01-01

193

Magnetic Resonance Imaging Methods in Soil Science  

Microsoft Academic Search

Magnetic Resonance Imaging (MRI) is a powerful technique to study water content, dynamics and transport in natural porous media. However, MRI systems and protocols have been developed mainly for medical purposes, i.e. for media with comparably high water contents and long relaxation times. In contrast, natural porous media like soils and rocks are characterized by much lower water contents, typically

A. Pohlmeier; D. van Dusschoten; P. Blümler

2009-01-01

194

Texture analysis methodologies for magnetic resonance imaging  

PubMed Central

Methods for the analysis of digital-image texture are reviewed. The functions of MaZda, a computer program for quantitative texture analysis developed within the framework of the European COST (Cooperation in the Field of Scientific and Technical Research) B11 program, are introduced. Examples of texture analysis in magnetic resonance images are discussed.

Materka, Andrzej

2004-01-01

195

Magnetic Resonance Imaging (MRI) of the Kidney.  

National Technical Information Service (NTIS)

The thesis reflects experience with Magnetic Resonance Imaging (MRI) in the diagnosis of kidney disease. Initial results were obtained on a 0.15 T resistive and a 0.5 T superconducting prototype MR scanner (Philips, Best, the Netherlands). Further clinica...

L. Te Strake

1987-01-01

196

Brain Morphometry Using Anatomical Magnetic Resonance Imaging  

ERIC Educational Resources Information Center

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

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

2008-01-01

197

Atomic Resolution Magnetic Resonance Diffraction using Magnetic Probes  

NASA Astrophysics Data System (ADS)

We will present our recent proposal [1] for the observation of sharp spectral peaks in the magnetic resonance signal for the case of a crystal in close proximity of a ferromagnetic nanosphere. The appearance of the peaks is a direct signature of the discrete atomic sites in the crystal lattice, and the positions of the spectral peaks are sensitive to the crystal unit cell size thereby providing a magnetic resonance diffraction method for determination of the basic parameters of the crystal at the atomic scale. The technique relaxes the challenging requirements for single spin detection instrument proposals by allowing many spins to coherently contribute to the magnetic resonance signal while still revealing atomic resolution information. Therefore, the technique provides a magnetic resonance alternative to the other three well-known atomic resolution crystallography techniques of x-ray, electron, and neutron diffraction. Applications to the studies of crystals, thin films, and crystallites will be discussed, and potential measurement methods for the confirmation of the diffraction theory will be proposed [2]. The analysis suggests that the long desired goal of detecting atomic resolution magnetic resonance diffraction [3] is well within reach of current experimental techniques such as Magnetic Resonance Force Microscopy (MRFM) [4]. [1] M. Barbic J. Appl. Phys. vol. 91, p. 9987 (2002). [2] M. Barbic and A. Scherer J. Appl. Phys. vol. 92, p. 7345 (2002). [3] P. Mansfield and P. K. Grannell J. Phys. C: Solid State Phys. vol. 6, p. L422 (1973). [4] Sidles J. A. et al. Rev. Mod. Phys. vol. 67, p. 249 (1995).

Barbic, Mladen

2003-03-01

198

21 CFR 892.1000 - Magnetic resonance diagnostic device.  

Code of Federal Regulations, 2010 CFR

...spatial distribution and/or magnetic resonance spectra which reflect frequency...of nuclei exhibiting nuclear magnetic resonance. Other physical parameters...includes hydrogen-1 (proton) imaging, sodium-23 imaging,...

2009-04-01

199

21 CFR 892.1000 - Magnetic resonance diagnostic device.  

Code of Federal Regulations, 2010 CFR

...spatial distribution and/or magnetic resonance spectra which reflect frequency...of nuclei exhibiting nuclear magnetic resonance. Other physical parameters...includes hydrogen-1 (proton) imaging, sodium-23 imaging,...

2010-04-01

200

The market for magnetic resonance spectroscopy  

SciTech Connect

The medical market is, at present, the most dominant market for low T{sub c} superconductors. Indeed, without magnetic resonance imaging (MRI), there would hardly be a low T{sub c} superconductor market at all. According to the author, any development that can expand the medical market for MRI machines would be a welcome one. This paper reports how the recent advances in magnetic resonance spectroscopy (MRS) are such a development. While the principle of MRS has bee around as long as MRI, only recently have advances in technique, computer programming and magnet technology allowed MRS to advance to a point where it may become an important technology-one that could increase the medical market for superconductors. The author discussed how MRS can be used to analyze oil core samples for their oil content, oil/water ratios, how the oil is bound and how to extract it.

Carlson, L.

1990-01-01

201

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

202

Geometric Optimization and Microstructuring of Magnetic Concentrators for a Resonant Magnetic Sensor  

Microsoft Academic Search

This paper reports the design and analysis of a planar magnetic field concentrator with two gaps used for a resonant magnetic sensor and technology steps towards its realization. The device is based on a previously published resonant magnetic sensor combining a magnetic field concentrator and a mechanical resonator. A physical model is reported to explain the magnetic forces acting between

S. Brugger; O. Paul

2007-01-01

203

The anatomy workbook  

SciTech Connect

This is an atlas of human anatomy presented in the form of line drawings, many of which correspond to imaging planes used in ultrasound (US), computed tomography (CT), and magnetic resonance (MR). The book is organized into 17 sections, each covering a specific structure or organ system. Large, uncluttered drawings are labeled for identification of structures of interest. Many illustrations include captions consisting of comments explaining major divisions within organs, specific anatomic relationships and landmarks, and pertinent vascular anatomy. Most organs are first depicted in isolation or in relation to important adjacent organs or blood vessels and are rendered as if viewed from anterior, posterior, inferior, or superior perspectives. The organs are demonstrated again in serial transverse, saggital, and coronal sections, each accompanied by a drawing of a body in anatomic position denoting the plane of the section.

Hagen-Ansert, S.L.

1986-01-01

204

Magnetic resonance of calcified tissues.  

PubMed

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

Wehrli, Felix W

2013-01-10

205

Magnetic resonance of calcified tissues  

NASA Astrophysics Data System (ADS)

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

Wehrli, Felix W.

2013-04-01

206

Magnetic Resonance Characterization of Ischemic Tissue Metabolism  

PubMed Central

Magnetic resonance imaging (MRI) and spectroscopy (MRS) are versatile diagnostic techniques capable of characterizing the complex stroke pathophysiology, and hold great promise for guiding stroke treatment. Particularly, tissue viability and salvageability are closely associated with its metabolic status. Upon ischemia, ischemic tissue metabolism is disrupted including altered metabolism of glucose and oxygen, elevated lactate production/accumulation, tissue acidification and eventually, adenosine triphosphate (ATP) depletion and energy failure. Whereas metabolism impairment during ischemic stroke is complex, it may be monitored non-invasively with magnetic resonance (MR)-based techniques. Our current article provides a concise overview of stroke pathology, conventional and emerging imaging and spectroscopy techniques, and data analysis tools for characterizing ischemic tissue damage.

Cheung, Jerry S; Wang, Xiaoying; Zhe Sun, Phillip

2011-01-01

207

A bandwidth indicator for magnetic resonance imagers.  

PubMed

Signal-to-noise ratios in magnetic resonance imaging are crucial in determining image quality, and dependent on a number of factors, one being the signal bandwidth per pixel. Not all manufacturers clearly state the bandwidth per pixel used for all sequences. A small battery-powered portable device is described which produces bright sharp lines on the magnetic resonance image at 10 kHz intervals in the frequency encoding direction. The bandwidth per pixel can then easily be calculated using electronic distance callipers, provided the image matrix and field of view are known. The device is expected to be especially of value when acceptance testing on poorly documented imaging systems. PMID:9167164

Date, T; Redpath, T W; Bussell, D M

1997-05-01

208

Magnetic resonance imaging of a mediastinal ependymoma.  

PubMed

Ependymomas typically occur in the brain and spinal cord, and represent 5% and 16% of primary intracranial and spinal cord tumors respectively. Ependymomas arising outside the central nervous systems are uncommon and when they do occur are usually seen in the sacrococcygeal region. Other reported sites include the pelvis, spinal nerve roots, and lung. An extraspinal mediastinal ependymoma is a rare occurrence, with only two previously reported cases to our knowledge. In both instances, the lesion arose in the posterior mediastinum, and were imaged with either chest radiographs alone or chest radiographs and computed tomography. In our case, plain radiography was followed by magnetic resonance imaging. This report documents the clinical, pathological, and magnetic resonance imaging findings in a case of a posterior mediastinal ependymoma. Primary mediastinal ependymomas are rare lesions that may be considered in the differential diagnosis of a posterior mediastinal mass. PMID:9785637

Neumann, D P; Scholl, R J; Kellet, H M; Simon, R H

1998-09-01

209

Quantitative spatial comparison of diffuse optical imaging with blood oxygen level-dependent and arterial spin labeling-based functional magnetic resonance imaging  

Microsoft Academic Search

Akin to functional magnetic resonance imaging fMRI, dif- fuse optical imaging DOI is a noninvasive method for measuring localized changes in hemoglobin levels within the brain. When com- bined with fMRI methods, multimodality approaches could offer an integrated perspective on the biophysics, anatomy, and physiology underlying each of the imaging modalities. Vital to the correct inter- pretation of such studies,

Theodore J. Huppert; Rick D. Hoge; Anders M. Dale; Maria A. Franceschini; David A. Boas

2006-01-01

210

Cardiac magnetic resonance imaging in Turner syndrome.  

PubMed

Girls and women with Turner syndrome (TS) have a highly increased morbidity as the result of cardiovascular disease, both congenital and acquired. Increased clinical use of cardiac magnetic resonance imaging (CMR) in patients with TS over recent years has allowed for characterization of disease not always possible with standard imaging modalities, such as echocardiography (echo). In this review, we discuss the current literature regarding CMR in patients with TS and guidelines for its use. PMID:23336808

Gutmark-Little, Iris; Backeljauw, Philippe F

2013-05-01

211

Sensorineural Hearing Loss after Magnetic Resonance Imaging  

PubMed Central

Magnetic resonance imaging (MRI) devices produce noise, which may affect patient's or operators' hearing. Some cases of hearing impairment after MRI procedure have been reported with different patterns (temporary or permanent, unilateral or bilateral, with or without other symptoms like tinnitus). In this report, a case of bilateral sensorineural hearing loss in an otherwise healthy patient underwent brain MRI was described. The patient's hearing loss was accompanied with tinnitus and was not improved after 3 months of followup.

Mollasadeghi, Abolfazl; Mehrparvar, Amir Houshang; Atighechi, Saeid; Mostaghaci, Mehrdad

2013-01-01

212

Sensors for Applications in Magnetic Resonance Environments  

Microsoft Academic Search

This paper analyzes sensing methods compatible with magnetic resonance imaging (MRI) and functional MRI (fMRI) reported in the literature, and presents the three generations of MR-compatible force\\/torque sensors we have developed for robotic systems to interact with human motion. Conventional sensors such as camera-based measurement systems, strain gauges or commercial force\\/torque sensors, and optical encoders may be used, if placed

Roger Gassert; Dominique Chapuis; Hannes Bleuler; Etienne Burdet

2008-01-01

213

Fat Segmentation in Magnetic Resonance Images  

Microsoft Academic Search

\\u000a Over the past two decades, many authors have investigated the use of magnetic resonance imaging (MRI) for the analysis of\\u000a body fat and body fat distribution. However, accurate isolation of fat in MR images is an arduous task when performed manually.\\u000a In order to alleviate this burden, numerous automated and semi-automated segmentation algorithms have been developed for the\\u000a quantification of

David P. Costello; Patrick A. Kenny

214

Magnetic Resonance Imaging Studies of Cigarette Smoking  

Microsoft Academic Search

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

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

215

Magnetic resonance imaging of palindromic rheumatism  

Microsoft Academic Search

A 44-year-old man with intermittent asymmetric migratory oligoarthritis lasting the recent decade was admitted to our hospital.\\u000a Considerable specific biomarkers for rheumatoid arthritis such as anti-agalactosyl IgG antibody are all negative. He was diagnosed\\u000a as palindromic rheumatism (PR). Although hand X-rays showed no remarkable findings, hand magnetic resonance imaging (MRI)\\u000a detected pannus and bone erosion. PR is defined as the

Satoko Ueda; Taro Horino; Kaoru Arii; Tatsuhito Morita; Toshihiro Takao; Kozo Hashimoto

2008-01-01

216

Magnetic resonance imaging in radiotherapy treatment planning  

Microsoft Academic Search

From its inception in the early 1970's up to the present, magnetic resonance imaging (MRI) has evolved into a sophisticated technique, which has aroused considerable interest in var-\\u000aious subelds of medicine including radiotherapy. MRI is capable of imaging in any plane\\u000aand does not use ionizing radiation by virtue of which MRI lends itself admirably to the\\u000apurpose of

Marinus Adriaan Moerland

1996-01-01

217

Magnetic resonance imaging of the fetus  

Microsoft Academic Search

Fetal magnetic resonance imaging (FMRI) has gained considerable interest during the last decade, especially in its intracranial\\u000a applications. Due to its high soft-tissue contrast and presumed safety, FMRI should be accepted as a complementary technique\\u000a in prenatal diagnosis, useful either to elucidate equivocal findings on routine US studies or to further delineate some pathological\\u000a entities. Normal patterns of fetal brain

C. Garel; Hervé Brisse; G. Sebag; Monique Elmaleh; Jean-François Oury; Max Hassan

1998-01-01

218

Magnetic resonance imaging evaluation of myocardial perfusion  

Microsoft Academic Search

Noninvasive qualitative\\/quantitative assessment of myocardial perfusion is considered to be fundamental in the management of known and suspected coronary artery disease patients, as shown by the widespread utilization of thallium-201– and technetium-99m–labeled agents in myocardial single-photon emission computed tomography (SPECT) scintigraphy for diagnostic as well as prognostic purposes. Recently, the availability of subsecond ultrafast magnetic resonance imaging (MRI) sequences (FLASH,

Roberto Passariello; Marcello De Santis

1998-01-01

219

Predicting anxiety in magnetic resonance imaging scans  

Microsoft Academic Search

This study evaluated a brief screening instrument for predicting psychological distress in patients undertaking magnetic resonance\\u000a imaging (MRI) scans. The scale is adapted from Wolpe and Lang’s (1964) Fear Survey Schedule (FSS; see Lukins, Davan, & Drummond,\\u000a 1997). Noise and\\/or confinement were identified as the most unpleasant feature of the MRI by 48.3% of 118 outpatients. The\\u000a MRI-FSS (Lukins et

Lynne M. Harris; Steven R. Cumming; Ross G. Menzies

2004-01-01

220

MAGNETIC RESONANCE MICROSYSTEMS FOR LJFE SCIENCE APPLICATIONS  

Microsoft Academic Search

Nuclear magnetic (MR) resonance spectroscopy and imaging technique are powerful methods available for determining molecular structures and non-invasive 3D imaging. In the effort of developing a nanoMRl microsystem, we have designed, fabricated, assembled and did preliminary characterization of the nanoMRI probe. A multilayer high aspect ratio metal process has been developed for this project. NanoMRI probes are designed through multi-physics

Long-Sheng Fan; C.-L. Cheng; J. Chu; C. Hao; C. Y. Hsieh; S. H. Hsu; A. Chin; K. Hsueh; C.-C. Lee; J. Chang; E. Liu; C. Chien; A. Yeh; J.-H. Chen; W. Wu; C. Lai

221

Magnetic resonance microsystems for life science applications  

Microsoft Academic Search

Nuclear magnetic (MR) resonance spectroscopy and imaging technique are powerful methods available for determining molecular structures and non-invasive 3D imaging. In the effort of developing a nanoMRI microsystem, the authors have designed, fabricated, assembled and did preliminary characterization of the nanoMRI probe. A multilayer high aspect ratio metal process has been developed for this project. NanoMRI probes are designed through

Long-Sheng Fan; W.-S. Huang; C.-L. Cheng; P.-J. Chu; H.-C. Hao; C. Y. Hsieh; S. H. Hsu; A. Chin; K. Hsueh; C.-C. Lee; J. Chang; E. Liu; A. Huang; C. Chien; A. Yeh; J.-H. Chen; W. Wu; C. Lai

2005-01-01

222

magnetic resonance imaging: anthropometric relationships?3  

Microsoft Academic Search

This study compared total and regional adi- pose tissue (AT) and lean tissue (LT) distribution measured by magnetic resonance imaging (MRI) in obese, android women (ii = 40) and men (n = 17). Women had significantly (P < 0.01) greater subcutaneous AT (39.6 ± 11.6 vs 30.7 ± 7.5 L) but significantly (P < 0.01) less visceral AT (2.5 ±

Robert Ross; Kimberley D Shaw; John Rissanen; Yves Martel; Jacques de Guise; Leonard Avruch

223

Claustrophobia and the Magnetic Resonance Imaging Procedure  

Microsoft Academic Search

We examined fear induced by the magnetic resonance imaging (MRI) procedure in 80 adult patients who were undergoing the procedure for the first time. Participants completed self-report measures of claustrophobia, anxiety sensitivity, thoughts about the scan, and pain. Participants were assessed pre- and postscan, and at 1-month follow-up. Twenty-five percent of the participants experienced moderate to severe anx iety during

Heather K. McIsaac; Dana S. Thordarson; Roz Shafran; S. Rachman; Gary Poole

1998-01-01

224

Magnetic resonance imaging: Principles and applications  

SciTech Connect

This text covers the physics underlying magnetic resonance (MR) imaging; pulse sequences; image production; equipment; aspects of clinical imaging; and the imaging of the head and neck, thorax, abdomen and pelvis, and musculoskeletal system; and MR imaging. The book provides about 150 examples of MR images that give an overview of the pathologic conditions imaged. There is a discussion of the physics of MR imaging and also on the spin echo.

Kean, D.; Smith, M.

1986-01-01

225

Magnetic Resonance Imaging of the Kidney  

Microsoft Academic Search

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

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

226

MAGNETIC RESONANCE STUDIES OF SELENIUM CONTAINING COMPOUNDS  

Microsoft Academic Search

The utility of selenium-77 nuclear magnetic resonance in studying the properties of a range of selenium-containing compounds from small organoselenium molecules to macromolecules which contain selenium bound covalently is discussed. Relaxation times, chemical shifts and spin-spin coupling constants are all useful indicators of structure, function and bonding in these systems. The origin of selenium-77 chemical shifts in organoselenium compounds as

R. Bruce Dunlap; Jerome D. Odom

1988-01-01

227

Magnetic resonance spectroscopy in cancer diagnostics  

Microsoft Academic Search

Magnetic resonance spectroscopy (MRS) is one of the most powerful analytical techniques, being frequently used to derive physical,\\u000a chemical, electronic, and structural information about molecules. Considering its potentialities and its evolution as cell\\/tissue\\u000a response predictor, it can be used to detect changes in the tumor pathophysiology before, during, and after treatment. Of\\u000a particular relevance to this analysis, due to its

Ana Margarida Abrantes; Joana Rio; Ludgero C. Tavares; Rui A. Carvalho; Maria Filomena Botelho

2010-01-01

228

Neurosurgical uses for intraprocedural magnetic resonance imaging.  

PubMed

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

Mutchnick, Ian S; Moriarty, Thomas M

2005-10-01

229

Confident Diagnosis of Bronchobiliary Fistula Using Contrast-Enhanced Magnetic Resonance Cholangiography  

PubMed Central

We report the utility of contrast-enhanced magnetic resonance cholangiography (MRC) using gadoxetic acid (Gd-EOB-DTPA) in the diagnosis of bronchobiliary fistula associated with liver hydatid cyst. Contrast-enhanced MRC clearly delineated the leakage of contrast agent from the biliary duct and its communication with the bronchial tree. Providing functional information about physiologic or pathologic biliary flow in addition to the display of biliary anatomy, contrast-enhanced MRC stands as a robust technique in confidently detecting bronchobiliary fistula and bile leaks.

Cakmak, Vefa; Kiter, Goksel

2010-01-01

230

Magnetic levitation of metamaterial bodies enhanced with magnetostatic surface resonances  

Microsoft Academic Search

We propose that macroscopic objects built from negative-permeability metamaterials may experience resonantly enhanced magnetic force in low-frequency magnetic fields. Resonant enhancement of the time-averaged force originates from magnetostatic surface resonances (MSR) which are analogous to the electrostatic resonances of negative-permittivity particles, well known as surface plasmon resonances in optics. We generalize the classical problem of MSR of a homogeneous object

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

2011-01-01

231

Use of magnetic resonance imaging and magnetic resonance angiography in diagnosis of sigmoid sinus thrombosis.  

PubMed

Magnetic resonance angiography is an established radiologic technique which is rapidly becoming useful in imaging the head and neck. Currently, this imaging modality is important in the diagnosis of sigmoid sinus thrombosis caused by otologic disease. Since the introduction of antibiotic therapy, the percentage of deaths attributed to intracranial complications from otitic disease has decreased from 2.5 to approximately 0.25% of documented deaths. Also, the incidence of sinus thrombosis within this group has decreased, but it is still a serious and potentially lethal condition. Sinus thrombosis is suspected clinically when mastoid disease progresses, with picket fence fever pattern, chills, headaches and signs of papilledema. Definitive diagnosis is necessary before surgical treatment. The Queckenstedt test is unreliable, computed tomography is better suited for demonstrating thrombosis of the sagittal sinus rather than the sigmoid sinus, and conventional angiography (although it provides excellent visualization) has the hazard of ionizing radiation and requires vessel puncture and the use of intraarterial contrast agents. We present two cases of thrombosis of the sigmoid sinus as an intracranial otologic complication which were diagnosed definitively with magnetic resonance imaging and magnetic resonance angiography. The combination of magnetic resonance imaging, which showed the thrombosis displaying abnormal signal intensity, and magnetic resonance angiography, which demonstrated the absence of flow in the sinus, was an ideal diagnostic tool. For both patients, treatment consisted of mastoidectomy, sigmoid sinus decompression and antibiotics. PMID:9248135

Davison, S P; Facer, G W; McGough, P F; McCaffrey, T V; Reder, P A

1997-07-01

232

Multiplane magnetic resonance imaging of the heart and major vessels: studies in normal volunteers  

SciTech Connect

The feasibility of magnetic resonance imaging for defining anatomy of internal cardiac structures and major blood vessels was assessed in 14 normal subjects. Both electrocardiogram-gated and standard spin-echo images were obtained. Gated images provided better visualization of internal cardiac morphology and of upper mediastinal vessels than did nongated images. Trabecular detail and components of the mitral valve could be resolved. All segments of the left ventricular wall could be evaluated by combining axial, coronal, and sagittal images. Gated acquisition of magnetic resonance images did not increase imaging time; five transverse slices of the left ventricle were obtained in 6.0-8.5 min. The good image quality, ease of gated acquisition, large field of view, capability of direct imaging in multiple planes, and noninvasiveness of the technique suggest that it will be an important imaging method in cardiovascular disease.

Higgins, C.B.; Stark, D.; McNamara, M.; Lanzer, P.; Crooks, L.E.; Kaufman, L.

1984-04-01

233

[Nursing participation in magnetic resonance applied to diagnosis of coronary syndromes].  

PubMed

The cardiovascular magnetic resonance is a method diagnose noninvasive that does not use radiation obtaining itself a space resolution and temporary that allows to analyze the anatomy and cardiovascular function. The material of used paramagnetic resistance is the gadolinium which causes increase of signal in vascularized weaves and better characterization of the visualized weave, acute east allows to the analysis of the perfusion of the myocardium Subsequent to the coronary syndrome study allows to determine with exactitude the extension of the zone of necrosis, to stratify the risk and of identifying the viable weave as well as of determining the affected territory. This revision must like intention describe the provided interventions of infirmary to the patient with acute coronary syndrome that is put under this type of study since without a doubt our recent incorporation to the Department of Magnetic Resonance has been translated in an integral attention. PMID:18938737

Nieto Romero, Rosa María

234

Browsing Software of the Visible Korean Data Used for Teaching Sectional Anatomy  

ERIC Educational Resources Information Center

|The interpretation of computed tomographs (CTs) and magnetic resonance images (MRIs) to diagnose clinical conditions requires basic knowledge of sectional anatomy. Sectional anatomy has traditionally been taught using sectioned cadavers, atlases, and/or computer software. The computer software commonly used for this subject is practical and…

Shin, Dong Sun; Chung, Min Suk; Park, Hyo Seok; Park, Jin Seo; Hwang, Sung Bae

2011-01-01

235

Magnetic Resonance Microscopy of Collagen Mineralization  

PubMed Central

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

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

2008-01-01

236

Electro-mechanical resonant magnetic field sensor  

NASA Astrophysics Data System (ADS)

We describe a new type of magnetic field sensor, which is termed as an Electro-Mechanical Resonant Sensor (EMRS). The key part of this sensor is a small conductive elastic element with low damping rate and therefore, a high /Q fundamental mode of frequency f1. An AC current is driven through the elastic element which, in the presence of a magnetic field, causes an AC force on the element. When the frequency of the AC current matches the resonant frequency of the element, maximum vibration of the element occurs and this can be measured precisely by optical means. We have built and tested a model sensor of this type by using for the elastic element, a length of copper wire of diameter 0.030mm formed into a loop shape. The wire motion was measured using a light-emitting diode photo-transistor assembly. This sensor demonstrated a sensitivity better than 0.001G for an applied magnetic field of ~1G and a good selectivity for the magnetic field direction. The sensitivity can be easily improved by a factor of /~10-100 by a more sensitive measurement of the elastic element motion and by having the element in vacuum to reduce the drag force.

Temnykh, Alexander B.; Lovelace, Richard V. E.

2002-05-01

237

Magnetic Resonance Elastography of the Ex-vivo Bovine Globe  

PubMed Central

Purpose To evaluate the feasibility of using magnetic resonance elastography (MRE) to assess the mechanical properties of the eye. Methods The elastic properties of the corneoscleral shell of an intact, enucleated bovine globe specimen were estimated using MRE and finite element modeling (FEM), assuming linear, isotropic behavior. The two-dimensional (2D), axisymetric model geometry was derived from a segmented 2D MR image, and estimations of the Young’s modulus in both the cornea and sclera were made at various intraocular pressures using an iterative flexural wave speed matching algorithm. Results Estimated values of the Young’s moduli of the cornea and sclera varied from 40 to 185 kPa and 1 to 7 MPa, respectively, over an intraocular pressure range of 0.85 to 9.05 mmHg (1.2 to 12.3 cmH2O). They also varied exponentially as functions of both wave speed and intraocular dP/dV, an empirical measure of “ocular rigidity”. Conclusion These results show that it is possible to estimate the intrinsic elastic properties of the corneoscleral shell in an ex vivo bovine globe, suggesting that MRE may provide a useful means to assess the mechanical properties of the eye and its anatomy. Further development of the technique and modeling process will enhance its potential, and further investigations are needed to determine its clinical potential.

Litwiller, Daniel V.; Lee, Sung J.; Kolipaka, Arunark; Mariappan, Yogesh K.; Glaser, Kevin J.; Pulido, Jose S.; Ehman, Richard L.

2010-01-01

238

Magnetic resonance imaging of live freshwater mussels (Unionidae)  

USGS Publications Warehouse

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

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

2008-01-01

239

The cardiac magnetic resonance (CMR) approach to assessing myocardial viability  

PubMed Central

Cardiac magnetic resonance (CMR) is a noninvasive imaging method that can determine myocardial anatomy, function, perfusion, and viability in a relative short examination. In terms of viability assessment, CMR can determine viability in a non-contrast enhanced scan using dobutamine stress following protocols comparable to those developed for dobutamine echocardiography. CMR can also determine viability with late gadolinium enhancement (LGE) methods. The gadolinium-based contrast agents used for LGE differentiate viable myocardium from scar on the basis of differences in cell membrane integrity for acute myocardial infarction. In chronic myocardial infarction, the scarred tissue enhances much more than normal myocardium due to increases in extracellular volume. LGE is well validated in pre-clinical and clinical studies that now span from almost a cellular level in animals to human validations in a large international multicenter clinical trial. Beyond infarct size or infarct detection, LGE is a strong predictor of mortality and adverse cardiac events. CMR can also image microvascular obstruction and intracardiac thrombus. When combined with a measure of area at risk like T2-weighted images, CMR can determine infarct size, area at risk, and thus estimate myocardial salvage 1–7 days after acute myocardial infarction. Thus, CMR is a well validated technique that can assess viability by gadolinium-free dobutamine stress testing or late gadolinium enhancement.

Arai, Andrew E.

2012-01-01

240

Perspective of functional magnetic resonance imaging in middle ear research.  

PubMed

Functional magnetic resonance imaging (MRI) studies have frequently been applied to study sensory system such as vision, language, and cognition, but have proceeded at a considerably slower speed in investigating middle ear and central auditory processing. This is due to several factors, including the intrinsic anatomy of the middle ear system and inherent acoustic noise during acquisition of MRI data. However, accumulating evidences have demonstrated that clarification of some fundamental neural underpinnings of audition associated with middle ear mechanics can be achieved using functional MRI methods. This mini review attempted to take a narrow snapshot of the currently available functional MRI procedures and gave examples of what may be learned about hearing from their application. It is hoped that with these technical advancements, many new high impact applications in audition would follow. In particular, because the fMRI can be used in humans and in animals, fMRI may represent a unique tool that should promote translational research by enabling parallel analyses of physiological and pathological processes in the human and animal auditory system. This article is part of a special issue entitled "MEMRO 2012". PMID:23291496

Chang, Yongmin; Lee, Sang-Heun

2013-01-02

241

Heart valve disease: investigation by cardiovascular magnetic resonance  

PubMed Central

Cardiovascular magnetic resonance (CMR) has become a valuable investigative tool in many areas of cardiac medicine. Its value in heart valve disease is less well appreciated however, particularly as echocardiography is a powerful and widely available technique in valve disease. This review highlights the added value that CMR can bring in valve disease, complementing echocardiography in many areas, but it has also become the first-line investigation in some, such as pulmonary valve disease and assessing the right ventricle. CMR has many advantages, including the ability to image in any plane, which allows full visualisation of valves and their inflow/outflow tracts, direct measurement of valve area (particularly for stenotic valves), and characterisation of the associated great vessel anatomy (e.g. the aortic root and arch in aortic valve disease). A particular strength is the ability to quantify flow, which allows accurate measurement of regurgitation, cardiac shunt volumes/ratios and differential flow volumes (e.g. left and right pulmonary arteries). Quantification of ventricular volumes and mass is vital for determining the impact of valve disease on the heart, and CMR is the 'Gold standard' for this. Limitations of the technique include partial volume effects due to image slice thickness, and a low ability to identify small, highly mobile objects (such as vegetations) due to the need to acquire images over several cardiac cycles. The review examines the advantages and disadvantages of each imaging aspect in detail, and considers how CMR can be used optimally for each valve lesion.

2012-01-01

242

Potential of magnetic resonance for imaging the fetal heart.  

PubMed

Significant congenital heart disease (sCHD) affects 3.6 per 1000 births, and is often associated with extracardiac and chromosomal anomalies. Although early mortality has been substantially reduced and the rate of long-term survival has improved, sCHD is, after preterm birth, the second most frequent cause of neonatal infant death. The prenatal detection of cardiac and vascular abnormalities enables optimal parental counselling and perinatal management. Echocardiography (ECG) is the first-line examination and gold standard by which cardiac malformations are defined. However, adequate examination by an experienced healthcare provider with modern technical imaging equipment is required. In addition, maternal factors and the gestational age may lower the image quality. Fetal magnetic resonance imaging (MRI) has been implemented over the last several years and is already used in the clinical routine as a second-line approach to assess fetal abnormalities. MRI of the fetal heart is still not routinely performed. Nevertheless, fetal cardiac MRI has the potential to complement ultrasound in detecting cardiovascular malformations and extracardiac lesions. The present work reviews the potential of MRI to delineate the anatomy and pathologies of the fetal heart. This work also deals with the limitations and continuing developments designed to overcome the current problems in cardiac imaging, including fast fetal heart rates, the lack of ECG-gating, and the presence of fetal movements. PMID:23742821

Wielandner, Alice; Mlczoch, Elisabeth; Prayer, Daniela; Berger-Kulemann, Vanessa

2013-06-03

243

Multifunctional magnetic nanoparticles for magnetic resonance imaging and cancer therapy  

Microsoft Academic Search

We have developed a multi-layer approach for the synthesis of water-dispersible superparamagnetic iron oxide nanoparticles for hyperthermia, magnetic resonance imaging (MRI) and drug delivery applications. In this approach, iron oxide core nanoparticles were obtained by precipitation of iron salts in the presence of ammonia and provided ?-cyclodextrin and pluronic polymer (F127) coatings. This formulation (F127250) was highly water dispersible which

Murali M. Yallapu; Shadi F. Othman; Evan T. Curtis; Brij K. Gupta; Meena Jaggi; Subhash C. Chauhan

2011-01-01

244

Gadolinium-Enhanced Magnetic Resonance Angiography for Pulmonary Embolism  

PubMed Central

Background The accuracy of gadolinium-enhanced magnetic resonance pulmonary angiography and magnetic resonance venography for diagnosing pulmonary embolism has not been determined conclusively. Objective To investigate performance characteristics of magnetic resonance angiography, with or without magnetic resonance venography, for diagnosing pulmonary embolism. Design Prospective, multicenter study from 10 April 2006 to 30 September 2008. (ClinicalTrials.gov registration number: NCT00241826) Setting 7 hospitals and their emergency services. Patients 371 adults with diagnosed or excluded pulmonary embolism. Measurements Sensitivity, specificity, and likelihood ratios were measured by comparing independently read magnetic resonance imaging with the reference standard for diagnosing pulmonary embolism. Reference standard diagnosis or exclusion was made by using various tests, including computed tomographic angiography and venography, ventilation–perfusion lung scan, venous ultra-sonography, D-dimer assay, and clinical assessment. Results Magnetic resonance angiography, averaged across centers, was technically inadequate in 25% of patients (92 of 371). The proportion of technically inadequate images ranged from 11% to 52% at various centers. Including patients with technically inadequate images, magnetic resonance angiography identified 57% (59 of 104) with pulmonary embolism. Technically adequate magnetic resonance angiography had a sensitivity of 78% and a specificity of 99%. Technically adequate magnetic resonance angiography and venography had a sensitivity of 92% and a specificity of 96%, but 52% of patients (194 of 370) had technically inadequate results. Limitation A high proportion of patients with suspected embolism was not eligible or declined to participate. Conclusion Magnetic resonance pulmonary angiography should be considered only at centers that routinely perform it well and only for patients for whom standard tests are contraindicated. Magnetic resonance pulmonary angiography and magnetic resonance venography combined have a higher sensitivity than magnetic resonance pulmonary angiography alone in patients with technically adequate images, but it is more difficult to obtain technically adequate images with the 2 procedures. Primary Funding Source National Heart, Lung, and Blood Institute.

Stein, Paul D.; Chenevert, Thomas L.; Fowler, Sarah E.; Goodman, Lawrence R.; Gottschalk, Alexander; Hales, Charles A.; Hull, Russell D.; Jablonski, Kathleen A.; Leeper, Kenneth V.; Naidich, David P.; Sak, Daniel J.; Sostman, H. Dirk; Tapson, Victor F.; Weg, John G.; Woodard, Pamela K.

2011-01-01

245

Quantitative Neuromorphometry Using Magnetic Resonance Histology  

PubMed Central

Magnetic resonance imaging (MRI), now common in the clinical domain, has been adapted for use by the neuropathologist by increasing the spatial resolution over 100,000-times what is common in human clinical imaging. This increase in spatial resolution has been accomplished through a variety of technical advances—higher magnetic fields, more sensitive receivers, and clever encoding methods. Magnetic resonance histology (MRH), i.e. the application of MRI to study tissue specimens, now makes three-dimensional imaging of the fixed brain in the cranium routine. Active staining (perfusion fixation with a paramagnetic contrast agent) has allowed us to reduce the scan time by more than 8-times over earlier methods. The result is a three-dimensional isotropic image array that can be viewed along any direction without loss of spatial resolution. Homologous slices can be chosen interactively. Since the tissue is still fully hydrated in the cranium, tissue shrinkage and distortion are virtually eliminated. Volume measurements of neural structures can be made with a high degree of precision and accuracy. MRH will not replace more traditional methods, but it promises enormous value in choosing particular areas and times for more traditional sectioning and assessment.

Johnson, G. Allan; Badea, Alexandra; Jiang, Yi

2010-01-01

246

Functional Magnetic Resonance Imaging of Eye Dominance at 4 Tesla  

Microsoft Academic Search

We studied eye dominance in visual cortex and lateral geniculate nucleus (LGN) using functional magnetic resonance imaging (fMRI) at a very high magnetic field (4 tesla). Eight normal volunteers were studied with fMRI at 4 tesla during alternating monocular visual stimulation. The acquisition was repeated twice in 4 subjects to confirm reproducibility. In addition, magnetic resonance signal intensities during three

Atsushi Miki; Grant T. Liu; Sarah A. Englander; Theo G. M. van Erp; Gabrielle R. Bonhomme; David O. Aleman; Chia-Shang J. Liu; John C. Haselgrove

2001-01-01

247

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

248

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

249

Nanodiamond graphitization: a magnetic resonance study.  

PubMed

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

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

2013-05-24

250

Nanodiamond graphitization: a magnetic resonance study  

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

251

Comparative anatomy of dipole magnets or the magnet designer's coloring book  

SciTech Connect

A collection of dipole magnet cross sections is presented together with an indication of how they are related geometrically. The relationships indicated do not necessarily imply the actual path of evolutionary development. Brief consideration is given to magnets of higher multipole order, i.e., quadrupole magnets, etc.). The magnets under consideration have currents parallel to the axis except at the ends, and are long. The relationship between current distribution and magnetic field is essentially two-dimensional. The coils are usually surrounded by an iron yoke, but the emphasis is on conductor-dominated configurations capable of producing a rather uniform magnetic field in the aperture; the iron usually has a small effect.

Meuser, R.B.

1983-04-01

252

Cardiovascular magnetic resonance imaging in small animals.  

PubMed

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

Botnar, René M; Makowski, Marcus R

2012-01-01

253

Magnetic levitation of metamaterial bodies enhanced with magnetostatic surface resonances  

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

254

Measuring nonconstant flow in magnetic resonance imaging.  

PubMed

An attempt is made to quantify rapid flow using magnetic resonance imaging techniques. An analysis is presented in which it is assumed that constant velocity gradients are present. A deconvolution scheme which can remove the blurring from motion with acceleration is developed. This allows improved resolution and velocity determination. Computer experiments were performed on simulated data, where the velocity drops from 100 cm/s to 50 cm/s over a distance of 5 cm. In noise-free data, velocities were recovered to within 2% of the lower velocity and, for data with 5% white noise, to within 6% PMID:18222793

Izen, S H; Haacke, E M

1990-01-01

255

Creating a magnetic resonance imaging ontology.  

PubMed

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

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

2011-01-01

256

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

257

Nuclear magnetic resonance study of ultrananocrystalline diamonds  

Microsoft Academic Search

.   \\u000a We report on a nuclear magnetic resonance (NMR) study of \\u000a ultrananocrystalline diamond (UNCD) materials produced by detonation \\u000a technique. Analysis of the 13C and 1H NMR spectra, spin-spin and \\u000a spin-lattice relaxation times in purified UNCD samples is presented. Our \\u000a measurements show that UNCD particles consist of a diamond core that is \\u000a partially covered by a sp\\u000a 2-carbon fullerene-like shell. The

A. M. Panich; A. I. Shames; H.-M. Vieth; E. ?sawa; M. Takahashi

2006-01-01

258

Magnetic Resonance Labeling of Stem Cells  

PubMed Central

Recent meta-analyses of clinical cellular therapy trials in cardiovascular disease have shown that these therapies are safe and perhaps yield a positive therapeutic benefit (1-5). However, 1 issue that has plagued these clinical studies is the inability to determine the percentage engraftment of exogenously administered stem cells and the stem cell fate. In this issue of iJACC, Adler et al. (6) propose a cardiac magnetic resonance (CMR) contrast based on a paramagnetic agent, gadolinium, to track the engraftment of embryonic stem cell-derived cardiovascular progenitor cells.

Kraitchman, Dara L.; Caravan, Peter

2010-01-01

259

Magnetic resonance perfusion imaging without contrast media  

Microsoft Academic Search

Purpose  Principles of magnetic resonance imaging techniques providing perfusion-related contrast weighting without administration\\u000a of contrast media are reported and analysed systematically. Especially common approaches to arterial spin labelling (ASL) perfusion imaging allowing quantitative assessment of specific perfusion rates are described in detail. The potential\\u000a of ASL for perfusion imaging was tested in several types of tissue.\\u000a \\u000a \\u000a \\u000a \\u000a Methods  After a systematic comparison of

Petros Martirosian; Andreas Boss; Christina Schraml; Nina F. Schwenzer; Hansjörg Graf; Claus D. Claussen; Fritz Schick

2010-01-01

260

Cardiovascular magnetic resonance in systemic hypertension  

PubMed Central

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

2012-01-01

261

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

262

Nuclear magnetic resonance imaging - Potential cardiac applications  

SciTech Connect

Potential clinical applications of nuclear magnetic resonance (NMR) imaging are discussed with particular emphasis on cardiac studies. The principles of NMR spectroscopy and the reconstruction of images from NMR data obtained in a magnetic field gradient are reviewed, and the sensitive point technique of Hinshaw et al. (1977) for producing three dimensional images is introduced. Possible uses of NMR imaging in the study of intact functional biological systems are then considered, including the differentiation of ischemic tissue areas including myocardial injuries by the proton NMR imaging of water, and metabolic studies of myocardial ischemia and infarction by P-31 imaging of ATP, creatine phosphate and inorganic phosphorus. Unresolved problems in the application of NMR imaging to clinical studies are pointed out, and possible solutions which would enable the development of the technique as a powerful aid in diagnosing disease are suggested.

Goldman, M.R.; Pohost, G.M.; Ingwall, J.S.; Fossel, E.T.

1980-12-18

263

BOLD magnetic resonance imaging of skeletal muscle.  

PubMed

Blood-oxygen-level-dependent (BOLD) imaging was a concept introduced in 1990 for evaluating brain activation. The method relies on magnetic resonance imaging (MRI) contrast resulting from changes in the microvascular ratio of oxyhaemoglobin (oxyHb) to deoxyhaemoglobin (deoxyHb). OxyHb is diamagnetic, whereas deoxyHb is paramagnetic, which produces a local bulk magnetic susceptibility effect and subsequent MRI signal change. The changes are typically observed in T(2)*-weighted functional MRI scans. However, there has recently been interest in BOLD as a way to evaluate microcirculation of any normal or diseased tissue. This review focuses on the application of BOLD imaging in the understanding of normal and diseased skeletal muscle. In addition we present new findings showing the possible application of BOLD imaging with hyperoxia for evaluating skeletal muscle physiology. PMID:14735429

Noseworthy, Michael D; Bulte, Daniel P; Alfonsi, Jeff

2003-12-01

264

Clinical applications of cardiovascular magnetic resonance imaging  

PubMed Central

Cardiovascular magnetic resonance imaging (MRI) has evolved from an effective research tool into a clinically proven, safe and comprehensive imaging modality. It provides anatomic and functional information in acquired and congenital heart disease and is the most precise technique for quantification of ventricular volumes, function and mass. Owing to its excellent interstudy reproducibility, cardiovascular MRI is the optimal method for assessment of changes in ventricular parameters after therapeutic intervention. Delayed contrast enhancement is an accurate and robust method used in the diagnosis of ischemic and nonischemic cardiomyopathies and less common diseases, such as cardiac sarcoidosis and myocarditis. First-pass magnetic contrast myocardial perfusion is becoming an alternative to radionuclide techniques for the detection of coronary atherosclerotic disease. In this review we outline the techniques used in cardiovascular MRI and discuss the most common clinical applications.

Marcu, Constantin B.; Beek, Aernout M.; van Rossum, Albert C.

2006-01-01

265

Magnetic resonance imaging and safety aspects.  

PubMed

Magnetic resonance imaging (MRI) is a technique that uses a magnetic field and radio waves to create detailed images of the organs and tissues within your body. MRI is safe, but if something goes wrong, it can go very wrong. Most reported cases of MRI-related injuries and the few fatalities that have occurred have apparently been the result of failure to follow safety guidelines or of use of inappropriate or outdated information related to the safety aspects of biomedical implants and devices. To prevent accidents in the MRI environment, therefore, it is necessary to revise information on biologic effects and safety according to changes that have occurred in MRI technology and with regard to current guidelines for biomedical implants and devices. This review provides an overview of and update on MRI biologic effects, discusses new or controversial MRI safety topics and issues, and presents evidence-based guidelines to ensure safety for patients and staff. PMID:21112927

Coskun, Ozlem

2010-11-26

266

Optically detected magnetic resonance (ODMR) of photoexcited triplet states  

Microsoft Academic Search

Optically Detected Magnetic Resonance (ODMR) is a double resonance technique which combines optical measurements (fluorescence,\\u000a phosphorescence, absorption) with electron spin resonance spectroscopy. After the first triplet-state ODMR experiments in\\u000a zero magnetic field reported in 1968 by Schmidt and van der Waals, the number of double resonance studies on excited triplet\\u000a states grew rapidly. Photosynthesis has proven to be a fruitful

Donatella Carbonera

2009-01-01

267

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

268

Nuclear magnetic resonance in compounds of variable composition  

NASA Astrophysics Data System (ADS)

The results of nuclear magnetic resonance studies of the hydrides, carbides, nitrides, and oxides of transition elements are reviewed. The discussion covers general capabilities of the nuclear magnetic resonance method, with emphasis placed on the relationship between the resonance parameters and the electron structure and properties of solids. Attention is also given to the interpretation of nuclear magnetic resonance data on the basis of quantum chemical calculations of the electron structure performed by means of cluster methods of molecular orbitals. The capabilities of the nuclear resonance method in studying the properties and the structure of phases of variable composition are illustrated by examples.

Pletnev, R. N.; Zolotukhina, L. V.; Gubanov, V. A.

269

Resonant circuit as magnetic device for cancer therapy  

NASA Astrophysics Data System (ADS)

Fabrication and characterization of a resonant circuit as magnetic device for hyperthermia treatment are discussed. The resonant circuit consisting of a closed connection of an inductor and a capacitor raised its temperature by an externally applied magnetic field. As the resonant circuit was heated efficiently, it could be excited by a weak RF magnetic field of magnetic resonance imaging (MRI). By using a ferrite core for the inductor, the efficiency of temperature rise of the circuit was improved, which attributed to the miniaturization of the implant size.

Takemura, Yasushi

2011-01-01

270

Geometric quantum computation using nuclear magnetic resonance  

PubMed

A significant development in computing has been the discovery that the computational power of quantum computers exceeds that of Turing machines. Central to the experimental realization of quantum information processing is the construction of fault-tolerant quantum logic gates. Their operation requires conditional quantum dynamics, in which one sub-system undergoes a coherent evolution that depends on the quantum state of another sub-system; in particular, the evolving sub-system may acquire a conditional phase shift. Although conventionally dynamic in origin, phase shifts can also be geometric. Conditional geometric (or 'Berry') phases depend only on the geometry of the path executed, and are therefore resilient to certain types of errors; this suggests the possibility of an intrinsically fault-tolerant way of performing quantum gate operations. Nuclear magnetic resonance techniques have already been used to demonstrate both simple quantum information processing and geometric phase shifts. Here we combine these ideas by performing a nuclear magnetic resonance experiment in which a conditional Berry phase is implemented, demonstrating a controlled phase shift gate. PMID:10706278

Jones; Vedral; Ekert; Castagnoli

2000-02-24

271

Prospects for neutron probed magnetic resonance imaging  

SciTech Connect

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

Granroth, Garrett E [ORNL

2009-01-01

272

Magnetic resonance imaging. Application to family practice.  

PubMed Central

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

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

1999-01-01

273

Magnetic resonance elastography hardware design: a survey.  

PubMed

Magnetic resonance elastography (MRE) is an emerging technique capable of measuring the shear modulus of tissue. A suspected tumour can be identified by comparing its properties with those of tissues surrounding it; this can be achieved even in deep-lying areas as long as mechanical excitation is possible. This would allow non-invasive methods for cancer-related diagnosis in areas not accessible with conventional palpation. An actuating mechanism is required to generate the necessary tissue displacements directly on the patient in the scanner and three different approaches, in terms of actuator action and position, exist to derive stiffness measurements. However, the magnetic resonance (MR) environment places considerable constraints on the design of such devices, such as the possibility of mutual interference between electrical components, the scanner field, and radio frequency pulses, and the physical space restrictions of the scanner bore. This paper presents a review of the current solutions that have been developed for MRE devices giving particular consideration to the design criteria including the required vibration frequency and amplitude in different applications, the issue of MR compatibility, actuation principles, design complexity, and scanner synchronization issues. The future challenges in this field are also described. PMID:19499839

Tse, Z T H; Janssen, H; Hamed, A; Ristic, M; Young, I; Lamperth, M

2009-05-01

274

Cardiovascular applications of nuclear magnetic resonance spectroscopy.  

PubMed

Nuclear magnetic resonance spectroscopy has great potential for defining noninvasively the metabolic status of the heart and skeletal muscle. This technique uses the spin properties of certain nuclei (such as phosphorus-31, hydrogen-1 and carbon-13) to measure high energy phosphates, intracellular pH, lactate and glycogen. Animal studies have formed the basis for human investigations and have demonstrated well-defined changes in high energy phosphates during myocardial ischemia and reperfusion, as well as in cardiomyopathies. Human studies have been limited by issues of sensitivity and localization, although techniques such as rotating frame, depth-resolved surface coil spectroscopy, image-selected in vivo spectroscopy and spectroscopic imaging have been used to acquire phosphorus-31 spectra from the human heart. The few human studies of patients with disease have demonstrated elevated inorganic phosphate peaks after myocardial infarction and abnormal phosphodiester peaks in patients with hypertrophic cardiomyopathy. Studies of patients with heart failure have shown that these patients acidify their peripheral muscles with exercise more easily than do control subjects. Clinical application of nuclear magnetic resonance spectroscopy will depend on technical advances and the demonstration of sensitivity of metabolic changes with disease. PMID:2672766

Schaefer, S

1989-09-01

275

Metabolic Tumor Imaging Using Magnetic Resonance Spectroscopy  

PubMed Central

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.

Glunde, Kristine; Bhujwalla, Zaver M.

2011-01-01

276

Reciprocity and gyrotropism in magnetic resonance transduction  

NASA Astrophysics Data System (ADS)

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

Tropp, James

2006-12-01

277

Reciprocity and gyrotropism in magnetic resonance transduction  

SciTech Connect

We give formulas for transduction in magnetic resonance - i.e., the appearance of an emf due to Larmor precession of spins - based upon the modified Lorentz reciprocity principle for gyrotropic (also called 'nonreciprocal') media, i.e., in which a susceptibility tensor is carried to its transpose by reversal of an external static field [cf., R. F. Harrington and A. T. Villeneuve IRE Trans. Microwave Theory and Technique MTT6, 308 (1958)]. Prior applications of reciprocity to magnetic resonance, despite much success, have ignored the gyrotropism which necessarily arises due to nuclear and/or unpaired electronic spins. For detection with linearly polarized fields, oscillating at the Larmor frequency, the emf is written in terms of a volume integral containing a product of two factors which we define as the antenna patterns, i.e. (H{sub 1x}{+-}iH{sub 1y}), where, e.g., for a single transceive antenna, the H's are just the spatially dependent oscillatory magnetic field strengths, per the application of some reference current at the antenna terminals, with the negative sign obtaining for transmission, and the positive for reception. Similar expressions hold for separate transmit and receive antennas; expressions are also given for circular polarization of the fields. We then exhibit a receive-only array antenna of two elements for magnetic resonance imaging of protons, which, due an intensity artifact arising from stray reactive coupling of the elements, produces, despite its own bilateral symmetry, asymmetric proton NMR images of a symmetric cylindrical phantom containing aqueous saline solution [J. Tropp and T. Schirmer, J. Magn. Reson. 151, 146 (2001)]. Modification of this two-port antenna, to function in transmit-receive mode, allows us to demonstrate highly nonreciprocal behavior: that is, to record images (of cylindrical test phantoms containing aqueous saline solution) whose appearance dramatically changes, when the roles of transmission and reception are swapped between the two antenna ports--giving in one instance a signal intensity pattern whose form resembles an umbrella (i.e., with a central column of moderate intensity surmounted by a bright canopy), and in the other, a distorted oval with slight concavities at its horizontal extremes, whose outline suggests that of a cat's eye. The relation between image patterns and drive scheme can be shown to reverse if the static polarizing field is reversed. Electromagnetic and circuit calculations, together with the modified reciprocity principle, allow us to reproduce these pattern changes in numerical simulations, closely and convincingly. Although the imaging experiments are performed at a static field of 3.0 T, and consequently a Larmor frequency of 128 MHz, the nonreciprocal effects are not related to the shortness of the wavelength in aqueous medium, but appear equally in simulations based in either the quasistatic or full electromagnetic regimes. Finally, we show that although antenna patterns for transmission and reception are swapped with reversal of the polarizing field, meaning that the receive pattern equals the transmit pattern with the field reversed, this in no way invalidates the familiar rotating wave model of spin dynamics in magnetic resonance.

Tropp, James [General Electric Healthcare Technologies, 47697 Westinghouse Drive, Fremont, California 94539 (United States)

2006-12-15

278

BROADBAND EXCITATION IN NUCLEAR MAGNETIC RESONANCE  

SciTech Connect

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

Tycko, R.

1984-10-01

279

Effects of surgical implants on high-field magnetic resonance images of the normal canine stifle.  

PubMed

To determine the effect of surgical implants on the depiction of canine stifle anatomy in magnetic resonance (MR) images, three canine cadaver limbs were imaged at 1.5 T before and after tibial plateau leveling osteotomy (TPLO), tibial tuberosity advancement (TTA), and extra-capsular stabilization (ECS), respectively. Susceptibility artifacts associated with implants were identified in MR images as a signal void and/or signal misregistration, which obscured or distorted the anatomy. Using the preoperative images as a reference, articular structures of the stifle in postoperative images were graded using an ordinal scale to describe to what degree each anatomic structure could be evaluated for clinical purposes. The TPLO implant, which contains ferromagnetic stainless steel, produced marked susceptibility artifacts that obscured or distorted most stifle anatomy. The titanium alloy TTA implants and the stainless steel crimps used for ECS produced susceptibility artifacts that mainly affected the lateral aspect of the stifle, but allowed the cruciate ligaments and medial meniscus to be evaluated satisfactorily. Susceptibility artifact was significantly less marked in images obtained using turbo spin-echo (TSE) sequences than in sequences employing spectral fat saturation. Clinical MR imaging of canine stifles containing certain metallic implants is feasible using TSE sequences without fat saturation. PMID:22372640

David, F H; Grierson, J; Lamb, C R

2012-02-28

280

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

281

Permanent Magnet Structure for a Nuclear Magnetic Resonance Imager for Medical Diagnostics.  

National Technical Information Service (NTIS)

The present invention relates to the utilization of magnetic fields established by means of permanent magnets for use in medical diagnosis, particularly of the human body or torsi. Whole-body nuclear magnetic resonance diagnostics has been available in th...

H. A. Leupold E. Potenziani

1987-01-01

282

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

283

Functional magnetic resonance imaging using RASER  

PubMed Central

Although functional imaging of neuronal activity by magnetic resonance imaging (fMRI) has become the primary methodology employed in studying the brain, significant portions of the brain are inaccessible by this methodology due to its sensitivity to macroscopic magnetic field inhomogeneities induced near air filled cavities in the head. In this paper, we demonstrate that this sensitivity is eliminated by a novel pulse sequence, RASER (rapid acquisition by sequential excitation and refocusing) (Chamberlain et al., 2007), that can generate functional maps. This is accomplished because RASER acquired signals are purely and perfectly T2 weighted, without any T2*-effects that are inherent in the other image acquisition schemes employed to date. T2-weighted fMRI sequences are also more specific to the site of neuronal activity at ultrahigh magnetic fields than T2*-variations since they are dominated by signal components originating from the tissue in the capillary bed. The RASER based fMRI response is quantified; it is shown to have inherently less noisy time series and to provide fMRI in brain regions, such as the orbitofrontal cortex, which are challenging to image with conventional techniques.

Goerke, Ute; Garwood, Michael; Ugurbil, Kamil

2010-01-01

284

Functional magnetic resonance imaging using RASER.  

PubMed

Although functional imaging of neuronal activity by magnetic resonance imaging (fMRI) has become the primary methodology employed in studying the brain, significant portions of the brain are inaccessible by this methodology due to its sensitivity to macroscopic magnetic field inhomogeneities induced near air-filled cavities in the head. In this paper, we demonstrate that this sensitivity is eliminated by a novel pulse sequence, RASER (rapid acquisition by sequential excitation and refocusing) (Chamberlain et al., 2007), that can generate functional maps. This is accomplished because RASER acquired signals are purely and perfectly T(2) weighted, without any T(2)*-effects that are inherent in the other image acquisition schemes employed to date. T(2)-weighted fMRI sequences are also more specific to the site of neuronal activity at ultrahigh magnetic fields than T(2)*-variations since they are dominated by signal components originating from the tissue in the capillary bed. The RASER based fMRI response is quantified; it is shown to have an inherently less noisy time series and to provide fMRI in brain regions, such as the orbitofrontal cortex, which are challenging to image with conventional techniques. PMID:20699123

Goerke, Ute; Garwood, Michael; Ugurbil, Kamil

2010-08-08

285

Immobilization of Iron Oxide Magnetic Nanoparticles for Enhancement of Vessel Wall Magnetic Resonance Imaging--An Ex Vivo Feasibility Study  

PubMed Central

Emerging data supports a role for negative wall remodeling in the failure of vascular interventions such as vein grafts, yet clinicians/researchers currently lack the ability to temporally/efficiently investigate adventitial surface topography/total vascular wall anatomy in vivo. We established a strategy of immobilizing commercially available iron oxide magnetic nanoparticles (Fe-NPs) onto the surface of human vein conduits to facilitate high-throughput total vascular wall demarcation with magnetic resonance (MR). Binding of activated Fe-NPs to amine groups on the surface of the veins induced a thin layer of negative contrast that differentiated the adventitia from surrounding saline signal in all MR images, enabling delineation of total wall anatomy; this was not possible in simultaneously imaged unlabeled control veins. Under the conditions of this ex vivo experiment, stable covalent binding of Fe-NPs can be achieved (dose-dependent) on human vein surface for MR detection, suggesting a potential strategy for enhancing the ability of MRI to investigate total wall adaptation and remodeling in vein graft failure.

2010-01-01

286

Nuclear magnetic resonance in environmental engineering: Principles and applications  

Microsoft Academic Search

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

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

1998-01-01

287

Classification of prostate magnetic resonance spectra using Support Vector Machine  

Microsoft Academic Search

Prostate cancer is the most common cancer in men over 50 years of age and it has been shown that nuclear magnetic resonance spectra are sensitive enough to distinguish normal and cancer tissues. In this paper, we propose a classification technique of spectra from magnetic resonance spectroscopy. We studied automatic classification with and without quantification of metabolite signals. The dataset

S. Parfait; P. M. Walker; G. Créhange; X. Tizon; J. Mitéran

288

Magnetic resonance imaging of anterior cruciate ligament rupture  

Microsoft Academic Search

BACKGROUND: Magnetic resonance (MR) imaging is a useful diagnostic tool for the assessment of knee joint injury. Anterior cruciate ligament repair is a commonly performed orthopaedic procedure. This paper examines the concordance between MR imaging and arthroscopic findings. METHODS: Between February, 1996 and February, 1998, 48 patients who underwent magnetic resonance (MR) imaging of the knee were reported to have

Kai-Jow Tsai; Hongsen Chiang; Ching-Chuan Jiang

2004-01-01

289

Magnetic response of nanostructured systems: A ferromagnetic resonance investigation  

Microsoft Academic Search

Ferromagnetic resonance (FMR) measurements probe the response of magnetic systems within the nanosecond-regime due to an excitation within the microwave regime. Due to the high sensitivity of FMR this technique is well suited for the investigation of nanostructures and ultrathin magnetic films or multilayers. As the resonance condition is determined by internal fields like anisotropy fields or interlayer coupling fields

J. Lindner; U. Wiedwald; K. Baberschke; M. Farle

2005-01-01

290

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

291

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

292

Hybrid Magnetic Resonance Angiography and Quantitative Volume Flow Measurement  

Microsoft Academic Search

Volume blood flow rate correlates directly with oxygen delivery for aerobic metabolism and is thus clinically more significant than velocity in the diagnosis of vascular diseases. In this dissertation, an magnetic resonance imaging (MRI) technique has been developed to directly measure flow rate. A two echo hybrid magnetic resonance angiography (MRA) pulse sequence has been designed and implemented to obtain

Ping Hou

1993-01-01

293

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

294

Supine magnetic resonance (MR) mammography in radiotherapy planning  

Microsoft Academic Search

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

Sadie Dunne; Amanda Gee

1999-01-01

295

Clinical applications of magnetic resonance imaging - current status  

Microsoft Academic Search

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

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

1985-01-01

296

Magnetic resonance imaging methods in developmental science: A primer  

Microsoft Academic Search

Structural and functional magnetic resonance imaging (MRI) are increasingly common research methods among investigators interested in typically and atypically developing populations. However, the effective use of these tools requires an understanding of the basis of the magnetic resonance signal, as well as some of the additional experimental complications that arise when collecting MRI data from developmental populations. This primer provides

Ruskin H. Hunt; Kathleen M. Thomas

2008-01-01

297

Toward Synthesizing a Selective Dopamine Binding Magnetic Resonance Contrast Agent  

Microsoft Academic Search

Magnetic resonance imaging (MRI) is a non-invasive diagnostic methodology used to provide a two-dimensional view of an internal organ or structure, especially the brain and spinal cord. Magnetic resonance contrast agents are usually injected into necessary parts of the body prior to imaging to increase the differences between different tissues or between normal and abnormal tissue, making it easier for

Judy Lau

2006-01-01

298

A personal computer-based nuclear magnetic resonance spectrometer  

Microsoft Academic Search

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

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

1994-01-01

299

Rotational Resonance of Nonaxisymmetric Magnetic Braking in the KSTAR Tokamak  

NASA Astrophysics Data System (ADS)

One of the important rotational resonances in nonaxisymmetric neoclassical transport has been experimentally validated in the KSTAR tokamak by applying highly nonresonant n=1 magnetic perturbations to rapidly rotating plasmas. These so-called bounce-harmonic resonances are expected to occur in the presence of magnetic braking perturbations when the toroidal rotation is fast enough to resonate with periodic parallel motions of trapped particles. The predicted and observed resonant peak along with the toroidal rotation implies that the toroidal rotation in tokamaks can be controlled naturally in favorable conditions to stability, using nonaxisymmetric magnetic perturbations.

Park, J.-K.; Jeon, Y. M.; Menard, J. E.; Ko, W. H.; Lee, S. G.; Bae, Y. S.; Joung, M.; You, K.-I.; Lee, K.-D.; Logan, N.; Kim, K.; Ko, J. S.; Yoon, S. W.; Hahn, S. H.; Kim, J. H.; Kim, W. C.; Oh, Y.-K.; Kwak, J.-G.

2013-08-01

300

Pattern recognition of magnetic resonance images with application to atherosclerosis  

SciTech Connect

Magnetic resonance imaging provides excellent soft tissue contrast enabling the non-invasive visualization of soft tissue diseases. The quantification of tissues visible in MR images would significantly increase the diagnostic information available. While tissue selection methods exist for CT images, those same methods do not work with MR images. This dissertation focuses on the application of image processing and pattern recognition techniques to MR images for the identification and quantification of soft tissues, atherosclerosis in particular. Atherosclerosis is a chronic disease of human arteries responsible for significant mortality and medical expense. Current diagnostic methods are invasive and carry significant risk. Supervised pattern recognition methods were investigated for tissue identification in MR images. The classifiers were trained A Fisher linear classifier successfully identified the tissues of interest from MR images of excised arteries, performing better than a minimum distance to the means classifier. Quantitative measures of the disease state were computed from the results and 3-D displays were generated of the diseased anatomy. For tissue in vivo, adequate histology can be difficult to collect, increasing the difficulty of training the classifiers and making the results less accurate. Cluster analysis was used in this dissertation to generate the training information. A new cluster analysis method was developed. ISODATA was modified to use hierarchical stopping rules. The new method was tested in a Monte Carlo study and with real world data sets. Comparisons were made with published methods using the same data. An information theoretic criterion, the CAIC, was found to be an excellent criteria for hierarchical stopping rules.

Carman, C.S.

1989-01-01

301

Automated Analysis of Craniofacial Morphology Using Magnetic Resonance Images  

PubMed Central

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 MR images, acquired to examine brain anatomy, can also be used to analyze facial features. Using a sample of typically developing adolescents from the Saguenay Youth Study (N?=?597; 292 male, 305 female, ages: 12 to 18 years), we quantified inter-individual variations in craniofacial structure in two ways. First, we adapted existing nonlinear registration-based morphological techniques to generate iteratively a group-wise population average of craniofacial features. The nonlinear transformations were used to map the craniofacial structure of each individual to the population average. Using voxel-wise measures of expansion and contraction, we then examined the effects of sex and age on inter-individual variations in facial features. Second, we employed a landmark-based approach to quantify variations in face surfaces. This approach involves: (a) placing 56 landmarks (forehead, nose, lips, jaw-line, cheekbones, and eyes) on a surface representation of the MRI-based group average; (b) warping the landmarks to the individual faces using the inverse nonlinear transformation estimated for each person; and (3) using a principal components analysis (PCA) of the warped landmarks to identify facial features (i.e. clusters of landmarks) that vary in our sample in a correlated fashion. As with the voxel-wise analysis of the deformation fields, we examined the effects of sex and age on the PCA-derived spatial relationships between facial features. Both methods demonstrated significant sexual dimorphism in craniofacial structure in areas such as the chin, mandible, lips, and nose.

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

2011-01-01

302

Small-Volume Nuclear Magnetic Resonance Spectroscopy  

NASA Astrophysics Data System (ADS)

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

Fratila, Raluca M.; Velders, Aldrik H.

2011-07-01

303

Stem cell labeling for magnetic resonance imaging.  

PubMed

In vivo applications of cells for the monitoring of their cell dynamics increasingly use non-invasive magnetic resonance imaging. This imaging modality allows in particular to follow the migrational activity of stem cells intended for cell therapy strategies. All these approaches require the prior labeling of the cells under investigation for excellent contrast against the host tissue background in the imaging modality. The present review discusses the various routes of cell labeling and describes the potential to observe both cell localization and their cell-specific function in vivo. Possibilities for labeling strategies, pros and cons of various contrast agents are pointed out while potential ambiguities or problems of labeling strategies are emphasized. PMID:18465447

Himmelreich, Uwe; Hoehn, Mathias

2008-01-01

304

Nuclear magnetic resonance imaging in medicine  

PubMed Central

Using the technique of nuclear magnetic resonance (NMR, MR, MRI), the first images displaying pathology in humans were published in 1980.1 Since then, there has been a rapid extension in the use of the technique, with an estimated 225 machines in use in the USA at the end of 1985.2 Considerable enthusiasm has been expressed for this new imaging technique,3 although awareness of its high cost in the present economic climate has led to reservations being expressed in other quarters.2 The aim of this article is to give an outline of the present state of NMR, and indicate some possible future developments. ImagesFig 1Fig 2Fig 3(a)Fig 3 (b)Fig 4Fig 5Fig 6Fig 7 (a)Fig 7 (b)Fig 8Fig 9Fig 10

McKinstry, C S

1986-01-01

305

Antenna coupling circuit for magnetic resonance imaging  

SciTech Connect

A coupling circuit for coupling an inductive coil antenna of a magnetic resonance imaging system to receiver circuitry is described comprising: capacitive means, coupled in parallel with the antenna, for providing capacitive reactance in the coupling circuit; resistive means, coupled in parallel with the antenna and with the capacitive means, for providing resistance R in the coupling circuit when the inductive reactance of the coupling circuit is equal to the capacitive reactance of the coupling circuit; and capacitive transformer means, coupled between the antenna and the receiver circuitry in series with the antenna, for transforming the resistance value R of the resistive means into a transformed resistance value R', thereby increasing the apparent resistance of the coupling circuit in parallel with the antenna.

Fox, T.R.

1988-03-15

306

Magnetic resonance spectroscopy in traumatic brain injury.  

PubMed

Magnetic resonance spectroscopy (MRS) offers a unique non-invasive approach for assessing the metabolic status of the brain in vivo and is particularly suited to studying traumatic brain injury (TBI). In particular, MRS provides a noninvasive means for quantifying such neurochemicals as N-acetylaspartate (NAA), creatine, phosphocreatine, choline, lactate, myo-inositol, glutamine, glutamate, adenosine triphosphate (ATP), and inorganic phosphate in humans following TBI and in animal models. Many of these chemicals have been shown to be perturbed following TBI. NAA, a marker of neuronal integrity, has been shown to be reduced following TBI, reflecting diffuse axonal injury or metabolic depression, and concentrations of NAA predict cognitive outcome. Elevation of choline-containing compounds indicates membrane breakdown or inflammation or both. MRS can also detect alterations in high energy phosphates reflecting the energetic abnormalities seen after TBI. Accordingly, MRS may be useful to monitor cellular response to therapeutic interventions in TBI. PMID:11275576

Brooks, W M; Friedman, S D; Gasparovic, C

2001-04-01

307

Magnetic Resonance Imaging in Amyotrophic Lateral Sclerosis  

PubMed Central

Amyotrophic lateral sclerosis (ALS) is a rapidly progressing neurodegenerative disorder which is incurable to date. As there are many ongoing studies with therapeutic candidates, it is of major interest to develop biomarkers not only to facilitate early diagnosis but also as a monitoring tool to predict disease progression and to enable correct randomization of patients in clinical trials. Magnetic resonance imaging (MRI) has made substantial progress over the last three decades and is a practical, noninvasive method to gain insights into the pathology of the disease. Disease-specific MRI changes therefore represent potential biomarkers for ALS. In this paper we give an overview of structural and functional MRI alterations in ALS with the focus on task-free resting-state investigations to detect cortical network failures.

Kollewe, Katja; Korner, Sonja; Dengler, Reinhard; Petri, Susanne; Mohammadi, Bahram

2012-01-01

308

Simulations of pulsed nuclear magnetic resonance experiments  

SciTech Connect

In order to help elucidate various aspects of pulsed nuclear magnetic resonance (NMR) experiments in the liquid state, a consistent mathematical treatment based on density matrix formalism was developed and implemented in a computer program, RELAX. Relaxation effects stemming from dipolar, chemical shift anisotropy (CSA), and random field mechanisms are accounted for, including contributions from dipole-CSA cross-correlation. The program was utilized to study para-fluorophenyl spin systems in dynamical regimes characteristic of both small and large molecules. Theory demonstrates that dipole-CSA cross-correlation can have pronounced effects in these systems and suggests that analysis of these effects will be useful in the study of protein conformation and dynamics.

Smith, S.A.

1991-01-01

309

Interactive Course on Magnetic Resonance Imagining  

NSDL National Science Digital Library

As the health care professions continue to attract talented individuals, online resources have become an attractive way to learn new skills and supplement classroom learning. This website offers interested parties a step-by-step, interactive course on magnetic resonance imaging (MRI). It's worth noting that the site has received several awards from organizations such as the Radiological Society of North America. The course is divided into 16 sections, including Cardiac MRI, Image Formation, and Functional MRI. Each section contains a table of contents and a detailed list of learning objectives. As a whole, the site is a great way to get acquainted with this important medical tool and it is a resource that educators will want to share with friends and colleagues. [KMG

2013-01-01

310

Magnetic resonance imaging of palindromic rheumatism.  

PubMed

A 44-year-old man with intermittent asymmetric migratory oligoarthritis lasting the recent decade was admitted to our hospital. Considerable specific biomarkers for rheumatoid arthritis such as anti-agalactosyl IgG antibody are all negative. He was diagnosed as palindromic rheumatism (PR). Although hand X-rays showed no remarkable findings, hand magnetic resonance imaging (MRI) detected pannus and bone erosion. PR is defined as the disease characterized by short-lasting attacks of acute oligoarthritis, without radiographic changes. To our knowledge, the findings of MRI for PR have not been previously described. We propose that MRI findings in patients with PR is useful tool to distinguish PR from rheumatoid arthritis (RA) or other RA related diseases. PMID:18663450

Ueda, Satoko; Horino, Taro; Arii, Kaoru; Morita, Tatsuhito; Takao, Toshihiro; Hashimoto, Kozo

2008-07-29

311

Cardiovascular magnetic resonance in pulmonary hypertension  

PubMed Central

Pulmonary hypertension represents a group of conditions characterized by higher than normal pulmonary artery pressures. Despite improved treatments, outcomes in many instances remain poor. In recent years, there has been growing interest in the use of Cardiovascular Magnetic Resonance (CMR) in patients with pulmonary hypertension. This technique offers certain advantages over other imaging modalities since it is well suited to the assessment of the right ventricle and the proximal pulmonary arteries. Reflecting the relatively sparse evidence supporting its use, CMR is not routinely recommended for patients with pulmonary hypertension. However, it is particularly useful in patient with pulmonary arterial hypertension associated with congenital heart disease. Furthermore, it has proven informative in a number of ways; illustrating how right ventricular remodeling is favorably reversed by drug therapies and providing explicit confirmation of the importance of the right ventricle to clinical outcome. This review will discuss these aspects and practical considerations before speculating on future applications.

2012-01-01

312

Magnetic Earth Ionosphere Resonant Frequencies (MEIRF) project  

NASA Astrophysics Data System (ADS)

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

Spaniol, Craig

1993-06-01

313

Magnetic Resonance Microscopy of Mammalian Neurons  

PubMed Central

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

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

2011-01-01

314

Magnetic resonance studies of dissolving particulate solids.  

PubMed

Magnetic resonance methods have been used to elucidate the internal pore structure of particulate solids, in particular detergent tablets. Such information is essential to a comprehensive understanding of the dissolution characteristics of these materials and how this property is related to processing conditions during tablet formation. In particular 3-D images of porosity are produced and 2-D self-diffusion maps are acquired as a function of observation time, which enables pore size to be quantified as a function of position via the extracted surface-to-volume ratio of the pore space. These properties are determined as a function of processing parameters, in particular the compression force used in tablet formation. PMID:12850743

Johns, M L; Gladden, L F

315

Magnetic resonance spectroscopy in Alzheimer's disease  

PubMed Central

Aging is the primary risk factor for dementia. With increasing life expectancy and aging populations worldwide, dementia is becoming one of the significant public health problems of the century. The most common pathology underlying dementia in older adults is Alzheimer’s disease. Proton magnetic resonance spectroscopy (MRS) may provide a window into the biochemical changes associated with the loss of neuronal integrity and other neurodegenerative pathology that involve the brain before the manifestations of cognitive impairment in patients who are at risk for Alzheimer’s disease. This review focuses on proton MRS studies in normal aging, mild cognitive impairment, and dementia, and how proton MRS metabolite levels may be potential biomarkers for early diagnosis of dementia-related pathologic changes in the brain.

Graff-Radford, Jonathan; Kantarci, Kejal

2013-01-01

316

Geochemical Controls on Nuclear Magnetic Resonance Measurements  

SciTech Connect

OAK-B135 Our research objectives are to determine, through an extensive set of laboratory experiments, the effect of the specific mineralogic form of iron and the effect of the distribution of iron on proton nuclear magnetic resonance (NMR) relaxation mechanisms. In the first nine months of this project, we have refined the experimental procedures to be used in the acquisition of the laboratory NMR data; have ordered, and conducted preliminary measurements on, the sand samples to be used in the experimental work; and have revised and completed the theoretical model to use in this project. Over the next year, our focus will be on completing the first phase of the experimental work where the form and distribution of the iron in the sands in varied.

Knight, Rosemary; Prasad, Manika; Keating, Kristina

2003-11-11

317

[Clinical application of functional magnetic resonance imaging].  

PubMed

Three types of researches have been carried out on brain-mind relationships: 1. researches on anatomical correlates of special talents (for example, perfect pitch) or deficits (for example, dyslexia), 2. researches to examine the relationship between a given cognitive syndrome and the site of brain damage, 3. researches to localize human cognitive function in the brain in vivo using functional magnetic resonance imaging (fMRI) and positron emission tomography (PET). fMRI is a particularly important because it is noninvasive. A tutorial covering basic aspects of this methodology is presented, along with a survey of recent fMRI data related to clinical application. Future investigations of the three types enumerated above are expected to further clarify brain-mind relationships. PMID:11905006

Sugishita, Morihiro

2002-03-01

318

Magnetic resonance imaging of atherosclerotic vascular disease.  

PubMed

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

Underwood, R S; Mohiaddin, R H

1993-11-01

319

Functional magnetic resonance imaging in schizophrenia  

PubMed Central

The integration of functional magnetic resonance imaging (fMRI) with cognitive and affective neuroscience paradigms enables examination of the brain systems underlying the behavioral deficits manifested in schizophrenia; there have been a remarkable increase in the number of studies that apply fMRI in neurobiological studies of this disease. This article summarizes features of fMRI methodology and highlights its application in neurobehavioral studies in schizophrenia. Such work has helped elucidate potential neural substrates of deficits in cognition and affect by providing measures of activation to neurobehavioral probes and connectivity among brain regions. Studies have demonstrated abnormalities at early stages of sensory processing that may influence downstream abnormalities in more complex evaluative processing. The methodology can help bridge integration with neuropharmacologic and genomic investigations.

Gur, Raquel E.; Gur, Ruben C.

2010-01-01

320

Burn injury by nuclear magnetic resonance imaging.  

PubMed

Nuclear magnetic resonance imaging has become a standard diagnostic procedure in clinical medicine and is well known to have hazards for patients with pacemaker or metallic foreign bodies. Compared to CT, the frequency of MRI examinations is increasing due to the missing exposure of the patients by X-rays. Furthermore, high-field magnetic resonance tomograph (MRT) with 3 T has entered clinical practice, and 7-T systems are installed in multiple scientific institutions. On the other hand, the possibility of burn injuries has been reported only in very few cases. Based on a clinical finding of a burn injury in a 31-year-old male patient during a routine MRI of the lumbar spine with standard protocol, the MR scanner was checked and the examination was simulated in an animal model. The patient received a third-degree burn injury of the skin of the right hand and pelvis in a small region of skin contact. The subsequent control of the MRI scanner indicated no abnormal values for radiofrequency (RF) and power. In the subsequent animal experiment, comparable injuries could only be obtained by high RF power in a microwave stove. It is concluded that 'tissue loops' resulting from a contact between hand and pelvis must be avoided. With regard to forensic aspects, the need to inform patients of such a minimal risk can be avoided if the patients are adequately positioned using an isolating material between the hands and pelvis. These facts must be emphasized more in the future, if high-field MRI with stronger RF gradients is available in routine imaging. PMID:20630342

Eising, Ernst G; Hughes, Justin; Nolte, Frank; Jentzen, Walter; Bockisch, Andreas

321

Magnetic resonance characterization of silicon nanowires  

NASA Astrophysics Data System (ADS)

Silicon nanowires (SiNWs) have been extensively investigated in the last decades. The interest in these nanostructures stems from both fundamental and applied research motivations. The functional properties of one- and zero-dimensional silicon structures are significantly different, at least below a certain critical dimension, from those well known in the bulk. The key and peculiar functional properties of SiNWs find applications in nanoelectronics, classical and quantum information processing and storage, optoelectronics, photovoltaics, thermoelectric, battery technology, nano-biotechnology, and neuroelectronics. We report our work on the characterization by continuous wave (CW) and pulse electron spin resonance (CW, FT-EPR) and electrically detected magnetic resonance (EDMR) measurements of silicon nanowires (SiNWs) produced by different top-down processes. SiNWs were fabricated starting from SOI wafers using standard e-beam lithography and anisotropic wet etching or by metal-assisted chemical etching. Further oxidation was used to reduce the wire cross section. Different EDMR implementations were used to address the electronic wave function of donors (P, As) and to characterize point defects at the SiNWs/SiO2 interface.

Fanciulli, Marco; Belli, Matteo; Vellei, Antonio; Canevali, Carmen; Rotta, Davide; Paleari, Stefano; Basini, Martina

2012-02-01

322

Chapter 1 Magnetic Resonance Contributions to Other Sciences  

Microsoft Academic Search

In 1947, I.I. Rabi invented the molecular beam magnetic resonance method for the important, but limited purpose, of measuring nuclear magnetic moments and five of us working in his laboratory immediately began such experiments. The first experiments with LiCl gave the expected single resonance for each nucleus, but we were surprised to discover six resonances for the proton in H2,

Norman F. Ramsey

2008-01-01

323

Magnetic moments of neutron resonances in rare-earth nuclei  

Microsoft Academic Search

The magnetic dipole moments muJ of compound states (neutron resonances) in holmium and terbium have been obtained by the neutron resonance energy shift method. This shift is due to the polarization of nuclei at ultra-low temperature in h.f. magnetic fields inside ferromagnetic samples. Shifts of resonances in neutron transmission were measured by the time-of-flight method in a booster mode of

V. P. Alfimenkov; L. Lason; Yu. D. Mareev; O. N. Ovchinnikov; L. B. Pikelner; E. I. Sharapov

1976-01-01

324

Role of chelates in magnetic resonance imaging studies.  

PubMed

Imaging studies are tests performed with a variety of techniques that produce pictures of the inside of a patient's body. Magnetic resonance imaging (MRI) is an imaging technique based on the principles of nuclear magnetic resonance. MRI uses a powerful magnetic field, radio waves, and a computer to produce detailed pictures of organs, soft tissues, bone, and virtually all other internal body structures. Chelates have a wide application in such imaging techniques. Chelates in imaging studies are used alone as radioactive agents or conjugated to monoclonal antibodies or to DNA as radioactive agents. Technetium chelates and gadolinium chelates are being widely used as magnetic resonance contrast media. PMID:19841554

Tripathi, Laxmi; Kumar, Praveen; Singh, Ranjit

325

Coronary magnetic resonance vein imaging: imaging contrast, sequence, and timing.  

PubMed

Recently, there has been increased interest in imaging the coronary vein anatomy to guide interventional cardiovascular procedures such as cardiac resynchronization therapy (CRT), a device therapy for congestive heart failure (CHF). With CRT the lateral wall of the left ventricle is electrically paced using a transvenous coronary sinus lead or surgically placed epicardial lead. Proper transvenous lead placement is facilitated by the knowledge of the coronary vein anatomy. Cardiovascular MR (CMR) has the potential to image the coronary veins. In this study we propose and test CMR techniques and protocols for imaging the coronary venous anatomy. Three aspects of design of imaging sequence were studied: magnetization preparation schemes (T(2) preparation and magnetization transfer), imaging sequences (gradient-echo (GRE) and steady-state free precession (SSFP)), and imaging time during the cardiac cycle. Numerical and in vivo studies both in healthy and CHF subjects were performed to optimize and demonstrate the utility of CMR for coronary vein imaging. Magnetization transfer was superior to T(2) preparation for contrast enhancement. Both GRE and SSFP were viable imaging sequences, although GRE provided more robust results with better contrast. Imaging during the end-systolic quiescent period was preferable as it coincided with the maximum size of the coronary veins. PMID:17969081

Nezafat, Reza; Han, Yuchi; Peters, Dana C; Herzka, Daniel A; Wylie, John V; Goddu, Beth; Kissinger, Kraig K; Yeon, Susan B; Zimetbaum, Peter J; Manning, Warren J

2007-12-01

326

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

2012-05-08

327

Cardiac imaging using gated magnetic resonance  

SciTech Connect

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

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

1984-01-01

328

Designing Magnetic Resonance Imaging Curriculum for Undergraduates  

NSDL National Science Digital Library

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

2009-10-29

329

Thoracic magnetic resonance imaging: pulmonary thromboembolism.  

PubMed

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

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

2013-05-01

330

In Vivo Assessment of Cold Adaptation in Insect Larvae by Magnetic Resonance Imaging and Magnetic Resonance Spectroscopy  

PubMed Central

Background Temperatures below the freezing point of water and the ensuing ice crystal formation pose serious challenges to cell structure and function. Consequently, species living in seasonally cold environments have evolved a multitude of strategies to reorganize their cellular architecture and metabolism, and the underlying mechanisms are crucial to our understanding of life. In multicellular organisms, and poikilotherm animals in particular, our knowledge about these processes is almost exclusively due to invasive studies, thereby limiting the range of conclusions that can be drawn about intact living systems. Methodology Given that non-destructive techniques like 1H Magnetic Resonance (MR) imaging and spectroscopy have proven useful for in vivo investigations of a wide range of biological systems, we aimed at evaluating their potential to observe cold adaptations in living insect larvae. Specifically, we chose two cold-hardy insect species that frequently serve as cryobiological model systems–the freeze-avoiding gall moth Epiblema scudderiana and the freeze-tolerant gall fly Eurosta solidaginis. Results In vivo MR images were acquired from autumn-collected larvae at temperatures between 0°C and about ?70°C and at spatial resolutions down to 27 µm. These images revealed three-dimensional (3D) larval anatomy at a level of detail currently not in reach of other in vivo techniques. Furthermore, they allowed visualization of the 3D distribution of the remaining liquid water and of the endogenous cryoprotectants at subzero temperatures, and temperature-weighted images of these distributions could be derived. Finally, individual fat body cells and their nuclei could be identified in intact frozen Eurosta larvae. Conclusions These findings suggest that high resolution MR techniques provide for interesting methodological options in comparative cryobiological investigations, especially in vivo.

Mietchen, Daniel; Manz, Bertram; Volke, Frank; Storey, Kenneth

2008-01-01

331

Magnetic susceptibility measurement using 2D magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

The authors describe a nuclear magnetic resonance (NMR) method for measuring the magnetic susceptibility of bar-shaped samples that have an arbitrary cross-section and do not produce an MR signal. The method is based on the measurement of the 2D map of the reaction field in the vicinity of a non-ferromagnetic sample and on the calculation of magnetic susceptibility from a known reaction field. The verification of the technique was realized via modelling the measured configuration in the ANSYS program by means of the finite element method and through an experimental measurement of MR-compatible and MR-incompatible materials carried out on a tomograph. A great advantage of the proposed susceptibility evaluation method consists in the use of only standard commercially used devices without the need of any special sequences. The method is suitable for bar-shaped samples having an arbitrary cross-section; moreover, conditions are given for the selection of the cross-section/length ratio of a sample to be measured.

Marcon, P.; Bartusek, K.; Burdkova, M.; Dokoupil, Z.

2011-10-01

332

Helmholtz superconducting receivers for magnetic resonance microscopy  

NASA Astrophysics Data System (ADS)

The use of coupled high temperature superconductor (HTS) coil arrays in construction of low noise volume imaging probes for magnetic resonance is investigated. Two probes designed to image different sample volumes were developed in collaboration with Conductus Inc. The design objectives were (1)a robust vacuum system, (2)increased signal to noise performance over copper imaging probes, and (3)improved magnetic field homogeneity over single coil HTS probes. The probes were evaluated using imaging data acquired on a 9.4 T microscopic imaging system operated from a Bruker Omega CSI console and electrical data acquired on a network analyzer. Signal to noise comparison yielded a factor of seven improvement for the smaller volume probe when compared to a copper Helmholtz probe with an identical imaging volume. However, only a factor of two gain for the larger probe was attained during comparison to a copper solenoid, although the Q values for both the HTS probes and copper comparison probes was comparable. Also, the poor homogeneity of the probe created shading artifacts in images acquired over the designed sample volumes. A model specific to cooled RF probes is presented to explain the differences between the performance advantages attained, and to indicate areas of potential design enhancement. The model combines data from measurement of several coil parameters including probe noise temperature, loaded and unloaded Q, inductance and magnetic field. The initial model is extended from a single point to three-dimensions by evaluating the B1 magnetic field using a combined Biot-Savart and method of moments analysis based on the magnetic field integral equation. The performance of the computation is validated using a field measurement technique. Based on this model, an optimization algorithm which adjusts coil size and shape is developed with the goal of improving B 1 field strength and homogeneity. To test the optimized design, a copper prototype was constructed along with a reference coil of the same size and shape as the larger HTS coil. The optimized design shows an improvement in homogeneity of ~50% and an increase in mean SNR of ~40%.

Hurlston, Sarah Elizabeth

333

SQUID-Detected Magnetic Resonance Imaging in MicroteslaFields  

Microsoft Academic Search

Magnetic resonance imaging (MRI) has developed into a powerful clinical tool for imaging the human body (1). This technique is based on nuclear magnetic resonance (NMR) of protons (2, 3) in a static magnetic field Bâ. An applied radiofrequency pulse causes the protons to precess about Bâ at their Larmor frequency νâ = (γ\\/2Ï)Bâ, where γ is the gyromagnetic ratio;

Michael Moessle; Michael Hatridge; John Clarke

2006-01-01

334

Optically Detected Magnetic Resonance (ODMR) of Triplet States in Photosynthesis  

Microsoft Academic Search

The triplet state of aromatic molecules and of polyenes is a versatile probe of molecular structure and of the interactions\\u000a with the environment, through the zero-field splitting (ZFS) parameters and the sublevel decay rates. These tripletproperties\\u000a can be determined accurately with magnetic resonance. Optical detection of magnetic resonance (ODMR) is often advantageous\\u000a because it pairs the frequency resolution of magnetic

Arnold J. Hoff

335

[Magnetic resonance contract agents and perfusion imaging].  

PubMed

Contrast agents may be categorised as non-specific or specific agents. Non-specific agents are freely diffusible in the extracellular and extravascular compartment with the exception of the brain where only blood brain barrier lesions enables the contrast agent to pass. In the specific agent group, a new class of products has been developed, that of blood pool contrast agent, which are distributed in the total intravascular volume and are slowly cleared from the blood. Crossing the healthy capillary wall is limited and depends both on the pathological state of the endothelial permeability tissue of the organ under interest and on the characteristics of the contrast agent (size, charge, molecular shape...). The diagnostic efficacy in perfusion imaging including cerebral perfusion is modulated by the pharmacokinetic profile of the blood pool contrast agent. One way to improve the vascular residence time, consists in binding a vector such as synthetic polymer or a biological macromolecule and a lanthanide like Gd3+, Mn2+, Dy3+ or metal ions. A second way is the synthesis of ultrasmall iron oxide nanoparticles which could escape rapid recognition by the monocyte macrophage phagocytic system mainly of liver and spleen. Because of their cristalline structure and the large number of non-paired spins, five electrons for the iron metal, the nanoparticles behave as magnetic domain when an external field is applied. They consequently have a high dipolar magnetic moment, and can produce a T2 effect in vivo, resulting in a drop in the magnetic resonance signal. Possible interests and developments toward perfusion imaging are demonstrated in experimental models studies. PMID:8656086

Benderbous, S; Bonnemain, B

1996-01-01

336

Direct Magnetic Resonances with Infrared Light from Plasmonic Single Closed Ring Resonators  

Microsoft Academic Search

We report here a spectroscopic study on plasmonic ring resonators at grazing angle incidence. With the magnetic component of the infrared light perpendicular to the ring plane (TM), we successfully observed a strong resonance signal at Mid- to Near-IR frequencies. Comparing to simulations, we identify that this signal is due to the resonance of the TM wave with the surface

Zhao Hao; Michael C. Martin; Bruce Harteneck; Stefano Cabrini; Erik H. Anderson; Willie J. Padilla

2007-01-01

337

Model of a magnetic field in poloidal divertor tokamaks affected by resonant magnetic perturbations  

Microsoft Academic Search

A generic analytical model for the description of magnetic field lines in poloidal divertor tokamaks in the presence of external resonant magnetic perturbations is proposed. It is based on the Hamiltonian description of magnetic field lines in tokamaks. The safety factor and the spectra of magnetic perturbations are chosen by the requirement to satisfy their generic behavior near the magnetic

S. S. Abdullaev

2009-01-01

338

Characterization of nitrides by electron paramagnetic resonance (EPR) and optically detected magnetic resonance (ODMR)  

Microsoft Academic Search

We will highlight our recent work on the properties of residual defects and dopants in GaN heteroepitaxial layers and on the nature of recombination from InGaN single quantum well (SQW) light emitting diodes (LEDs) through magnetic resonance techniques. Electron paramagnetic resonance (EPR) and optically detected magnetic resonance (ODMR) were performed on undoped (highly resistive and n-type) and intentionally doped (Si,

E. R Glaser; W. E Carlos; G. C. B Braga; J. A Freitas; W. J Moore; B. V Shanabrook; A. E Wickenden; D. D Koleske; R. L Henry; M. W Bayerl; M. S Brandt; H Obloh; P Kozodoy; S. P DenBaars; U. K Mishra; S Nakamura; E Haus; J. S Speck; J. E Van Nostrand; M. A Sanchez; E Calleja; A. J Ptak; T. H Myers; R. J Molnar

2002-01-01

339

Head and neck vascular anatomy.  

PubMed

Conventional computed tomography (CT) and magnetic resonance (MR) angiography provide excellent vascular images; however, every radiologist interpreting routine cross-sectional imaging of the head and neck must recognize normal and abnormal vascular structures. Knowledge of the normal cross-sectional appearance of vessels can help to define spacial anatomy and provide for recognition of abnormal vessels. Intracranially, the major arterial branches of the Circle of Willis are routinely visualized on MR and CT, as are the dural venous sinuses and major tributaries to the deep and superficial venous system. Using a combination of CT and MR images, we demonstrate the normal cross-sectional vascular anatomy of the head and neck and the important anatomic relationships key to accurate imaging analysis. PMID:9449756

Johnson, M H

1998-02-01

340

Self-sensing magnetic levitation using a LC resonant circuit  

Microsoft Academic Search

A self-sensing magnetic levitation system utilizing a LC resonant circuit is proposed by using the characteristic that the inductance of the magnetic system is varied with respect to the air gap displacement. An external capacitor is added into the electric system to make the levitation system statically stable, which much relieves the control effort required to stabilize the magnetic levitation

Changhwan Choi

1999-01-01

341

Micro magnetic thin-film sensor using LC resonance  

Microsoft Academic Search

This paper reports the performance of a new micro magnetic thin-film magnetic field sensor which makes use of LC resonance of the sensor element as well as the impedance change due to the permeability change of the magnetic film. A large impedance change of 105% was achieved at a carrier frequency of 100 MHz. The large change was realized when

M. Takezawa; H. Kikuchi; K. Ishiyama; M. Yamaguchi; K. I. Arai

1997-01-01

342

Phosphorus31 magnetic resonance spectroscopy of the human liver  

Microsoft Academic Search

During the last decade, progresses in the field of nuclear magnetic resonance spectroscopy (MRS), have allowed metabolic studies of complex biological systems. Since the coming out of whole body magnets, clinical applications are possible; they utilize magnetic field gradients coupled with selective pulse sequences. The main nuclei which can be observed in vivo are the proton, the phosphorus-31 (31P) and

Marc Biran; Gerard Raffard; Pascal Kien; Paul CanioniI

1992-01-01

343

Magnetic field generation by resonance absorption of light  

Microsoft Academic Search

We consider the self-generated dc magnetic fields due to resonant excitation of plasma waves by intense laser light. From Ampere's law we show that the time scale associated with the growth of the magnetic field is essentially the same as the time scale for the growth of the plasma wave. Further, we obtain a simple expression for the steady-state magnetic

B. Bezzerides; D. F. DuBois; D. W. Forslund

1977-01-01

344

Magnetic Field Gradient Waveform Monitoring for Magnetic Resonance  

NASA Astrophysics Data System (ADS)

Linear magnetic field gradients have played a central role in Magnetic Resonance Imaging (MRI) since Fourier Transform MRI was proposed three decades ago. Their primary function is to encode spatial information into MR signals. Magnetic field gradients are also used to sensitize the image contrast to coherent and/or incoherent motion, to selectively enhance an MR signal, and to minimize image artifacts. Modern MR imaging techniques increasingly rely on the implementation of complex gradient waveforms for the manipulation of spin dynamics. However, gradient system infidelities caused by eddy currents, gradient amplifier imperfections and group delays, often result in image artifacts and other errors (e.g., phase and intensity errors). This remains a critical problem for a wide range of MRI techniques on modern commercial systems, but is of particular concern for advanced MRI pulse sequences. Measuring the real magnetic field gradients, i.e., characterizing eddy currents, is critical to addressing and remedying this problem. Gradient measurement and eddy current calibration are therefore a general topic of importance to the science of MRI. The Magnetic Field Gradient Monitor (MFGM) idea was proposed and developed specifically to meet these challenges. The MFGM method is the heart of this thesis. MFGM methods permit a variety of magnetic field gradient problems to be investigated and systematically remedied. Eddy current effects associated with MR compatible metallic pressure vessels were analyzed, simulated, measured and corrected. The appropriate correction of eddy currents may enable most MR/MRI applications with metallic pressure vessels. Quantitative imaging (1D/2D) with model pressure vessels was successfully achieved by combining image reconstruction with MFGM determined gradient waveform behaviour. Other categories of MR applications with metallic vessels, including diffusion measurement and spin echo SPI T2 mapping, cannot be realized solely by MFGM guided image reconstruction. A new 'demand compensation' gradient waveform adjustment method was proposed to address this particular challenge. This idea was verified in this thesis. It should also be noted that, in a general sense, this new waveform compensation method will potentially provide a novel solution to a variety of gradient related problems in MRI.

Han, Hui

345

Quantifying Mixing using Magnetic Resonance Imaging  

PubMed Central

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

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

2012-01-01

346

Breast magnetic resonance imaging: an overview for nonradiologists.  

PubMed

Magnetic resonance imaging is a major component of breast imaging. Many studies have shown that magnetic resonance imaging is the most sensitive imaging method for detecting invasive breast cancer in comparison with mammography, ultrasound, and clinical breast examinations. Evidence-based clinical indications for breast magnetic resonance imaging include screening patients at high risk for breast cancer, including those with breast/ovarian cancer genes (BRCA1 and BRCA2), those who are untested first-degree relatives of carriers of these genes, those whose lifetime risk of developing breast cancer is 20% to 25% or greater, those who had chest radiation when they were 10 to 30 years old, and those who have or are first-degree relatives of people with Li-Fraumeni syndrome, Cowden syndrome, or Bannayan-Riley-Ruvalcaba syndrome. Breast magnetic resonance imaging is performed in conjunction with mammography and does not replace mammography. Outside of the screening population, utilization of breast magnetic resonance imaging for newly diagnosed breast cancer patients and its use as a problem-solving technique for equivocal mammographic or clinical findings remain controversial. An understanding of the current evidence facilitates appropriate utilization of this important medical resource. This article discusses indications for ordering breast magnetic resonance imaging and how to read the breast magnetic resonance imaging report and understand the lexicon used. PMID:20014426

Margolies, Laurie; Ha, Richard

2009-12-01

347

Electric and magnetic resonances in symmetric pairs of split ring resonators  

NASA Astrophysics Data System (ADS)

Orientation of the gap of a split ring resonator determines whether the resonance is an electric or magnetic response. When the gap of a split ring resonator is parallel to the incident E-field, an electric resonance is excited, and when the gap is perpendicular to the E-field, a magnetic resonance is excited. In this paper, we show that strong coupling between adjacent symmetric split ring resonators can give rise to dual electric and magnetic resonances if the intercell spacing is small enough. By varying the interparticle spacing within a unit cell, we can position the dual resonances as desired. Inverting the simulated reflection and transmission coefficients of a periodic slab of symmetric pairs of split ring resonators, the permittivity and permeability can be extracted and are shown to result in negative properties at resonance. Through a careful analysis of the extracted and Lorentz model fits of the permittivity and permeability, together with the simulated S-parameters, we have established a clear guideline for identifying electric and magnetic resonances. We also present measurement data that agree well with our simulated data. Applications of this design to band-pass filters and microstrip antenna substrates are envisaged.

Kim, In Kwang; Varadan, Vasundara V.

2009-10-01

348

Nuclear magnetic resonance for cultural heritage.  

PubMed

Nuclear magnetic resonance (NMR) portable devices are now being used for nondestructive in situ analysis of water content, pore space structure and protective treatment performance in porous media in the field of cultural heritage. It is a standard procedure to invert T(1) and T(2) relaxation data of fully water-saturated samples to get "pore size" distributions, but the use of T(2) requires great caution. It is well known that dephasing effects due to water molecule diffusion in a magnetic field gradient can affect transverse relaxation data, even if the smallest experimentally available half echo time tau is used in Carr-Purcell-Meiboom-Gill experiments. When a portable single-sided NMR apparatus is used, large field gradients due to the instrument, at the scale of the sample, are thought to be the dominant dephasing cause. In this paper, T(1) and T(2) (at different tau values) distributions were measured in natural (Lecce stone) and artificial (brick samples coming from the Greek-Roman Theatre of Taormina) porous media of interest for cultural heritage by a standard laboratory instrument and a portable device. While T(1) distributions do not show any appreciable effect from inhomogeneous fields, T(2) distributions can show strong effects, and a procedure is presented based on the dependence of 1/T(2) on tau to separate pore-scale gradient effects from sample-scale gradient effects. Unexpectedly, the gradient at the pore scale can be, in some cases, strong enough to make negligible the effects of gradients at the sample scale of the single-sided device. PMID:17466764

Brai, Maria; Camaiti, Mara; Casieri, Cinzia; De Luca, Francesco; Fantazzini, Paola

2007-01-18

349

Microscopic magnetic resonance elastography (?MRE) applications  

NASA Astrophysics Data System (ADS)

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

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

2005-04-01

350

Accurate Temperature Imaging Based on Intermolecular Coherences in Magnetic Resonance  

PubMed Central

Conventional magnetic resonance methods that provide interior temperature profiles, which find use in clinical applications such as hyperthermic therapy, can develop inaccuracies caused by the inherently inhomogeneous magnetic field within tissues or by probe dynamics, and work poorly in important applications such as fatty tissues. We present a magnetic resonance method that is suitable for imaging temperature in a wide range of environments. It uses the inherently sharp resonances of intermolecular zero-quantum coherences, in this case flipping up a water spin while flipping down a nearby fat spin. We show that this method can rapidly and accurately assign temperatures in vivo on an absolute scale.

Galiana, Gigi; Branca, Rosa T.; Jenista, Elizabeth R.; Warren, Warren S.

2010-01-01

351

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

352

Ultrahigh-Resolution Magnetic Resonance in Inhomogeneous Magnetic Fields: Two-Dimensional Long-Lived-Coherence Correlation Spectroscopy  

NASA Astrophysics Data System (ADS)

A half-century quest for improving resolution in Nuclear Magnetic Resonance (NMR) and Magnetic Resonance Imaging (MRI) has enabled the study of molecular structures, biological interactions, and fine details of anatomy. This progress largely relied on the advent of sophisticated superconducting magnets that can provide stable and homogeneous fields with temporal and spatial variations below ?B0/B0<0.01ppm. In many cases however, inherent properties of the objects under investigation, pulsating arteries, breathing lungs, tissue-air interfaces, surgical implants, etc., lead to fluctuations and losses of local homogeneity. A new method dubbed “long-lived-coherence correlation spectroscopy” (LLC-COSY) opens the way to overcome both inhomogeneous and homogeneous broadening, which arise from local variations in static fields and fluctuating dipole-dipole interactions, respectively. LLC-COSY makes it possible to obtain ultrahigh resolution two-dimensional spectra, with linewidths on the order of ??=0.1 to 1 Hz, even in very inhomogeneous fields (?B0/B0>10ppm or 5000 Hz at 9.7 T), and can improve resolution by a factor up to 9 when the homogeneous linewidths are determined by dipole-dipole interactions. The resulting LLC-COSY spectra display chemical shift differences and scalar couplings in two orthogonal dimensions, like in “J spectroscopy.” LLC-COSY does not require any sophisticated gradient switching or frequency-modulated pulses. Applications to in-cell NMR and to magnetic resonance spectroscopy (MRS) of selected volume elements in MRI appear promising, particularly when susceptibility variations tend to preclude high resolution.

Chinthalapalli, Srinivas; Bornet, Aurélien; Segawa, Takuya F.; Sarkar, Riddhiman; Jannin, Sami; Bodenhausen, Geoffrey

2012-07-01

353

Magnetic resonance force microscopy with a permanent magnet on the cantilever  

SciTech Connect

The magnetic resonance force microscope (MRFM) is a microscopic 3-D imaging instrument based on a recent proposal to detect magnetic resonance signals mechanically using a micro-mechanical resonator. MRFM has been successfully demonstrated in various magnetic resonance experiments including electron spin resonance, ferromagnetic resonances and nuclear magnetic resonance. In order to apply this ultra-high, 3-D spatial resolution technique to samples of arbitrary size and shape, the magnetic particle which generates the field gradient {del}{bold B}, (and, therefore, the force {bold F = (m {center_dot} {del}B)} between itself and the spin magnetization {bold m} of the sample) will need to be mounted on the mechanical resonator. Up to the present, all experiments have been performed with the sample mounted on the resonator. This is done, in part, to avoid the spurious response of the mechanical resonator which is generated by the variation of the magnetization of the magnetic particle as the external field is varied.

Zhang, Z.; Hammel, P.C.

1997-02-01

354

Constraining groundwater modeling with magnetic resonance soundings.  

PubMed

Magnetic resonance sounding (MRS) is a noninvasive geophysical method that allows estimating the free water content and transmissivity of aquifers. In this article, the ability of MRS to improve the reliability of a numerical groundwater model is assessed. Thirty-five sites were investigated by MRS over a ?5000 km(2) domain of the sedimentary Continental Terminal aquifer in SW Niger. Time domain electromagnetic soundings were jointly carried out to estimate the aquifer thickness. A groundwater model was previously built for this section of the aquifer and forced by the outputs from a distributed surface hydrology model, to simulate the observed long-term (1992 to 2003) rise in the water table. Uncertainty analysis had shown that independent estimates of the free water content and transmissivity values of the aquifer would facilitate cross-evaluation of the surface-water and groundwater models. MRS results indicate ranges for permeability (K = 1 × 10(-5) to 3 × 10(-4) m/s) and for free water content (w = 5% to 23% m(3) /m(3) ) narrowed by two orders of magnitude (K) and by ?50% (w), respectively, compared to the ranges of permeability and specific yield values previously considered. These shorter parameter ranges result in a reduction in the model's equifinality (whereby multiple combinations of model's parameters are able to represent the same observed piezometric levels), allowing a better constrained estimate to be derived for net aquifer recharge (?22 mm/year). PMID:22150349

Boucher, Marie; Favreau, Guillaume; Nazoumou, Yahaya; Cappelaere, Bernard; Massuel, Sylvain; Legchenko, Anatoly

2011-12-07

355

Small Animal Imaging with Magnetic Resonance Microscopy  

PubMed Central

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

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

2009-01-01

356

Nuclear magnetic resonance imaging of the kidney  

SciTech Connect

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

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

1983-02-01

357

NUCLEAR MAGNETIC RESONANCE STUDIES OF URANOCENES  

SciTech Connect

In the past several years a substantial amount of work has been devoted toward evaluation of the contact and pseudocontact contributions to the observed isotropic shifts in H nuclear magnetic resonance (NMR) spectra of uranium(IV) organometallic compounds. One reason for interest in this area arises from using the presence of contact shifts as a prcbe for covalent character in the uranium carbon bonds in these compounds. Several extensive {sup 1}H NNR studies on Cp{sub 3} U-X compounds and less extensive studies on uranocenes have been reported. Interpretation of these results suggests that contact shifts-contribute significantly to the observed isotropic shifts. Their presence has been taken as indicative of covalent character of metal carbon bonds in these systems, but agreement is not complete. In this paper we shall review critically the work reported on uranocenes in the light of recent results and report recent work on attempted separation of the observed isotropic shifts in alkyluranocenes into contact and pseudocontact components.

Luke, Wayne D.; Streitwieser, Jr., Andrew

1979-12-01

358

Vibration safety limits for magnetic resonance elastography  

NASA Astrophysics Data System (ADS)

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

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

2008-02-01

359

Magnetic resonance imaging for lung cancer.  

PubMed

Since the publication of the Radiologic Diagnostic Oncology Group Report in 1991, the clinical application of pulmonary magnetic resonance imaging (MRI) in patients with lung cancer has been limited. In contrast, MRI for lung cancer has undergone continuous development, and several promising techniques have been introduced to overcome the previously suggested limitations. In addition, comparative studies involving multidetector-row computed tomography and positron emission tomography or positron emission tomography/computed tomography with 2-deoxy-2-[F]fluoro-D-glucose have shown useful new clinical applications for MRI in lung cancer. Moreover, MRI can provide not only morphologic information based on various parameters such as T1 and T2 relaxation times, tissue diffusion, perfusion, etc. but also functional information; it also has a significant role in nuclear medicine studies. In this review article, we describe recent advances made in MRI with respect to lung cancer, focusing on (1) detection of solid pulmonary nodules; (2) characterization of solid pulmonary nodules; (3) TNM staging assessment using chest and whole-body MRI examinations; (4) prediction of postsurgical lung function; and (5) prediction of tumor treatment response. We believe that further basic studies, as well as studies on clinical applications of new MRI techniques, are important for improving the management of lung cancer patients. PMID:23549390

Koyama, Hisanobu; Ohno, Yoshiharu; Seki, Shinichiro; Nishio, Mizuho; Yoshikawa, Takeshi; Matsumoto, Sumiaki; Sugimura, Kazuro

2013-05-01

360

Magnetic resonance imaging: present and future applications  

PubMed Central

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

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

1985-01-01

361

Magnetic resonance imaging of acute Maisonneuve fractures.  

PubMed

Magnetic resonance imaging (MRI) studies were performed on five patients with acute Maisonneuve fractures. All patients had sustained a twisting injury to their ankles and complained of ankle pain and pain over their proximal fibula. High quality images with excellent visualization of all the ankle ligamentous structures were obtained. MRI showed that the anterior inferior tibiofibular ligament was disrupted in all patients and the posterior inferior tibiofibular ligament was intact in three of five patients. Also, the anterior talofibular ligament was disrupted in all patients and the calcaneofibular ligament was ruptured in two of five patients. This raises the question of whether patients with Maisonneuve fractures have lateral ankle instability at long-term follow-up. Although the superficial deltoid ligament was disrupted in all patients, the deep deltoid ligament was intact in one patient, partially disrupted in one patient, and completely disrupted in three patients. The interosseous ligament was disrupted at the ankle in all patients, while the interosseous membrane was disrupted in the leg in all patients except one. This patient had an intact interosseous membrane despite rupture of the interosseous ligament at the ankle and the presence of a proximal one third fibula fracture. PMID:8734795

Morris, J R; Lee, J; Thordarson, D; Terk, M R; Brustein, M

1996-05-01

362

Scatter-based magnetic resonance elastography  

NASA Astrophysics Data System (ADS)

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

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

2009-04-01

363

Imaging intelligence with proton magnetic resonance spectroscopy  

PubMed Central

Proton magnetic resonance spectroscopy (1H-MRS) is a technique for the assay of brain neurochemistry in vivo. N-acetylaspartate (NAA), the most prominent metabolite visible within the 1H-MRS spectrum, is found primarily within neurons. The current study was designed to further elucidate NAA–cognition relationships, particularly whether such relationships are moderated by sex, or tissue type (gray or white matter). We administered standard measures of intelligence to 63 young, healthy subjects and obtained spectroscopic imaging data within a slab of tissue superior to the lateral ventricles. We found that lower NAA within right anterior gray matter predicted better performance VIQ (F=6.83, p=.011, r2=.10), while higher NAA within the right posterior gray matter region predicted better PIQ (F=8.175, p=.006, r2=.12). These findings add to the small but growing body of literature linking brain biochemistry to intelligence in normal healthy subjects using 1H-MRSI.

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

2009-01-01

364

Magnetic Resonance Angiography of the Aorta  

PubMed Central

Magnetic resonance angiography (MRA) is capable of imaging arteries in the half to whole body by a single acquisition without a nephrotoxic contrast medium, and acquired images can be reconstructed into a specific cross-sectional view in an arbitrary directions. MRA is applicable for vessels non-reachable by a catheter approach, and collateral vessels can be fully visualized. Since MRA is minimally-invasive with no exposure to ionized radiation, it can be repeatedly applied for follow-up. However, there are also disadvantages: the temporal and spatial resolutions are inferior to those of X-ray angiography, and, at present, it cannot be used as a guide for intervention. Moreover, gadolinium administrations may cause NSF in patients who have lost renal function, as a new risk. Accordingly, strict consideration is required for an indication of its application. Development of non-contrast MRA and evaluation of the wall itself may draw more attention in the future. Plaque imaging is being routinely performed nowadays, and the measurement of vascular wall shear stress, which has a close association with arteriosclerosis, may become possible by utilizing the time-resolved phase-contrast method capable of measuring the time-resolved velocity vectors of blood flow throughout the body. (*English Translation of J Jpn Coll Angiol, 2009, 49: 503-516.)

Takehara, Yasuo; Yamashita, Shuhei; Sakahara, Harumi; Masui, Takayuki; Isoda, Haruo

2011-01-01

365

Segmentation of neuroanatomy in magnetic resonance images  

NASA Astrophysics Data System (ADS)

Segmentation in neurological magnetic resonance imaging (MRI) is necessary for feature extraction, volume measurement and for the three-dimensional display of neuroanatomy. Automated and semi-automated methods offer considerable advantages over manual methods because of their lack of subjectivity, their data reduction capabilities, and the time savings they give. We have used dual echo multi-slice spin-echo data sets which take advantage of the intrinsically multispectral nature of MRI. As a pre-processing step, a rf non-uniformity correction is applied and if the data is noisy the images are smoothed using a non-isotropic blurring method. Edge-based processing is used to identify the skin (the major outer contour) and the eyes. Edge-focusing has been used to significantly simplify edge images and thus allow simple postprocessing to pick out the brain contour in each slice of the data set. Edge- focusing is a technique which locates significant edges using a high degree of smoothing at a coarse level and tracks these edges to a fine level where the edges can be determined with high positional accuracy. Both 2-D and 3-D edge-detection methods have been compared. Once isolated, the brain is further processed to identify CSF, and, depending upon the MR pulse sequence used, the brain itself may be sub-divided into gray matter and white matter using semi-automatic contrast enhancement and clustering methods.

Simmons, Andrew; Arridge, Simon R.; Barker, G. J.; Tofts, Paul S.

1992-06-01

366

Magnetic resonance in quantum spin chains  

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

367

TOPICAL REVIEW: Endovascular interventional magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

Minimally invasive interventional radiological procedures, such as balloon angioplasty, stent placement or coiling of aneurysms, play an increasingly important role in the treatment of patients suffering from vascular disease. The non-destructive nature of magnetic resonance imaging (MRI), its ability to combine the acquisition of high quality anatomical images and functional information, such as blood flow velocities, perfusion and diffusion, together with its inherent three dimensionality and tomographic imaging capacities, have been advocated as advantages of using the MRI technique for guidance of endovascular radiological interventions. Within this light, endovascular interventional MRI has emerged as an interesting and promising new branch of interventional radiology. In this review article, the authors will give an overview of the most important issues related to this field. In this context, we will focus on the prerequisites for endovascular interventional MRI to come to maturity. In particular, the various approaches for device tracking that were proposed will be discussed and categorized. Furthermore, dedicated MRI systems, safety and compatibility issues and promising applications that could become clinical practice in the future will be discussed.

Bartels, L. W.; Bakker, C. J. G.

2003-07-01

368

Cardiovascular magnetic resonance in pericardial diseases  

PubMed Central

The pericardium and pericardial diseases in particular have received, in contrast to other topics in the field of cardiology, relatively limited interest. Today, despite improved knowledge of pathophysiology of pericardial diseases and the availability of a wide spectrum of diagnostic tools, the diagnostic challenge remains. Not only the clinical presentation may be atypical, mimicking other cardiac, pulmonary or pleural diseases; in developed countries a shift for instance in the epidemiology of constrictive pericarditis has been noted. Accurate decision making is crucial taking into account the significant morbidity and mortality caused by complicated pericardial diseases, and the potential benefit of therapeutic interventions. Imaging herein has an important role, and cardiovascular magnetic resonance (CMR) is definitely one of the most versatile modalities to study the pericardium. It fuses excellent anatomic detail and tissue characterization with accurate evaluation of cardiac function and assessment of the haemodynamic consequences of pericardial constraint on cardiac filling. This review focuses on the current state of knowledge how CMR can be used to study the most common pericardial diseases.

Bogaert, Jan; Francone, Marco

2009-01-01

369

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

370

Magnetic resonance imaging of the kidneys  

SciTech Connect

A study of the magnetic resonance imaging (MRI) appearance of the kidneys in six normal volunteers and 52 patients is reported. Corticomedullary differentiation was seen with the inversion-recovery (IR 1400/400) sequence in the normal volunteers and in patients with functioning transplanted kidneys and acute tubular necrosis. Partial or total loss of corticomedullary differentiation was seen in glomerulonephritis, acute and chronic renal failure, renal artery stenosis, and transplant rejection. The T1 of the kidneys was increased in glomerulonephritis with neuphrotic syndrome, but the T1 was within the normal range for renal medulla in glomerulonephritis without nephrotic syndrome, renal artery stenosis, and chronic renal failure. A large staghorn calculus was demonstrated with MRI, but small calculi were not seen. Fluid within the hydonephrosis, simple renal cysts, and polycystic kidneys displayed very low signal intensity and long T1 values. Tumors displayed varied appearances. Hypernephromas were shown to be hypo- or hyperintense with the renal medulla on the IR 1400/400 sequence. After intravenous injection of gadolinium-DTPA, there was marked decrease in the tumor T1.

Leung, A.W.L.; Bydder, G.M.; Steinter, R.E.; Bryant, D.J.; Young, I.R.

1984-12-01

371

Scatter-based magnetic resonance elastography.  

PubMed

Elasticity is a sensitive measure of the microstructural constitution of soft biological tissues and increasingly used in diagnostic imaging. Magnetic resonance elastography (MRE) uniquely allows in vivo measurement of the shear elasticity of brain tissue. However, the spatial resolution of MRE is inherently limited as the transformation of shear wave patterns into elasticity maps requires the solution of inverse problems. Therefore, an MRE method is introduced that avoids inversion and instead exploits shear wave scattering at elastic interfaces between anatomical regions of different shear compliance. This compliance-weighted imaging (CWI) method can be used to evaluate the mechanical consistency of cerebral lesions or to measure relative stiffness differences between anatomical subregions of the brain. It is demonstrated that CWI-MRE is sensitive enough to reveal significant elasticity variations within inner brain parenchyma: the caudate nucleus (head) was stiffer than the lentiform nucleus and the thalamus by factors of 1.3 +/- 0.1 and 1.7 +/- 0.2, respectively (P < 0.001). CWI-MRE provides a unique method for characterizing brain tissue by identifying local stiffness variations. PMID:19293467

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

2009-03-17

372

Moderne Entwicklung der NMR (Nuclear Magnetic Resonance)  

NASA Astrophysics Data System (ADS)

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

Lösche, Artur

373

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

PubMed

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

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

374

Resonant Magnetic X-ray Diffraction.  

National Technical Information Service (NTIS)

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

S. Longridge S. W. Lovesey

2000-01-01

375

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

PubMed

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

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

2013-07-01

376

Microwave resonances of a hairpin probe in a magnetized plasma  

SciTech Connect

The effect due to the electron cyclotron frequency on the microwave resonances of a hairpin probe is investigated in a moderate to strongly magnetized plasma. The magnetic field is independently varied over a wide range from 0.01-0.13 T while maintaining the local plasma density constant. At strong magnetic fields the resonance frequency is found to be lower than that measured in vacuum implying that the relative plasma dielectric permittivity, epsilon{sub p}>1. It is proposed that the experiments reported here are consistent with a permittivity model that includes magnetic field.

Gogna, G. S.; Karkari, S. K. [National Centre for Plasma Science and Technology, School of Physics, Dublin City University, Dublin 9 (Ireland)

2010-04-12

377

Prediction of Chemotherapy Response by Magnetic Resonance Spectroscopy.  

National Technical Information Service (NTIS)

This research seeks to validate the use of MRS to assess therapeutic response in patients with locally-advanced breast cancer receiving primary Systemic therapy (PST), or neoadjuvant chemotherapy. 35 women were enrolled in this study. Magnetic resonance s...

M. Garwood

2004-01-01

378

Guidelines for the Introduction of Nuclear Magnetic Resonance (NMR) Technology.  

National Technical Information Service (NTIS)

In August 1983 the CAHSA Governing Body appointed the High Technology Committee to plan for the rational introduction of high medical technology in HSA 1, with the immediate task of examining Nuclear Magnetic Resonance (NMR) and determining guidelines for...

1983-01-01

379

Nuclear magnetic resonance data of CHF3Se  

NASA Astrophysics Data System (ADS)

This document is part of Part 6 `Organic Metalloid Compounds' of Subvolume D 'Chemical Shifts and Coupling Constants for Carbon-13' of Landolt-Börnstein III/35 'Nuclear Magnetic Resonance Data', Group III 'Condensed Matter'.

Mikhova, B. M.

380

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

381

21 CFR 892.1000 - Magnetic resonance diagnostic device.  

Code of Federal Regulations, 2013 CFR

...reflect the spatial distribution and/or magnetic resonance spectra which reflect frequency and distribution of nuclei exhibiting...Other physical parameters derived from the images and/or spectra may also be produced. The device includes...

2013-04-01

382

Nuclear magnetic resonance data of C9H11NSe  

NASA Astrophysics Data System (ADS)

This document is part of Part 6 `Organic Metalloid Compounds' of Subvolume D 'Chemical Shifts and Coupling Constants for Carbon-13' of Landolt-Börnstein III/35 'Nuclear Magnetic Resonance Data', Group III 'Condensed Matter'.

Mikhova, B. M.

383

Nuclear magnetic resonance data of C9H11NO  

NASA Astrophysics Data System (ADS)

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

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

384

Nuclear magnetic resonance data of C9H11NS  

NASA Astrophysics Data System (ADS)

This document is part of Part 6 `Organic Metalloid Compounds' of Subvolume D 'Chemical Shifts and Coupling Constants for Carbon-13' of Landolt-Börnstein III/35 'Nuclear Magnetic Resonance Data', Group III 'Condensed Matter'.

Mikhova, B. M.

385

Nuclear magnetic resonance data of C9H11ITe  

NASA Astrophysics Data System (ADS)

This document is part of Part 6 `Organic Metalloid Compounds' of Subvolume D 'Chemical Shifts and Coupling Constants for Carbon-13' of Landolt-Börnstein III/35 'Nuclear Magnetic Resonance Data', Group III 'Condensed Matter'.

Mikhova, B. M.

386

Transient left ventricular apical ballooning: magnetic resonance imaging evaluation.  

PubMed

The magnetic resonance imaging characteristics of transient left ventricular apical ballooning are described in this report, and the features that distinguish it from acute myocardial infarction are emphasized. PMID:15665680

Fritz, Jan; Wittstein, Ilan S; Lima, João A C; Bluemke, David A

387

Toward clinical risk assessment inhypertrophic cardiomyopathy withgadolinium cardiovascular magnetic resonance  

Microsoft Academic Search

ObjectivesWe sought to assess whether hyperenhancement by gadolinium cardiovascular magnetic resonance (CMR) occurs in hypertrophic cardiomyopathy (HCM) and correlates with the risk of heart failure and sudden death.

James C. C Moon; William J McKenna; Jane A McCrohon; Perry M Elliott; Gillian C Smith; Dudley J Pennell

2003-01-01

388

Nuclear magnetic resonance data of CH3NSSi  

NASA Astrophysics Data System (ADS)

This document is part of Part 6 `Organic Metalloid Compounds' of Subvolume D 'Chemical Shifts and Coupling Constants for Carbon-13' of Landolt-Börnstein III/35 'Nuclear Magnetic Resonance Data', Group III 'Condensed Matter'.

Mikhova, B. M.

389

Nuclear magnetic resonance data of C9H12INSe  

NASA Astrophysics Data System (ADS)

This document is part of Part 6 `Organic Metalloid Compounds' of Subvolume D 'Chemical Shifts and Coupling Constants for Carbon-13' of Landolt-Börnstein III/35 'Nuclear Magnetic Resonance Data', Group III 'Condensed Matter'.

Mikhova, B. M.

390

Orthopaedic magnetic resonance imaging challenge: apophyseal avulsions at the pelvis.  

PubMed

Apophyseal avulsion injuries of the hip and pelvis are frequent athletic injuries in children and adolescents, most commonly associated with explosive movement or sprinting. This article details typically encountered apophyseal injuries and their appearance on magnetic resonance imaging. PMID:23015945

Kjellin, Ingrid; Stadnick, Michael E; Awh, Mark H

2010-05-01

391

Infantile fibrosarcoma: Magnetic resonance imaging findings in six cases  

Microsoft Academic Search

PurposeTo retrospectively review magnetic resonance (MR) imaging features in a series of six infantile fibrosarcomas to find out if MR can suggest this unusual diagnosis and to highlight the value of MR during and following treatment.

Sandra Canale; Daniel Vanel; Dominique Couanet; Catherine Patte; Caroline Caramella; Clarisse Dromain

2009-01-01

392

Magnetic Resonance Imaging of the Rectum During Distension  

Microsoft Academic Search

PURPOSE  A knowledge of the relationships between the rectum and its surrounding structures during distention may improve our understanding of the results of studies assessing rectal sensory-motor responses to distention. This magnetic resonance imaging study was designed to assess the shape of the rectum and the degree of distention at which the surrounding structures are compressed.METHODS  Nine healthy patients underwent magnetic resonance

Annalisa Dal Lago; Alberto E. Minetti; Pietro Biondetti; Maura Corsetti; Guido Basilisco

2005-01-01

393

Delayed enhancement magnetic resonance imaging in nonischemic myocardial disease.  

PubMed

This review highlights the role of delayed enhancement magnetic resonance imaging for the diagnosis of patients with nonischemic myocardial disease. The authors discuss the use of delayed enhancement for differentiation between ischemic and nonischemic myocardial disease and for narrowing the differential diagnosis when nonischemic etiologies are suspected. In addition, special focus is given to the prognostic applications of delayed enhancement magnetic resonance imaging. PMID:23422782

Moraes, Gustavo L; Higgins, Charles B; Ordovas, Karen G

2013-03-01

394

Pediatric functional magnetic resonance neuroimaging: tactics for encouraging task compliance  

Microsoft Academic Search

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

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

2011-01-01

395

Health Effects and Safety of Magnetic Resonance Imaging  

Microsoft Academic Search

Magnetic Resonance Imaging (MRI) is a rapidly advancing diagnostic imaging modality. Hazards, intrinsic to the magnetic resonance\\u000a (MR) environment, are to be understood, acknowledged and respected. MRI is safe, but if something goes wrong, it can be serious.\\u000a MRI-related accidents do happen, unfortunately in most countries they go unreported and there is no central database which\\u000a keeps track of these

Kwan-Hoong Ng; Oliver Faust; Rajendra Acharya U

396

Magnetic Resonance Angiography of the Aorta and Peripheral Arteries  

Microsoft Academic Search

Magnetic resonance angiography (MRA) has virtually replaced diagnostic conventional X-ray angiography and has become the primary\\u000a imaging tool for the evaluation of the diseases of the aorta and branches for many indications (1–13). Development of faster magnetic resonance imaging (MRI) scanners with shorter TR (relaxation time) and TE (echo time) and\\u000a powerful gradients, allowing completion of principal MRA sequences within

Servet Tatli

397

Cost effectiveness of magnetic resonance imaging in the neurosciences.  

PubMed Central

OBJECTIVES--To measure, in a service setting, the effect of magnetic resonance imaging on diagnosis, diagnostic certainty, and patient management in the neurosciences; to measure the cost per patient scanned; to estimate the marginal cost of imaging and compare this with its diagnostic impact; to measure changes in patients' quality of life; and to record the diagnostic pathway leading to magnetic resonance imaging. DESIGN--Controlled observational study using questionnaires on diagnosis and patient management before and after imaging. Detailed costing study. Quality of life questionnaires at the time of imaging and six months later. Diagnostic pathways extracted from medical records for a representative sample. SETTING--Regional superconducting 1.5 T magnetic resonance service. SUBJECTS--782 consecutive neuroscience patients referred by consultants for magnetic resonance imaging during June 1988-9; diagnostic pathways recorded for 158 cases. MAIN OUTCOME MEASURES--Costs of magnetic resonance imaging and preliminary investigations; changes in planned management and resulting savings; changes in principal diagnosis and diagnostic certainty; changes in patients' quality of life. RESULTS--Average cost of magnetic resonance imaging was estimated at 206.20/patient pounds (throughput 2250 patients/year, 1989-90 prices including contrast and upgrading). Before magnetic resonance imaging diagnostic procedures cost 164.40/patient pounds (including inpatient stays). Management changed after imaging in 208 (27%) cases; saving an estimated 80.90/patient pounds. Confidence in planned management increased in a further 226 (29%) referrals. Consultants' principal diagnosis changed in 159 of 782 (20%) referrals; marginal cost per diagnostic change was 626 pounds. Confidence in diagnosis increased in 236 (30%) referrals. No improvement in patients' quality of life at six month assessment. CONCLUSIONS--Any improvement in diagnosis with magnetic resonance imaging is achieved at a higher cost. Techniques for monitoring the cost effectiveness of this technology need to be developed.

Szczepura, A K; Fletcher, J; Fitz-Patrick, J D

1991-01-01

398

Magnetic Resonance Spectroscopy of Traumatic Brain Injury and Concussion  

Microsoft Academic Search

Imaging modalities such as CT and magnetic resonance imaging (MRI) are powerful tools to detect and assess focal injury such\\u000a as hemorrhagic lesions and edema and brain swelling in severe injury. However, acute and chronic injury at a cellular level\\u000a is sometimes difficult to discern from normal features by anatomical imaging. Magnetic resonance spectroscopy (MRS) offers\\u000a a unique non-invasive approach

Stefan Blüml; William M. Brooks

399

Anatomic magnetic resonance imaging studies of attention-deficit/hyperactivity disorder  

PubMed Central

Neuroimaging techniques are increasingly being applied to the study of attention-deficit/hyperactivity disorder (ADHD). This review focuses on magnetic resonance imaging studies of the brain anatomy of ADHD. Such studies were first conducted over a decade ago, and most focus on frontal-striatal regions and tend to find smaller volumes in ADHD children than in controls. Recently published analyses with the largest sample so far of patients and controls found that ADHD is associated with a statistically significant 3% to 4% global reduction in brain volume in both boys and girls, with abnormally small caudate nuclei only being found in younger patients. After adjusting for global brain differences, only cerebellar hemispheric volumes remained significantly smaller in ADHD, and these differences continued throughout childhood and adolescence. Pathophysiological models of ADHD need take into account cerebellar dysfunction, as well as prefrontal-striatal dysregulation.

Castellanos, Francisco Xavier

2002-01-01

400

Magnetic resonance imaging of muscle disease: a pattern-based approach.  

PubMed

Magnetic resonance imaging (MRI) is a powerful tool to assess the severity, distribution, and progression of muscle injury and disease. However, a muscle's response to a pathological insult is limited to only a few patterns on MRI, and findings can be nonspecific. A pattern-based approach is therefore essential to correctly interpret MR studies of abnormal muscle. In this article we review the anatomy, function, and normal MRI appearance of skeletal muscle. We present a classification scheme that categorizes abnormal MR appearances of muscle into 4 main pattern descriptors: (1) distribution; (2) change in size and shape; (3) T1 signal; and (4) T2 signal. Each category is further subdivided into the various patterns seen on MRI. Such an approach allows one to systematically assess abnormal findings on muscle MRI studies and ascertain clues to the diagnosis or differential diagnosis, particularly when findings are correlated with the clinical context. PMID:22987686

Costa, Andreu F; Di Primio, Gina A; Schweitzer, Mark E

2012-10-01

401

[Usefulness of magnetic resonance imaging in the prenatal study of malformations of the face and neck].  

PubMed

Sonography has been the fundamental pillar of fetal diagnosis, and until relatively recently, no other valid and reliable noninvasive technique that could adequately determine fetal morphology was available. However, even after the technological advances in obstetric sonography, is still unable to detect some anomalies. One example of this shortcoming is the morphological study of the face and neck. Owing to the ossification of adjacent structures and interposition of the tongue, sonography is not accurate in the detection of some of the most common anomalies. Enormous advances have been made in fetal magnet resonance imaging since it was first described 25 years ago. The usefulness of this modality as a tool to complement sonography in fetal evaluation is now firmly established. MRI provides useful information about orofacial anatomy, enabling accurate evaluation of both the primary and secondary palates. PMID:22424643

Zugazaga Cortazar, A; Martín Martínez, C

2012-03-15

402

Merging the computed tomography and magnetic resonance imaging images for the visualization of temporomandibular joint disk.  

PubMed

Computed tomography (CT) depicts intricate bony details well, whereas magnetic resonance imaging (MRI) offers excellent contrast to the anatomy of soft tissues. This technical report offers a method to merge the CT and MRI images using Photoshop software and yield hybrid images that combine the key features of both CT and MRI. In this hybrid image, the temporomandibular joint (TMJ) disk was clearly displayed, and the relationship between the TMJ disk and surrounding skeleton structures, including glenoid fossa and condyle, also was finely demonstrated. Although the merging process is not absolutely accurate, the method presented in this article can be applied as a supplementary way to help the physicians to read the image of TMJ in an even better fashion and also may offer a useful method to help the junior physicians to quickly identify the TMJ disk. PMID:23172513

Dai, Jiewen; Dong, Yuefu; Shen, Steve Guofang

2012-11-01

403

Equivalent Magnetization Current Method Applied to the Design of Gradient Coils for Magnetic Resonance Imaging  

Microsoft Academic Search

A new method is described for the design of gradient coils for magnetic resonance imaging systems. The method is based on the known equivalence between a magnetized volume surrounded by a conducting surface and its equivalent representation by a surface current density. The curl of a vertical magnetization vector of a magnetized thin volume is equivalent to a surface current

Hector Sanchez Lopez; Feng Liu; Michael Poole; Stuart Crozier

2009-01-01

404

Computed tomographic and magnetic resonance coronary angiography: are you ready?  

PubMed

Within the next year or two, magnetic resonance angiography (MRA) and computed tomographic angiography (CTA) most likely will be used to deliver clinically useful images of the coronary arteries. The spatial resolution of CTA combined with new 16-detector scanners and cardiac imaging software will render views of the coronary arteries that will rival or surpass the spatial resolution and far surpass the contrast resolution of conventional coronary angiography (CA). MRA will potentially offer coronary artery imaging without the need for iodinated contrast injection. CTA and MRA of the coronary arteries offer distinct advantages over CA. Both CTA and MRA may be able to characterize plaques of the coronary arteries. Currently, CA can only detect degree of stenosis, collateral patterns and presence of dense calcification of the coronary arteries. CTA and MRA offer the promise of improved plaque characterization. CTA and MRA of the coronary arteries promise, at the least, to detect plaque not seen by CA and to offer some degree of characterization. According to some non-published data, advances in CT in the next five years may offer characterization of plaque equal to or superior to IVUS. To prepare for this "certainty," radiology departments must answer many questions. Each department will have it's own unique equipment requirements, though the size of the department and imaging volumes will determine what type of scanner will be purchased for CTA/MRA of the coronary arteries. Each department will require physicians and technologists trained in advanced CT and MRI imaging techniques including cardiac gating, 3D and 4D multi-planar reconstructions, advanced coronary artery and cardiac anatomy, and personnel with advanced patient management skills to handle the unique needs of patients with coronary artery disease. To transition a department into full-service cardiac CT or MRI, small steps can be taken over the next few years to allow referring physicians and department personnel to acquaint themselves to the needs of patients seeking coronary imaging. Current multi-detector CT scanners with two, four or eight detector rows perform prospectively gated coronary CT calcification scoring. While still controversial, coronary calcium scoring offers a reasonable non-invasive method for determining risk of significant coronary artery disease in asymptomatic patients. Once a department has experience with coronary calcium imaging of asymptomatic patients, the next step would be to consider coronary artery imaging. While four-detector or eight-detector CT scanners may be useful for this task, there is a growing consensus that 16 or more detector rows are required to perform consistent high quality CTA of the coronary arteries. The cost of these scanners is still undetermined. However, one can expect to pay at least double the cost of a conventional scanner for a 16-detector unit at this time. With additional software for cardiac imaging, the costs can be well over a million dollars for a CT scanner. If the volume of additional patients from coronary CTA meets the promise of this new technology, the cost difference should be affordable even to smaller hospitals. As radiology professionals we possess equipment knowledge and have the imaging and technical skills to perform high quality cardiac imaging with CT and MRI. We need to add to and refine our knowledge of anatomy and become "team players" for management of patients with coronary and cardiac disease. If not us, then who? Are you ready? Are you willing to get ready? PMID:12229053

Gaylord, Gregg M

405

Characterization of microwave magnetic narrow band filters by ferromagnetic resonance  

NASA Astrophysics Data System (ADS)

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

Bousbahi, Khaled; Marcelli, Romolo

2000-05-01

406

Magnetic resonance reversals in optically pumped alkali-metal vapor  

Microsoft Academic Search

We report an unusual phenomenon, peculiar sign reversals of the ground-state magnetic resonances and of the zero-dip resonance (Zeeman resonance at zero field) of optically pumped, alkali-metal vapors. These anomalies occur when a weak circularly polarized D1 laser light is tuned to pump atoms predominantly from the lower ground-state hyperfine multiplet. One can understand the signal reversals in a simple,

F. Gong; Y.-Y. Jau; W. Happer

2007-01-01

407

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

408

Wide-range dynamic magnetic resonance elastography.  

PubMed

Tissue mechanical parameters have been shown to be highly sensitive to disease by elastography. Magnetic resonance elastography (MRE) in the human body relies on the low-dynamic range of tissue mechanics <100 Hz. In contrast, MRE suited for investigations of mice or small tissue samples requires vibration frequencies 10-20 times higher than those used in human MRE. The dispersion of the complex shear modulus (G(?)) prevents direct comparison of elastography data at different frequency bands and, consequently, frequency-independent viscoelastic models that fit to G(*) over a wide dynamic range have to be employed. This study presents data of G(*) of samples of agarose gel, liver, brain, and muscle measured by high-resolution MRE in a 7T-animal scanner at 200-800 Hz vibration frequency. Material constants ? and ? according to the springpot model and related to shear elasticity and slope of the G(*)-dispersion were determined. Both ? and ? of calf brain and bovine liver were found to be similar, while a sample of fibrotic human liver (METAVIR score of 3) displayed about fifteen times higher shear elasticity, similar to ? of bovine muscle measured in muscle fiber direction. ? was the highest in fibrotic liver, followed by normal brain and liver, while muscle had the lowest ?-values of all biological samples investigated in this study. As expected, the least G(*)-dispersion was seen in soft gel. The proposed technique of wide-range dynamic MRE can provide baseline data for both human MRE and high-dynamic MRE for better understanding tissue mechanics of different tissue structures. PMID:21295305

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

2011-02-03

409

Magnetic Resonance Imaging in Postprostatectomy Radiotherapy Planning  

SciTech Connect

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

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

2012-02-01

410

Chapter 1 Magnetic Resonance Contributions to Other Sciences  

NASA Astrophysics Data System (ADS)

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

Ramsey, Norman F.

411

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

NASA Astrophysics Data System (ADS)

Magnetic resonance velocimetry (MRV) is a non-invasive technique capable of measuring the three-component mean velocity field in complex three-dimensional geometries with either steady or periodic boundary conditions. The technique is based on the phenomenon of nuclear magnetic resonance (NMR) and works in conventional magnetic resonance imaging (MRI) magnets used for clinical imaging. Velocities can be measured along single lines, in planes, or in full 3D volumes with sub-millimeter resolution. No optical access or flow markers are required so measurements can be obtained in clear or opaque MR compatible flow models and fluids. Because of its versatility and the widespread availability of MRI scanners, MRV is seeing increasing application in both biological and engineering flows. MRV measurements typically image the hydrogen protons in liquid flows due to the relatively high intrinsic signal-to-noise ratio (SNR). Nonetheless, lower SNR applications such as fluorine gas flows are beginning to appear in the literature. MRV can be used in laminar and turbulent flows, single and multiphase flows, and even non-isothermal flows. In addition to measuring mean velocity, MRI techniques can measure turbulent velocities, diffusion coefficients and tensors, and temperature. This review surveys recent developments in MRI measurement techniques primarily in turbulent liquid and gas flows. A general description of MRV provides background for a discussion of its accuracy and limitations. Techniques for decreasing scan time such as parallel imaging and partial k-space sampling are discussed. MRV applications are reviewed in the areas of physiology, biology, and engineering. Included are measurements of arterial blood flow and gas flow in human lungs. Featured engineering applications include the scanning of turbulent flows in complex geometries for CFD validation, the rapid iterative design of complex internal flow passages, velocity and phase composition measurements in multiphase flows, and the scanning of flows through porous media. Temperature measurements using MR thermometry are discussed. Finally, post-processing methods are covered to demonstrate the utility of MRV data for calculating relative pressure fields and wall shear stresses.

Elkins, Christopher J.; Alley, Marcus T.

2007-12-01

412

Magnetic Resonance Studies of Defects in GaN With Reduced Dislocation Densities.  

National Technical Information Service (NTIS)

Magnetic resonance experiments, including optically detected magnetic resonance (ODMR) and electron paramagnetic resonance (EPR), have been performed on Si-doped homoepitaxial GaN layers grown by MOCVD and on high quality, free-standing (approximately 200...

E. Glasera G. C. Braga J. J. Freitas M. E. Twigg W. E. Carlos

2001-01-01

413

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

SciTech Connect

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

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

2008-03-27

414

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

Microsoft Academic Search

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

Eduard Schreibmann; Lei Xing

2005-01-01

415

A Sex-Specific Metabolite Identified in a Marine Invertebrate Utilizing Phosphorus-31 Nuclear Magnetic Resonance  

PubMed Central

Hormone level differences are generally accepted as the primary cause for sexual dimorphism in animal and human development. Levels of low molecular weight metabolites also differ between men and women in circulating amino acids, lipids and carbohydrates and within brain tissue. While investigating the metabolism of blue crab tissues using Phosphorus-31 Nuclear Magnetic Resonance, we discovered that only the male blue crab (Callinectes sapidus) contained a phosphorus compound with a chemical shift well separated from the expected phosphate compounds. Spectra obtained from male gills were readily differentiated from female gill spectra. Analysis from six years of data from male and female crabs documented that the sex-specificity of this metabolite was normal for this species. Microscopic analysis of male and female gills found no differences in their gill anatomy or the presence of parasites or bacteria that might produce this phosphorus compound. Analysis of a rare gynandromorph blue crab (laterally, half male and half female) proved that this sex-specificity was an intrinsic biochemical process and was not caused by any variations in the diet or habitat of male versus female crabs. The existence of a sex-specific metabolite is a previously unrecognized, but potentially significant biochemical phenomenon. An entire enzyme system has been synthesized and activated only in one sex. Unless blue crabs are a unique species, sex-specific metabolites are likely to be present in other animals. Would the presence or absence of a sex-specific metabolite affect an animal's development, anatomy and biochemistry?

Kleps, Robert A.; Myers, Terrell C.; Lipcius, Romuald N.; Henderson, Thomas O.

2007-01-01

416

Ferromagnetic resonance of isotropic heterogeneous magnetic materials: theory and experiments  

Microsoft Academic Search

Experimental variations of the ferromagnetic resonance (FMR) recorded on soft composite bodies are presented and their interpretation is undertaken. A successful application is performed for the Kittel expression of the FMR, initially written for an ellipsoid placed in vacuum, to a magnetic inclusion of the composite. This model includes the demagnetizing effects due to the magnetic inclusions.

Alexis Chevalier; Jean-Luc Mattei; Marcel Le Floc'h

2000-01-01

417

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

418

Surprising connections: the diverse world of magnetic resonance  

Microsoft Academic Search

When Rutherford discovered the atomic nucleus he could not possibly have imagined that it might be a window to understanding molecular biology, or how the brain works. And yet so it has come to pass. It is the through the magnetism of the nucleus that these insights, and so much more, are possible. The phenomenon of ``Nuclear Magnetic Resonance'' has

Paul Callaghan

2004-01-01

419

Resonant Magnetic Field Sensors Based On MEMS Technology  

Microsoft Academic Search

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

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

2009-01-01

420

Cell Potassium by K39 Spin Echo Nuclear Magnetic Resonance.  

National Technical Information Service (NTIS)

Pulsed nuclear magnetic resonance (NMR) measurements of K39 in solutions and bacteria were made, by the use of a super-conducting magnet with a field of 50,300 gauss, which provides the necessary increase in sensitivity. Transverse relaxation time (T2) of...

F. W. Cope R. Damadian

1970-01-01

421

Magnetic resonance angiography of dialysis access shunts: Initial results  

Microsoft Academic Search

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

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

1996-01-01

422

Active contour models for tracking magnetic resonance tags  

Microsoft Academic Search

Cardiac magnetic resonance imaging with orthogonal stripes of magnetic tags (SPAMM) has enabled quantitative noninvasive analysis of regional myocardial motion and deformation ( 11. Manual detection and tracking of cardiac tags by visual inspection remains a time- consuming process. We have developed an interactively guided semi-automated method of detecting and tracking cardiac tags. A template matching approach combined with a

Dara L. Kraitchman; Alistair A. Young; Leon Axel

1993-01-01

423

Magnetic-resonance-based system for chemical agent screening  

Microsoft Academic Search

Quantum Magnetics is developing a system based on magnetic resonance (MR), combined with a proprietary technology, to screen for chemical agents in nonmetallic containers, without the need to open the container. It derives from the successful design and testing of a similar system for detecting liquid explosives. Preliminary measurements indicate that the system promises to quickly screen for many chemical

Sankaran Kumar; Erik E. Magnuson; David E. Newman; Pablo J. Prado; Jess Lawton

2003-01-01

424

Unsaturated hydraulic conductivity from nuclear magnetic resonance measurements  

Microsoft Academic Search

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

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

2006-01-01

425

Magnetic direct generation of acoustic resonances in silicon membranes  

Microsoft Academic Search

High-Q silicon membranes have been fabricated as resonator elements for excitation by magnetic direct generation of acoustic waves. Operating in the thickness shear mode, these inexpensive sensor elements are remotely excited by a planar spiral coil, driven by a radio frequency current and a strong static magnetic field. Modelling and FEM simulation have been done to improve the understanding of

Frieder Lucklum; Peter Hauptmann; Nico F. de Rooij

2006-01-01

426

Inverse resonance absorption in an inhomogeneous magnetized plasma  

Microsoft Academic Search

The linear mode conversion of a plasma wave to a light wave in a magnetized plasma has been examined theoretically and by computer simulation. This conversion is the inverse of resonance absorption exhibiting an identical dependence on magnetic field and density scale length with an optimum conversion efficiency of approximately 60 percent. Radiation from this source may contribute to the

H. C. Barr; T. J. M. Boyd; G. A. Gardner; R. Rankin

1985-01-01

427

Application of integrated magnetics in resonant converters  

Microsoft Academic Search

The physical size of inductors in resonant converters was examined in terms of inductor to transformer size ratio. Following the general discussion of the issue, the inductor size in a series resonant DC-DC converter is examined in detail. It is shown that the inductor to transformer size ratio is a function of the peak voltage of the inductor to the

Arkadiy Kats; Gregory Ivensky; Sam Ben-Yaakov

1997-01-01

428

Magnetic assembly of gold core-shell necklace resonators  

NASA Astrophysics Data System (ADS)

Gold core-shell necklace structures are assembled by inducing magnetic moments of gold-coated paramagnetic microspheres and a diamagnetic sphere using an external magnetic field. Sphere numbers in a necklace structure was tuned solely by controlling magnetic permeability of background medium. A necklace structure consisting of evenly spaced metal spheres or disks is known to be a good medium for a plasmonic resonance. Therefore, their optical properties were numerically studied. The electric field enhancement by a factor of 1800 was estimated in the gaps between adjacent spheres at a resonant wavelength. The wavelength-scaling strategies of our structures to visible wavelength are also discussed.

Aoki, Kanna; Furusawa, Kentaro; Tanaka, Takuo

2012-04-01

429

Cardiovascular magnetic resonance with an MR compatible pacemaker  

PubMed Central

Magnetic resonance imaging (MRI) within FDA guidelines for the MRI-conditional pacemaker precludes placing the heart at the center of the magnet’s bore. This in effect appears to preclude cardiovascular MR. In this manuscript, we describe a protocol for cardiovascular MR of patients with a Revo pacemaker system while operating within FDA guidelines, and the first US case of cardiovascular MR in a patient with a Revo MRI-conditional pacing system despite position constraints.

2013-01-01

430

Spin microscope based on optically detected magnetic resonance  

DOEpatents

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

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

2010-07-13

431

Spin microscope based on optically detected magnetic resonance  

DOEpatents

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

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

2010-06-29

432

Spin microscope based on optically detected magnetic resonance  

DOEpatents

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

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

2009-10-27

433

Spin microscope based on optically detected magnetic resonance  

DOEpatents

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

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

2009-11-10

434

Spin microscope based on optically detected magnetic resonance  

DOEpatents

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

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

2007-12-11

435

Magnetic Resonance Imaging of Surgical Implants Made from Weak Magnetic Materials  

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

436

Tailoring magnetic dipole emission with plasmonic split-ring resonators.  

PubMed

We numerically explore the emission behavior of magnetic dipole emitters located next to resonant plasmonic split-ring resonators (SRRs), which are well known for their large magnetic moment at their fundamental resonance in the near infrared. Our results are compared to the situation for electric dipole emitters, where the SRR can be described by solely its electric dipole moment. We show that a similar approach in the case of magnetic dipole emitters is not sufficient, as the symmetry breaking due to the gap has to be taken into account. We demonstrate how retardation between the emitter and the SRR can be used as an additional degree of freedom to manipulate the emission spectrum. Our concept will pave the road towards efficient plasmonic antennas for magnetic dipole emitters. PMID:23889429

Hein, Sven M; Giessen, Harald

2013-07-10

437

Tailoring Magnetic Dipole Emission with Plasmonic Split-Ring Resonators  

NASA Astrophysics Data System (ADS)

We numerically explore the emission behavior of magnetic dipole emitters located next to resonant plasmonic split-ring resonators (SRRs), which are well known for their large magnetic moment at their fundamental resonance in the near infrared. Our results are compared to the situation for electric dipole emitters, where the SRR can be described by solely its electric dipole moment. We show that a similar approach in the case of magnetic dipole emitters is not sufficient, as the symmetry breaking due to the gap has to be taken into account. We demonstrate how retardation between the emitter and the SRR can be used as an additional degree of freedom to manipulate the emission spectrum. Our concept will pave the road towards efficient plasmonic antennas for magnetic dipole emitters.

Hein, Sven M.; Giessen, Harald

2013-07-01

438

Functional magnetic resonance imaging: measuring versus estimating.  

PubMed

Brain imaging techniques largely spread in neuroscience literature. Due to initial technical limitations such as the very low signal-to-noise ratio, group experiments became the rule. This fact, together with the wide use of standard brains to localize the activations, lead several experimenters to the wrong idea that the brain can be described by a Cartesian coordinate system, neglecting at the same time the importance of individual neuroanatomy. My commentary on the paper by Devlin and Poldrack reinforces their reminder that it is necessary to deal with anatomy. Moreover, it adds some considerations on the relevance of single subjects studies and on the importance of the BOLD intensity signal, which should be used to describe brain activity together with the most used statistical tools. PMID:17428686

Fadiga, Luciano

2007-03-06

439

Resonant frequency multiplication in microscopic magnetic dots  

NASA Astrophysics Data System (ADS)

We demonstrate the phenomenon of nonlinear frequency multiplication in sub-micrometer Permalloy dots. The efficiency of multiplication is strongly enhanced when the harmonic is resonant with the normal dynamical modes of the dot. We find that the characteristics of resonant enhancement are dependent on the spatial symmetry of the dynamical mode and are different for the double- and the triple-frequency harmonics. The resonant frequency tripling is particularly efficient, providing a practical route for the implementation of microscopic integrated microwave frequency multipliers.

Demidov, V. E.; Ulrichs, H.; Urazhdin, S.; Demokritov, S. O.; Bessonov, V.; Gieniusz, R.; Maziewski, A.

2011-07-01

440

Fast Talairach Transformation for magnetic resonance neuroimages.  

PubMed

We introduce and validate the Fast Talairach Transformation (FTT). FTT is a rapid version of the Talairach transformation (TT) with the modified Talairach landmarks. Landmark identification is fully automatic and done in 3 steps: calculation of midsagittal plane, computing of anterior commissure (AC) and posterior commissure (PC) landmarks, and calculation of cortical landmarks. To perform these steps, we use fast and anatomy-based algorithms employing simple operations. FTT was validated for 215 diversified T1-weighted and spoiled gradient recalled (SPGR) MRI data sets. It calculates the landmarks and warps the Talairach-Tournoux atlas fully automatically in about 5 sec on a standard computer. The average distance errors in landmark localization are (in mm): 1.16 (AC), 1.49 (PC), 0.08 (left), 0.13 (right), 0.48 (anterior), 0.16 (posterior), 0.35 (superior), and 0.52 (inferior). Extensions to FTT by introducing additional landmarks and applying nonlinear warping against the ventricular system are addressed. Application of FTT to other brain atlases of anatomy, function, tracts, cerebrovasculature, and blood supply territories is discussed. FTT may be useful in a clinical setting and research environment: (1) when the TT is used traditionally, (2) when a global brain structure positioning with quick searching and labeling is required, (3) in urgent cases for quick image interpretation (eg, acute stroke), (4) when the difference between nonlinear and piecewise linear warping is negligible, (5) when automatic processing of a large number of cases is required, (6) as an initial atlas-scan alignment before performing nonlinear warping, and (7) as an initial atlas-guided segmentation of brain structures before further local processing. PMID:16845295

Nowinski, Wieslaw L; Qian, Guoyu; Bhanu Prakash, K N; Hu, Qingmao; Aziz, Aamer

441

Novel Detection Schemes of Nuclear Magnetic Resonance and Magnetic Resonance Imaging: Applications from Analytical Chemistry to Molecular Sensors  

NASA Astrophysics Data System (ADS)

Nuclear magnetic resonance (NMR) is a well-established analytical technique in chemistry. The ability to precisely control the nuclear spin interactions that give rise to the NMR phenomenon has led to revolutionary advances in fields as diverse as protein structure determination and medical diagnosis. Here, we discuss methods for increasing the sensitivity of magnetic resonance experiments, moving away from the paradigm of traditional NMR by separating the encoding and detection steps of the experiment. This added flexibility allows for diverse applications ranging from lab-on-a-chip flow imaging and biological sensors to optical detection of magnetic resonance imaging at low magnetic fields. We aim to compare and discuss various approaches for a host of problems in material science, biology, and physics that differ from the high-field methods routinely used in analytical chemistry and medical imaging.

Harel, Elad; Schröder, Leif; Xu, Shoujun

2008-07-01

442

Design and development of a novel nuclear magnetic resonance detection for the gas phase ions by magnetic resonance acceleration technique  

NASA Astrophysics Data System (ADS)

Nuclear magnetic resonance (NMR) technique is a well-established powerful tool to study the physical and chemical properties of a wide range of materials. However, presently, NMR applications are essentially limited to materials in the condensed phase. Although magnetic resonance was originally demonstrated in gas phase molecular beam experiments, no application to gas phase molecular ions has yet been demonstrated. Here, we present a novel principle of NMR detection for gas phase ions based on a ``magnetic resonance acceleration'' technique and describe the design and construction of an apparatus which we are developing. We also present an experimental technique and some results on the formation and manipulation of cold ion packets in a strong magnetic field, which are the key innovations to detect NMR signal using the present method. We expect this novel method to lead new realm for the study of mass-selected gas-phase ions with interesting applications in both fundamental and applied sciences.

Fuke, K.; Tona, M.; Fujihara, A.; Sakurai, M.; Ishikawa, H.

2012-08-01

443

Resonance splitting effect through magnetic superlattices in graphene  

NASA Astrophysics Data System (ADS)

Using the transfer-matrix formalism, the resonance splitting effect of Dirac electrons through two types of magnetic superlattices in graphene is studied theoretically. The numerical results show that the transmission presents (n - 1)-fold resonance splitting for the both magnetic superlattices with n-barrier, similar to Schrödinger electrons in semiconductor superlattices. It is believed that the Dirac electrons possess a general (n - 1)-fold splitting rule for n-barrier magnetic superlattices, of which the corresponding vector potential is periodic field. The magnetic superlattices with strong magnetic field can be used as a very efficient wave-vector filter for Dirac electrons. The splitting feature of the transmission probability also reflects in the conductance and shot noise. These properties should be useful for the design of graphene-based electronic devices.

Lu, Wei-Tao; Li, Wen; Wang, Yong-Long; Ye, Cheng-Zhi; Jiang, Hua

2012-10-01

444

Magnetic Field Interactions of Orthodontic Wires during Magnetic Resonance Imaging (MRI) at 1.5 Tesla  

Microsoft Academic Search

Background: Orthodontic appliances pose a potential risk during magnetic resonance imaging (MRI) due to forces on metallic objects within the static magnetic field of MRI systems. The aim of the present investigation was to measure forces on orthodontic wires caused by the static magnetic field of a 1.5-Tesla MRI system, and to assess the safety hazards associated with these forces.

Dirk Schulze; Gerhard Adam; Bärbel Kahl-Nieke

2005-01-01

445

Design of a Nuclear Magnetic Resonance Fast Field Cycling Air Cored Magnet  

Microsoft Academic Search

A method for the design of a nuclear magnetic resonance fast field cycling air-cored magnet is presented in this paper. General analytic expressions relating the geometric parameters of the magnet with the flux density, the current density and the power losses were obtained. An optimization algorithm based on the thin circular loop coil model to determine the positions of the

Duarte M. Sousa; G. D. Marques; P. J. Sebastiao; A. C. Ribeiro

2007-01-01

446

Magnetic resonance imaging (MRI): effects of electro-magnetic radiation and safety aspects  

Microsoft Academic Search

Magnetic resonance imaging (MRI) is a widely used noninvasive imaging modality for obtaining diagnostic radiological images. An MRI scanner consists of several diverse technological components such as powerful static magnetic field, rapidly varying local gradient magnetic fields, pulsed radiofrequency (RF) field and liquid helium and\\/or liquid nitrogen. At present, there is no conclusive evidence for adverse biological effects in patients

N. R JAGANNATECAN

1999-01-01

447

Desktop fast-field cycling nuclear magnetic resonance relaxometer.  

PubMed

In this paper a new type of Fast Field Cycling (FFC) Nuclear Magnetic Resonance (NMR) relaxometer with low power consumption (200W) and cycle to cycle field stability better than 10(-4) is described. The new high-permeability magnet was designed to allow for good magnetic field homogeneity and allows for the sample rotation around an axis perpendicular to magnetic field, operating with magnetic fields between 0 and 0.21T. The power supply of the new relaxometer was specially developed in order to have steady state accurate currents and allow for magnetic field switching times less than 3ms. Additional control circuits were developed and included to compensate the Earth magnetic field component parallel to the field axis and to compensate for parasitic currents. The main aspects of the developed circuits together with some calibrating experimental results using the liquid crystal compounds 5CB and 8CB are presented and discussed. PMID:20688489

Sousa, Duarte Mesquita; Marques, Gil Domingos; Cascais, José Manuel; Sebastião, Pedro José

2010-07-16

448

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

449

Grain Sizing in Porous Media using Bayesian Magnetic Resonance  

NASA Astrophysics Data System (ADS)

We introduce a Bayesian inference approach to analyze magnetic resonance data of granular solids. To characterize structure using magnetic resonance, it is usual to acquire data in k space which are then Fourier transformed to obtain an image. An alternative approach, adopted here, is to utilize the Rayleigh distribution observed in the signal intensity for a given k when a random selection of grains is measured in k space, to define a likelihood function for Bayesian analysis. This Bayesian likelihood function is used to noninvasively characterize grains within a porous medium on length scales below the practical resolution of magnetic resonance imaging. A pore size distribution is then calculated from the measured grain size distribution using a Monte Carlo approach. We demonstrate this general technique with specific examples of water-saturated rock cores.

Holland, D. J.; Mitchell, J.; Blake, A.; Gladden, L. F.

2013-01-01

450

[Diagnostic approach to cardiopathies by means of magnetic resonance imaging].  

PubMed

Cardiomyopathies encompass a broad spectrum of heart pathologies having a basic principle, the intrinsic injury of the myocardial fiber. By definition, cardiomyopathies could be primary (dilated cardiomyopathy), or can be a consequence of another cardiovascular illness (high blood pressure), or of genetic anomalies, such as hypertrophic cardiomyopathy, or due to alterations in myocytes due to fibrolipidic material as occurs in right ventricle arrhythmogenic dysplasia. Currently, magnetic resonance imaging is the best method to approach the diagnosis of these pathologies. Magnetic resonance imaging has allowed us to study histological sections through adequate sequences and using gadolinium as contrast agent. We present herein a simple way to approach the diagnosis of cardiomyopathies by means of magnetic resonance imaging methods. PMID:15909747

Gutiérrez Zamora, Agustín

451

Carbon-13 magnetic resonance spectroscopy of drugs. Sulfonamides.  

PubMed

The natural abundance 13C magnetic resonance spectra of a series of sulfonamide drugs(sulfanilamide, sulfaguanidine,sulfathiazole, sulfasuxidine, sulfadiazine, sulfamerazine, sulfamethiazine, and sulfapyridine) have been determined at 25.15 MHz employing the pulse Fourier transform technique. The chemical shefts have been assigned with the aid of off-resonance and selective proton decoupling techniques, as well as by long-range carbon-13 proton coupling patterns. PMID:1151960

Chang, C; Floss, H G; Peck, G E

1975-05-01

452

A Faraday effect position sensor for interventional magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

An optical sensor is presented which determines the position and one degree of orientation within a magnetic resonance tomograph. The sensor utilizes the Faraday effect to measure the local magnetic field, which is modulated by switching additional linear magnetic fields, the gradients. Existing methods for instrument localization during an interventional MR procedure often use electrically conducting structures at the instruments that can heat up excessively during MRI and are thus a significant danger for the patient. The proposed optical Faraday effect position sensor consists of non-magnetic and electrically non-conducting components only so that heating is avoided and the sensor could be applied safely even within the human body. With a non-magnetic prototype set-up, experiments were performed to demonstrate the possibility of measuring both the localization and the orientation in a magnetic resonance tomograph. In a 30 mT m-1 gradient field, a localization uncertainty of 1.5 cm could be achieved. This paper has been presented in parts at the 11th Annual Meeting of the International Society for Magnetic Resonance in Medicine in Toronto, 2003.

Bock, M.; Umathum, R.; Sikora, J.; Brenner, S.; Aguor, E. N.; Semmler, W.

2006-02-01

453

Magnetization exchange observed in human skeletal muscle by non-water-suppressed proton magnetic resonance spectroscopy.  

PubMed

Many metabolites in the proton magnetic resonance spectrum undergo magnetization exchange with water, such as those in the downfield region (6.0-8.5 ppm) and the upfield peaks of creatine, which can be measured to reveal additional information about the molecular environment. In addition, these resonances are attenuated by conventional water suppression techniques complicating detection and quantification. To characterize these metabolites in human skeletal muscle in vivo at 3 T, metabolite cycled non-water-suppressed spectroscopy was used to conduct a water inversion transfer experiment in both the soleus and tibialis anterior muscles. Resulting median exchange-independent T(1) times for the creatine methylene resonances were 1.26 and 1.15 s, and for the methyl resonances were 1.57 and 1.74 s, for soleus and tibialis anterior muscles, respectively. Magnetization transfer rates from water to the creatine methylene resonances were 0.56 and 0.28 s(-1) , and for the methyl resonances were 0.39 and 0.30 s(-1) , with the soleus exhibiting faster transfer rates for both resonances, allowing speculation about possible influences of either muscle fibre orientation or muscle composition on the magnetization transfer process. These water magnetization transfer rates observed without water suppression are in good agreement with earlier reports that used either postexcitation water suppression in rats, or short CHESS sequences in human brain and skeletal muscle. Magn Reson Med, 2012. © 2012 Wiley Periodicals, Inc. PMID:23172828

Macmillan, Erin L; Boesch, Chris; Kreis, Roland

2012-11-21

454

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

455

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 basi